RG 1.200 (Rev 2)
RG 1.200 (Rev 2)
RG 1.200 (Rev 2)
March 2009
Revision 2
REGULATORY GUIDE
OFFICE OF NUCLEAR REGULATORY RESEARCH
depth review of the base PRA by NRC reviewers, allowing them to focus their review on key
assumptions and areas identified by peer reviewers as being of concern and relevant to the application.
Consequently, this guide will provide for a more focused and consistent review process. In this
regulatory guide, the quality of a PRA analysis used to support an application is measured in terms of its
appropriateness with respect to scope, level of detail, and technical acceptability.
This regulatory guide contains information collections that are covered by the requirements of 10
CFR Part 50 which the Office of Management and Budget (OMB) approved under OMB control number
3150-0011. The NRC may neither conduct nor sponsor, and a person is not required to respond to, an
information collection request or requirement unless the requesting document displays a currently valid
OMB control number.
B. DISCUSSION
Existing Guidance Related to the Use of PRA in Reactor Regulatory Activities
Since the NRC issued its PRA Policy Statement, a number of risk-informed regulatory activities
have been implemented and the necessary technical documents are being developed to provide guidance
on the use of PRA information. For these activities, the technical adequacy of the base PRA should be
sufficient to provide the needed confidence in the results being used in the decision. A list of some of
these documents is provided below.
Regulatory Guide 1.174 (Ref. 2) and its associated standard review plan (SRP), Section 19.2
(Ref. 3), provide general guidance on applications that address changes to the licensing basis. Key
aspects of this document include the following:
It reflects the staffs recognition that the PRA needed to support regulatory decisions can vary
(i.e., that the scope, level of detail, and quality of the PRA is to be commensurate with the
application for which it is intended and the role the PRA results play in the integrated decision
process). For some applications and decisions, only particular pieces 1 of the PRA need to be
used. In other applications, a full-scope PRA is needed. General guidance regarding scope, level
of detail, and quality for a PRA is provided in the application-specific documents.
While RG 1.174 is written in the context of one reactor regulatory activity (license amendments),
the underlying philosophy and principles are applicable to a broad spectrum of reactor regulatory
activities.
Regulatory Guide 1.201, Guidelines for Categorizing Structures, Systems, and Components in
Nuclear Power Plants According to Their Safety Significance (Ref. 4), discusses an approach to support
the new rule established as Title 10, Section 50.69, Risk-Informed Categorization and Treatment of
Structures, Systems, and Components for Nuclear Power Reactors, of the Code of Federal Regulations
(10 CFR 50.69) (Ref. 5).
1
In this regulatory guide, a piece of a PRA can be understood to be equivalent to that piece of the analysis for which an
applicable PRA standard identifies a supporting level requirement.
Regulatory Guide 1.205, Risk-Informed, Performance-Based Fire Protection for Existing LightWater Nuclear Power Plants (Ref. 6), provides guidance for use in complying with requirements that the
NRC has promulgated for risk-informed and performance-based fire protection progress that meet the
requirements of 10 CFR 50.48(c) (Ref. 7) and National Fire Protection Association 805, PerformanceBased Standard for Fire Protection for Light-Water Reactor Electric Generating Plants, 2001 Edition
(Ref. 8).
Section C.I.19 of Regulatory Guide 1.206, Combined License Applications for Nuclear Power
Plants (LWR Edition) (Ref. 9), discusses the requirements in 10 CFR Part 52, Early Site Permits;
Standard Design Certifications; and Combined Licenses for Nuclear Power Plants (Ref. 10), for a
combined license (COL) applicant to conduct a plant-specific PRA and to describe the plant-specific PRA
and its results within its final safety analysis report. The revision to 10 CFR Part 50 included a
requirement for the COL holder to maintain and upgrade the PRA periodically throughout the life of the
plant, and a requirement to demonstrate PRA technical adequacy.
In addition, there are other regulatory guides that provide guidance for such specific applications
as inservice testing (Ref. 11), inservice inspection (Ref. 12), and technical specifications (Ref. 13). The
NRC has also prepared SRP sections for each of the application-specific regulatory guides.
PRA standards have also been under development by the American Society of Mechanical
Engineers (ASME) and the American Nuclear Society (ANS):
ASME and ANS jointly issued an at-power Level 1 and limited Level 2 PRA standard for internal
and external hazards (requirements for low power shutdown conditions to be added) (Ref. 14). 2
ASME is developing PRA standards for new LWRs applying for design certification (DC) and
COLs, and for future advanced non-LWRs. ANS is developing a Level 1 and limited Level 2
PRA standard for low-power shutdown operating mode (to be incorporated into the ASME/ANS
joint standard), and is also developing Level 2 and Level 3 PRA standards.
Reactor owners groups have been developing and applying a PRA peer review program for
several years. The Nuclear Energy Institute (NEI) has issued several peer review guidance documents:
NEI 00-02, Probabilistic Risk Assessment Peer Review Process Guidance. This document
provides historical guidance for performing a PRA peer review and a self-assessment of the peer
review criteria against PRA standard requirements. (Ref. 15)
NEI 05-04, Process for Performing Follow-On PRA Peer Reviews Using the ASME PRA
Standard. This document provides guidance for conducting and documenting a follow-on peer
review for PRAs using the ASME PRA Standard. (Ref. 16)
NEI 07-12, Fire Probabilistic Risk Assessment (FPRA) Peer Review Process Guidelines. This
document provides guidance for conducting and documenting a peer review of an internal fire
PRA using the ASME/ANS PRA standard. (Ref. 17)
Previous revisions and addendum to this standard are listed in Reference 14.
SECY-04-0118, Plan for the Implementation of the Commissions Phased Approach to PRA
Quality (Ref. 19), presents the staffs approach to defining the needed PRA quality for current or
anticipated applications, as well as the process for achieving this quality, while allowing risk-informed
decisions to be made using currently available methods until all of the necessary guidance documents are
developed and implemented. SECY-07-0042, Status of the Plan for the Implementation of the
Commissions Phased Approach to Probabilistic Risk Assessment Quality (Ref. 20), provides an update
to the staff plan.
(2)
the NRCs position on PRA consensus standards and industry PRA peer review program
documents
(3)
demonstration that the baseline PRA (in total or specific pieces) used in regulatory applications is
of sufficient technical adequacy
(4)
This regulatory guide provides guidance on the PRA technical adequacy needed for the base PRA
that is used in a risk-informed integrated decision-making process. It does not provide guidance on how
the base PRA is revised for a specific application or how the PRA results are used in application-specific
decision-making processes; that guidance is provided in such documents as References 2, 4, and 6.
The regulatory guides that address specific applications, such as Regulatory Guide 1.201, allow
for the use of PRAs that are not full-scope (e.g., they do not include contributions from external initiating
events or low-power and shutdown (LPSD) modes of operation). Those regulatory guides do, however,
state that the missing scope items are to be addressed in some way, such as by using bounding analyses,
or by limiting the scope of the application. This regulatory guide does not address such alternative
methods to the evaluation of risk contributions; rather, this guide only addresses PRA methods. NUREG1855 provides guidance on acceptable bounding analyses and on limiting the scope of the application. 3
NUREG-1855 is being finalized and is expected to be publicly available in late March 2009.
the rule (e.g., 10 CFR Part 52). In addition, the NRC has prepared corresponding SRP chapters for the
application-specific guides.
Figure 1 shows the relationship of this regulatory guide to risk-informed activities, applicationspecific guidance, consensus PRA standards, and industry programs (e.g., NEI 00-02, 05-04, 07-12).
APPLICATION
Licensing
Risk-Informed
Licensing
Changes
APPLICATION
SPECIFIC
REGULATORY
GUIDE
Regulatory
Guide 1.174
50.69
Risk-Informed
Categorization
and Treatment
of SSCs
Regulatory
Guide 1.201
50.48(c)
Fire Protection, National
Fire Protection
Association Standard
NFPA 805
Regulatory
Guide 1.205
10 CFR part 52
Licenses,
Certifications, And
Approvals For
Nuclear Power Plants
Regulatory
Guide 1.206
Regulatory Guide
1.200
GENERIC SUPPORTING
GUIDANCE
National PRA Consensus
Standards and Industry Related
Guidance
C. REGULATORY POSITION
1.
This section describes one acceptable approach for defining the technical adequacy of an
acceptable base PRA of a commercial light water reactor nuclear power plant. However, the term PRA
needs to be defined. For a method or approach to be considered a PRA, the method or approach
(1) provides a quantitative assessment of the identified risk in terms of scenarios that result in undesired
consequences (e.g., core damage or a large early release) and their frequencies, and (2) is comprised of
specific technical elements in performing the quantification. A method that does not provide a quantified
assessment of the defined risk or does not include the technical elements specified in Regulatory
Position 1.2 is not considered to be a PRA.
The scope of the PRA is determined by its intended use. It is envisioned, however, that for
currently operating reactors and for reactor at the DC or COL application stage, some applications may
require a full-scope Level 1 and some aspects of a Level 2 PRA. Consequently, in this section, the
guidance provided is for a full-scope Level 1 and Level 2 PRA. The scope is defined in terms of (1) the
metrics used to characterize risk, (2) the plant operating states for which the risk is to be evaluated, and
(3) the causes of initiating events (hazard groups) that can potentially challenge and disrupt the normal
operation of the plant and, if not prevented or mitigated, would eventually result in core damage and/or a
large release.
The level of detail of the PRA is also determined by its intended use. Nonetheless, a minimal
level of detail is necessary to ensure that the impacts of designed-in dependencies (e.g., support system
dependencies, functional dependencies, and dependencies on operator actions) are correctly captured.
This minimal level of detail is implicit in the technical elements comprising the PRA and their associated
characteristics and attributes.
As noted, PRAs used in risk-informed activities may vary in scope and level of detail, depending
on the specific application. However, the PRA results used to support an application must be derived
from a baseline PRA model that represents the as-built, as-operated plant 4 to the extent needed to support
the application. Consequently, the PRA needs to be maintained and upgraded, where necessary, to ensure
it represents the as-built and as-operated plant.
This section provides guidance in four areas:
(1)
scope of a PRA
(2)
technical elements of a full-scope Level 1 and Level 2 PRA and their associated attributes and
characteristics
(3)
(4)
Some applications may involve the plant at the DC or COL application stage, at which point the plant is neither built nor
operated. At these stages, the intent is for the PRA model to reflect the as-designed plant.
1.1
Scope of a PRA
The scope of a PRA is defined by the challenges included in the analysis and the level of analysis
performed. Specifically, the scope is defined in the following terms:
causes of initiating events (hazard groups) that can potentially challenge and disrupt the normal
operation of the plant.
Risk characterization is typically expressed by metrics of core damage frequency (CDF) and
large early release frequency (LERF) (as surrogates for latent and early fatality risks, respectively, for
operating light-water reactors). Large release frequency (LRF) is used as a risk metric for LWR DC and
COL applicants 5 . These metrics are defined in a functional sense as follows:
Core damage frequency is defined as the sum of the frequencies of those accidents that result in
uncovery and heatup of the reactor core to the point at which prolonged oxidation and severe fuel
damage are anticipated and involving enough of the core, if released, to result in offsite public
health effects.
Large early release frequency is defined as the sum of the frequencies of those accidents
leading to rapid, unmitigated release of airborne fission products from the containment to the
environment occurring before the effective implementation of offsite emergency response and
protective actions such that there is the potential for early health effects. (Such accidents
generally include unscrubbed releases associated with early containment failure shortly after
vessel breach, containment bypass events, and loss of containment isolation.)
Issues related to the reliability of barriers (in particular, containment integrity and consequence
mitigation) are addressed through other parts of the decision-making process, such as consideration of
defense-in-depth. To provide the risk perspective for use in decision-making, a Level 1 PRA needs to
provide CDF. A limited Level 2 PRA is needed to address LERF and a full Level 2 to address LRF.
Plant operating states (POSs) are used to subdivide the plant operating cycle into unique states,
such that the plant response can be assumed to be the same within the given POS for a given initiating
event. Operational characteristics (such as reactor power level; in-vessel temperature, pressure, and
coolant level; equipment operability; and changes in decay heat load or plant conditions that allow new
success criteria or reactor coolant system or containment configuration) are examined to identify those
relevant to defining POSs. These characteristics are used to define the states, and the fraction of time
spent in each state is estimated using plant-specific information. The risk perspective is based on the total
risk associated with the operation of the reactor, which includes not only at-power operation, but also
low-power and shutdown conditions. For some applications, the risk impact may affect some modes of
operation, but not others.
Initiating events are the plant system perturbations to the steady state of the plant that
challenge plant control and safety systems whose failure could lead to core damage and or
radioactivity release. These initiating events include failure of equipment from either internal
5
The Commission staff requirements memorandum (SRM dated June 26, 1990, in response to SECY-90-016 established the
identified goals.
plant causes (such as hardware faults, operator actions, floods, or fires), or external plant causes
(such as earthquakes or high winds). These are referred to as internal hazards and external
hazards, respectively. The risk perspective is based on a consideration of the total risk, which
includes contributions from initiating events whose causes are attributable to both internal and
external hazards.
A hazard group is a group of similar causes of initiating events that are assessed in a
PRA using a common approach, methods, and likelihood data for characterizing the effect on the
plant. The hazard groups addressed in this regulatory guide include the following:
Internal Hazards
-- Internal Events
-- Internal Floods
-- Internal Fires
1.2
External Hazards
-- Seismic Events
-- High Winds
-- External Floods
-- Other External Hazards
Table 1 provides the list of general technical elements that are necessary for a Level 1 and
Level 2 PRA. A PRA that is missing one or more of these elements would not be considered a complete
PRA.
Table 1. Technical Elements of a PRA
SCOPE OF
ANALYSIS
Level 1
Level 2
TECHNICAL ELEMENT
Initiating event analysis
Quantification
Systems analysis
Plant damage state analysis
Quantification
Accident progression analysis
Interpretation of results and documentation are technical elements of both Level 1 and Level 2 PRAs.
These technical elements are applicable to the PRA models constructed to address each of the
contributors (hazard groups) to risk for each of the POSs. Because additional analyses are required to
characterize their impact on the plant in terms of causing initiating events and mitigating equipment
failures, internal floods, internal fires, and external hazards are discussed separately in Regulatory
Positions 1.2.3 through 1.2.9, respectively. Further, to understand the results, it is important to examine
the different contributors on both an individual and relative basis. Therefore, this element, interpretation
of results, is discussed separately in Regulatory Position 1.2.10. Another major element that is common
to all of the technical elements is documentation; it is discussed separately in Regulatory Position 1.2.11.
While the technical elements are the same for each POS, other considerations, within a specific technical
element, may need to be addressed for LPSD conditions. Table 2 discusses these considerations.
1.2.1
The following briefly discusses the objective of each technical element, and, for each element,
provides the technical characteristics and attributes for accomplishing the objective. The objective and
characteristics and attributes are given within the context of internal events.
Initiating event analysis identifies and characterizes the events that both challenge normal plant
operation during power or shutdown conditions and require successful mitigation by plant equipment and
personnel to prevent core damage from occurring. Events that have occurred at the plant and those that
have a reasonable probability of occurring are identified and characterized. An understanding of the
nature of the events is performed such that a grouping of the events, with the groups defined by similarity
of system and plant responses (based on the success criteria), may be performed to manage the large
number of potential events that can challenge the plant.
Success criteria analysis determines the minimum requirements for each function (and
ultimately the systems used to perform the functions) to prevent core damage (or to mitigate a release)
given an initiating event. The requirements defining the success criteria are based on acceptable
engineering analyses that represent the design and operation of the plant under consideration. For a
function to be successful, the criteria are dependent on the initiator and the conditions created by the
initiator. The computer codes used to perform the analyses for developing the success criteria are
validated and verified for both technical integrity and suitability to assess plant conditions for the reactor
pressure, temperature, and flow range of interest, and they accurately analyze the phenomena of interest.
Calculations are performed by personnel who are qualified to perform the types of analyses of interest and
are well trained in the use of the codes.
Accident sequence analysis models, chronologically (to the extent practical), the different
possible progressions of events (i.e., accident sequences) that can occur from the start of the initiating
event to either successful mitigation or core damage. The accident sequences account for the systems that
are used (and available) and operator actions performed to mitigate the initiator based on the defined
success criteria and plant operating procedures (e.g., plant emergency and abnormal operating
procedures) and training. The availability of a system includes consideration of the functional,
phenomenological, and operational dependencies and interfaces between the various systems and operator
actions during the course of the accident progression.
Systems analysis identifies the various combinations of failures that can prevent the system from
performing its function as defined by the success criteria. The model representing the various failure
combinations includes, from an as-built and as-operated perspective, the system hardware and
instrumentation (and their associated failure modes) and human failure events that would prevent the
system from performing its defined function. The basic events representing equipment and human
failures are developed in sufficient detail in the model to account for dependencies among the various
systems and to distinguish the specific equipment or human events that have a major impact on the
systems ability to perform its function.
Parameter estimation analysis quantifies the frequencies of the initiating events, as well as the
equipment failure probabilities and equipment unavailabilities of the modeled systems. The estimation
process includes a mechanism for addressing uncertainties and has the ability to combine different
sources of data in a coherent manner, including the actual operating history and experience of the plant
when it is of sufficient quality, as well as applicable generic experience.
Human reliability analysis identifies and provides probabilities for the human failure events that
can negatively impact normal or emergency plant operations. The human failure events associated with
normal plant operation include the events that leave the system (as defined by the success criteria) in an
unrevealed, unavailable state. The human failure events associated with emergency plant operation
represent those human actions that, if not performed, do not allow the needed system to function.
Quantification of the probabilities of these human failure events is based on plant- and accident-specific
conditions, where applicable, including any dependencies among actions and conditions.
Quantification provides an estimation of the CDF given the design and/or operation the plant
(depending whether the plant is in the design or operating stage). Regardless of the plant stage, the CDF
is based on the summation of the estimated CDF from each accident sequence for each initiator group. If
truncation of accident sequences and cutsets is applied, truncation limits are set so that the overall model
results are not impacted in such a way that significant accident sequences or contributors 6 are eliminated.
Therefore, the truncation value is selected so that the required results are stable with respect to further
reduction in the truncation value.
Table 2 provides a summary of the needed characteristics and attributes for the technical elements
for a Level 1 PRA for internal events. The characteristics and attributes are provided for both at-power
conditions and for low power and shutdown (LPSD) conditions.
Table 2. Summary of Technical Characteristics and Attributes of a Level 1 PRA for Internal
Events
Element
Technical Characteristics and Attributes
PRA At-Power
Initiating
Event
Analysis
Success
Criteria
Analysis
Accident
Sequence
Development
Analysis
Note: It is recognized that for those new reactor designs with substantially lower risk
profiles (e.g., internal events CDF below 10-6/year) that the quantitative screening
value should be adjusted according to the corresponding baseline risk value.
The determination of significance is a function of how the PRA is being, or is intended to be, used. When a PRA is being
used to support an application, the significance of an accident sequence or contributor is measured with respect to whether
its consideration has an impact on the decision being made. For the base PRA model, significance can be measured with
respect to the contribution to the total CDF or LERF, or it can be measured with respect to the contribution to the CDF or
LERF/LRF for a specific hazard group or POS, depending on the context. For example, for the purposes of defining
capability categories, the ASME/ANS PRA Standard, defines significance at the hazard group level. Whatever the context,
the following numerical criteria are recommended:
Significant accident sequence: A significant sequence is one of the set of sequences, defined at the functional or systemic
level that, when ranked, compose 95% of the CDF or the LERF/LRF, or that individually contribute more than ~1% to the
CDF or LERF/LRF.
Significant basic event/contributor: The basic events (i.e., equipment unavailabilities and human failure events) that have a
Fussell-Vesely importance greater than 0.005 or a risk-achievement worth greater than 2.
Table 2. Summary of Technical Characteristics and Attributes of a Level 1 PRA for Internal
Events
Element
Technical Characteristics and Attributes
Models
developed
in
sufficient detail to achieve the following purposes:
Systems
Reflect
the
as-designed,
as-built, as-operated plant (as applicable) including how
Analysis
it has performed during the plant history for operating plants
Reflect the success criteria for the systems to mitigate each identified accident
sequence
Include both active and passive components and failure modes that impact the
function of the system
Identification and definition of the human failure events that would result in
Human
initiating events or pre- and post-accident human failure events that would impact
Reliability
the mitigation of initiating events
Analysis
NUREG-1792 (Ref. 21) and NUREG-1842 (Ref. 22) provide good practices for
meeting the above attribute and characteristics
Estimation of the CDF for modeled sequences that are not screened as a result of
Quantification
truncation, given as a mean value
Estimation of the accident sequence CDFs for each initiating event group
Truncation values set relative to the total plant CDF such that the CDF is stable
with respect to further reduction in the truncation value
PRA Low Power and Shutdown
The LPSD evolution is divided into POSs based on the unique impact on plant
response to facilitate the practicality and efficiency of the PRA
The conditions include decay heat level, reactor coolant system configuration,
reactor level, pressure and temperature, containment configuration, and the
assumed representative plant system configurations within the POS
LPSD POSs that are subsumed into each other are shown to be represented by the
characteristics of the subsuming group
The duration and number of entries into each POS are determined
Table 2. Summary of Technical Characteristics and Attributes of a Level 1 PRA for Internal
Events
Element
Technical Characteristics and Attributes
The
initiating
event
analysis includes the same attributes and characteristics as for
Initiating
at-power,
as
well
as
the following:
Event
examination
of
human-induced
initiating events, for example, those resulting
Analysis
from maintenance activities, including different types of LOCAs (e.g., draindown events as opposed to pipe breaks)
The
success criteria analysis includes the same attributes and characteristics as for atSuccess
power, as well as an analysis appropriate to the POS definition and characterization
Criteria
Analysis
The accident sequence development analysis includes the same attributes and
Accident
characteristics as for at-power, as well as an accounting for changing plant
Sequence
conditions within a POS
Development
Analysis
The systems analysis includes the same attributes and characteristics as for atSystems
power, as well as the identification of conditions varying from POS to POS for
Analysis
spatial and environmental hazards, systems actuation signals, system inventories
(e.g., air)
The parameter estimation analysis includes the same attributes and characteristics
Parameter
as for at-power, as well as the following:
Estimation
The
human reliability analysis includes the same attributes and characteristics as
Human
for
at-power,
as well as the following:
Reliability
differentiation
between calibration errors that may impact equipment
Analysis
performance at-power versus low-power and shutdown POSs
Quantification
includes the same attributes and characteristics for at-power, as
Quantification
well as the estimation of CDF and LERF/LRF for each POS
1.2.2
The following briefly discusses the objective of each technical element, and for each element, provides
the technical characteristics and attributes for accomplishing the objective. The objective and
characteristics and attributes are given in the context of internal events
Plant damage state analysis groups similar core damage scenarios together to allow a practical
assessment of the severe accident progression and containment response resulting from the full spectrum
of core damage accidents identified in the Level 1 analysis. The plant damage state analysis defines the
attributes of the core damage scenarios that represent boundary conditions to the assessment of severe
accident progression and containment response that ultimately affect the resulting radionuclide releases.
Revision 2 of RG 1.200, Page 12
The attributes address the dependencies between the containment systems modeled in the Level 2 analysis
with the core damage accident sequence models to fully account for mutual dependencies. Core damage
scenarios with similar attributes are grouped together to allow for efficient evaluation of the Level 2
response.
Accident progression analysis models the different series of events that challenge containment
integrity for the core damage scenarios represented in the plant damage states. The accident progressions
account for interactions among severe accident phenomena and system and human responses to identify
credible containment failure modes, including failure to isolate the containment. The timing of major
accident events and the subsequent loadings produced on the containment are evaluated against the
capacity of the containment to withstand the potential challenges. The containment performance during
the severe accident is characterized by the timing (e.g., early versus late), size (e.g., catastrophic versus
bypass), and location of any containment failures. The codes used to perform the analysis are validated
and verified for both technical integrity and suitability. Calculations are performed by personnel qualified
to perform the types of analyses of interest and well-trained in the use of the codes.
Source term analysis characterizes the radiological release to the environment resulting from
each severe accident sequence leading to containment failure or bypass. The characterization includes the
time, elevation, and energy of the release and the amount, form, and size of the radioactive material that is
released to the environment. The source term analysis is sufficient to determine whether a large early
release or a large late release occurs. A large early release is one involving the rapid, unmitigated release
of airborne fission products from the containment to the environment occurring before the effective
implementation of offsite emergency response and protective actions such that there is a potential for
early health effects. Such accidents generally include unscrubbed releases associated with early
containment failure at or shortly after vessel breach, containment bypass events, and loss of containment
isolation. With large late release, unmitigated release from containment occurs in a timeframe that allows
effective evacuation of the close-in population making early health effects are unlikely.
Quantification integrates the accident progression models and source term evaluation to provide
estimates of the frequency of radionuclide releases that could be expected following the identified core
damage accidents. This quantitative evaluation reflects the different magnitudes and timing of
radionuclide releases and specifically allows for identification of LERF or LRF.
Table 3 provides a summary of the needed characteristics and attributes for the technical elements
for a Level 2 PRA for internal events. The characteristics and attributes are provided for both at-power
conditions and for LPSD conditions.
Table 3. Summary of Technical Characteristics and Attributes of a Level 2 PRA for Internal
Events
Element
Technical Characteristics and Attributes
PRA At-Power
Plant Damage
State Analysis
Severe
Accident
Progression
Analysis
Quantification
Source Term
Analysis
Identification of the attributes of the core damage scenarios that influence severe
accident progression, containment performance, and any subsequent radionuclide
releases
Grouping of core damage scenarios with similar attributes into plant damage
states
Carryover of relevant information from Level 1 to Level 2
Use of appropriate codes by qualified trained users with an understanding of the
code limitations and the means for addressing the limitations
Assessment of the credible severe accident phenomena via a structured process
Assessment of containment system performance including linkage with failure
modes on non-containment systems
Establishment of the capacity of the containment to withstand severe accident
environments
Assessment of accident progression timing, including timing of loss of
containment failure integrity
Estimation of the frequency of different containment failure modes and resulting
radionuclide source terms
Assessment of radionuclide releases including appreciation of timing, location,
amount, and form of release
Grouping of radionuclide releases into smaller subsets of representative source
terms with emphasis on large early release and large late release
The severe accident progression analysis includes the same attributes and
Severe
characteristics as for at-power, as well as the following:
Accident
The source term analysis includes the same attributes and characteristics as for atSource Term
power.
Analysis
1.2.3
PRA models of internal floods are based on the internal events PRA model, modified to include
the impact of the identified flood scenarios in terms of causing initiating events, and failing equipment
used to respond to initiating events. An important step in this process is to define flood areas which is
done in the flood area partitioning. Flood scenarios are developed by the process of flood source
analysis, flood scenario analysis, and subsequent flood scenario delineation and quantification. The
quantification task specific to internal floods is similar in nature to that for the internal events. Because of
its dependence on the internal events model, the flooding analysis incorporates the elements of
Sections 1.2.1 and 1.2.2, as necessary.
Flood area partitioning divides the plant into flood areas that are used as the basis for the flood
analysis. Flooding areas are defined on the basis of physical barriers, mitigation features, and propagation
pathways.
Flood source analysis identifies the flood sources in each flood area that are attributable to
equipment (e.g., piping, valves, pumps) and other sources internal to the plant (e.g., tanks) along with the
affected structures, systems, and components (SSCs). Flooding mechanisms examined include failure
modes of components, human-induced mechanisms, and other water-releasing events. Flooding types
(e.g., leak, rupture, spray) and flood sizes are determined. Plant walkdowns are performed to verify the
accuracy of the information. It is recognized that at the design and initial licensing stage, plant
walkdowns are not possible.
Flood scenario analysis identifies the potential flooding scenarios for each flood source by
identifying flood propagation paths of water from the flood source to its accumulation point (e.g., pipe
and cable penetrations, doors, stairwells, failure of doors or walls). Plant design features or operator
actions that have the ability to terminate the flood are identified. The susceptibility of each SSC in a
flood area to flood-induced mechanisms is examined (e.g., submergence, spray, pipe whip, and jet
impingement). Flood scenarios are developed by examining the potential for propagation and giving
credit for flood mitigation. Flood scenarios can be eliminated on the basis of screening criteria. The
screening criteria used are well-defined and justified.
Flood scenario delineation and quantification provide an estimation of the CDF of the plant
that includes internal floods. The frequency of flooding-induced initiating events that represent the
design, operation, and experience of the plant are quantified. The Level 1 models are modified and the
internal flood accident sequences quantified to (1) modify accident sequence models to address flooding
phenomena, (2) perform necessary calculations to determine success criteria for flooding mitigation, (3)
perform parameter estimation analysis to include flooding as a failure mode, (4) perform human
reliability analysis to account for performance shaping factors that are attributable to flooding, and (5)
quantify internal flood accident sequence CDF.
Table 4 summarizes the needed characteristics and attributes for the technical elements of an
internal flood analysis.
Flood
ScenarioAnalysis
Flood Scenario
Delineation and
Quantification
NOTE:
(1) For low-power and shutdown conditions, the following attributes and characteristics are also needed:
verification of temporary alignments for the specific outage or average modeled outage for data collection
identification of existing flood barriers that may be impaired or disabled that could impact the flood zone
1.2.4
PRA models of internal fires are based on the internal events PRA model, modified to include the
impact of the identified fire scenarios in terms of causing initiating events (plant transients and loss-ofcoolant accidents (LOCAs)) and the failing equipment used to respond to initiating events. The
incorporation of the set of fire scenarios into a fire PRA model is performed using a number of technical
elements discussed below. Because of its dependence on the internal events model, the internal fire
analysis incorporates the elements of Sections 1.2.1 and 1.2.2 of this guide as necessary.
Plant boundary definition and partitioning establish the overall boundaries of the fire PRA and
divides the area within that boundary into smaller regions (i.e., physical analysis units), commonly known
as fire areas or compartments. The entire fire PRA is generally organized according to these physical
analysis units.
Revision 2 of RG 1.200, Page 16
Equipment selection identifies the equipment to be included in the fire PRA model. This
equipment is selected from the equipment included in the internal events PRA and in the plants fire
protection program and analysis (i.e., the postfire safe-shutdown analysis) that, if failed by a fire, could
produce a plant initiator or affect the plant response. Fire-induced spurious actuations are of particular
interest. The selected equipment is mapped to the physical analysis units.
Cable selection identifies those cables associated with the equipment identified in the equipment
selection technical element. The selected cables are mapped to the physical analysis units.
Qualitative screening is an optional element that may be used to eliminate certain physical
analysis units defined in the plant boundary definition and partitioning element that can be shown to be
unimportant to fire risk. General, qualitative criteria are typically applied. Those physical analysis units
screened out in this technical element play no role in the more detailed quantitative assessment.
Fire PRA plant response model develops a logic model that represents the plant response
following a fire. This model is based upon the internal events PRA model which is modified to account
for fire effects. These modifications include system, structure, and component failures that specifically
result from fires and consider of fire-specific procedures. The latter are processed through the human
reliability analysis technical element.
Fire scenario selection and analysis defines and analyzes fire event scenarios that capture the
plant fire risk associated with each physical analysis unit. Fire scenarios are defined in terms of ignition
sources, fire growth and propagation, fire detection, fire suppression, and cables and equipment
(targets) damaged by the fire. Main control room fire scenarios, including control room abandonment,
are analyzed explicitly. Multicompartment fire propagation scenarios, including scenarios from all
screened physical analysis units, are also assessed.
Fire ignition frequencies are estimated for the ignition sources postulated for the fire scenarios.
Ignition sources consist of in situ sources, such as electrical cabinets or batteries, and other sources such
as transient fires. U.S. nuclear power industry fire event frequencies, possibly augmented with plantspecific experience, are used where available to establish the fire ignition frequencies. Other sources are
generally used only for cases when the U.S. nuclear power industry does not provide the representative
frequency.
Quantitative screening involves eliminating physical analysis units from further quantitative
analysis based on their quantitative contribution to fire risk. Quantitative screening criteria are
established in terms of fire-induced CDF and LERF/LRF. This element is not required, although it is
expected to be used in most applications. Note that, unlike the physical analysis units screened during
qualitative screening, the CDF and LERF/LRF contributions of each of these quantitatively screened units
are retained and reported as a part of the total plant fire risk in the fire risk quantification element. All
physical analysis units are reconsidered as a part of the multicompartment fire scenario analysis,
regardless of the quantitative screening results.
Circuit failure analysis treats the impact of fire-induced circuit failures upon the plant response.
In particular, spurious actuations from hot shorts (inter-cable and intra-cable) are analyzed. The
conditional probability of the particular circuit failure is identified and assigned.
Post-fire human reliability analysis is conducted to identify operator actions and related human
failure events (HFEs), both within and outside the main control room, for inclusion in the plant response
model. This element also includes quantification of human error probabilities for the modeled actions.
Modeled operator actions include those introduced into the plant response model resulting strictly from
fire-related emergency procedures and those actions retained from the internal events PRA. The latter
HFEs are modified to account for fire effects.
Fire risk quantification calculates the fire-induced CDF and LERF/LRF contributions to plant
risk and identifies significant contributors to each. In this element, the plant response model is quantified
for the set of fire scenarios to produce conditional core damage probability and conditional large early
release probability (CLERP) or conditional large release probability (CLRP) values. The conditional core
damage probability and CLERP/CLRP values are mathematically combined with the corresponding fire
ignition frequencies and the conditional probabilities of fire damage for the appropriate fire scenario to
yield fire-induced CDF and LERF/LRF.
Seismic/fire interactions is a qualitative review of the plant fire risk caused by a potential
earthquake. This element seeks to ensure that such seismic/fire interactions have been considered and
their impacts assessed.
Uncertainty and sensitivity analysis identifies and characterizes sources of uncertainty as well
as the potential sensitivities of the results to related assumptions and modeling approximations. The
impact of parameter uncertainties on the quantitative results is assessed.
Table 5 summarizes the needed characteristics and attributes for the technical elements of an
internal fire analysis.
Table 5. Summary of Technical Characteristics and Attributes of an Internal Fire Analysis
Element
Plant Boundary
Definition and
Partitioning
Equipment Selection
Cable Selection
Qualitative Screening
(Optional Element)
Global analysis boundary captures all plant locations relevant to the fire
PRA.
Physical analysis units are identified by credited partitioning elements
that are capable of substantially confining fire damage behaviors.
Equipment is selected for inclusion in the plant response model that will
lead to a fire-induced plant initiator, or that is needed to respond to such
an initiator (including equipment subject to fire-induced spurious
actuation that affects the plant response).
The number of spurious actuations to be addressed increases according to
the significance of the consequence (e.g., interfacing systems LOCA).
Instrumentation and support equipment are included.
Cables that are required to support the operation of fire PRA equipment
(defined in the equipment selection element) are identified and located.
Screened out physical analysis units represent negligible contributions to
risk and are considered no further.
Based upon the internal events PRA, the logic model is adjusted to add
new fire-induced initiating events and modified or new accident
sequences, operator actions, and accident progressions (in particular
those from spurious actuations).
Inapplicable aspects of the internal events PRA model are bypassed.
Fire Scenario
Selection and Analysis
Fire Ignition
Frequencies
Quantitative Screening
Circuit Failure
Analysis
Postfire Human
Reliability Analysis
Fire Risk
Quantification
Fire scenarios are defined in terms of ignition sources, fire growth and
propagation, fire detection, fire suppression, and cables and equipment
(targets) damaged by fire.
The effectiveness of various fire protection features and systems is
assessed (e.g., fixed suppression systems).
Appropriate fire modeling tools are applied.
The technical basis is established for statistical and empirical models in
the context of the fire scenarios (e.g., fire brigade response).
Scenarios involving the fire-induced failure of structural steel are
identified and assessed (at least qualitatively).
Frequencies are established for ignition sources and consequently for
physical analysis units.
Transient fires should be postulated for all physical analysis units
regardless of administrative controls.
Appropriate justification must be provided to use nonnuclear experience
to determine fire ignition frequency.
Physical analysis units that are screened out from more refined
quantitative analysis are retained to establish CDF and LERF/LRF.
Typically, those fire PRA contributions to CDF and LERF/LRF that are
established in the quantitative screening phase are conservatively
characterized.
The conditional probability of occurrence of various circuit failure modes
given cable damage from a fire is based upon cable and circuit features.
Operator actions and related post-initiator HFEs, conducted both within
and outside of the main control room, are addressed.
The effects of fire-specific procedures are identified and incorporated
into the plant response model.
Plausible and feasible recovery actions, assessed for the effects of fire,
are identified and quantified.
Undesired operator actions resulting from spurious indications are
addressed.
Operator actions from the internal events PRA that are retained in the fire
PRA are assessed for fire effects.
For each fire scenario, the fire risk results are quantified by combining
the fire ignition frequency, the probability of fire damage and the
conditional core damage probability (and CLRP/CLERP) from the fire
PRA plant response model
Total fire-induced CDF and LERF/LRF are calculated for the plant and
significant contributors identified
The contribution of quantitatively screened scenarios (from the
quantitative screening element) is added to yield the total risk values
Seismic Fire
Interactions
Uncertainty and
Sensitivity
1.2.5
Screening methods can often be employed to show that the contribution of many external events
to CDF and/or LERF/LRF is insignificant. The fundamental criteria that have been recognized for
screening-out events are the following: an event can be screened out either (1) if it meets the criteria in
the NRCs 1975 Standard Review Plan (SRP) or a later revision; or (2) if it can be shown using a
demonstrably conservative analysis that the mean value of the design-basis hazard used in the plant
design is less than 10-5 per year and that the conditional core damage probability is less than 10-1, given
the occurrence of the design-basis-hazard event; or (3) if it can be shown using a demonstrably
conservative analysis that the CDF is less than 10-6 per year. It is recognized that for those new reactor
designs with substantially lower risk profiles (e.g., internal events CDF below 10-6/year), the quantitative
screening value should be adjusted according to the relative baseline risk value.
Screening and Conservative Analysis is usually the first task an analyst performs when
conducting an external events PRA. All natural hazards and man-made events that apply to the site under
consideration are first identified. A preliminary screening, using a defined set of screening criteria, is
used to eliminate events matching the criteria from further consideration. Further screening can be
performed by using a bounding or demonstrably conservative analysis with defined quantitative screening
criteria to demonstrate that the risk from some external events is sufficiently low to eliminate them from
additional consideration. Walkdowns of the plant site and plant buildings are used to confirm the
assumptions used for the screening basis.
Table 6 summarizes the needed characteristics and attributes for the technical elements of an
external hazard screening analysis.
Table 6. Summary of Technical Characteristics and Attributes of Screening and Conservative
Analysis of Other External Hazard
Element
Technical Characteristics and Attributes
Screening and
All potential external events that can affect the site identified.
Conservative
Preliminary screening performed using a defined set of criteria.
Analysis
Bounding or conservative analysis performed using defined quantitative
screening criteria.
Basis for screening confirmed with walkdown.
1.2.6
Earthquakes can cause different initiating events than those considered in an internal-event PRA,
and can cause simultaneous failures of multiple redundant components, an important common-cause
Revision 2 of RG 1.200, Page 20
effect that needs to be included in a probabilistic seismic analysis. All possible levels of earthquakes
along with their frequencies of occurrence and consequential damage to plant systems and components
are considered in a probabilistic seismic analysis. The key elements of a seismic PRA are (1) the seismic
hazard analysis used to estimate the frequencies of occurrence of different levels of ground motion at the
site, (2) the seismic-fragility evaluation used to estimate the conditional probability of failure of important
SSCs whose failure may lead to core damage and/or a large release, and (3) the plant response analysis.
The latter involves modeling and quantification of the various combinations of structural and equipment
failures that can lead to a seismic induced core damage event, and the integration of these results to
quantify the risk.
Seismic Hazard Analysis is used to express the seismic hazard in terms of the frequency of
exceedance for selected ground motion parameters during a specified time interval. The analysis involves
identification of earthquake sources, evaluation of the regional earthquake history, and an estimate of the
intensity of the earthquake-induced ground motion at the site. At most sites the objective is to estimate
the probability or frequency of exceeding different levels of vibratory ground motion. However, in some
cases other seismic hazards are included, such as fault displacement, soil liquefaction, soil settlement, and
earthquake-induced external flooding. For all the various hazards the objective is to estimate the
probability or frequency of the hazard as a function of its intensity. The complexity of the hazard analysis
depends on the complexity of the seismic situation at the site, as well as the ultimate intended use of the
seismic PRA. Where no prior study exists, the site-specific probabilistic seismic hazard needs to be
generated, however, in many cases an existing study can be used for a site-specific assessment. For
example, the Lawrence Livermore National Laboratory (LLNL) and the Electric Power Research Institute
(EPRI) have developed regional hazard studies for east of the Rocky Mountains that can be used to
develop a site-specific PSHA for most of the central and eastern U.S. sites after certain checks or updates
are made. In a probabilistic seismic hazard analysis, an essential part of the methodology is the
consideration of both aleatory and epistemic uncertainties, and typically results in generating a set of
hazard curves, defined at specified fractile (confidence) levels and a mean hazard curve.
Seismic Fragility Analysis estimates the conditional probability of SSC failures at a given value
of a seismic motion parameter such as peak ground acceleration, peak spectral acceleration, floor spectral
acceleration, etc. Seismic fragilities used in a seismic PRA are realistic and plant-specific based on actual
current conditions of the SSCs in the plant, as confirmed through a detailed walkdown of the plant. The
fragilities of all the systems that participate in the accident sequences are included.
Seismic Plant Response Analysis calculates the frequencies of severe core damage and
radioactive release to the environment by combining the plant logic model with component fragilities and
seismic hazard estimates. The analysis is usually carried out by adding some earthquake-related basic
events to the PRA internal events model, as well as eliminating some parts of the internal events model
that do not apply or that can be screened out. For example, recovery of off-site power is highly unlikely
after a large earthquake and therefore parts of the internal events model related to power recovery can
often be eliminated. Further screening of out of low-probability, non-seismic failures and human-error
events may also be possible, although significant non-seismic failures and human errors must be included.
Therefore the seismic PRA model is usually adapted from the internal events, at-power PRA model to
incorporate unique seismic related aspects that are different from the at-power, internal events PRA
model. In some cases, instead of starting with the internal events model and adapting it, a special seismic
model is created from scratch. In this case it is especially important to check for consistency with the
internal events model regarding plant response and the cause-effect relationships of the failures. In any
case, the seismic PRA model includes all significant seismic causes initiating events and seismic induced
SSC failures, as well as significant non-seismic failures and human errors. The model reflects the as-built
and as-operated plant.
Table 7 provides a summary of the needed characteristics and attributes for the technical elements
for a seismic event analysis.
Table 7. Summary of Technical Characteristics and Attributes of Seismic PRA (See Note)
Element
Technical Characteristics and Attributes
Probabilistic
Need to assess whether for the specific application, other seismic hazards need
to be included in the seismic PRA, such as
- fault displacement
- landslide,
- soil liquefaction
- soil settlement
Seismic Fragility
walkdowns focus on
- anchorage
- lateral seismic support
Revision 2 of RG 1.200, Page 22
Table 7. Summary of Technical Characteristics and Attributes of Seismic PRA (See Note)
Element
Technical Characteristics and Attributes
- potential systems interactions
Seismic Plant
Screening methods can often be used to show that the contribution of high winds to CDF and/or
LERF/LRF is insignificant. The considerations in this section apply to those high-wind phenomena that
have not been screened out. The technical elements for a high-winds PRA are similar to those for a
seismic PRA. The major elements are wind hazard analysis, wind fragility analysis, and the plant
response analysis, which produces the quantified results. The types of high-wind events that need to be
considered in the analysis are site dependent. These can include tornados and their effects, cyclones,
hurricanes, and typhoons, as well as thunderstorms, squall lines, and other weather fronts. It is assumed
that the high-winds-PRA is based on modifications made to an existing up-to-date internal events, atpower Level 1 and Level 2 /LERF PRA.
High Wind Hazard Analysis estimates the frequency of high winds at the site using a sitespecific probabilistic wind hazard analysis that incorporates the available recent regional and site-specific
information and uses up-to-date databases. Uncertainties in the models and parameter values are properly
accounted for and fully propagated to allow the derivation of a mean hazard curve from the family of
hazard curves obtained.
High Wind Fragility Analysis is an evaluation that is performed to estimate plant-specific,
realistic wind fragilities for those structures, or systems, or components (or their combination) whose
failure contributes to core damage or large early release.
High Wind Plant Response Analysis uses a wind-PRA systems model that includes all
significant wind-caused initiating events and other failures that can lead to core damage or large early
release. The model is adapted from the internal events, at-power PRA model to incorporate unique windanalysis aspects that are different from the at-power, internal events PRA model.
Table 8 summarizes the needed characteristics and attributes for the technical elements of a high
winds analysis.
Screening methods can often be employed to show that the contribution of some external flood
events to core damage frequency and/or large release frequency is insignificant. The considerations in
this section apply to those flooding phenomena that have not been screened out. The technical elements
for an external flooding PRA are similar to those for an internal flooding PRA and seismic PRA. The
major elements of the PRA methodology are flooding hazard analysis, flooding fragility analysis, and the
plant response analysis, which produces the quantified results. The analysis of how the flooding
pathways and water levels cause the failure of SSCs following ingress into the plant structures is similar
to the analysis in the internal flooding PRA. The types of external flooding phenomena that need to be
considered in the analysis are dependent on the site. Both natural phenomena, such as river or lake
flooding, ocean flooding from high tides or storm surges, unusually high precipitation, tsunamis, seiches,
etc., as well as man-made events such as failures of dams, levees, and dikes, are considered. It is assumed
that the external flooding PRA is based on modifications made to an existing up-to-date internal events,
at-power PRA.
External Flood Hazard Analysis estimates the frequency of external flooding at the site using a
site-specific probabilistic hazard analysis that incorporates the available recent site-specific information
and uses up-to-date databases. Uncertainties in the models and parameter values are properly accounted
for and fully propagated to allow the derivation of a mean hazard curve from the family of hazard curves
obtained.
External Flood Fragility Analysis is an evaluation that is performed to estimate plant-specific,
realistic flooding fragilities for those structures, or systems, or components (or their combination) whose
failure contributes to core damage or large early release.
External Flood Plant Response Analysis uses an external flooding-PRA model that includes all
significant flood-caused initiating events and other failures that can lead to core damage or large early
release. The model is adapted from the internal events, at-power PRA model to incorporate unique floodanalysis aspects that are different from the at-power, internal events PRA model.
Table 9 summarizes the needed characteristics and attributes for the technical elements of an
external flood analysis.
Table 9. Summary of Technical Characteristics and Attributes of External Floods
Element
Technical Characteristics and Attributes
External Flood
Probabilistic flood hazard analysis
Hazard Analysis
- results in frequency of external flooding at the site
- based on site-specific data
- reflects recent information
Uncertainties in the models and parameter values
- properly accounted for
- fully propagated
- allow estimate of mean hazard curve
External Flood
Flooding fragility estimate
Fragility Analysis
- plant-specific,
- realistic
- all SSCs whose failure contributes to core damage or large early release
included
External Flood
External flooding-PRA model
Plant Response
- includes all significant flood-caused initiating events
Analysis
- includes other significant failures (both those that are caused by the
flooding and those that are random failures) that can lead to CDF or
LERF/LRF
- adapted from the internal events, at-power PRA model
- incorporates unique flood-analysis aspects that are different from the atpower, internal events PRA model.
1.2.9
Screening methods can often be employed to show that the contribution of many external hazards
to CDF and/or LERF/LRF is insignificant. The considerations in this section apply to those other external
hazards that have not been screened out. Therefore, this set of technical elements applies to a detailed
PRA analysis of an external hazard category. The structure of the PRA of any external hazard is based on
the following technical requirements: external hazard analysis, external hazard fragility analysis, and the
plant response analysis, which produces the quantified results. It should be noted that because of the
limited collective experience of the analysis community in the area of other external events PRA, an
extensive peer review is particularly important for such an analysis.
External Hazards Analysis establishes the frequency of occurrence of different intensities of the
external hazard being analyzed and uses a site-specific probabilistic evaluation that is based on recent
available data and site-specific information. Historical data or a phenomenological model, or a mixture of
the two is used in the analysis.
External Hazard Fragility Analysis is an evaluation that is performed to estimate the fragility or
vulnerability of a structure, or system, or component (or their combination) whose failure contributes to
core damage or large early release. The fragility analysis uses plant-specific information and an accepted
engineering method for evaluating failures.
External Hazard Plant Response Analysis uses a model that includes all important initiating
events and other important failures caused by the effects of the external event that can lead to core
damage or large early release. The model is adapted from the internal events, at-power PRA model to
incorporate unique aspects related to the hazard analyzed that are different from the at-power, internal
events PRA model.
Table 10 summarizes the needed characteristics and attributes for the technical elements of other
external hazards analysis.
Table 10. Summary of Technical Characteristics and Attributes of Other External Hazards
Element
Technical Characteristics and Attributes
External Hazard
Other hazard analysis
Analysis
- results in frequency of occurrence of other hazards at site
- based on site-specific data
- reflects recent information
- uses historical data or a phenomenological model, or a mixture of the two
External Hazard
Fragility estimate
Fragility Analysis
- plant-specific,
- SSC-specific information
- uses accepted engineering methods
External Hazard
Hazard model
Plant Response
- includes all important initiating events related to hazard analyzed
Analysis
- includes other significant failures (both those that are caused by the
external hazard and those that are not) that can lead to CDF or LERF/LRF
- adapted from the internal events, at-power PRA model
- incorporates unique aspects related to hazard analyzed that are different
from the at-power, internal events PRA model.
For many applications, it is necessary to combine the PRA results from different hazard groups
(e.g., from internal events, internal fires, and seismic events). For this reason, an important aspect in
interpreting the PRA results is understanding both the level of detail associated with the modeling of each
of the hazard groups, and the hazard group-specific model uncertainties. With respect to the level of
detail, for example, the analysis of specific scope items such as internal fire, internal flooding, or seismic
events typically involves a successive screening approach, so that more detailed analysis can focus on the
more significant contributions. The potential conservatism associated with the evaluation of the less
significant contributors using this approach is assessed for each hazard group. In addition, each of the
hazard groups has unique sources of model uncertainty. The assumptions made in response to these
sources of model uncertainty and any conservatisms introduced by the analysis approaches can bias the
assessment of importance measures with respect to the combined risk assessment and the relative
contributions of the hazard groups to the various risk metrics. Therefore, the sources of model
uncertainty are identified and their impact on the results analyzed for each hazard group individually, so
that, when it is necessary to combine the PRA results, the overall results can be characterized
appropriately. The sensitivity of the model results to model boundary conditions and other assumptions is
evaluated, using sensitivity analyses to look at assumptions both individually and in logical combinations.
The combinations analyzed are chosen to account for interactions among the variables. NUREG-1855
provides guidance on the treatment of uncertainties associated with PRA. 7 The understanding gained
from these analyses is used to appropriately characterize the relative significance of the contributions
from each hazard group.
Table 11 summarizes the needed characteristics and attributes for the technical elements of
interpretation of results.
Table 11. Summary of Technical Characteristics and Attributes for Interpretation of Results
Element
Level 1 PRA
Interpretation
of Results
Level 2 PRA
Interpretation
of Results
This NUREG also provides guidelines with regard to defining, identifying and characterizing the different sources of
uncertainty.
either through documenting the actual process or through reference to existing methodology documents.
Sources of uncertainty (both parameter and model) are identified and their impact on the results assessed.
A source of model uncertainty is one that is related to an issue for which there is no consensus approach
or model (e.g., choice of data source, success criteria, reactor coolant pressure seal LOCA model, human
reliability model) and where the choice of approach or model is known to have an impact on the PRA
results in terms of introducing new accident sequences, changing the relative importance of sequences, or
significantly affecting the overall CDF, LERF, or LRF estimates that might have an impact on the use of
the PRA in decision-making. Assumptions made in performing the analyses are identified and
documented along with their justification to the extent that the context of the assumption is understood.
The results (e.g., products and outcomes) from the various analyses are documented.
Table 12 summarizes the needed characteristics and attributes for the technical elements of other
external hazards analysis.
Table 12. Summary of Technical Characteristics and Attributes for Documentation
Element
Traceability
and
Justification
1.3
For each given technical element, the level of detail may vary. The detail may vary from the
degree to which (1) plant design and operation is modeled, (2) specific plant experience is incorporated
into the model, and (3) realism is incorporated into the analyses that reflect the expected plant response.
Regardless of the level of detail developed in the PRA, the characteristics and attributes provided below
are addressed. That is, each characteristic and attribute is always addressed, but the degree to which it is
addressed may vary. In general, the level of detail for the base PRA needs to be consistent with current
good practice 8 .
The level of detail needed is dependent on the application. The application may involve using the
PRA during different plant stages (i.e., design, construction, and operation). Consequently, a PRA used
to support a design certification will not have the same level of detail as a PRA of a plant that has years of
operating experience. While it is recognized that the same level of detail is not needed, each of the
technical elements and its attributes has to be addressed.
Current good practices are those practices that are generally accepted throughout the industry and have shown to be
technically acceptable in documented analyses or engineering assessments.
1.4
The PRA results used to support an application are derived from a PRA model that represents the
as-designed, as-built, as-operated plant 9 to the extent needed to support the application. 10 Therefore, a
process for developing, maintaining, and upgrading a PRA is established. This process involves
identifying and using plant information to develop the original PRA and to modify the PRA. The process
is performed such that the plant information identified and used in the PRA in reflecting the as-designed,
as-built, as-operated plant, is as realistic as possible in assessing the risk. The information sources
include the applicable design, operation, maintenance, and engineering characteristics of the plant.
For those SSCs and human actions used in the development of the PRA, the following
information is identified, integrated, and used in the PRA:
plant design information reflecting the normal and emergency configurations of the plant
plant operational information with regard to plant procedures and practices
plant test and maintenance procedures and practices
engineering aspects of the plant design
Further, plant walkdowns are conducted to ensure that information sources being used actually
reflect the plants as-built, as-operated condition. In some cases, corroborating information obtained from
the documented information sources for the plant and other information may only be gained by direct
observations. It is recognized that at the design and initial licensing stages, plant walkdowns are not
possible.
Table 13 describes the characteristics and attributes that need to be included for the above types
of information.
As-built, as-operated is a conceptual term that reflects the degree to which the PRA matches the current plant design, plant
procedures, and plant performance data, relative to a specific point in time. At the DC or AOL stage, the plant is neither
built nor operated. For these situations, the intent of the PRA model is to reflect the as-designed, as-to-be-built, and as-tobe-operated.
10
It is recognized that at the design certification or combined operating license stage where the plant is not built or operated,
the term as-built, as-operated is meant to reflect the as-designed plant assuming site and operational conditions for the
given design.
Identification of those SSCs that are credited in the PRA to perform the above
functions
The functional relationships among the SSCs including both functional and
hardware dependencies
Spatial layout, sizing, and accessibility information related to the credited SSCs
Other design information needed to support the PRA modeling of the plant
That information needed to reflect the actual operating procedures and practices
Operational
used at the plant including when and how operators interface with plant
equipment as well as how plant staff monitor equipment operation and status
That information needed to reflect the operating history of the plant as well as
any events involving significant human interaction
That information needed to reflect planned and typical unplanned tests and
Maintenance
maintenance activities and their relationship to the status, timing, and duration of
the availability of equipment
Other engineering information needed to support the PRA modeling of the plant
It is recognized that for reactors in the design or construction stage, the level of operational and
maintenance information may vary.
As a plant operates over time, its associated risk may change. This change may occur for the
following reasons:
Operating data may change the availability or reliability of the plants structures, systems, and
components.
Therefore, to ensure that the PRA represents the risk of the current as-built and as-operated plant,
the PRA needs to be maintained and upgraded over time. Table 14 provides the attributes and
characteristics of an acceptable process.
Table 14. Summary of Characteristics and Attributes for PRA Maintenance and Upgrade
Characteristics and Attributes
2.
In general, if a PRA standard is used to demonstrate conformance with Regulatory Position 1, the
standard should be based on a set of principles and objectives. Table 15 provides an acceptable set of
principles and objectives that were established and used by ASME/ANS in development of their Level
1/LERF PRA standard. Principle 3 recognizes that the technical requirements of a PRA can be, and
generally are, performed to different capabilities. In developing the various models in the PRA, the
different capabilities are distinguished by three attributes, determined by the degree to which the
following criteria are met:
The scope and level of detail that reflects the plant design, operation, and maintenance.
Plant-specific information versus generic information to represent the as-designed, as-built and
as-operated plant.
11
The standards are written in terms of requirements. Therefore, the use of this work in this regulatory guide is standards
language (e.g., in a standard, it states the standards sets forth requirements) and is not meant to imply a regulatory
requirement.
determines whether methods identified in the standard have been used appropriately
determines that, when acceptable methods are not specified in the standard, or when alternative
methods are used in lieu of those identified in the standard, the methods used are adequate to
meet the requirements of the standard
assesses the significance of the results and insights gained from the PRA of not meeting the
technical requirements in the standard
highlights assumptions that may significantly impact the results and provides an assessment of
the reasonableness of the assumptions
includes a peer review team that is composed of members who are knowledgeable in the technical
elements of a PRA, are familiar with the plant design and operation, and are independent with no
conflicts of interest that may influence the outcome of the peer review [this clause was not in the ASME
definition]
6. The standard addresses the maintenance and update of the PRA to incorporate changes that can
substantially impact the risk profile so that the PRA adequately represents the current as-designed
[added], as-built and as-operated plant.
7. The standard is a living document. Consequently, it should not impede research. It is structured so
that, when improvements in the state of knowledge occur, the standard can easily be updated.
It is recognized that a PRA may not satisfy each technical requirement to the same degree
(i.e., capability category as used in the ASME/ANS PRA standard); that is, the capability category
achieved for the different technical requirements may vary. This variation can range from (1) the
minimum needed to meet the attributes and characteristics for each technical element, to (2) the minimum
to meet current good practice for each technical element, to (3) the minimum to meet the state-of-the-art
for each technical element. Further, which capability category is needed to be met for each technical
requirement is dependent on the specific application. In general, the staff anticipates that current good
practice, i.e., Capability Category II of the ASME/ANS standard, is the level of detail that is adequate for
the majority of applications. However, for some applications, Capability Category I may be sufficient for
some requirements, whereas for other applications it may be necessary to achieve Capability Category III
for specific requirements.
These requirements are either process in nature, or technical in nature. The process type
requirements address the process for application, development, maintenance and upgrade, and peer
review. The technical requirements address the technical elements of the PRA and what is necessary to
adequately perform that element.
For process requirements, the intent is generally straightforward and the requirement is either met
or not met. For the technical requirements, it is not always as straightforward. Many of the technical
requirements in a standard are applied more than once in developing the PRA model. For example, the
requirements for systems analysis apply to all systems modeled, and certain of the data requirements
apply to all parameters for which estimates are provided. If among these systems or parameter estimates
there are a few examples in which a specific requirement has not been met, it is not necessarily indicative
that this requirement has not been met. If the requirement has been met for the majority of the systems or
parameter estimates, and the few examples can be put down to mistakes or oversights, the requirement
would be considered to be met. If, however, there is a systematic failure to address the requirement
(e.g., component boundaries have not been defined anywhere), then the requirement has not been met. In
either case, the instances of noncompliance are to be (1) rectified or demonstrated not to be relevant to the
application and (2) documented.
Further, the technical requirements may be defined at two different levels: (1) high-level
requirements and (2) supporting requirements. High-level requirements are defined for each technical
element and capture the objective of the technical element. These high-level requirements are defined in
general terms, need to be met regardless of the capability category, and accommodate different
approaches. Supporting requirements are defined for each high-level requirement. These supporting
requirements are those minimal requirements needed to satisfy the high-level requirement. Consequently,
determination of whether a high-level requirement is met, is based on whether the associated supporting
requirements are met. Whether or not every supporting requirement is needed for a high-level
requirement is application dependent and is determined by the application process requirements.
The ASME/ANS standard is one example of a national consensus PRA standard; its scope
encompasses a PRA for Level 1 and limited Level 2 (LERF) for at-power operation and internal and
external hazards. Appendix A to this regulatory guide provides the staff regulatory position regarding this
document. If it is demonstrated that the parts of a PRA that are used to support an application comply
with the ASME/ANS standard, when supplemented to account for the staffs regulatory positions
contained in Appendix A, it is considered that the PRA is considered to be adequate to support that riskinformed regulatory application.
2.2
A peer review of the PRA is performed to determine whether the requirements established in the
standard (as endorsed by the NRC in the appendices to this guide) have been met. An acceptable peer
review approach is one that is performed according to an established process and by qualified personnel
and documents the results and identifies both strengths and weaknesses of the PRA.
The peer review process includes a documented procedure used to direct the team in evaluating
the adequacy of a PRA. The review process compares the PRA against established criteria (e.g., technical
requirements defined in a PRA standard that conforms to the PRA characteristics and attributes such as
those provided in Regulatory Position 1.2). In addition to reviewing the methods used in the PRA, the
peer review determines whether the methods were applied correctly. The PRA models are compared
against the plant design and procedures to validate that they reflect the as-designed, or the as-built and asoperated plant. Assumptions are reviewed to determine if they are appropriate and to assess their impact
on the PRA results. The PRA results are checked for fidelity with the model structure and for consistency
with the results from PRAs for similar plants based on the peer reviewers knowledge. Finally, the peer
review process examines the procedures or guidelines in place for updating the PRA to reflect changes in
plant design, operation, or experience. The process also needs to provide criteria ensuring that the peer
review is current. That is, (1) the peer review needs to address the modifications made to the PRA since
any previous peer reviews, and (2) the peer review needs to address modifications made to the standard
since any previous peer reviews.
The team qualifications determine the credibility and adequacy of the peer reviewers. To avoid
any perception of a technical conflict of interest, the peer reviewers will not have performed any actual
work on the PRA. Each member of the peer review team must have technical expertise in the PRA
elements he or she reviews, including experience in the specific methods that are used to perform the
PRA elements. This technical expertise includes experience in performing (not just reviewing) the work
in the element assigned for review. Knowledge of the key features specific to the plant design and
operation is essential. 12 Finally, each member of the peer review team needs to be knowledgeable about
the peer review process, including the desired characteristics and attributes used to assess the adequacy of
the PRA.
Documentation provides the necessary information to ensure that the peer review process and
the findings are traceable and the bases of the findings are defensible. Descriptions of the qualifications
of the peer review team members and the peer review process are documented. The results of the peer
review for each technical element and the PRA update process are described, including the areas in which
the PRA does not meet or exceed the desired characteristics and attributes used in the review process.
This includes an assessment of the importance of any identified deficiencies on the PRA results and
potential uses and how these deficiencies were addressed and resolved.
Table 16 summarizes the characteristics and attributes of a peer review.
12
For new reactor designs that have not yet gone into commercial operation, it is recognized that a peer reviewer will not have
knowledge of plant operation, and familiarity with some plant features (e.g., passive mitigation systems) may be limited.
This is not to be construed as a limitation for performing a peer review using personnel who are otherwise qualified and
generally familiar with the design and operation of similar plant types (e.g., pressurized-water reactors).
Uses as a basis for review a set of desired PRA characteristics and attributes
Process
Independent with no conflicts of interest (i.e., have not performed any work on
Team
the
PRA)
Qualifications
Documents where PRA does not meet desired characteristics and attributes
Describes the scope of the peer review performed (i.e., what was reviewed by the
peer review team)
The ASME/ANS standard requires a peer review to be performed. The peer review, per
ASME/ANS, requires that (1) a peer review process be established, and (2) provides requirements for
team qualifications and documentation. A peer review methodology (i.e., process) is provided in the
industry-developed peer review programs (i.e., Refs. 1517), and noted in the ASME/ANS standard as an
acceptable process. Appendices A, B, C and D to this regulatory guide the staff regulatory position on the
peer review requirements in the ASME/ANS PRA standard and the peer review process in NEI 00-02, 0504, and 07-12 (Refs. 1517). When the staffs regulatory positions contained in the appendices are taken
into account, use of a peer review can be used to demonstrate that the PRA [with regard to an at-power
Level 1/LERF PRA for internal events (excluding external hazards)] is adequate to support a riskinformed application.
As stated earlier, the peer review is to be performed against established standards (e.g., the
ASME/ANS PRA standard). If different criteria are used than those in the established standard, then it
needs to be demonstrated that these different criteria are consistent with the established standards, as
endorsed by the NRC. NEI 00-02 (Ref. 15) provides separate criteria for a peer review of an at-power
Level 1 LERF PRA for internal events, excluding internal flood and fire and external hazards. NEI 00-02
also provides guidance for resolving the differences between a prior version of the internal events
standard (ASME Ra Sb-2005) (Ref. 14), as endorsed by the NRC in Revision 1 of this regulatory guide,
and its peer review criteria. Appendix B to this guide provides the staff position on this guidance
(referred to as the Licensee Self-Assessment Guidance). The NRC expects that, if the results of this
self-assessment are used to demonstrate the technical adequacy of a PRA for an application, differences
between the current version of the standard as endorsed in Appendix A and the earlier version be
identified and addressed. In addition, future peer reviews should be performed against the established
standards, as endorsed in this guide.
3.
This section of the regulatory guide addresses the third purpose identified above, namely, to
provide guidance to licensees on an approach acceptable to the NRC staff to demonstrate that the
technical adequacy of the PRA used, in total or the pieces that are used to support a regulatory
application, is sufficient to support the analysis.
The application-specific regulatory guides identify the specific PRA results to support the
decision-making and the analysis needed to provide those results. The pieces of the PRA to support that
analysis need to be identified and the guidance in this regulatory guide applies to those pieces.
Regulatory Positions 3.1 and 3.2 summarize the expected outcome of the application of the applicationspecific regulatory guides in determining the scope of application of this regulatory guide. One
acceptable approach to demonstrate conformance with Regulatory Positions 3.1 and 3.2 is to use a
national consensus standard. The ASME/ANS PRA standard provides the technical requirements for
achieving such a process. If the ASME/ANS PRA standard is implemented, supplemented to account for
the staffs regulatory positions contained in Appendix A, it is considered that Regulatory Positions 3.1
and 3.2 are met.
When using this regulatory guide, it is anticipated that the licensees description of the
application will include the following:
SSCs, operator actions, and plant operational characteristics affected by the application
a description of the cause-effect relationships among the change and the above SSCs, operator
actions, and plant operational characteristics
identification of the PRA results that will be used to compare against the applicable acceptance
criteria or guidelines and how the comparison is to be made
the scope of risk contributors (hazard groups and modes of operation) included in the PRA to
support the decision
3.1
Based on the definition of the application, and in particular the acceptance criteria or guidelines,
the scope of risk contributors (internal and external hazard events and modes of plant operation) for the
PRA is identified. For example, if the application is designed around using the acceptance guidelines of
Regulatory Guide 1.174, the evaluations of CDF, CDF, LERF, and LERF should be performed with a
full-scope PRA, including all hazard groups and all modes of operation. However, since many PRAs do
not address this full scope, the decision-makers need to allow for these omissions. Examples of
approaches to making allowances may in some cases include the introduction of compensatory measures,
restriction of the implementation of the proposed change to those aspects of the plant covered by the risk
model, and use of bounding arguments to cover the risk contributions not addressed by the model.
However, it should be noted, that consistent with the Commission endorsed phased PRA quality initiative,
all risk contributors that cannot be shown as insignificant to the decision, should be assessed through
quantitative risk assessment methods to support risk-informed licensing actions. This regulatory guide
does not address this aspect of decision-making, but it is focused specifically on the quality of the PRA
information used. As noted elsewhere in this guide, a PRA is considered a quantitative risk assessment
method.
The PRA standards and industry PRA programs that have been developed, or are in the process of
being developed, address a specific scope. For example, the ASME/ANS PRA standard addresses
internal events, internal flood, internal fire, seismic, wind, external flood and other external hazards, atpower for a limited Level 2 PRA analysis. NEI 00-02 is a peer review process for internal events (note
that the internal flooding is only addressed in the self-assessment portion of NEI 00-02 (Appendix D)).
Neither addresses internal fire, external hazards, or the LPDS modes of operation. The appendices to this
regulatory guide address the different PRA standards or industry PRA programs separately. In using this
regulatory guide, the applicant will identify which of these appendices is applicable to the PRA analysis.
3.2
Based on an understanding of how the PRA model is to be used to achieve the desired results, the
licensee will have identified the pieces of the PRA for each hazard group required to support a specific
application. These include: (1) the logic model events elements onto which the cause-effect relationships
are mapped (i.e., those directly affected by the application), and (2) all the events that appear in the
accident sequences in which the first group of logic model elements appear. For some applications, this
may be a limited set, but for others (e.g., risk-informing the scope of special treatment requirements), all
pieces of the PRA model are relevant.
3.3
There are two aspects to demonstrating the technical adequacy of the pieces of the PRA to
support an application. The first aspect is the assurance that the pieces of the PRA used in the application
have been performed in a technically correct manner. The second aspect is the assurance that the
assumptions and approximations used in developing the PRA are appropriate.
For the first, assurance that the pieces of the PRA used in the application have been performed in
a technically correct manner implies that (1) the PRA model, or those pieces of the model required to
support the application, represents the as-designed or as-built and as-operated plant, which, in turn,
implies that the PRA is up to date and reflects the current design and operating practices, where
appropriate, (2) the PRA logic model has been developed in a manner consistent with industry good
practice (see footnote in Section 1.3 that defines good practice) and that it correctly reflects the
dependencies of systems and components on one another and on operator actions, and (3) the probabilities
and frequencies used are estimated consistently with the definitions of the corresponding events of the
logic model.
For the second, the current state-of-the-art in PRA technology is that there are issues for which
there is no consensus on methods of analysis. Furthermore, PRAs are models, and in that sense the
developers of those models rely on certain approximations to make the models tractable and on certain
assumptions to address uncertainties as to how to model specific issues. Regulatory Guide 1.174, and, in
more detail, NUREG-1855 provide guidance on how to address and treat the uncertainties associated with
a PRA. In accordance with that guidance, the impact of these assumptions and approximations on the
results of interest to the application needs to be understood.
3.3.1
When using risk insights based on a PRA model, the applicant must ensure that the PRA model,
or at least those pieces of it needed to provide the results, is technically correct as discussed above.
The licensee is to demonstrate that the model is up-to-date in that it represents the current plant
design and configuration and represents current operating practices to the extent required to support the
application. This demonstration can be achieved through a PRA maintenance plan that includes a
commitment to update the model periodically to reflect changes that impact the significant accident
sequences.
The various consensus PRA standards and industry PRA programs that provide guidance on the
performance of, or reviews of, PRAs are addressed individually in the appendices to this regulatory guide.
These appendices document the staffs regulatory position on each of these standards or programs.
When the issues raised by the staff are taken into account, the standard or program in question
may be interpreted to be adequate for the purpose for which it was intended. If the pieces of the PRA can
be shown to have met the requirements of these documents, with attention paid to the NRCs objections,
it can be assumed that the analysis is technically correct. Therefore, other than an audit, a detailed review
by NRC staff of the base model PRA will not be necessary. When deviations from these documents exist,
the applicant must demonstrate either that its approach is equivalent or that the influence on the results
used in the application are such that no changes occur in the significant accident sequences or
contributors.
3.3.2
Since the standards and industry PRA programs are not (or are not expected to be) prescriptive,
there is some freedom on how to model certain phenomena or processes in the PRA; different analysts
may make different assumptions and still be consistent with the requirements of the standard or the
assumptions may be acceptable under the guidelines of the peer review process. The choice of a specific
assumption or a particular approximation may, however, influence the results of the PRA. For each
application that calls upon this regulatory guide, the applicant identifies the key assumptions 13 and
approximations relevant to that application. This will be used to identify sensitivity studies as input to the
decision-making associated with the application. Each of the documents addressed in the appendices
either requires, or represents (in the case of the industry peer review program) a peer review. One of the
functions of the peer review is to address the assumptions and make judgments as to their
appropriateness.
13
A key assumption is one that is made in response to a key source of model uncertainty in the knowledge that a different
reasonable alternative assumption would produce different results, or an assumption that results in an approximation made
for modeling convenience in the knowledge that a more detailed model would produce different results. For the base PRA,
the term different results refers to a change in the risk profile (e.g., total CDF and total LERF, the set of initiating events
and accident sequences that contribute most to CDF and to LERF) and the associated changes in insights derived from the
changes in the risk profile. A reasonable alternative assumption is one that has broad acceptance within the technical
community and for which the technical basis for consideration is at least as sound as that of the assumption being
challenged.
A key source of uncertainty is one that is related to an issue in which there is no consensus approach or model and where the
choice of approach or model is known to have an impact on the risk profile (e.g., total CDF and total LERF, the set of
initiating events and accident sequences that contribute most to CDF and to LERF) such that it influences a decision being
made using the PRA. Such an impact might occur, for example, by introducing a new functional accident sequence or a
change to the overall CDF or LERF estimates significant enough to affect insights gained from the PRA.
4.
The licensee develops documentation of the PRA model and the analyses performed to support
the risk-informed regulatory activity. This documentation comprises both archival (i.e., available for
audit) and submittal (i.e., submitted as part of the risk-informed request) documentation. The former may
be required on an as needed basis to facilitate the NRC staffs review of the risk-informed submittal.
4.1
Archival Documentation
Archival documentation associated with the base PRA includes the following:
A detailed description of the process used to determine the adequacy of the PRA is provided.
The results of the peer review and/or self-assessment 14 , and a description of the resolution of all
the peer review or self-assessment findings and observations are included. The results are
documented in such a manner that it is clear why each requirement is considered to have been
met. This can be done, for example, by providing a reference to the appropriate section of the
PRA model documentation.
The complete documentation of the PRA model is included. If the staff elects to perform an audit
on all or any parts of the PRA used in the risk-informed application, the documentation
maintained by the licensee must be legible, retrievable (i.e., traceable), and of sufficient detail
that the staff can comprehend the bases supporting the results used in the application. Regulatory
Position 1.3 of this guide provides the attributes and characteristics of archival documentation
associated with the base PRA.
A description of the process for maintenance and upgrade of the PRA is provided. The history is
maintained of the maintenance and upgrade activities, and the history includes the results of any
peer reviews that were performed as a result of an upgrade.
The archival documentation associated with a specific application is expected to include enough
information to demonstrate that the scope of the review of the base PRA is sufficient to support the
application. This includes the following information:
the impact of the application on the plant design, configuration, or operational practices
the risk assessment, including a description of the methodology used to assess the risk of the
application, how the base PRA model was modified to appropriately model the risk impact of the
application, and details of quantification and the results
the scope of the risk assessment in terms of hazard groups and specific accident scenarios and
operating modes modeled
the parts of the PRA required to provide the results needed to support comparison with the
acceptance guidelines
14
When referring to self-assessment, this term is meant to refer to the self-assessment process in NEI 00-02 for at-power
Level 1/LERF PRA for internal events and internal flood.
4.2
To demonstrate that the technical adequacy of the PRA used in an application is of sufficient
quality, the staff expects the following information will be submitted to the NRC. Previously submitted
documentation may be referenced if it is adequate for the subject submittal:
To address the need for the PRA model to represent the as-designed or as-built, as-operated plant,
Identification of permanent plant changes (such as design or operational practices) that have an
impact on those things modeled in the PRA but have not been incorporated in the baseline PRA
model. If a plant change has not been incorporated, the licensee provides a justification of why
the change does not impact the PRA results used to support the application. This justification
should be in the form of a sensitivity study that demonstrates the accident sequences or
contributors significant to the application decision were not adversely impacted (remained the
same).
Documentation that the parts of the PRA required to produce the results used in the decision are
performed consistently with the standard as endorsed in the appendices of this regulatory guide.
If a requirement of the standard (as endorsed in the appendix to this guide) has not been met, the
licensee is to provide a justification of why it is acceptable that the requirement has not been
met. This justification should be in the form of a sensitivity study that demonstrates the accident
sequences or contributors significant to the application were not impacted (remained the same).
A summary of the risk assessment methodology used to assess the risk of the application,
including how the base PRA model was modified to appropriately model the risk impact of the
application and results. (Note that this is the same as that required in the application-specific
regulatory guides.)
Identification of the key assumptions and approximations relevant to the results used in the
decision-making process. Also, include the peer reviewers assessment of those assumptions.
These assessments provide information to the NRC staff in their determination of whether the
use of these assumptions and approximations is appropriate for the application, or whether
sensitivity studies performed to support the decision are appropriate.
A discussion of the resolution of the peer review (or self-assessment, for peer reviews performed
using the criteria in NEI 00-02) findings and observations that are applicable to the parts of the
PRA required for the application. This decision should take the following forms:
a discussion of how the PRA model has been changed
a justification in the form of a sensitivity study that demonstrates the accident sequences or
contributors significant to the application decision were not adversely impacted (remained the
same) by the particular issue
The standards or peer review process documents may recognize different capability categories or
grades that are related to level of detail, degree of plant specificity, and degree of realism. The
licensees documentation is to identify the use of the parts of the PRA that conform to capability
categories or grades lower than deemed required for the given application (Section 1-3 of
ASME/ANS RA-Sa-2009).
D. IMPLEMENTATION
The purpose of this section is to provide information to applicants and licensees regarding the
NRCs plans for using this regulatory guide. The NRC does not intend or approve any imposition or
backfit in connection with its issuance.
In some cases, applicants or licensees may propose an alternative or use a previously established
acceptable alternative process or method. Otherwise, the methods described in this guide will be used
in evaluating license applications, license amendment applications, and amendment requests.
REFERENCES
1.
60 FR 42622, Use of Probabilistic Risk Assessment Methods in Nuclear Activities: Final Policy
Statement, Federal Register, Volume 60, Number 42622, August 16, 1995.
2.
Regulatory Guide 1.174, An Approach for Using Probabilistic Risk Assessment in RiskInformed Decisions on Plant-Specific Changes to the Licensing Basis, U.S. Nuclear Regulatory
Commission, Washington, DC.
3.
NUREG-0800, Standard Review Plan for the Review of the Safety Analysis Reports for Nuclear
Power Plants, Section 19, Use of Probabilistic Risk Assessment in Plant-Specific, RiskInformed Decisionmaking: General Guidance, U.S. Nuclear Regulatory Commission,
Washington, DC.
4.
Regulatory Guide 1.201, Guidelines for Categorizing Structures, Systems, and Components in
Nuclear Power Plants According to Their Safety Significance, U.S. Nuclear Regulatory
Commission, Washington, DC.
5.
10 CFR Part 50, Domestic Licensing of Production and Utilization Facilities, 10 CFR 50.69,
Risk-Informed Categorization and Treatment of Structures, Systems and Components for
Nuclear Power Reactors, U.S. Nuclear Regulatory Commission, Washington, DC.
6.
Regulatory Guide 1.205, Risk-Informed, Performance-Based Fire Protection for Existing LightWater Nuclear Power Plants, U.S. Nuclear Regulatory Commission, Washington, DC.
7.
10 CFR Part 50, Domestic Licensing of Production and Utilization Facilities, 10 CFR 50.48(c),
Fire Protection -- National Fire Protection Association Standard NFPA 805, U.S. Nuclear
Regulatory Commission, Washington, DC.
8.
National Fire Protection Association Standard 805, Performance-Based Standard for Fire
Protection for Light-Water Reactor Electric Generating Plants, 2001 Edition, Quincy, MA.
9.
Regulatory Guide 1.206, Combined License Applications for Nuclear Power Plants (LWR
Edition), U.S. Nuclear Regulatory Commission, Washington, DC.
10.
10 CFR Part 52, Early Site Permits; Standard Design Certifications; and Combined Licenses for
Nuclear Power Plants, U.S. Nuclear Regulatory Commission, Washington, DC.
11.
12.
13.
14.
ASME/ANS RA-Sa-2009, Standard for Level 1/Large Early Release Frequency Probabilistic
Risk Assessment for Nuclear Power Plant Applications, Addendum A to RA-S-2008, ASME,
New York, NY, American Nuclear Society, La Grange Park, Illinois, February 2009.
NEI 00-02, Probabilistic Risk Assessment Peer Review Process Guidance, Revision A3,
Nuclear Energy Institute, Washington, DC, March 20, 2000.
Nuclear Energy Institute, Letter from Anthony Pietrangelo, Director of Risk- and PerformanceBased Regulation Nuclear Generation, Nuclear Energy Institute, to Mary Drouin, Office of
Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC, NEI
00-02, Probabilistic Risk Assessment Peer Review Process Guidance, Revision 1, May 19,
2006.
Nuclear Energy Institute, Letter from Biff Bradley, Manager of Risk Assessment, Nuclear
Energy Institute, to Mary Drouin, Office of Nuclear Regulatory Research, U.S. Nuclear
Regulatory Commission, Washington, DC, Update of Appendix D to Revision 1 of NEI-00-02,
Probabilistic Risk Assessment Peer Review Process Guidance, November 15, 2006.
16.
NEI 05-04, Process for Performing Follow-On PRA Peer Reviews Using the ASME PRA
Standard, Revision 2, Nuclear Energy Institute, Washington, DC, November 2008.
17.
NEI 07-12, Fire Probabilistic Risk Assessment (FPRA) Peer Review Process Guidelines,
Draft Version H, Revision 0, Nuclear Energy Institute, Washington, DC, November 2008.
18.
19.
20.
SECY-07-0042, Status of the Plan for the Implementation of the Commission's Phased Approach
to Probabilistic Risk Assessment Quality, U.S. Nuclear Regulatory Commission, Washington,
DC, March 7, 2007.
21.
NUREG-1792, Good Practices for Implementing Human Reliability Analysis (HRA), U.S.
Nuclear Regulatory Commission, Washington, DC, April 2005.
22.
BIBLIOGRAPHY
ASME RA-Sb-2005, Standard for Probabilistic Risk Assessment for Nuclear Power Plant
Applications, Addendum B to ASME RA-S-2002, ASME, New York, New York,
December 30, 2005.
ASME RA-Sc-2007, Standard for Probabilistic Risk Assessment for Nuclear Power Plant
Applications, Addendum C to ASME RA-S-2002, ASME, New York, NY, July 6, 2007.
ASME/ANS RA-S-2008, Standard for Probabilistic Risk Assessment for Nuclear Power Plant
Applications, Revision 1 RA-S-2002, ASME, New York, NY, April 2008.
ASME/ANS RA-Sa-2009, Standard for Probabilistic Risk Assessment for Nuclear Power Plant
Applications, Addendum A to Revision 1 of ASME RA-S-2002, ASME, New York, NY,
February 2009.
NEI 00-02, Probabilistic Risk Assessment Peer Review Process Guidance, Revision A3,
Nuclear Energy Institute, Washington, DC, March 20, 2000.
Nuclear Energy Institute, Letter from Anthony Pietrangelo, Director of Risk- and PerformanceBased Regulation Nuclear Generation, Nuclear Energy Institute, to Mary Drouin, Office of
Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC, NEI
00-02, Probabilistic Risk Assessment Peer Review Process Guidance, Revision 1, May 19,
2006.
Nuclear Energy Institute, Letter from Biff Bradley, Manager of Risk Assessment, Nuclear
Energy Institute, to Mary Drouin, Office of Nuclear Regulatory Research, U.S. Nuclear
Regulatory Commission, Washington, DC, Update of Appendix D to Revision 1 of NEI-00-02,
Probabilistic Risk Assessment Peer Review Process Guidance, November 15, 2006.
NEI 05-04, Process for Performing Follow-on PRA Peer Reviews Using the ASME PRA
Standard, Revision 2, Nuclear Energy Institute, Washington, DC, November 2008.
NEI 07-12, Fire Probabilistic Risk Assessment (FPRA) Peer Review Process Guidelines,
Draft Version H, Revision 0, Nuclear Energy Institute, Washington, DC, November 2008.
.
APPENDIX A
NRC REGULATORY POSITION ON ASME/ANS PRA STANDARD
Introduction
The American Society of Mechanical Engineers (ASME) and the American Nuclear Society
(ANS) has published ASME RA-Sa-2009, Standard for Probabilistic Risk Assessment for Nuclear
Power Plant Applications (Ref. 14)). The standard states that it sets forth requirements for probabilistic
risk assessments (PRAs) used to support risk-informed decision for commercial nuclear power plants, and
describes a method for applying these requirements for specific applications. The NRC staff has
reviewed ASME/ANS RA-Sa-2009 against the characteristics and attributes for a technically acceptable
PRA as discussed in Regulatory Positions 1 and 2 of this regulatory guide. The staffs position on each
requirement (referred to in the standard as a requirement, a high-level requirement, or a supporting
requirement) in ASME/ANS RA-Sa-2009 is categorized as no objection, no objection with
clarification, or no objection subject to the following qualification, and defined as follows:
No objection with clarification. The staff has no objection to the requirement. However,
certain requirements, as written, are either unclear or ambiguous, and therefore the staff has
provided its understanding of these requirements.
No objection subject to the following qualification. The staff has a technical concern with the
requirement and has provided a qualification to resolve the concern.
ASME/ANS RA-Sa-2009 PRA standard is divided into ten parts:
Tables A-1 through A-10 provides the staffs position on each requirement in Parts 1 thru 10,
respectively. A discussion of the staffs concern (issue) and the staff proposed resolution is provided. In
the proposed staff resolution, the staff clarification or qualification to the requirement is indicated in
either bolded text (i.e., bold) or strikeout text (i.e., strikeout); that is, the necessary additions or deletions
to the requirement (as written in the ASME/ANS standard) for the staff to have no objection are provided.
Issue
Position
Resolution
Global
References
Section 1-1
1-1.1 thru 1-1.7
--------------------
No objection
--------------------
Section 1-2
1-2.1
Acronyms
COL
Acronym is needed
Other acronyms
1-2.2
Definitions
--------------------
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
Definitions
Section 1-3
1-3.1 thru 1-3.4,
1-3.6
1-3.5, 2nd
paragraph
Issue
Position
Clarification
See staff proposed
resolution for Section 11.4.2, text in Box 4 of
Figure 1-3.1-1 needs to be
modified be consistent
with the text.
Resolution
For each relevant Hazard
Group,
Section 1-4
1-4.1 thru 14.3.2, 1-4.3.4
thru 1-4.5
1-4.3.3, 2nd
paragraph
--------------------
No objection
--------------------
Section 1-5
1-5.1 thru 1-5.7
--------------------
No objection
--------------------
Issue
Position
Resolution
--------------------
No objection
--------------------
Section 1-6
1-6.1.1, 1-6.1.2,
1-6.2, 1-6.4,
1-6.5, 1-6.6.2
1-6.1
1-6.3
As written, there does not Clarification The peer review team shall use the
requirements of this Standard. For
appear to be a minimum
set. The requirement as
each PRA element, a set of review topics
written provides
required for the peer review team are
suggestions. A
provided in the subparagraphs of para.
6.3. Additional material for those
minimal set of items is to
Elements may be reviewed depending on
be provided; the peer
the results obtained. These suggestions
reviewers have flexibility
in deciding on the scope
are not intended to be a minimum or
and level of detail for
comprehensive list of requirements. The
each of the minimal
judgment of the reviewer shall be used to
items.
determine the specific scope and depth of
the review in each of each review topic
for each PRA element.
Issue
Position
Resolution
Section 1-7
References
Appendix 1-A
Global
Issue
Position
Resolution
--------------------
No objection
--------------------
1-A.1, 4th
paragraph
As written, it could be
inferred that a newly
developed method would
not be considered an
upgrade.
Clarification
1-A.2
An internal review is
recommended in several
places. This
recommendation is made
instead of an outside
peer review. It needs to
be made clear that this
internal review is a type
of peer review and
should follow the process
and requirements for the
peer review requirements.
1-A.3,
Examples 1 thru
7, 9, 11-16, 19,
20, 22 thru
1-A.3,
Example 21
1-A.4
Issue
Position
Resolution
Discussion and/or Alternative
Changing the definition of Clarification
Recommendation: While this change may
core damage without
not be a new methodology, it could
changing the thermalresult in changing the success criteria
hydraulic methodology
with implications for the development of
may result in changed
accident sequences, and potentially on
success criteria which
the HRA (through timing), data, and
could change the accident
quantification. If this change leads to a
progression delineated by
significant change in risk insights, a
the accident sequences. It
focused peer review should be performed
is not a foregone
conclusion that this is a
simple change to the PRA
model. It needs to be
reviewed to ensure that
the resulting changes are
appropriate. Further,
what would be a
significant change is open
to interpretation, and
would be prudent is not
as strong as should.
This assumes that the
important human
actions are of the same
nature as the new ones
being added and utilize
the ASEP method in the
exact same manner. This
cannot be assumed.
Clarification
References
Clarification
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
2-2.1.1
--------------------
No objection
--------------------
Table 2-2.1-1
--------------------
No objection
--------------------
No objection
--------------------
Section 2-1
2-1.1 thru 2-1.3
Section 2-2
2-2.1
2-2.1 IE
--------------------
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
IE-A6
Issue
Position
Resolution
IE-B1 thru
IE-B5
--------------------
No objection
--------------------
IE-C1 thru
IE-C11, IE-C13
thru IE-C15
--------------------
No objection
--------------------
IE-C12
Footnote (1)(a)
to Table 2-2.14(c)
IE-D1 thru
IE-D3
--------------------
Clarification Thus,
f bus at power = 110-7/hr * 8760 hrs/yr * 0.90
= 7.910-4/reactor year.
In the above example, it is assumed the
bus failure rate is applicable for atpower conditions. It should be noted
that initiating event frequencies may be
variable from one operating state to
another due to various factors. In such
cases, the contribution from events
occurring only during at-power
conditions should be utilized.
No objection
--------------------
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
Issue
Position
Resolution
2-2.2 AS
2-2.2.1
Table 2-2.2-1
No objection
--------------------
No objection
--------------------
--------------------
AS-B1 thru
AS-B7
--------------------
No objection
--------------------
AS-C1 thru
AS-C3
--------------------
No objection
--------------------
2-2.3 SC
2-2.3.1
Table 2-2.3-1
No objection
--------------------
No objection
--------------------
SC-B1 thru
SC-B5
--------------------
No objection
--------------------
SC-C1 thru
SC-C3
--------------------
No objection
--------------------
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
Issue
Position
Resolution
2-2.4.1
--------------------
No objection
--------------------
Table 2-2.4-1
--------------------
No objection
--------------------
No objection
--------------------
2-2.4 SY
SY-B1 thru
SY-B13, SYB15
SY-B14
SY-C1 thru
SY-C3
--------------------
No objection
--------------------
--------------------
No objection
--------------------
2-2.5.1
--------------------
No objection
--------------------
Table 2-2.5-1
--------------------
No objection
--------------------
2-2.5 HR
--------------------
No objection
--------------------
HR-B1,
HR-B2
--------------------
No objection
--------------------
HR-C1 thru
HR-C3
--------------------
No objection
--------------------
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
HR-D1,
HR-D2HR-D4,
HR-D5, HR-D7
HR-D3
Issue
Position
Resolution
--------------------
No objection
--------------------
HR-D6
HR-E1 thru
HR-E4
--------------------
No objection
--------------------
HR-F1,
HR-F2
--------------------
No objection
--------------------
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
HR-G1, HR-G2,
HR-G5 thru
HR-G7
HR-G3
Issue
Position
Resolution
--------------------
No objection
--------------------
Clarification Cat I:
In item (d) of CC II, III,
clarify that clarity refers
(a) the complexity of detection,
the meaning of the cues,
diagnosis, decision-making and
etc.
executing the required response
In item (a) of CC I and
(b)
item (g) of CC II, III,
Cat II, and III:
clarify that complexity
refers to both determining
(d) degree of clarity of the cues/indications
the need for and
in supporting the detection, diagnosis,
executing the required
and decision-making give the plantresponse.
specific and scenario-specific context of
the event.
(g) complexity of detection, diagnosis
and decision-making, and executing the
required response.
HR-G4
HR-G8
HR-H1 thru
HR-H3
--------------------
No objection
--------------------
HR-I1 thru
HR-I3
--------------------
No objection
--------------------
2-2.6.1
--------------------
No objection
--------------------
Table 2-2.6-1
--------------------
No objection
--------------------
No objection
--------------------
2-2.6 - DA
--------------------
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
Issue
Position
Resolution
DA-B1, DA-B2
--------------------
No objection
--------------------
DA-C1 thru
DA-C14,
DA-C16
--------------------
No objection
--------------------
DA-C15
DA-D2 thru
DA-D8
No objection
--------------------
DA-D1
DA-D9
DA-E1 thru
DA-E3
--------------------
No objection
--------------------
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
Issue
Position
Resolution
2-2.7 - QU
2-2.7.1
Table 2-2.7-1
--------------------
--------------------
HLR-QU-A,
HLR-QU-B,
HLR-QU-C,
HLR-QU-E,
HLR-QU-F
Table 2-2.7-1
HLR-QU-D
--------------------
No objection
--------------------
QU-A2
Need to acknowledge
LERF quantification
QU-A3
The state-of-knowledge
correlation should be
accounted for all event
probabilities. Left to the
analyst to determine the
extent of the events to be
correlated. Need to also
acknowledge LERF
quantification
Clarification Cat I:
ESTIMATE the point estimate CDF (and
LERF)
Cat II:
ESTIMATE the mean CDF (and LERF),
accounting for the state-of-knowledge
correlation between event probabilities
when significant (see NOTE 1).
Cat III:
CALCULATE the mean CDF (and
LERF) by
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
QU-B1 thru, ,
QU-B5, QU-B7
thru
QU-B10
QU-B6
QU-C1 thru
QU-C3
Issue
Position
Resolution
--------------------
No objection
--------------------
Need to acknowledge
LERF quantification
--------------------
--------------------
Table 2-2.7-5(d) HLR-QU-D and Table 2- Clarification significant contributors to CDF (and
LERF), such as initiating events, accident
2.7-2(d) objective
sequences
statement just before table
need to agree; SRs for
LERF quantification
reference the SRs in 2-2.7
and, therefore, need to be
acknowledged in 2-2.7.
QU-D1 thru
QU-D7
--------------------
No objection
--------------------
QU-E1, QU-E2
--------------------
No objection
--------------------
QU-E3
QU-E4
QU-F1, QU-F3
thru QU-F6
Need to acknowledge
LERF quantification
The note has no relevance Clarification For each source of model uncertainty
introduction of a new initiating event)
to the base model and
[Note (1)].
could cause confusion; it
should be deleted.
NOTE: For specific applications, And
in logical combinations.
--------------------
No objection
--------------------
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
QU-F2
Issue
Position
Resolution
2-2.8 LE
2-2.8.1
--------------------
No objection
--------------------
Table 2-2.8-1
--------------------
No objection
--------------------
--------------------
No objection
--------------------
LE-B1 thru
LE-B3
--------------------
No objection
--------------------
LE-C1 thru
LE-C13
--------------------
No objection
--------------------
LE-D1 thru
LE-D7
--------------------
No objection
--------------------
LE-E1 thru
LE-E4
--------------------
No objection
--------------------
LE-F1 thru
LE-F3
--------------------
No objection
--------------------
LE-G1, LE-G3
thru
LE-G6
--------------------
No objection
--------------------
LE-G2
Table 2-2.8-9
There is no requirement
to perform sensitivity
studies.
--------------------
--------------------
Table A-2. Staff Position on ASME/ANS RA-Sa-2009 Part 2, Technical and Peer Review
Requirements for At-Power Internal Events
Index No
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
Clarification
Section 2-3
2-3.1 thru
2-3.3.8.2
Section 2-4
References
Table A-3. Staff Position on ASME/ANS RA-Sa-2008 Part 3, Technical and Peer Review
Requirements for At-Power Internal Flood
Index No
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
3-2.1.1
--------------------
No objection
--------------------
Table 3-2.1-1
--------------------
No objection
--------------------
Section 3-1
3-1.1 thru 3-1.3
Section 3-2
3-2
3-2.1 IFPP
--------------------
No objection
--------------------
IFPP-B1 thru
IFPP-B3
--------------------
No objection
--------------------
3-2.2.1
--------------------
No objection
--------------------
Table 3-2.2-1
--------------------
No objection
--------------------
No objection
--------------------
3-2.2 IFSO
--------------------
Table A-3. Staff Position on ASME/ANS RA-Sa-2008 Part 3, Technical and Peer Review
Requirements for At-Power Internal Flood
Index No
IFSO-A5
IFSO-B1 thru
IFSO-B3
Issue
Position
Resolution
No objection
--------------------
3-2.3.1
--------------------
No objection
--------------------
Table 3-2.3-1
--------------------
No objection
--------------------
No objection
--------------------
3-2.3 IFSN
--------------------
Table A-3. Staff Position on ASME/ANS RA-Sa-2008 Part 3, Technical and Peer Review
Requirements for At-Power Internal Flood
Index No
IFSN-A6
Issue
For Cat II, it is not
acceptable to just note
that a flood-induced
failure mechanism is not
included in the scope of
the internal flooding
analysis. Some level of
assessment is required.
Position
Resolution
Qualification Cat I:
For the SSCs identified in IFSN-A5,
IDENTIFY the susceptibility of each SSC
in a flood area to flood-induced failure
mechanisms. INCLUDE failure by
submergence and spray in the
identification process.
EITHER:
(a) ASSESS by using conservative
assumptions; OR
(b) NOTE that these mechanisms are not
included in the scope of the evaluation.
Cat II:
For the SSCs identified in IFSN-A5,
IDENTIFY the susceptibility of each
SSC in a flood area to flood-induced
failure mechanisms. INCLUDE failure
by submergence and spray in the
identification process.
ASSESS qualitatively the impact of
flood-induced mechanisms that are not
formally addressed (e.g., using the
mechanisms listed under Capability
Category III of this requirement), by
using conservative assumptions.
IFSN-B1 thru
IFSN-B3
--------------------
No objection
--------------------
3-2.4.1
--------------------
No objection
--------------------
Table 3-2.4-1
--------------------
No objection
--------------------
3-2.4 IFEV
--------------------
No objection
--------------------
IFEV-B1 thru
IFEV-B3
--------------------
No objection
--------------------
3-2.5 IFQU
Table A-3. Staff Position on ASME/ANS RA-Sa-2008 Part 3, Technical and Peer Review
Requirements for At-Power Internal Flood
Index No
Issue
Position
Resolution
3-2.5.1
--------------------
No objection
--------------------
Table 3-2.5-1
--------------------
No objection
--------------------
No objection
--------------------
IFQU-B1 thru
IFQU-B3
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
Clarification
Section 3-3
3-3.1 thru 3-3.3
Section 3-4
References
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
PP-B1 thru
PP-B7
--------------------
No objection
--------------------
PP-C1 thru
PP-C4
--------------------
No objection
--------------------
--------------------
No objection
--------------------
Section 4-1
4-1.1 thru 4-1.6
Section 4-2
4-2
4-2.1 PP
4-2.1.1, 4-2.1.2
Table 4-2.1-1
4-2.2 ES
4-2.2
Table 4-2.2-1
HLR-ES-A
ES-A2 thru
ES-A6
--------------------
--------------------
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
ES-A1
ES-B2, ES-B3,
ES-B5
ES-B1
Issue
Conforming change to
HLR-ES-A
--------------------
Position
Resolution
--------------------
ES-B4
SR refers to incorrect SR
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
ES-C1
ES-C2
ES-D1
Issue
Position
Resolution
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
--------------------
4-2.3 CS
4-2.3
Table 4-2.3-1
--------------------
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
CS-A10
CS-B1
CS-C1 thru
CS-C4
Issue
Position
Resolution
Clarification Cat I:
PP-B1 already allows
physical analysis units to
IDENTIFY the fire areas and
be defined in terms of fire
CONFIRM terminal end locations.
areas. As such the
Cat II:
distinction between CCI
IDENTIFY and CONFIRM terminal
and CCII is unnecessary.
end locations.
Cat I and II:
IDENTIFY the physical analysis units,
consistent with the plant partitioning
analysis, through which each cable
associated with a credited Fire PRA
function passes and CONFIRM that the
information includes treatment of cable
terminal end locations.
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
4-2.4 QLS
4-2.4
Table 4-2.4-1
--------------------
No objection
--------------------
QLS-B1 thru
QLS-B3
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
--------------------
4-2.5 PRM
4-2.5
Table 4-2.5-1
--------------------
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
PRM-B1 thru
PRM-B15
PRM-C1
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
--------------------
4-2.6 FSS
4-2.6
Table 4-2.6-1
FSS-A4
FSS-A5
FSS-B1, B2
FSS-C1, FSSC3 thru FSS-C8
--------------------
No objection
--------------------
--------------------
No objection
--------------------
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
FSS-C2
Issue
See Issue for ES-C1
Position
Resolution
FSS-D1,
FSS-D2,
FSS-D4 thru
FSS-D11
FSS-D3
--------------------
No objection
--------------------
FSS-E1 thru
FSS-E4
FSS-F1
FSS-F2, FSS-F3
FSS-G1 thru
FSS-G6
--------------------
No objection
--------------------
No objection
--------------------
--------------------
No objection
--------------------
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
FSS-H1 thru
FSS-H10
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
4-2.7 IGN
4-2.7
Table 4-2.7-1
IGN-A2 thru
IGN-A10
--------------------
No objection
--------------------
IGN-B1 thru
IGN-B5
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
4-2.8 QNS
4-2.8
Table 4-2.8-1
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
QNS-C1
Issue
Position
Resolution
Cat III:
and
and
QNS-D1,
QNS-D2
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
4-2.9 CF
4-2.9
Table 4-2.9-1
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
CF-A2
CF-B1
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
4-2.10 HRA
4-2.10
Table 4-2.10-1
--------------------
No objection
--------------------
HRA-B1 thru
HRA-B4
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
HRA-C1
HRA-D1
HRA-D1 [Note
(1)]
HRA-E1
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
4-2.11 SF
4-2.11
Table 4-2.11-1
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
Issue
Position
Resolution
--------------------
No objection
--------------------
4-2.12 FQ
4-2.12
Table 4-2.12-1
HLR-FQ-E
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
FQ-E1
FQ-F1
FQ-F2
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
4-2.13 -- UNC
4-2.13
Table 4-2.13-1
UNC-A1, UNCA2
Table A-4. Staff Position on ASME/ANS RA-Sa-2009 Part 4, Technical and Peer Review
Requirements for At-Power Internal Fire
Index No
Issue
Position
Resolution
--------------------
No objection
--------------------
Section 4-3
4-3.1
4-3.2
4-3.3
--------------------
No objection
--------------------
4-3.3.1 thru
4-3.3.13
--------------------
No objection
--------------------
--------------------
Clarification
Section 4-4
References
Appendix 4-A
The staff does not endorse the material in this appendix, and as such, does not have a position (i.e., no
objections, no objection with clarification, or no objection with qualification) on any of the material
contained in this appendix. However, it should be noted, that consistent with the Commission endorsed
phase PRA Quality Initiative, all risk contributors that cannot be shown as insignificant, should be
assessed through quantitative risk assessment methods to support risk informed licensing actions.
Table A-5. Staff Position on ASME/ANS RA-Sa-2009 Part 5, Technical and Peer Review
Requirements for At-Power Seismic Events
Index No
Section 5-1
5-1
Section 5-2
5-2
5-2.1 SHA
5-2.1
Table 5-2.1.1,
HLR-SHA-A
thru
HLR-SHA-F,
HLR-SHA-J
Table 5-2.1-1,
HLR-SHA-G
Table 5-2.1-1,
HLR-SHA-H
Table 5-2.1-1,
HLR-SHA-I
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
Clarification
Clarification
Clarification
Table A-5. Staff Position on ASME/ANS RA-Sa-2009 Part 5, Technical and Peer Review
Requirements for At-Power Seismic Events
Index No
Issue
SHA-G1
Position
Resolution
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
Clarification
Clarification
Table A-5. Staff Position on ASME/ANS RA-Sa-2009 Part 5, Technical and Peer Review
Requirements for At-Power Seismic Events
Index No
Issue
Position
Table 5-2.19(h)
Clarification
SHA-H
Clarification
Table 5-2.110(i)
Clarification
Resolution
components. Additional discussion
on this issue can be found in Ref. 17.
In the quantification of fragilities and
of final risk results, it is important to
use as realistic a shape as possible.
Semi-site specific shapes, such as
those given in NUREG-0098, have
been used in the past and are
considered may be adequate for this
purpose, provided that they are
shown to be reasonably appropriate
for the site [42]. The uniform hazard
response spectrum (UHS) is
acceptable for this purpose if it can
be shown that the UHS shape is
appropriate for the site. unless
evidence comes to light (e.g., within
the technical literature) that these
UHS do not reflect the spectral shape
of the site-specific events. Recent
developments [42] indicate that
these spectral shapes are not
appropriate for CEUS sites where
high frequency content is dominant
at hard rock sites.
When use ... for the intended
application. It shall be confirmed
that the basic data and
interpretations from an existing
study are valid.
SHA-H1
Cat I and II:
Use of existing studies
ENSURE, in light of established
current information, the study
meets the requirements in HLRSHA-A thru HLR-SHA-G.
Cat III:
Use of existing studies not allowed.
DO NOT USE existing studies.
A screening analysis ... or the
magnitude of hazard consequences, or
both. The hazard analysis shall
include hazards other than
vibratory ground motion if
necessary.
Table A-5. Staff Position on ASME/ANS RA-Sa-2009 Part 5, Technical and Peer Review
Requirements for At-Power Seismic Events
Index No
SHA-I
Issue
See issue for Table 52.1-1, HLR-SHA-I
Position
Resolution
Clarification
SHA-I
There are no supporting requirements
here.
SHA-I1
Cat I, II and III:
PERFORM a screening to
determine whether to include other
seismic hazards such as fault
displacement, landslide, soil
liquefaction, or soil settlement in
the seismic PRA.
SHA-I2
Cat I, II and III:
ADDRESS the effect of these other
seismic hazards through assessment
of the frequency of hazard
occurrence or the magnitude of
hazard consequences, or both.
SHA-J1, thru
SHA-J3
5-2.2 SFR
5-2.2
5-2.2
Table 5-2.2-1
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
--------------------
Table A-5. Staff Position on ASME/ANS RA-Sa-2009 Part 5, Technical and Peer Review
Requirements for At-Power Seismic Events
Index No
5-2.3
Table 5-2.3-1
Issue
Position
Resolution
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
--------------------
Section 5-4
References
Appendix 5-A
5-A.1 thru 5A.3
5-A.4
-------------------References
Clarification
No objection
Clarification
Table A-6. Staff Position on ASME/ANS RA-Sa-2009 Part 6, Technical and Peer Review
Requirements for At-Power Screening and Conservative Analysis of Other External Hazards
Index No
Section 6-1
6-1
Section 6-2
6-2.1 thru 6-2.3
Table 6-2-1
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
--------------------
Section 6-4
References
Clarification
Appendix 6-A
-------------------6-A-1
References
No objection
Clarification
Table A-7. Staff Position on ASME/ANS RA-Sa-2009, Part 7, Technical and Peer Review
Requirements for At-Power High Wind Events
Index No
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
--------------------
Qualification
Section 7-1
7-1
Section 7-2
7-2
7-2.1 WHA
7-2.1
Table 7-2.1-1
WHA-A1
Table A-7. Staff Position on ASME/ANS RA-Sa-2009, Part 7, Technical and Peer Review
Requirements for At-Power High Wind Events
Index No
Issue
Position
Resolution
found in Refs. 13, 56, and 57.
Tornado wind hazard analysis
SHOULD include the following
elements:
(a) variation of tornado intensity with
occurrence
(f) variation of tornado differential
pressure across the tornado path
width.
WHA-A2 thru
WHA-A5
WHA-B1 thru
WHA-B3
7-2.2 WFR
7-2.2
Table 7-2.2-1
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
Clarification
--------------------
No objection
Table 7-2.3-1
HLR-WPR-B
and HLRWPR-C
Clarification
Table A-7. Staff Position on ASME/ANS RA-Sa-2009, Part 7, Technical and Peer Review
Requirements for At-Power High Wind Events
Index No
Issue
Position
Resolution
initiating events and other failures
that are significant contributors
that can
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
Section 7-4
References
Clarification
Table A-8. Staff Position on ASME/ANS RA-Sa-2009, Part 8, Technical and Peer Review
Requirements for At-Power External Flood Events
Index No
Section 8-1
8-1
Section 8-2
8-2
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
--------------------
Clarification
No objection
--------------------
No objection
--------------------
No objection
--------------------
Clarification
No objection
--------------------
No objection
--------------------
No objection
8-2.1 XFHA
8-2.1
Table 8-2.1-1
--------------------
-------------------Table 8-2.3-1
The word significant
HLR-XFPR-A
needs to be added in this
HLR in Table 8-2.3 and
in the HLR statement in
Table 8-2.3-2(a)
Tables 8-2.3-2(a) and 8-2.3-4(c)
Table 8-2.3The word significant
2(a)
needs to be added the
HLR statement in Table
8-2.3-2(a)
Clarification
Clarification
Table A-8. Staff Position on ASME/ANS RA-Sa-2009, Part 8, Technical and Peer Review
Requirements for At-Power External Flood Events
Index No
XFPR-A thru
XFPR-A11
XFPR-B1,
XFPR-B2
XFPR-C1 thru
XFPR-C3
Section 8-3
8-3 thru 8-3.3.5
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
Section 8-4
References
Clarification
Table A-9. Staff Position on ASME/ANS RA-Sa-2009, Part 9, Technical and Peer Review
Requirements for At-Power Other External Hazards
Index No
Issue
Position
Resolution
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
--------------------
No objection
--------------------
No objection
--------------------
No objection
--------------------
Section 9-1
9-1
Section 9-2
9-2
9-2.1 XHA
9-2.1
Table 9-2.1-1
9-2.2 XFR
9-2.2
Table 9-2.2-1
9-2.3 XPR
9-2.3
Table 9-2.3-1
HLR-XPR-A
-------------------No objection
The word significant
Clarification
should be added in this
HLR in Table 9-2.3-1
and in the HLR
statement in Table 9-2.32(a)
Clarification
Table A-9. Staff Position on ASME/ANS RA-Sa-2009, Part 9, Technical and Peer Review
Requirements for At-Power Other External Hazards
Index No
Issue
Position
9-2.3-2(a)
XPR-A thru
XPR-A11
XPR-B1 thru
XFPR-B2
XPR-C1 thru
XPR-C3
Section 9-3
9-3.1 thru 93.4.5
Resolution
that are significant contributors
that can
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
--------------------
No objection
--------------------
Section 9-4
References
Clarification
Table A-10. Staff Position on ASME/ANS RA-Sa-2009 Part 10, Technical and Peer Review
Requirements for At-Power Seismic Margins Assessment
The staff does not endorse the material in this Part of the standard, and as such, does not have a
position (i.e., no objections, no objection with clarification, or no objection with qualification) on
any of the material contained in Part 10 of the standard. However, it should be noted, that consistent
with the Commission endorsed phase PRA Quality Initiative, all risk contributors that cannot be
shown as insignificant, should be assessed using a PRA (as defined in Section C.1) to support riskinformed licensing actions.
APPENDIX B
NRC POSITION ON THE NEI PEER REVIEW PROCESS (NEI 00-02)
Introduction
The Nuclear Energy Institute (NEI) Peer Review Process is documented in NEI 00-02, Revision 1
(Ref. 15). It provides guidance for the peer review of probabilistic risk assessments (PRAs) and subtier
criteria for assigning a grade (i.e., Grade 1, 2, 3 or 4) to each PRA sub-element. The ASME PRA
Standard provides requirements for three capability categories (i.e., Category I, II or III).
The NEI subtier criteria for a Grade 3 PRA have been compared by NEI to the requirements in
the ASME PRA Standard (ASME RA-Sb-2005) (Ref. 19) listed for a Capability Category II PRA. The
comparison of the NEI subtier criteria with the ASME PRA Standard has indicated that some of the
Capability Category II ASME PRA Standard requirements are not addressed in the NEI Grade 3 PRA
subtier criteria. Thus, NEI 00-02 also provides guidance for performing a self-assessment of a PRA
against the requirements in the ASME PRA Standard (ASME RA-Sb-2005) that were not addressed
during the NEI peer review.
A comparison of the criteria for other grades against the other categories in the standard was not
performed since NEI contends that the results of the peer review process generally indicate the reviewed
PRAs are consistent with the Grade 3 criteria in NEI 00-02. However, the PRAs reviewed have contained
a number of Grade 2, and even Grade 4 elements.
Since the issuance of ASME RA-Sb-2005, addenda and a major revision have been issued
(Ref. 14). These documents contain requirements that were either revised or added, as compared to RASb-2005. Consequently, the comparison of the NEI subtier criteria is not complete because there may still
exist requirements in ASME/ANS RA-Sa-2009 not addressed by the subtier criteria.
This appendix provides the staffs position on NEI 00-02, Revision 1. The staffs positions are
categorized as following:
In the proposed staff resolution, the staff clarification or qualification that is needed for the staff
to have no objection are provided.
NEI 00-02, Revision 1 report contains guidance in four areas:
In general, the guidance in NEI 00-02 is historical. However, if the peer review process guidance in NEI
00-02 (documented in Section 1 through 4 and Appendices A through C) is used in the future and
supplemented with the staffs regulatory position contained in this appendix, then it is considered
adequate to support the risk-informed application under consideration.
Tables B-1 through B-4 provide the NRC position of the four areas addressed in NEI 00-02,
respectively. Moreover, the staff has the following global objection (in the form of a qualification):
The peer review process and self-assessment process in NEI 00-02 is based on
Addendum B to the ASME PRA standard (RA-Sb-2005).
The staff position on ASME PRA standard RA-Sb-2005 is documented in Appendix A
of Revision 1 of Regulatory Guide 1.200.
The staff position on NEI 00-02 (both the process and self-assessment portions of the
guidance) is based on the staff position of RA-Sb-2005 as documented in Appendix A of
Revision 1 of Regulatory Guide 1.200.
The staffs position on NEI 00-02 was originally documented in Appendix B of
Revision 1 of Regulatory Guide 1.200. The staff position documented in Appendix B of
Revision 2 of Regulatory Guide repeats what is documented in Appendix B of Revision
1 of Regulatory Guide 1.200.
Since RA-Sb-2005 was issued, ASME has issued Addendum C (RA-Sc-2007) and
ASME and ANS have issued both a revision and an addendum (ASME/ANS RA-S-2008
and ASME/ANS RA-Sa-2009, respectively).
The subsequent versions of the PRA standard (i.e., ASME RA-Sc-2007, ASME/ANS
RA-S-2008, and ASME/ANS RA-Sa-2009), as compared to ASME RA-Sb-2005,
contain either requirements that were revised or new requirements that were added.
There may be requirements in ASME/ANS RA-Sa-2009 that were not addressed by the
criteria in NEI 00-02, and not identified in the self-assessment. This potential
discrepancy becomes important if licensees plan to use the self-assessment performed
under NEI 00-02.
Staff Position:
It is NRCs expectation that, if the results of the self-assessment are used to demonstrate
the technical adequacy of a PRA for an application, differences between the current
version of the Standard (as endorsed in Appendix A of Revision 2 of this Regulatory
Guide), and the earlier version of the ASME PRA Standard (i.e., ASME RA-Sb-2005) be
identified and addressed.
Position
Commentary/Resolution
Section 1. Introduction
1.1
Clarification
Clarification
1.1
Clarification
This section states that the NEI peer review process is a one-time
evaluation process but indicates that additional peer review may
be required if substantial changes are made to the PRA models or
methodology. The staff position on additional peer reviews is to
follow the guidance in Section 1-5 of Part 1 of the ASME/ANS
PRA Standard which requires a peer review for PRA upgrades
(PRA methodology changes).
1.2
No objection
--------------------
1.3
Clarification
1.4
Clarification
The NEI peer review process provides a summary grade for each
PRA element. The use of a PRA for risk-informed applications
needs to be determined at the sub-element level. The staff does
not agree with the use of an overall PRA element grade in the
assessment of a PRA.
1.5
Position
Commentary/Resolution
Clarification
This section indicates that the process requires that the existing
PRA meet the process criteria or that enhancements necessary to
meet the criteria have been specifically identified by the peer
reviewers and committed to by the host utility. Thus, the assigned
grade for a sub-element can be contingent on the utility
performing the prescribed enhancement. An application submittal
that utilizes the NEI peer review results needs to identify any of
the prescribed enhancements that were not performed.
Clarification
No Objection
--------------------
Clarification
2.2
Clarification
Clarification
2.2
Steps 4, 7, &
8
Position
Clarification
Commentary/Resolution
The peer reviewer qualifications do not appear to be consistent
with the following requirements specified in Part 1, Section 1-6.2
of the ASME/ANS PRA Standard:
the need for familiarity with the plant design and operation
No objection
--------------------
No objection
--------------------
3.2, 3.3
Clarification
3.3
Clarification
The NEI peer review process grades each PRA element from 1 to
4, while the ASME/ANS PRA Standard uses Capability
Categories I, II, and III. The staff interpretation of Grades 2, 3,
and 4 is that they correspond broadly to Capability Categories I, II,
and III, respectively. This statement is not meant to imply that the
supporting requirements, for example, for Category I are equally
addressed by Grade 2 of NEI-00-02. The review of the supporting
requirement for Category II against Grade 3 of NEI-00-02
indicated discrepancies and consequently the need for a selfassessment. The existence of these discrepancies would indicate
that it would not be appropriate to assume that there are not
discrepancies between Category I and Grade 2. A comparison
between the other grades and categories has not been performed.
The implications of this are addressed in item 7a on Table B-2.
Qualification
Position
Clarification
Commentary/Resolution
The general use and interpretation of the checklists in the grading
of PRA sub-elements is addressed in this section. The subtier
criteria provide a more substantial documentation of the
interpretations of the criteria listed in the checklists. However,
as previously indicated, the subtier criteria do not fully address all
of the PRA standard requirements. The PRA standard
requirements that are not included in the NEI subtier criteria
(identified for a Grade 3 PRA in Table B-3) need to be addressed
in the NEI self-assessment process as endorsed by the staff in this
appendix.
4.2, 4.3
Clarification
Qualification
The NEI peer review report provides a summary grade for each
PRA element. The use of a PRA for risk-informed applications
needs to be determined at the sub-element level. The staff does
not agree with the use of an overall PRA element grade in the
assessment of a PRA.
No objection
--------------------
No objection
--------------------
A.7
Clarification
Position
No objection
Commentary/Resolution
--------------------
No objection
No objection
--------------------
C.2
No objection
--------------------
C.3
Clarification
C.4
Clarification/
Qualification
C.5
No objection
--------------------
C.6
Qualification
C.7
Clarification
The staff does not agree with the use of an overall PRA element
grade (documented in Tables C.7-5 & C.7-6) in the assessment of
a PRA.
Position
Commentary/Resolution
Summary
No objection
--------------------
Regulatory
Framework
No objection
Industry PRA
Peer Review
Process
Clarification
See the staff comments on the NEI peer review process provided
in Table B-1.
ASME PRA
Standard
Clarification
Comparison of
NEI 00-02 and
ASME
Standard
Clarification
--------------------
The staff does not agree or disagree with the number of supporting
requirements of the ASME PRA Standard that are addressed
(completely or partially) in the NEI subtier criteria. The staffs
focus is on ensuring that the self-assessment addresses important
aspects of a PRA that are not explicitly addressed in the NEI
subtier criteria. [See Note (1) at end of Table B-2.]
Clarification
No objection
--------------------
Clarification
Position
Commentary/Resolution
Clarification
SelfAssessment
Process
Attributes
No objection
--------------------
Overall Peer
Review
Process and
Decision
No objection
--------------------
No objection
--------------------
7.a
Clarification
7.b thru 8.
No objection
--------------------
9.
No objection
--------------------
No objection
--------------------
14.
Clarification
Utility Actions
Regulatory
Position
Comment/Resolution
None
No objection
--------------------
YES and
clarifications
included in
Action column
No objection
--------------------
PARTIAL
No objection
--------------------
NO
No objection
--------------------
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
Global
The self-assessment was performed against the ASME PRA Standard RA-Sb-2005, and was originally
endorsed by the staff in Revision 1 to Regulatory Guide 1.200. The staff position is based on staff
review of the ASME PRA Standard RA-Sb-2005. However, since that time, the PRA standard has been
revised. In performing the self-assessment action,
the action has to conform with the staff position in Appendix A of this document for the action to
be acceptable
the self-assessment has to account for the differences between the NEI subties criteria with the
requirements in Part 2 of the ASME/ANS PRA standard (as endorsed in Appendix A of this
document) as opposed to the ASME standard (RA-Sb-2005).
Initiating Events
IE-A1
Yes
IE-7, IE-8,
IE-9, IE-10
None
No objection
IE-A2
Yes
IE-5, IE-7,
IE-9, IE-10
No objection
Confirm that the
initiators [including
human-induced
initiators, and steam
generator tube rupture
(PWRs)] were
included. This can be
done by citing either
peer review
documentation/conclu
sions or examples
from your model.
NEI 00-02 does not
explicitly mention
human-induced
initiators; however, in
practice, peer reviews
have addressed this;
the definition of active
component provided
in the Addendum B of
the ASME standard
needs to be used when
verifying ISLOCAs
were modeled.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IE-A3
Yes
IE-8, IE-9
None
No objection
IE-A3a(1)
Yes
IE-8, IE-9
None
No objection
IE-A4
Partial
IE-5, IE-7,
IE-9, IE-10
No objection
IE-A4a(1)
Partial
No objection
Check for initiating
events that can be
caused by multiple
failures, if the
equipment failures
result from a common
cause or from routine
system alignments.
IE-A5
Yes
IE-8
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IE-A6
No
---
IE-A7
Yes
IE-16, IE-10
None
No objection
IE-A8
Deleted from
ASME PRA
Standard
---
---
---
IE-A9
Deleted from
ASME PRA
Standard
---
---
---
IE-A10
Yes
IE-6
None
No objection
IE-B1
Yes
AS-4, IE-4
None
No objection
IE-B2
Yes
IE-4, IE-7
None
No objection
IE-B3
Yes
IE-4, IE-12
No objection
IE-B4
Yes
IE-4
None
No objection
IE-B5(3)
Yes
IE-6
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IE-C1
Yes
None
IE-C1a(1)
Yes
None
IE-C1b(1)
Yes
IE-C2
Yes
IE-13, IE-16
Justify informative
priors used in
Bayesian update.
No objection
IE-C3
No
---
No objection
IE-C4
No
---
No objection
Document that the
ASME standard
requirements were
met. Specific
screening criteria were
not used in NEI 00-02,
but bases for
screening of events
were examined in the
peer reviews. The text
of the ASME standard
needs to be assessed.
Acceptable criteria for
dismissing IEs are
listed in IE-C4 in the
ASME PRA Standard.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IE-C5
No requirement N/A
for Category II
IE-C6
Yes
IE-15, IE-17
No objection
Check that fault tree
analysis, when used to
quantify IEs, meets
the appropriate
systems analysis
requirements.
IE-C7
No
---
No objection
IE-C8
No
---
No objection
IE-C9
Yes
IE-15, IE-16
No objection
Check that the
recovery events
included in the IE
fault trees meet the
appropriate recovery
analysis requirements.
This can be done by
citing either peer
review
documentation/conclu
sions or examples
from your model.
IE-C10
Yes
IE-13
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IE-C11
Yes
IE-C12
Yes
IE-14
No objection
Confirm that
secondary pipe system
capability and
isolation capability
under high flow or
differential pressures
are included.
IE-C13(3)
No
None
Confirm IE-C13 is
met.
IE-D1
Partial
IE-9, IE-18,
IE-19, IE-20
No objection
Action is to confirm
availability of
documentation. In
general, specified
documentation items
not explicitly
addressed in NEI 0002 checklists were
addressed by the peer
review teams. If not
available,
documentation may
need to be generated
to support particular
applications or
respond to NRC
requests for additional
information (RAIs)
regarding applications.
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IE-D2
Partial
IE-9, IE-18,
IE-19, IE-20
No objection
Action is to confirm
availability of
documentation. In
general, specified
documentation items
not explicitly
addressed in NEI 0002 checklists were
addressed by the peer
review teams. If not
available,
documentation may
need to be generated
to support particular
applications or
respond to NRC RAIs
regarding applications.
IE-D3
Partial
QU-27, QU-28,
QU-29, QU-34
No objection with
Clarification: See staff
position on definition of key
assumption and key source
of uncertainty in Appendix
A.
IE-D4
Deleted from
ASME PRA
Standard
---
---
---
Yes
AS-4, AS-8
None
No objection
AS-A2
Yes
None
No objection
AS-A3
Yes
No objection
AS-A4
Yes
AS-19, SY-5
None
No objection
AS-A5
Yes
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
AS-A6
Yes
No objection
AS-A7
Yes
None
No objection
AS-A8
Partial
AS-20, AS-21,
AS-22, AS-23
No objection
Since there is no
explicit requirement
for steady-state
condition for end state
in NEI 00-02
checklists, this should
be evaluated even
though this was an
identified issue in
some reviews. This
can also be done by
citing either peer
review
documentation/conclu
sions or examples
from your model.
Refer to SC-A5.
AS-A9
Yes
AS-18, TH-4
AS-A10
Yes
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
AS-A11
Yes
No objection
AS-B1
Yes
No objection
AS-B2
Yes
AS-10, AS-11,
DE-4, DE-5, DE6
None
AS-B3
Yes
DE-10, SY-11,
TH-8, AS-10
None
AS-B4
Yes
Confirm requirement
met.
No objection
AS-B5
Yes
None
No objection elements.
AS-B5a(1)
Yes
AS-B6
Yes
AS-13
None
No objection
AS-C1(2)
Yes
AS-11, AS-24,
AS-25, AS-26
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
AS-C2(2)
Partial
AS-11, AS-24,
AS-25, AS-26
No objection
Action is to confirm
availability of
documentation. In
general, specified
documentation items
not explicitly
addressed in NEI 0002 checklists were
addressed by the peer
review teams. If not
available,
documentation may
need to be generated
to support particular
applications or
respond to NRC RAIs
regarding applications.
AS-C3(2)
Partial
QU-27, QU-28,
QU-29, QU-34
No objection with
Clarification: See staff
position on definition of key
assumption and key source
of uncertainty in Appendix
A.
AS-C4
Deleted from
ASME PRA
Standard
---
---
---
Success Criteria
SC-A1
Yes
AS-20, AS-22,
AS Footnote 4
None
No objection
SC-A2
Yes
None
No objection
SC-A3
Deleted from
ASME PRA
Standard
---
---
---
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
SC-A4
Yes
No objection
SC-A4a(1)
Yes
IE-6, DE-5
No objection
Confirm that this
requirement is met.
This can be done by
citing either peer
review documentation
conclusions or
examples from your
model. Although
there is no explicit
requirement in NEI
00-02 that mitigating
systems shared
between units be
identified, in practice,
review teams have
evaluated this.
SC-A5
Partial
AS-21, AS-23,
AS-20
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
SC-A6
Yes
No objection
SC-B1
Yes
AS-18, SY-17,
TH-4, TH-6, TH7
None
No objection
SC-B2
No
TH-4, TH-8
No objection
SC-B3
Yes
No objection
SC-B4
Yes
No objection
SC-B5
Yes
TH-9, TH-7
None
No objection
SC-B6
Deleted from
ASME PRA
Standard
---
---
---
SC-C1(2)
Yes
None
ST-13, SY-10,
SY-17, SY-27,
TH-8, TH-9, TH10, AS-17, AS-18,
AS-24, HR-30
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
SC-C2(2)
Partial
ST-13, SY-10,
SY-17, SY-27,
TH-8, TH-9, TH10, AS-17, AS-18,
AS-24, HR-30
No objection
Action is to confirm
availability of
documentation. In
general, specified
documentation items
not explicitly
addressed in NEI 0002 checklists were
addressed by the peer
review teams. If not
available,
documentation may
need to be generated
to support particular
applications or
respond to NRC RAIs
regarding applications.
SC-C3(2)
Partial
QU-27, QU-28,
QU-29, QU-34
No objection with
Clarification: See staff
position on definition of key
assumption and key source
of uncertainty in Appendix
A.
SC-C4
Deleted from
ASME PRA
Standard
---
---
---
Systems Analysis
SY-A1
Yes
SY-4, SY-19
None
No objection
SY-A2
Yes
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
SY-A3
Yes
SY-A4
Partial
DE-11, SY-10,
SY Footnote 5
No objection
Confirm that this
requirement is met.
This can be done by
citing either peer
review results or
example
documentation. NEI
00-02 does not
address interviews
with system engineers
and plant operators to
confirm that the model
reflects the as-built,
as-operated plant.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
Confirm this
requirement is met,
and that the PRA
considered both
normal and abnormal
system alignments.
This can be done by
citing either peer
review results or
example
documentation.
Although NEI 00-02
does not explicitly
address both normal
and abnormal
alignments, their
impacts are generally
captured in the peer
review of the listed
elements.
No objection
SY-A5
Partial
QU-12, QU-13,
SY-8, SY-11
SY-A6
Yes
No objection
SY-A7
Yes
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
SY-A8
Partial
SY-6, SY-9
No objection
Check to ensure
boundaries are
properly established.
This can be done by
citing either peer
review results or
example
documentation. NEI
00-02 does not
address component
boundaries except for
EDGs. There is no
explicit requirement
that addresses
modeling shared
portions of a
component boundary.
In practice, the peer
reviews have
examined consistency
of component and data
analysis boundaries.
SY-A9
Deleted from
ASME PRA
Standard
---
---
SY-A10
Partial
SY-9
SY-A11
Yes
AS-10, AS-13,
AS-16, AS-17,
AS-18, SY-12,
SY-13, SY-17,
SY-23
None
---
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
Partial
No objection
Document that
modeling is consistent
with exclusions
provided in SY-A14.
Consistent with subelement SY-A12 of
the ASME PRA
Standard, critical
passive components
whose failure affects
system operability
should be included in
system models.
SY-A12a(1) Partial
Document that
No objection
modeling is consistent
with exclusions
provided in SY-A12a.
SYA12b(3)
Partial
SY-15, SY-17
Document that
No objection
modeling incorporates
flow diversion failure
modes.
SY-A13
Yes
DA-4, SY-15,
SY-16
None
No objection
SY-A14
No
No objection
SY-A15
Yes
No objection
SY-A16
Yes
No objection
SY-A12
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
SY-A17
Yes
AS-13, SY-10,
SY-11, SY-13,
SY-17
None. SY-A17 is
evaluated in the NEI
00-02 PRA peer
review as follows:
No objection
SY-10 Failures or
system termination
(trip) due to spatial or
environmental effects.
SY-11 Failure modes
induced by accident
conditions.
SY-13 System
Termination (failure
or trip) due to
exhaustion of
inventory (water, air).
SY-17 Success
Criteria evaluation
determined by plantspecific analysis that
includes system trips
or isolations on plant
parameters.
AS-13 Failure of
systems due to time
phased effects such as
loss of battery voltage.
SY-A18
Yes
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
SY-A18a(3) No
No objection
Confirm this is
accounted for in the
PRA. NEI 00-02 does
not explicitly identify
the criteria for
tracking and modeling
of coincident
maintenance actions
that may lead to
unavailability of
multiple redundant
trains or systems.
Verify SY-A19 has
been met. Ensure
there is a documented
basis (engineering
calculations are not
necessary) for
modeling of the
conditions addressed.
NEI 00-02 focuses on
environmental
limitations.
No objection
SY-A19
Yes
AS-18, DE-10,
SY-11, SY-13,
SY-17, TH-8
SY-A20
Partial
SY-A21
Yes
SY-18
No objection
None. Comment:
Footnote to SY-18
explains lack of Grade
provision for this subelement.
SY-A22
Yes
SY-24, DA-15,
QU-18, SY-12
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
SY-A23
Deleted from
ASME PRA
Standard
---
---
---
SY-B1
Yes
DA-8, DA-14,
None
DE-8, DE-9, SY-8
No objection
SY-B2
Not required
for Capability
Category II
None
No objection
SY-B3
Yes
None
No objection
SY-B4
Yes
DA-8, DA-10,
DA-11, DA-12,
DA-13, DA-14,
DE-8, DE-9, QU9, SY-8
None
No objection
SY-B5
Yes
None
No objection
SY-B6
Yes
SY-12, SY-13
SY-B7
Yes
AS-18, SY-13,
None
SY-17, TH-7, TH8
No objection
SY-B8
Yes
DE-11, SY-10
None
No objection
SY-B9
Deleted from
ASME PRA
Standard
---
---
---
SY-B10
Yes
SY-12, SY-13
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
SY-B11
Yes
No objection
SY-8, SY-12, SY- Confirm by citing
13
either peer review
documentation/conclu
sions or examples
from your model.
NEI 00-02 does not
explicitly address
permissives and
control logic. In
practice, the items in
SY-B11 have
generally been
examined in the peer
reviews.
SY-B12
Yes
SY-13
SY-B13
No
SY-B14
Partial
DE-6, AS-6
No objection
Confirm by citing
either peer review
documentation/conclu
sions or examples
from your model.
Ensure that modeling
includes situations
where one component
can disable more than
one system.
SY-B15
Yes
SY-11
None
No objection
SY-B16
Yes
SY-8
None
No objection
None
No objection
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
SY-C1(2)
Yes
None
SY-C2(2)
Partial
No objection
Action is to confirm
availability of
documentation. In
general, specified
documentation items
not explicitly
addressed in NEI 0002 checklists were
addressed by the peer
review teams. If not
available,
documentation may
need to be generated
to support particular
applications or
respond to NRC RAIs
regarding applications.
Comment: Footnote
to SY-18 explains lack
of Grade provision for
this sub-element.
SY-C3(2)
Partial
QU-27, QU-28,
QU-29, QU-34
No objection with
Clarification: See staff
position on definition of key
assumption and key source
of uncertainty in Appendix
A.
HR-4, HR-5
Determine if analysis
has included and
documented failure to
restore equipment
following test or
maintenance.
No objection
No objection
Yes
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
HR-A2
Yes
HR-4, HR-5
None
No objection
HR-A3
Yes
DE-7, HR-5
None
No objection
HR-B1
Yes
HR-5, HR-6
None
No objection
HR-B2
Partial
HR-C1
Yes
HR-C2
Yes
HR-7, HR-27,
SY-8, SY-9
No objection
Confirm that this
requirement is met.
The specific list of
impacts in HR-C2 is
not included in NEI
00-02; however, in
practice, the peer
reviewers (in
reviewing subelements HR-7 and
related sub-elements)
addressed these items.
HR-C3
Yes
HR-5, HR-27,
SY-8, SY-9
None
No objection
HR-D1
Yes
HR-6
None
No objection
HR-D2
Yes
HR-6
None
No objection
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
No objection
Action is to confirm
that HR-D3 is met.
This item is implicitly
included in the peer
review of HRA by
virtue of the
assessment of the
crews ability to
implement the
procedure in an
effective and
controlled manner.
The pre-initiator HRA
adequacy is
determined reasonable
and representative
considering the
procedure quality.
HR-D3
No
HR-D4
Partial
HR-6
No objection
Use the ASME
standard for
requirements. NEI
00-02 does not
explicitly cite the
treatment of recovery
actions for preinitiators. PRA
implementation varied
among utilities with
some using screening
values and others
incorporating
recovery. The peer
review team examines
this treatment.
HR-D5
Yes
DE-7, HR-26,
HR-27
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
HR-D6
No
No objection
HR-D7
Not required
for Capability
Category II
None
No objection
HR-E1
Yes
AS-19, HR-9,
HR-10, HR-16,
SY-5
None
HR-E2
Yes
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
HR-E3
Partial
HR-10, HR-14,
HR-20
No objection
The ASME standard
supporting
requirements are to be
used during the selfassessment to confirm
that the ASME intent
is met for this
requirement. NEI 0002 does not explicitly
specify the same level
of detail that is
included in the ASME
standard. The peer
review team
experience is relied
upon to investigate the
PRA given general
guidance and criteria.
HR-E4
Partial
HR-14, HR-16
No objection
The ASME standard
supporting
requirements are to be
used during the selfassessment to confirm
that the ASME intent
is met for this
requirement. NEI 0002 does not explicitly
specify the same level
of detail that is
included in the ASME
standard. The peer
review team
experience is relied
upon to investigate the
PRA given general
guidance and criteria.
HR-F1
Yes
AS-19, HR-16,
SY-5
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
HR-F2
Partial
AS-19, HR-11,
HR-16, HR-17,
HR-19, HR-20,
SY-5
HR-G1
Yes
HR-15, HR-17,
HR-18
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
HR-G2
Yes
HR-2, HR-11
No objection
None. NEI 00-02
criteria for Grade 3
require a methodology
that is consistent with
industry practice.
This includes the
incorporation of both
the cognitive and
execution (human
error probabilities) in
the HEP assessment.
HR-11 provides
further criteria to
ensure that the
cognitive portion of
the HEP uses the
correct symptoms to
formulate the crews
response. Selfassessment needs to
document if both
cognitive and
execution errors are
included in the
evaluation of HEPs.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
HR-G3
Partial
HR-17, HR-18
No objection
The ASME standard
supporting
requirements are to be
used during the selfassessment to confirm
that the ASME intent
is met for this
requirement. NEI 0002 does not explicitly
enumerate the same
level of detail that is
included in the ASME
standard. However,
by invoking the
standard HRA
methodologies the
performance shape
factors are necessarily
evaluated. The peer
review team
experience is relied
upon to investigate the
PRA given general
guidance and criteria.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
HR-G4
Partial
AS-13, HR-18,
HR-19, HR-20
No objection
The ASME standard
supporting
requirements are to be
used during the selfassessment to confirm
that the ASME intent
is met for this
requirement. NEI 0002 does not explicitly
cite the necessity to
define the time at
which operators are
expected to receive
indications. However,
invoking the standard
HRA methods leads to
the necessity for the
analysts to define this
input to the HRA.
The peer review team
experience is relied
upon to investigate the
PRA given general
guidance and criteria.
HR-G5
Partial
HR-16, HR-18,
HR-20
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
HR-G6
Yes
HR-12
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
HR-G7
Partial
DE-7, HR-26
HR-G8
Not required
for Capability
Category II
---
---
---
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
No objection
HR-G9
No
HR-H1
Yes
HR-21, HR-22,
HR-23
No objection
The self-assessment
needs to confirm that
the requirements in
HR-H1 in the ASME
standard were
addressed in the HRA.
HR-H2
Yes
HR-22, HR-23
No objection
The self-assessment
needs to confirm that
all the requirements of
HR-H2 in the ASME
standard were
included in the HRA.
HR-H3
Yes
HR-26
None
No objection
HR-I1(2)
Partial
HR-28, HR-30
None
No objection
HR-I2(2)
Partial
HR-28, HR-30
No objection
Action is to confirm
availability of
documentation. In
general, specified
documentation items
not explicitly
addressed in NEI 0002 checklists were
addressed by the peer
review teams. If not
available,
documentation may
need to be generated
to support particular
applications or
respond to NRC RAIs
regarding applications.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
HR-I3(2)
Partial
QU-27, QU-28,
QU-29, QU-34
No objection with
Clarification: See staff
position on definition of key
assumption and key source
of uncertainty in Appendix
A.
Data Analysis
DA-A1
Yes
DA-A1a(1)
No
No objection
DA-A2
No
No objection
DA-A3
Yes
No objection with
Qualification: The subject
matter in DA-A3 is not
explicitly addressed in NEI
00-02 (not a critical
requirement since
identification of the needed
parameters would be a
natural part of the data
analysis).
DA-B1
Yes
DA-5
No objection
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
No objection
Confirm that this
requirement is met.
NRC comment:
Grouping criteria
listed in DA-5 should
be supplemented with
a caution to look for
unique components
and/or operating
conditions and to
avoid grouping them.
Peer review teams
were careful to assess
plant-specific data
evaluations to identify
cases where outlier
data values or
components were not
properly accounted
for.
DA-B2
Yes
DA-5, DA-6
DA-C1
Yes
No objection
DA-C2
Yes
No objection
DA-C3
Partial
No objection
DA-4, DA-5, DA- Use the ASME
6, DA-7, MU-5
standard for
requirements. NEI
00-02 does not
enumerate the items
considered appropriate
in a plant-specific data
analysis.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
DA-C4
No
No objection
DA-C5
No
No objection
DA-C6
Yes
DA-6, DA-7
No objection
DA-C7
Yes
DA-6, DA-7
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
DA-C8
Yes
No objection
DA-C9
Yes
No objection
DA-C10
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
No objection
DA-C11
No
DAC11a(3)
No
No objection
Use the ASME PRA
Standard for
requirements. PRA
peer review teams
found that support
system unavailabilities
are treated within the
support system and
not within the
associated frontline
system.
DA-C12
No
No objection
DA-C13
No
No objection
DA-C14
Yes
None
No objection
DA-15, AS-16,
SY-24
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
No objection
IE-13, IE-15, IE- Confirm that this
16, AS-16, DArequirement is met.
15, SY-24, QU-18 Although it is
relatively rare to see
credit taken for repair
of failed equipment in
PRAs (except in
modeling of support
system initiating
events), any credit
taken for repair should
be well-justified,
based on ease of
diagnosis, the
feasibility of repair,
ease of repair, and
availability of
resources, time to
repair and actual data.
This can be done by
citing either peer
review results or
example
documentation.
DA-C15
Yes
DA-D1
No
No objection
DA-D2
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
DA-D3
Partial
DA-D4
No
QU-30
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
DA-D5
Partial
DA-D6
Partial
DA-D6a(3)
Partial (see
SelfAssessment
Action)
DA-14
No objection
No objection
Plant-specific
screening and
mapping of industrywide data is not
required for Capability
Category II.
However, if this
approach is used, DAD6a should be
confirmed to be met.
If it is performed, see
DE-9 from NEI 00-02.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
No objection
Use the ASME
standard for
requirements. NEI
00-02 does not
specifically address
how to deal with data
for equipment that has
been changed.
DA-D7
No
DA-E1(2)
Partial
DA-1, DA-19,
DA-20, DE-9
None
DA-E2(2)
Partial
DA-1, DA-19,
DA-20, DE-9
No objection
Action is to confirm
availability of
documentation. In
general, specified
documentation items
not explicitly
addressed in NEI 0002 checklists were
addressed by the peer
review teams. If not
available,
documentation may
need to be generated
to support particular
applications or
respond to NRC RAIs
regarding applications.
DA-E3(2)
Partial
QU-27, QU-28,
QU-29, QU-34
No objection
No objection with
Clarification: See staff
position on definition of key
assumption and key source
of uncertainty in Appendix
A.
Internal Flooding
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-A1
No
No objection
IF-A1a(1)
No
No objection
IF-A1b(1)
No
No objection
IF-A2
ASME PRA
Deleted from
Standard
---
---
IF-A3
No
No objection
IF-A4
No
No objection
---
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-B1
No
No objection
IF-B1a(4)
No
No objection
IF-B1b(3)
No
No objection
IF-B2
No
No objection
IF-B3
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-B3a(3)
No
IF-B4
Deleted from
ASME PRA
Standard
IF-C1
No objection
---
---
No
No objection
IF-C2
No
No objection
IF-C2a(1)
No
No objection
IF-C2b(2)
No
No objection
---
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-C2c(5)
No
No objection
IF-C3
No
No objection
IF-C3a(1)
No
No objection
IF-C3b(3)
No
No objection
IF-C3c(6)
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-C4
No
No objection
IF-C4a(4)
No
No objection
IF-C5
No
No objection
IF-C5a(1)
No
No objection
IF-C6
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-C7(3)
No
No objection
IF-C8(3)
No
No objection
IF-C9(3)
No
No objection
IF-D1
No
No objection
IF-D2
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-D3
No
No objection
IF-D3a(3)
No
No objection
IF-D4
No
No objection
IF-D5
No
No objection
IF-D5a(1)
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-D6(3)
No
No objection
IF-D7(3)
No
No objection
IF-E1
No
No objection
IF-E2
Deleted from
ASME PRA
Standard
---
---
IF-E3
No
No objection
IF-E3a(3)
No
No objection
---
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-E4
No
No objection
IF-E5
No
No objection
IF-E5a(1)
No
No objection
IF-E6
No
No objection
IF-E6a(1)
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-E6b(1)
No
No objection
IF-E7
No
No objection
IF-E8(3)
No
No objection
IF-F1(2)
No
No objection
IF-F2(2)
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IF-F3(2)
No
No objection
Quantification Analysis
QU-A1
Yes
No objection
The requirement in
QU-A1 is not
explicitly stated in any
element, but is
achieved through
compliance with the
identified NEI 00-02
elements and others
that support
complying with those
elements.
QU-A2a
Yes
QU-8
None
QU-A2b(1) No
QU-A3
Yes
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
QU-A4
Yes
QU-18, QU-19
None
No objection
QU-B1
Yes
QU-6
None
No objection
QU-B2
Yes
QU-21, QU-22,
QU-23, QU-24
QU-B3
Partial
QU-21, QU-22,
QU-23, QU-24
The self-assessment
should confirm that
the final truncation
limit is such that
convergence toward a
stable CDF is
achieved.
No objection
QU-B4
Yes
QU-4
None
QU-B5
Yes
QU-14
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
QU-B6
Yes
No objection
Check for proper
accounting of success
terms. The NEI 00-02
guidance adequately
addresses this
requirement, but QU25 should not be
restricted to
addressing just delete
terms.
QU-B7a
Yes
QU-26
None
No objection
QU-B7b(1)
Yes
QU-26
None
No objection
QU-B8
No
No objection
QU-B9
Partial
SY-9
QU-C1
Yes
QU-10, QU-17,
HR-26, HR-27
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
QU-C2
Yes
QU-10, QU-17
No objection
Verify dependencies
in cutsets/sequences
are assessed. Verify
that dependence
between the HFEs in a
cutset or sequence is
assessed in accordance
with ASME SRs HRD5 and HR-G7.
QU-C3
Yes
QU-20
QU-D1a
Yes
No objection
No objection; the
requirements in QU-D1 are
addressed primarily in QU8. The requirements in QU9, QU-10, QU-14, QU-16,
and QU-17 appear to be
focused on modeling and not
interpretation of results. As
such, they are redundant to
elements in the data,
dependent failure, and HRA
sections.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
QU-D1b(1) Yes
No objection; the
requirements in QU-D1 are
addressed primarily in QU8. The requirements in QU9, QU-10, QU-14, QU-16,
and QU-17 appear to be
focused on modeling and not
interpretation of results. As
such, they are redundant to
elements in the data,
dependent failure, and HRA
sections.
QU-D1c(1)
Yes
No objection; the
requirements in QU-D1 are
addressed primarily in QU8. The requirements in QU9, QU-10, QU-14, QU-16,
and QU-17 appear to be
focused on modeling and not
interpretation of results. As
such, they are redundant to
elements in the data,
dependent failure, and HRA
sections.
QU-D2
Deleted from
ASME PRA
Standard
---
---
---
QU-D3
Yes
QU-8, QU-11,
QU-31
None
No objection; consistency
with other PRA results is
addressed in QU-11 and
QU-31.
QU-D4
Yes
QU-15
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
QU-D5a
Yes
QU-8, QU-31
QU-D5b(5) No
QU-E1
Yes
QU-27, QU-28,
QU-30
No objection
No objection
No objection with
Clarification: QU-30 does
not provide guidance on
sources of uncertainty.
See staff position on
definition of key assumption
and key source of
uncertainty in Appendix A.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
QU-E2
Yes
QU-27, QU-28,
QU-30
No objection.
Confirm that this
requirement is met.
QU-27 and QU-28
focus on the
assumptions and
unusual sources of
uncertainty.
Assumptions and
unusual sources of
uncertainty
correspond to plantspecific hardware,
procedural, or
environmental issues
that would
significantly alter the
degree of uncertainty
relative to plants that
have previously been
assessed, such as
NUREG-1150 or the
Risk Methodology
Integration and
Evaluation Program
(RMIEP). Unusual
sources of uncertainty
could also be
introduced by the
PRA methods and
assumptions. In
practice, when
applying NEI 00-02
sub-elements QU-27
and QU-28, the
reviewers considered
the appropriateness of
the assumptions.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
QU-E3
Partial
QU-30
QU-E4
Partial
QU-28, QU-29,
QU-30
No objection
QU-F1(2)
Partial
QU-31, QU-32,
QU-34
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
QU-F2(2)
Yes
QU-F3(2)
Partial
QU-31
No objection
QU-F4(2)
No
QU-27, QU-28,
QU-32
No objection
QU-F5(2)
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
QU-F6(3)
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LERF Analysis
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-A1
Partial
AS-14, AS-21,
AS-23, L2-7
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-A2
Partial
No objection
L2-7, L2-8, AS-21 Confirm that the
specifics identified in
LE-A2 are included in
the PRA.
NUREG/CR-6595
methodology is not
adequate for
Capability Category II
and III. It is noted
that NEI 00-02 does
not address criteria for
the grouping into
PDSs (i.e., there are
no criteria provided as
to what information
has to be transferred
from the Level 1 to
the Level 2 analysis).
L2-7 states the
transfer from Level 1
to Level 2 should be
done to maximize the
transfer of relevant
information, but does
not identify the type
of information that
must be transferred.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-A3
Partial
L2-7, L2-8
No objection
Confirm that the
specifics identified in
LE-A3 are included in
the PRA.
NUREG/CR-6595
methodology is not
adequate for
Capability Category II
and III. It is further
noted that NEI 00-02
does not address
criteria for the
grouping into PDSs
(i.e., there are no
criteria provided as to
what information has
to be transferred from
the Level 1 to the
Level 2 analysis). L27 states the transfer
from Level 1 to Level
2 should be done to
maximize the transfer
of relevant
information, but does
not identify the type
of information that
must be transferred.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-A4
Partial
L2-7,L2-8, L29,
L2-24, L2-25
No objection
Confirm that the
specifics identified in
LE-A4 are included in
the PRA.
NUREG/CR-6595
methodology is not
adequate for
Capability Category II
and III. It is further
noted that NEI 00-02
does not address
criteria for the
grouping into PDSs
(i.e., there are no
criteria provided as to
what information has
to be transferred from
the Level 1 to the
Level 2 analysis). L27 states the transfer
from Level 1 to Level
2 should be done to
maximize the transfer
of relevant
information, but does
not identify the type
of information that
must be transferred.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-A5
Partial
L2-7, L2-8,
L2-9, L2-24, L225
No objection
Confirm that the
specifics identified in
LE-A5 are included in
the PRA.
NUREG/CR-6595
methodology is not
adequate for
Capability Category II
and III. It is further
noted that NEI 00-02
does not address
criteria for the
grouping into PDSs
(i.e., there are no
criteria provided as to
what information has
to be transferred from
the Level 1 to the
Level 2 analysis). L27 states the transfer
from Level 1 to Level
2 should be done to
maximize the transfer
of relevant
information, but does
not identify the type
of information that
must be transferred.
L2-24 and L2-25
clearly indicate that
the dependencies of
systems, crew actions,
and phenomena in the
entire PRA need to be
integrated into the
model.
LE-B1
Yes
None
No objection
LE-B2
Yes
L2-13, L2-14
None
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-B3(3)
No
LE-C1
Yes
No objection
Confirm that the
specifics identified in
LE-C1 with regard to
the basis for assigning
sequences to the
LERF and non-LERF
category meet the
intent of LE-C1.
LE-C2a
Yes
LE-C2b(1)
Partial
No objection
Confirm that the
specifics identified in
LE-C2b are included
in the PRA. Repair of
equipment would be
subsumed under
recovery actions in
L2-9 and L2-5. If
credit was taken for
repair, actual data and
sufficient time must
be available and
justified.
No objection
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-C3
Partial
No objection
Confirm that the
justification for
inclusion of any of the
features listed in LEC3 meets the revised
requirements of LEC3 in Addendum B of
the ASME standard.
LE-C4
Partial
L2-4, L2-5,
L2-6
The self-assessment
needs to confirm the
revised requirements
of LE-C4 in
Addendum B of the
ASME standard.
No objection
LE-C5
Yes
AS-20, AS-21,
L2-7, L2-11, L225
None
No objection
LE-C6
Yes
No objection
LE-C7
Partial
No objection
Confirm that the
requirements in LEC7 are included in the
PRA.
LE-C8a
Partial
L2-11, L2-12
No objection
Confirm that the
treatment of
environmental impacts
meets the revised
requirements in LEC8a in Addendum B
of the ASME
standard.
LE-C8b(1)
Partial
L2-11, L2-12
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-C9a
Partial
No objection
AS-20, L2-11, L2- Confirm that the
12, L2-16, L2-24, treatment of
L2-25
environmental impacts
meets the revised
requirements of LEC9a in Addendum B
of the ASME
standard. NEI 00-02
does not differentiate
between containment
harsh environments
and containment
failure effects on
systems and operators.
This was typically
addressed during peer
reviews.
LE-C9b(1)
Partial
LE-C10
Partial
No objection
L2-7, L2-8,
The revised
L2-13, L2-24, L2- requirements of LE25
C10 in Addendum B
of the ASME standard
need to be considered
in the self-assessment.
Containment bypass is
explicitly identified in
the failure modes
addressed by the
LERF analysis.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
No objection
LE-D1a
Partial
LE-D1b(1)
Partial
LE-D2
Partial
L2-14, L2-19
No objection
Confirm the
requirements of LED2 are implemented.
NEI 00-02 does not
explicitly enumerate
this supporting
requirement.
However, the
containment failure
analysis includes by
its nature for
Capability Category II
the location of the
failure mode.
Therefore, both the
analysis and the peer
review have typically
addressed this SR.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
IE-14, ST-9
No objection
Confirm the
requirements of LED3 are implemented
in accordance with
Addendum B. In
practice, peer review
teams evaluated the
ISLOCA frequency
calculation. F&Os
under IE and AS
would be written if
this was not adequate.
LE-D3
Partial
LE-D4
No
No objection
LE-D5
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-D6
Partial
No objection
L2-16, L2-18, L2- Confirm that the
19, L2-24, L2-25 containment isolation
treatment meets the
revised requirements
of LE-D6 in
Addendum B of the
ASME standard. The
guidance provided in
NEI 00-02 does not
explicitly enumerate
the requirements in
LE-D6. However, the
PRAs were
constructed to address
the requirements of
NUREG1335, which
explicitly required
containment isolation
evaluation. Therefore,
the PRAs and the Peer
Reviews have
typically addressed
this SR.
LE-E1
Yes
L2-11, L2-12
None
No objection
LE-E2
Partial
No objection
LE-E3(3)
No
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-E4(7)
Partial
QU sub-elements
applicable to
LERF
LE-F1a
Yes
No objection
LE-F1b(1)
Yes
L2-26
None
No objection
LE-F2
No
QU-27, L2-26
No objection
LE -F3(3)
No
No objection
LE-G1(2)
Yes
The self-assessment
needs to confirm that
the parameter
estimation meets the
revised requirements
of LE-E4 in
Addendum B of the
ASME standard.
No objection
No objection
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-G2(2)
Partial
No objection
L2-26, L2-27, L2- In general, specified
28
documentation items
not explicitly
addressed in NEI 0002 checklists were
addressed by the peer
review teams. Action
is to confirm
availability of
documentation. If not
available,
documentation may
need to be generated
to support particular
applications or
respond to NRC RAIs
regarding applications.
LE-G3(2)
Partial
No objection
L2-26, L2-27, L2- In general, specified
28
documentation items
not explicitly
addressed in NEI 0002 checklists were
addressed by the peer
review teams. Action
is to confirm
availability of
documentation. If not
available,
documentation may
need to be generated
to support particular
applications or
respond to NRC RAIs
regarding applications.
LE-G4(2)
Partial
QU-27, QU-28,
QU-29, QU-34
No objection with
Clarification: See staff
position on definition of key
assumption and key source
of uncertainty in Appendix
A.
ASME
Std SR
Addressed by
NEI 00-02?
NEI Assessment
Applicable NEI
00-02 Elements
Regulatory Position
Note: Index number referenced in ASME Std SR column references the index numbers in the ASME PRA
Standard RA-Sb-2005. The index numbers have changed in the ASME/ANS PRA Standard RA-Sa-2009.
LE-G5(2)
Partial
LE-G6(3)
No
No objection
L2-26, L2-27, L2- In general, specified
28
documentation items
not explicitly
addressed in NEI 0002 checklists were
addressed by the peer
review teams. Action
is to confirm
availability of
documentation. If not
available,
documentation may
need to be generated
to support particular
applications or
respond to NRC RAIs
regarding applications.
NEI 00-02 does not
address this
supporting
requirement. Use
ASME PRA Standard
Addendum B SR LEG6 for requirements.
No objection
Subdivided from a previous SR in Addendum A of the ASME PRA Standard. It is noted that Addendum B of the
ASME PRA Standard has subdivided a number of SRs for the purpose of clarifying and separating the assignment of
Capability Category of the SR in a clearly delineated fashion.
New SR added.
Formerly IF-A2.
Formerly IF-E2.
Formerly LE-E3.
APPENDIX C
NRC POSITION ON THE NEI PROCESS FOR PERFORMING FOLLOWON PRA PEER REVIEWS FOR INTERNAL EVENTS (NEI 05-04)
The Nuclear Energy Institute (NEI) Peer Review Process for performing follow-on probabilistic
risk assessments (PRAs) peer reviews is documented in NEI 05-04, Revision 1.
This appendix provides the staffs position on the NEI 05-04. The staffs positions are
categorized as following:
Table C-1 provides the NRC position on the NEI Follow-on Peer Review Process documented in
NEI 05-04, Revision 1. A discussion of the staffs concern (issue) and the staff proposed resolution is
provided. In the proposed staff resolution, the staff clarification or qualification is indicated in either
bolded text (i.e., bold) or strikeout text (i.e., strikeout); that is, the necessary additions or deletions to the
guidance (as written in NEI 05-04) for the staff to have no objection are provided.
Issue
NEI 05-04 allows the use of
a peer review and self
assessment performed in
accordance with NEI 00-02
as a basis for the
demonstration of the
technical adequacy of the
PRA. The peer review
process and self-assessment
process in NEI 00-02 is based
on Addendum B to the
ASME PRA standard (RASb-2005). The staff position
on NEI 00-02 documented in
Appendix B of Revision 1 of
Regulatory Guide 1.200 is
based on the staff position of
RA-Sb-2005 as documented
in Appendix A of Revision 1
of Regulatory Guide 1.200.
However, since that time,
ASME has issued Addendum
C (RA-Sc-2007) and ASME
and ANS has issued a
revision and an addendum
(ASME/ANS RA-S-2008 and
RA-Sa-2009, respectively)
that incorporates the changes
in RA-Sc-2007. These
subsequent versions of the
PRA standard (e.g.,
ASME/ANS RA-Sa-2009)
contain requirements that
were revised or new
requirements that were added
(as compared to RA-Sb2005).
Position
Qualification
Resolution
It is the NRCs expectation that if the
results of the self-assessment are used to
demonstrate the technical adequacy of a
PRA for an application, differences
between the current version of the
Standard as endorsed in Appendix A and
the earlier version of the ASME PRA
Standard (i.e., RA-Sb-2005) be identified
and addressed.
No objection
--------------------
--------------------
Issue
Position
Resolution
Clarification
4th paragraph
Clarification
3.0
2nd paragraph
Clarification
Clarification
3.1
nd
2 paragraph
3.1
th
5 paragraph
Clarification
Clarification
3.2
Comparison
Against
Grading
Process for
NEI 00-02
Clarification
Clarification
Grade 1
No equivalent grade
Grade 2
Capability Category I
Grade 3
Capability Category II
Grade 4
th
12 and 13
paragraphs
4.7
--------------------
No objection
--------------------
Clarification
--------------------
No objection
--------------------
--------------------
No objection
--------------------
APPENDICES
A,B
Clarification
--------------------
No objection
--------------------
APPENDIX D
NRC POSITION ON THE NEI INTERNAL FIRE PEER REVIEW
PROCESS (NEI-07-12)
The Nuclear Energy Institute (NEI) Peer Review Process for a fire probabilistic risk assessment
(PRA) is documented in NEI 07-12, Revision 0, Version H. It provides guidance for the peer review of
probabilistic risk assessments (PRAs) and the grading of the PRA sub-elements into one of four capability
categories.
This appendix provides the staffs position on the NEI Fire PRA Peer Review Process (i.e., NEI
07-12). The staffs positions are categorized as following:
Table D-1 provides the NRC position on the NEI Fire PRA Peer Review Process documented in
NEI 07-12, Revision 0, Version H. A discussion of the staffs concern (issue) and the staff proposed
resolution is provided. In the proposed staff resolution, the staff clarification or qualification is indicated
in either bolded text (i.e., bold) or strikeout text (i.e., strikeout); that is, the necessary additions or
deletions to the guidance (as written in NEI 07-12) for the staff to have no objection are provided.
Index No
Global
--------------------
No objection
--------------------
Index No
1.6, 3rd
paragraph
Clarification
Clarification
2.2, footnote 5 Education beyond the
Bachelor's degree does not
necessarily equate to
practical experience
2.3, 2.4
--------------------
No objection
--------------------
--------------------
No objection
--------------------
Clarification
Index No
3.2 15th
paragraph
Clarification
Although the context
implies as much, it is only
the model uncertainty
characterization that
should be qualitative.
Parameter uncertainty
should be quantitative.
3.3, 2nd
paragraph
3.3.1
Clarification
--------------------
No objection
--------------------
th
9 paragraph
3.4 through
Index No
3.5
--------------------
No objection
--------------------
No objection
--------------------
Clarification
No objection
--------------------
--------------------
Appendices D through G:
--------------------
No objection
--------------------