ASTM E94-93 Radiograph
ASTM E94-93 Radiograph
ASTM E94-93 Radiograph
P
Standard Guide for
Radiographic Testing'
v. ,;,
Copyright by the American Society For Testing & Materials
Tue Oct 17 09:29:46 2000
A S T N E 9 4 73 1 0 7 5 9 5 3 0 0 5 3 0 7 2 3 B3b I
@E94
I
_ and techniques where industrial X-ray fdms are used as the TABLE 1 Typical SUIl HVL TNcknass h inch.s (mm) for
CQMtlQn Emrnhs
fY.:
recording media
4.2 Limitatiom-This d d e does not take into consider-
ation special benefits andhitations resulting fmm the use
of nonfdm recording media or readouts such as paper, t a m
xeroradiography, fluoroscopy, and'electronic image intensi-
fication devices. Although reference is made to documents
that may be used in the identification and grading, where
applicabk, of representative discontinuitiesin common metal
castings and welds, no attempt has been made to set standards
of acceptance for any material or production prows. Radi-
omohv will be consistent in xnsitivity and resolution only if
t6e dfT& of all details of techniques, buch as geometry, film,
filtration, viewing, etc., is obtained and maintained.
some situations for X-ray energies in the 1 to 25 MV range
PART I-EQUIPMENT AND PROCEDURE primarily because of reduced scatter.
5. Rsdiogrnphic Quality h v e l 7. Radiographic Equivalence Factors
5.1 The quality level usually required for radiography is 7.1 The radiographic equivalence factor of a material is
2 56 (2-2T when using hole type IQI) unless a higher or lower that factor by which the thickness of the material must be
quality is agreed upon between the pu~haserand the multiplied to give the thickness of a 'standard" material
supplier. At the 2 % subject contrast level, thm quality (often steel) which has the same absorption. Radiographic
levels of inspection, ZIT, 2-2T, and 2-4T, are available equivalence factors of several of the more common metals
through the design and application of the IQI (Practice are given in Table 2, with steel arbitrarily assigned a factor of
E 1025, Table I). Other levels of inspection are available in 1.0. The factors may be used:
Practice E 1025. Table 1. The level of insmtion s~ecified 7.1.1 To determine the practical thickness limits for
should be ba.&on the service rcquiremenk of the product. radiation s o u m for materials other than steel, and
Great care should be taken in s~ecifvinxaualitv levels 2-IT. 7.1.2 To determine exposun factors for one metal from
LIT, and I-2T by first determkinith; ihese$uality level;: exposure techniques for other metals.
can be maintained in production radiography.
8. Film
/I, NOTE2-The first number of the aualih, level dcdnnntion rrfm to
.. ~ ~
material of the filter will vary depending upon the following: subject to the same considerations as outlined in 9.4. Lead
9.4.1 The material radiographed. screens lessen the scatter reaching the film regardless of
9.4.2 Thickness of the material radiographed. whether the screens permit a decrease or n d t a t e an
9.4.3 Variation of thickness of the material radiographed. increase in the radiographic exposure. To avoid image
9.4.4 E n e w sDectrum of the radiation used. unsharpness due to screens, there should be intimate contact
9.4.5 The Tmprovement desired (increasing or decreasing between the lead scnen and the fim during exposure.
contrast). Filter thickness and material can be calculated or 12.1.2 Lead foil screens of appropriatethickness should
determiiled empirically. be used whenever they improve radiographic quality or pene-
trameter sensitivity or both. The thickness of the front lead
10. Masking screens should be klected with care to avoid excessive filtra-
10.1 Masking or blocking (surrounding spximens or
covering thin sections with an absorptive material) is helpful
tion in the radiom~hy
ularly at the lower kilovoltages. ~ n g e n e dthere
,
.
- - .of thin or Liaht alloy materials..Dartic-
is no expo-
in reducing scattered radiation. Such a material can also be sure advantage to the use of 0.005 in. in front and back lead
used to equalize the absorption of different sections, but the screens below 125 kV in the radiography of %in. (6.35-mm)
loss of detail may be high in the thinner sections. or lesser thickness steel. As the kilovoltage is increased to
penetrate thicker sections of steel, however, then is a signifi-
11. BackScntter Protection cant exposure advantage. In addition to intensifying action.
11.1 Effects of back-scattered radiation can be reduced by the back lead screens -are used as protection back:
confining the radiation beam to the smallest practical cross scattered radiation (see W o n 1I) and their thickness is
section and by placing lead behind the fim. In some cases only imlmrtant for this function. As exposun energy is
either or boththe back lead scrcen and the lead contained in increased to penetrate greater thickneswa of a given subject
the back of the cassette or fim holder will furnish adequate material, it is customary to increase lead screen thickness.
pmtection against back-scattered radiation. In other in- For radiography using radioactive sources, the minimum
stances, this must be supplemented by additional lead thickness of the front lead screen should be 0.005 in. (0.13
shielding behind the casette or fdm holder. mm) for iridium-192, and 0.010 in. (0.25 mm) for cobalt-60.
11.2 If there is any question about the adequacy of 12.2 OfherMetallic Screen Materials:
protection from back-scattered radiation, a characteristic 12.2.1 Lead oxide screens perform in a similar manner to
symbol (frequently a %in. (3.2-mm) thick letter B) should lead foil meens e x w t that their euuivalence in lead foil
be anached to the back of the cassette or film holder, and a thickness approximat& 0.0005 in. (0.013 mm).
radiograph made in the normal manner. If the image of this 12.2.2 C o m r m e n s have somewhat less absomtion and
symbol appears on the radiograph as a l i i t e r density than intensification than lead screens, but may provide somewhat
background, it is an indication that protection against better radiographic sensitivity with higher energy above I
back-scattered radiation is insufficient and that additional ..-V. .~
M
precautions must be taken. 12.2.3 Gold, tantalum, or other heavy metal screens may
be used in caxs where lead cannot be used.
12. Screens 12.3 Fluorescenf Screens-Fluoresant screens may be
12.1 Mefallic Foil Screens: used as required providing the required image quality is
12.1.1 Lead foil screens are commonly used in direct con- achieved. Proper selection of the fluorescent meen is re-
tact with the films, and, depending upon their thickness, and quired to minimize image unsharpness. Technical informa-
composition of the s k m e n material. will exhibit an inten- tion about specific fluorescent screen products can be
sifying action at as low as 90 kV. In addition, any screen used obtained fmm the manufacturers. Good fdm-screen contact
in front of the film acts as a filter (Section 9) to preferentially and screen cleanliness are required for successful use of
absorb scattered radiation arising from the specimen, thus fluorescent scnens.
improving radiographic quality. The selection of lead meen 12.4 Screen Care-AU screens should be handled care
thickness, or for that matter, any metallic meen thickness, is filly to avoid dents and scratches, din, or gnase on active
O.n'lty
LOW- Ten4 Torord L o r Contrast
Hiqh-Tend Toror4 Hiph Contrast
>
surfaces. Grease and lint may be removed from lead screens Us= Ftld.
with a solvent. nuorcscent screens should be cleaned in when:
accordance with the rewmmendations of the manufacturer. (, = geometric unsharpness,
I
Screens showing evidence of physical damage should be F = size of the radiation source,
discarded. t = specimen thickness, when in contact with the Nm,
and
- - do = sourc~bjectdistance.
13.1 The various radiation intensities that penetrate an
obiect are rendered as different ohotomohic densities in a
ra&ograph. Using transmitted or re& light to view a -.NOTE 3 - 4 and 1 must be in the s m e units of m m n ; the units of
U. will k in the same units u F.
NOTE4-A n o m b i k t h e dcfcrmioation of U,is pivea in F a 3
fn'radiogmph, an observed change in film density over a (inch-pound units). Fy 4 nprrrcnu 8 nomogram in mcvic uniU
background is defined as contrast. Radiographic contrast Example:
depends mostly upon subject contrast and the film gradient. Given:
13.2 Subiect contrast is the ratio of radiation intensities
transmittedb~two selected portions of a specimen.
13.3 The fdm gradient is thc'value of the slope of the
tangent line drawn to a particular density point on the Draw a stlPiPht line ldadud in FE 3) betwan 500 mils on the F d e
characteristic curve to the abscissa. Film manufacturers can nad 1.5 in. 6 Ule t & ~ o t e th;pdint on intaration (6of& tine
furnish characteristic curves of their products. with the pivot line. Dnw 1Itrnipbt line (solid in Fa 3) from 40 in. on
13.4 The quality of radiography is influenced by many the do d e through point P md extend lo the Usxak. Intenstion of
variables; the effects of changes in some of these variables are thir Line with the Usd e g i gmmetTical
~ unsharpnas in mils, which
illustrated in Fig. 1.
Inasmuch as the source size, F,is usually fued for a given
14. Geometry
14.1 The focus-film distance necessary to reduce geo-
-
radiation source, the value of U. is essentially controlled by
the simple dJt ratio.
metric undramness to a nerrlimblc amount dewnds u w n the 14.2 Because X and gamma radiation is divergent, the
fdm or film-&n combi&tik, focal-spot Lze, andobject- radiographic image of an object, or of a structure within an
-
film d i c e . Geometric unshamnm is riven (see Fie.2(0N objcd, will be larger than the object or the structure itself.
The degree of enlargement will incnase with d e d n g
:+.by the equation:
E 94
sourcaobject (structun) distance and with increasing object 15.2.6 S o m or focus-fdm distance,
(structure)-film distance (Fig. 2(b)). 15.2.7 Kilovoltage or isotope type,
14.3 If the film is not parallel to the object, the radio- NOTE%For detailed information on Nm density and dewily
graphic image will be distorted because different parts of the mcarunment calibration, sss Rscticc E 1079.
radiographic image will be enlarged by different amounts. A
measun of the degree of distortion is given by the ratio of the 15.2.8 Screen type and thickness,
change in image size caused by distortion to the size of the 15.2.9 Curies or milliampere/minutes,
undistorted image (Fig. 2(c)). 15.2.10 Time of exposure,
14.4 Final acceptance of radiographs should be based on 15.2.11 Filter (in the primary beam),
T' the ability to see the prescribed penetrameter image and the 15.2.12 Timetemperature development for hand pro-
specified hole. The unsharpness formula is included for cessing; access time for automatic processing; timetemper-
information and guidance, and will operate within practical ature development for dry prowsing, and
limits, but is of less consequence as d/t ratios increase. 15.2.13 Processing chemistry brand name, if applicable.
15.3 The essential elements listed in 15.2 will be accurate
for isotopes of the same type, but will vary with X-ray
15. Exposure Cnlculntionr or Chnrts equipment of the same kilovoltage and milliampere rating.
15.1 Development or procurement of an exposure chart 15.4 Exposun charts should be developed for each X-ray
or calculator is the responsibility of the individual labora- machine and corrected each time a major camponent is
tory. replad, such as the X-ray tube or high-voltage transformer.
15.2 The essential elements of an exposure chart or 15.5 The exposun chart should be corrected when the
calculator must relate the following: processing chemicals an changed to a different manufactur-
15.2.1 Source or machine, er's brand or the timetemperature relationship of the
15.2.2 Material type, processor may be adjusted to suit the wcwsure chart. The
15.2.3 Material thickness, exposure chart, whenusing a dry processing method, should
15.2.4 Film type (relative speed), be comcted based u w n the timetem~eraturechances of the
15.2.5 Film density, (see Note 5), processor.
E 94
17.2.4 While Test Method E 746 plaque can be useful in exact locations should also be marked on the surface of the
quantifying relative radiographic image quality, these other part being radiographed, thus permitting the area of interest
applications of the plaque may be useful. to be located accurately on the part, and they should remain
,P on the part during radiographic inspection. Their exact
18. Identir~cationof and h t i o n Markers on Rndicgraphs location may be permanently marked in accordance with the
customer's requirements.
18.1 IdeMflcalion of Radiographs: 18.2.2 Location markers are also used in assisting the
18.1.1 Each radiograph must be identified uniquely so
that there is a permanent correlation between the part radiographic interpreter in marking off defective areas of
radiographed and the fdm. The type of identif~cationand components, castings, or defects in weldments: also, sorting
method by which identificationis achieved shall be as agreed good and rejectable items when more than one item is
upon between the customer and inspector. radiographed on the same fdm.
18.1.2 The minimum identification should at least in- 18.2.3 Sufficient markers must be used to provide evi-
clude the following: the radiographic facility's name, the dence on the radiograph that the required coverage of the
date, part number and serial number, if used, for unmislak- object being examined has been obtained, and that overlap is
able identification of radiographs with the specimen. The evident, especially during radiography of weldments and
letter R should be used to designate a radiograph of a repair castings.
area, and may include -1, -2, etc., for the number of repair. 18.2.4 Parks that must be identifled permanently may
18.2 Loeotion Markers: have the serial numbers or section numbers, or both,
18.2.1 Location markers (that is, lead or high-atomic stamped or written upon them with a marking pen with a
number metals or letters that are to appear as images on the Jpecial indelible ink, engraved, die stamped, or etched. In
radiographic fdm) should be placed on the part being any case, the part should be marked in an area not to be
,-\ examined, whenever practical, and not on the cassette. Their removed in subsequent fabrication. If die stamps an used.
E 94
caution is required to prevent breakage or future fatigue with promsing conditions It is, therefore, essential that the
I-. failure. The lowest stressed surface of the part should be used recommendations of the film, processor, and chemical
for this stamping. Where marking or stamping of the part is manufacturers be followed.
not permitted for some reason, a marked refmnce drawing 23.2 Aulomatic process in^. Dn-The essence of dw au-
or shooting sketch is recommended. tomatic processing is the p&se Mntrol of developmen<time
and temuerature which results in reoroducihiditv of radio-
PART 11-PROTECTION AND CARE OF UNPROCESSED graphic density. Film characteristic; must be compatible
FILM with processing conditions. It is, therefore, essential that the
19. Storage of FUm recommendations of the film and processor manufacturers
be followed.
19.1 Unexposed films should be stored in such a manner
that they are protected from the effects of light, pressure,
excessive heat, excessive humidity, damaging fumes or 24. Manual Recessing
vapors, or penetrating radiation. Fdm manufacturers should 24.1 Film and chemical manufacturers should be wn-
be consulted for detailed recommendations on fdm storage. sulted for detailed recommendations on manual film pro-
Storage of fdm should be on a "fmt in," "first out" basii. w i n g . This section outlines the steps for one acceptable
19.2 More detailed information on film storage is pro- method of manual processing.
vided in Guide E 1254. 24.2 Preparalion-No more film should be p r d
than can be accommodated with a minimum separation of
20. Safelight Test lh in. (12.7 mm). Hangers are loaded and solutions stimd
-'f 20.1 Fdms should be handled under s a f e l i t conditions before starting development.
in accordance with the film manufacturer's recommenda- 24.3 Start ofDevelopment-Start the timer and place the
tions. ANSI PH2.22 can be used to determine the adequacy films into the developer tank. Separate to a minimum
of safelight conditions in a darkroom. distance of 1/z in. (12.7 mm) and agitate in two directions for
about 15 s.
21. Cleanliness and Film Handling 24.4 Development-Normal development is 5 to 8 min at
21.1 Cleanliness is one of the most important require- 68'F (20%). Longer development time generally yields faster
ments for good radiography. Cassettes and screens must be film speed and slightly more contrast. The manufacturer's
kept clean, not only because dirt retained may cause recommendation should be followed in choosing a develop
exposure or processing artifacts in the radiographs, but ment time. When the temperahue is higher or lower,
development time must be changed. Again, consult manu-
because such dirt may also be transferred to the loadina
r...
bench, and subseguenily to other film or screens.
- facturer-recommended develovment time versus temvera-
21.2 The surface ofthe loadinn bench must be keot clean. lure charts. Other recommendations of the manufactukr to
Where manual processing is us% cleanliness will'be pro- be followed are re~lenishmentrates. renewal of solutions.
moted by arranging the darkroom with processing facilities and other smc ibstructions.
on one side and film-handling facilities on the other. The 24.5 Agitation--Shake the film horizontally and verti-
darkroom will then have a wet side and a dry side and the cally, ideally for a few seconds each minute during develop
chance of chemical contamination of the loading bench will ment. This will help film develop evenly.
be relatively slight. 24.6 Slop Bath or Rinse-ARer development is complete,
21.3 Films should be handled only at their edges, and with the activity of developer remaining in the emulsion should
dry, clean hands to avoid finger marks on film surfaces. be neutralized by an acid stop bath or, if this is not possible,
21.4 Sharp bending, exassive pressure, and rough han- by rinsing with vigorous agitation in clear water. Follow the
A fdm mandacturer's recommendation of stop bath composi-
I dling of any kind must be avoided.
tion (or length
- of alternative rinse).
.. time immersed. and life
PART Ill-PROCESSING PILMS AND MEWING AND of bath.
STORING RADIOGRAPHS 24.7 Fixing-The films must not touch one another in
the fixer. Agitate the hangers vertically for about 10 s and
22. Film Processing, Genenl again at the end of the first minute, to ensure uniform and
22.1 To produce a satisfactory radiograph, the care used rapid fixation. Keep them in the fixer until fixation is
in making the exposure must be followed by q u a l care in complete (that is, at least twice the clearing time), but not
processing. The most careful radiographic techniques can be more than 15 min in relativdy fresh fixer. Frequent agitation
n u l l i d by incorrect or improper darkroom procedures. will shorten the time of fmtion.
22.2 More detailed information on film processing is 24.8 Fixer Neutralizing-The use of a hypo eliminator or
provided in Guide E 999. fixer neutralizer between Gxation and washing may be
advantapus. These materials permit a reduction of both
23. Automatic Processing time and amount of water necessary for adequate washing.
23.1 AutomaficProcessing-The essence of the automatic The recommendations of the manufacturers as to prepara-
processing system is control. The p r m s o r maintains the tion, use, and useful life of the baths should be obaewed
chemical solutions at the proper temperature, agitates and rigorously.
noknishes the solutions automaticallv. and transwrts the 24.9 Washing-The washing efficiency is a fuction of
I- fiims mechanically at a carefully contrc&d speed thkghout wash water, its temperature, and flow, and the fdm being
the proaYing cycle. Film characteristics must be compatible washed. Generally, washing is very slow below 60'F (WC).
- PH1.41.
24.12 Drying-Drying is a function of (I) film (base and
emulsion); (2) processing (hardness of emulsion after
washing, use of wetting agent); and (3) drying air (temper-
ature, humidity, flow). Manual drying can vary from still air
drying at ambient temperature to as high as 140%' (60'C)
maintained. This record should comprise, initially, a job
number (which should appear also on the films), the
identification of the parts, material or area radiographed, the
date the fdms are exposed, and a complete record of the
radiographic procedure, in sufficient detail so that any
with air circulated by a fan. Film manufacturers should again radiographic techniques may be duplicated readily. If cali-
be contacted for recommended drying conditions. Take bration data, or other records such as card fdes or p r a -
precaution to tighten film on hangers, so that it cannot touch dures, are used to determine the procedure, the log ne& refer
in the dryer. T& hot a drying t e & & t u r e at low humidity only to the appropriate data or other m r d . Subseauentlv.
can result in uneven drying and should be avoided. the interpret& iindings and disposition (accep&ce &
rejection), if any, and his initials, should also be entered for
25. Testing Developer each job.
25.1 It is desirable to monitor the activity of the radio- 30. Reports
graphic developing solution. This can be done by periodic 30.1 When written reports of radiographic examinations
development of film strips exposed under carefully wn- are required, they should include the following, plus such
trolled conditions, to a g d e d series of radiation intensities other items as may be agned upon:
or time, or by using a commercially available strip c a d d y 30.1.1 Identification of parts, material, or area.
controlled for film speed and latent image fading. 30.1.2 Radiographicjob number.
30.1.3 Findings and disposition, if any. This information
26. Viewing Radiographs can be obtained direclly from the log.
26.1 Transmission-The illuminator must provide l i t
of an intensity that will illuminate the average density anas 31. Identification of Completed Work
of the radiographs without glare and it must diffuse the light 31.1 Whenever radiography is an inspective (rather than
evenly over the viewing area. Commercial fluorescent illumi- investigative) operation whereby material is accepted or
nators are satisfactory for radiographs of moderate density; rejected, all parts and material that have been accepted
however, high l i t intensity illuminators are available for should be marked permanently, if possible, with a character-
densities up to 3.5 or 4.0. Masks should be available to istic identifying symbol which will indicate to subsequent or
exclude any extraneous light from the eyes of the viewer final inspectors the fact of radiographic acceptance.
when viewing radiographs smaller than the.viewing port or 31.2 Whenever possible, the completed radiographs
to cover lowdensity areas. should be kept on file for reference. The custody of radio-
26.2 Rdection-Radiographs on a translucent or opaque graphs and the length of time they are presemed should be
I
backing may be viewed by reflected light. It is recommended atsed upon between the contracting parties.
E 94
APPENDIX
(Nomandatory Information)
XI. USEOFFLUORBCENTSCREENS
XI. 1 Description-Fluorescent intensifying screens have ness, is minimized by using screens having small, evenly
a cardboard or plastic support coated with a uniform layer of spaced crystals in a thin aytalline layer. Fluorescent screens
inorganic phosphor (crystalline substance). The support and are highly sensitive to longer wavelength scattered radiation.
phosphor are held together by a radiotranspareat biding Consequently, to maximize contrast when this non-image
material. Fluorescent screens derive their name h m the fact forming radiation is excessive, fluorometallic intensifying
that their phosphor crystals "fluoresccreScc'
(emit visible light) screens or fluorescent screens backed by lead screens of
when struck by X or gamma radiation. Some phosphors like appropriate thickness an recommended. Screen technology
calcium tungstate (CaWO,) give bff blue light while others has seen significant advances in recent yean, and today's
known as rare earth emit light green. fluorescent screens have smaller crystal size, more uniform
X1.2 Purpose and Film Types-Fluorescent mecn expo- crystal packing, and reduad phosphor thickness. This trans-
sures are usually much shorter than those made without lates into greater scncnlfilm speed with reduced unsharpness
r'. screens or with lead intensifying screens, because radio- and mottle. These improvements can represent some mean-
ingful benefits for inductrial radiogra~hy,
- - ..as indicated by the
graphic films generally are more responsive to visible light
than to direct X-radiation, gamma radiation, and electrons. three examples as follows:
XI.2.1 Films fall into one of two categories: non-screen XI .3.1 Reduced Exposure (Increased Productivity)-
type fdm having moderate light response, and mecn type There arc instances when prohibitively long exposure times
film specifically sensitized to have a very high blue or gncn make conventional radiography impractical. An example is
the inspection of thick, high atomic number materials with
light response. Fluorescent screens can reduce wnventional low curie isotopes. Depending on many variables, exposun
exposures by as much as 150 times, depending on film type. time may be reduced by factors ranging from 2x to lO5x
X1.3 Image Quality and Use-The image quality associ- when the appropriate fluorescent screenlfdm combination is
ated with fluorexent screen exposures is a function of used.
sharpness, mottle, and contrast. Screen sharpness depends on X1.3.2 Improved S&y Conditions (Field Sites)-Be-
phosphor crystal size, thickness of the crystal layer, and the cause fluorescent screens provide reduced exposure, the
reflective base coating. Each crystal emits light relative to its length of time that non-radiation workers must evacuate a
size and in all directions thus producing a relative degree of radiographic inspection sitc can be reduced significantly.
image unsharpness. To minimize this unsharpness, screen to X1.3.3 Extended Epui~ment Ca~abilit~-Utilizina the
film contact should be as intimate as possible. Mottle sped advantage of fludnsfent screek by &arlating ii into
adversely affects image quality in two ways. First, a reduad enemy level. An exam~leis that a 150 kV X-rav
"quantum" mottle is dependent upon the amount of X or tube may do-ihe job of a 300 kv tube, or that iridium 19i
gamma radiation actually absorbed by the fluorescent screen, may be used in applications normally requiring cobalt 60. It
that is, faster screenlfilm systems lead to greater mottle and is possible for overall image auality to be better at the lower
poorer image quality. A "structural" mottle, which is a kV with fluorescent screins-than7at a higher energy level
T-J function of crystal size, crystal uniformity, and layer thick- using lead mecns.
f
BIBLIOGRAPHY ON INDUSTFUAL RADIOGRAPHY
For conciseness, this bibliography has been limited to books and specifically to books ia English published a f t e ~1950.
(I) Clark,G. I^,AppliedX-Rays.4th cd., MffirawHill Book Co., Inc., C. Thomas, Springfield, I I 1951.
New York, 1955. (9) W i l s b i W. J. (Editor), A FurfherHandbwk 4/Indu(1riialRadId.
(2) Clnuwr, H. R., Pradiut Radiographyjbr I n d w ~ vReinhold
, Pub- o m Edward Arnold and Company, London, 1957.
lishing Carp.. New York, 1952. (10) M c O o ~ cW ,. J.. Nondcstnu~iveTesting, MffirawHill Book
(3)Howth, C. A.. and Blitz, I. (Editon), Techniques of Co., Inc, New York, 1961.
Nonderrnrcrive Testing. Bunc Wonh and Co., Ltd.,London, 1960. (11) Handbwk on Radiography, Rcvixd edition, Atomic E n q y of
(4) McMortcr, R. C. (Editor), Nondestiuctive Testing Handbook, 'Ihc Canada Ltd. Ottawa,Ont, 1950.
Ronald Pms,New York, 1960. ( 1 9 Papers on Radiography, ASTM STP 96,ASTM, 1950.
(5) Mown, R. H., a d C o w ,K.E (Editors), H d b w k of R* (13) Symparium on the Role of NondesIrunive Testing in the EW
d i d o w The Year Book Publishen. Inc, Chicago, 1955. nomiu ofF7oduclion. ASTM STP 112, ASTM, 1951.
(6) Reed, M. E,Cobalt4 Radiography in IndwIry. TIUCU-lab. Inc, (14) Radioirotow TEehnipur. Vol 11, H.M. Stationcry Oflice, London,
Banon, 1954. 1952.
(7) Robsruon, J. K,Radidom Physics, 3rd cd.. D. Van Nostrand (15) Symposium on Nondenwive Testng. ASTM STP 145. ASTM,
Company,New York, 1956. 1953.
/-' (8) Weyl, C., and W m n , S. R, Radidodc Phy~iu.2nd cd., Chpr1~~ (16) MmorMdum on Gamma-Ray Sowcesjor Radiography, R e v i d
edition, lartitute of Phpia, London. 1954. (19) S'ymgosiwn on Nondesl~ucIiw Tests in the Field of Nwiear
(17) Papers on Nondes1mIive Tesing, sa Prmdings, ASTM. Vol54, Energy, ASTM STP 223, ASTM. 1958.
:p 1954. (20) Radiopaphw's Rderenn (3rd edition), E. I.du Pont dc Ncrnovra
(18) Radiography in Modern lndiulry (3rd edition), Eastman Kcdak & Co., k, W i n , DE. 1974 (or Ltat nviian).
Co.. Rochertcr. NY. 1969.