JP2021071313A - Nuclear reactor output monitoring device - Google Patents

Abstract

To provide a nuclear reactor output monitoring device capable of accurately correcting, by fast response, delay of a detection signal for a nuclear reactor output during output change.SOLUTION: A nuclear reactor output monitoring device comprises: a self-output type gamma-ray detector; a delayed gamma-ray correction device for correcting a delayed gamma-ray in real time; a data sampling device for sampling a detection signal from the self-output type gamma-ray detector; and a delayed gamma-ray ratio calculation device for calculating a delayed gamma-ray ratio on the basis of the sampled detection signal. The data sampling device includes an output operation signal input device, detects a start and an end of output fluctuation of a nuclear reactor on the basis of the output operation signal input into the output operation signal input device, and samples the detection signal from the self-output type gamma-ray detector in a constant output state during output fluctuation and after output fluctuation. The delayed gamma-ray correction device corrects the delayed gamma-ray for the detection signal using the delayed gamma-ray ratio calculated by the delayed gamma-ray ratio calculation device.SELECTED DRAWING: Figure 1

Description

The present invention relates to a reactor power monitoring device that monitors the reactor power using a self-powered gamma ray detector fixed in the reactor.

Conventionally, in order to monitor the output of a reactor, a system for measuring the output of the reactor with a radiation detector inside or outside the reactor has been used.
For example, in a boiling water reactor, a fixed neutron detector fixed in the reactor and a mobile neutron detector for calibrating this fixed neutron detector were combined and generated by a nuclear split reaction in the reactor. We have detected neutrons and measured the output and output distribution.
Since the sensitivity of uranium, which is a sensitive substance, deteriorates due to neutron irradiation, fixed neutron detectors are periodically calibrated during operation by mobile neutron detectors.

In recent years, it has been studied to use a fixed gamma ray detector instead of the mobile neutron detector for calibration.

Patent Document 1 describes a set of detectors in which a local power detector (fixed neutron detector) is calibrated in a boiling water reactor using a γ-ray thermometer arranged adjacent to the local power detector. The body is disclosed. That is, instead of the mobile neutron detector, a γ-ray thermometer, which is a kind of fixed gamma-ray detector, is used.

However, the measurement principle of the γ-ray thermometer is that the sensor unit generates heat due to the γ-rays generated in the furnace, and by measuring the temperature of the sensor unit, information on the output of the γ-rays and adjacent fuel is obtained. Response is delayed in response to changes in reactor power in.
The first reason for the delay in response is that it takes time for the temperature to equilibrate after the output changes due to the heat capacity of the sensor unit.
The second reason for the delayed response is that the γ-rays themselves change with a time delay after the output changes due to the influence of the delayed γ-rays emitted from the fission products. Delayed γ-rays occupy about 30% of all γ-rays generated in the core, and are present in a wide range from components having a time constant of 1 second or less to components having a time constant of more than 1 year, resulting in a long-term response delay.

Here, an example of the response of γ-rays when the output is increased stepwise is shown in FIG.
As shown in FIG. 9, after the output increases, the prompt components other than the delayed components of the γ-rays increase instantaneously, but the remaining delayed components gradually approach the steady-state value.

In Patent Document 2, the delayed gamma component contained in the signal of the gamma thermometer (γ-ray thermometer) is represented by its time constant and weight, and the delayed gamma component represented by the time constant and weight is removed from the signal. Disclosed is an in-core instrumentation signal processor equipped with a gamma thermometer field panel and a control panel for obtaining a gamma thermometer signal that is not affected by a delayed gamma component.

Further, in Patent Document 3, a γ-ray measurement value is used, the contribution of a delayed γ-ray component that does not immediately respond to the output is corrected according to a correction model built in in advance, and the correction value is output at an arbitrary time. A reactor power measuring device to which a γ-ray correction means and a means for changing / adjusting parameters of a correction model built in the delayed γ-ray correction means are added is disclosed.

Examples of gamma ray detectors other than gamma ray thermometers include ionization chambers and self-powered gamma ray detectors (SPGD; Self-Powered Gamma Detector).
The self-output type gamma ray detector (SPGD) measures the current value generated by ejecting electrons in a member called a central emitter by irradiation with gamma rays, and responds to the output due to the influence of delayed gamma rays. Although there is a delay in response, there is no delay in response due to the heat capacity of a detector such as a gamma thermometer.
Patent Document 4 discloses a self-output type gamma ray detector in which tungsten having a heat resistance of 600 ° C. or higher and having high sensitivity to gamma rays is applied to an emitter.

Japanese Unexamined Patent Publication No. 3-65696 Japanese Unexamined Patent Publication No. 2001-83280 JP-A-2002-202395 Japanese Patent No. 6095099

In the reactor power measuring apparatus according to Patent Document 3 described above, two types of methods are disclosed as means for changing / adjusting the parameters of the correction model built in the delayed gamma ray correction means.

In the first method, the parameter value is updated based on the information on the fuel burnup and the void rate near the gamma ray detector from the relationship between the parameter value and the fuel burnup evaluated in advance and the parameter value and the void rate. How to do it.
However, since this method does not adjust the parameters based on the actual measured values, the uncertainty of the preliminary evaluation remains.

The second method is to change / adjust the parameters of the correction model based on the comparison of the time series data between the output measured by the fixed neutron detector and the γ-ray measurement value corrected for the delayed γ-ray component. is there.
However, this method requires a fixed neutron detector adjacent to the gamma ray detector. Therefore, when removing the fixed neutron detector as a configuration of only the gamma ray detector for rationalization of the detector, or reducing the number of fixed neutron detectors installed, the fixed neutron detector adjacent to the gamma ray detector Cannot be used when there is not always.

In Patent Document 2 and Patent Document 3, a fixed gamma ray detector is used instead of the mobile neutron detector for calibration.
The fixed gamma ray detector has little deterioration in sensitivity due to neutron irradiation, and can measure the same output as the fixed neutron detector in a steady state.
Therefore, by substituting a part or all of the conventional fixed neutron detector with a fixed gamma ray detector, it is conceivable to rationalize the detector for output monitoring and reduce the cost.
However, in the fixed gamma ray detector, the detection signal is delayed in the output due to the delayed gamma ray described above. In addition, the proportion of delayed gamma rays varies depending on the fuel composition and void ratio, and is not constant.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to accurately correct a delay of a detection signal with respect to a reactor output when the output changes with a fast response. The purpose is to provide an output monitoring device.

In addition, the above-mentioned object and other object and novel features of the present invention will be clarified by the description and the accompanying drawings of the present specification.

The reactor power monitoring device of the present invention includes a self-powering gamma ray detector including a metal emitter that emits electrons by irradiation with gamma rays and a metal collector that electrically insulates and contains the emitters. , Equipped with a delayed gamma ray correction device that corrects delayed gamma rays in real time.
The reactor power monitoring device of the present invention further calculates the delayed gamma ray ratio based on the data collecting device that collects the detection signal from the self-powered gamma ray detector and the detection signal collected by the data collecting device. It is equipped with a delayed gamma ray ratio calculation device.
Further, the data collection device includes an output operation signal input device to which an output operation signal is input by an operator or a control device. Then, the data collection device detects the start and end of the output fluctuation of the reactor based on the output operation signal, and the detection from the self-output type gamma ray detector in the state of constant output during and after the output fluctuation. Collect the signal.
In addition, the delayed gamma ray correction device uses the delayed gamma ray ratio calculated by the delayed gamma ray ratio calculation device for the detection signal from the self-output type gamma ray detector in a constant output state collected by the data collection device. , Correct late gamma rays in real time.

According to the present invention, the self-powered gamma ray detector has little deterioration in sensitivity due to neutrons, and the delayed gamma ray correction device can correct the delayed gamma ray in real time, so that the delay of the detection signal with respect to the change in the reactor output is accurate. It is possible to measure the reactor power with good correction and quick response.
This makes it possible to measure the reactor power with a fast response even when there is not necessarily an adjacent fixed neutron detector.
Therefore, the costly scanning neutron detector can be abolished, and by substituting a part or all of the fixed neutron detector with a self-powered gamma ray detector, the detector can be rationalized and the cost can be reduced. ..

Further, according to the present invention, since the fixed neutron detector can be replaced with a self-powered gamma ray detector with less sensitivity deterioration due to neutrons, the life of the detector can be extended, and the cost and the amount of waste can be reduced. Can be planned.

Issues, configurations and effects other than the above will be clarified by the following description of the embodiments.

It is an overall block diagram of the reactor power monitoring apparatus of Example 1. FIG. It is a structural diagram of an example of the self-output type gamma ray detector of FIG. It is a block diagram of an example of the delayed gamma ray correction apparatus of FIG. It is a figure which shows the example of the interface screen of the input device of FIG. It is a block diagram of an example of the data collection apparatus of FIG. It is a flowchart of the process based on the output operation signal carried out by the arithmetic unit of the data collection apparatus shown in FIG. It is a schematic diagram of the fitting for calculating the prompt gamma ray ratio and the delayed gamma ray ratio. It is an overall block diagram of the reactor power monitoring apparatus of Example 2. FIG. It is a figure which shows an example of the response of γ-rays when the output is increased stepwise.

Hereinafter, embodiments and examples according to the present invention will be described with reference to text or drawings. However, the structure, materials, and various other specific configurations shown in the present invention are not limited to the embodiments and examples taken up here, and can be appropriately combined and improved without changing the gist. Is. In addition, elements not directly related to the present invention are not shown.

In order to solve the above-mentioned problems, the reactor power monitoring device of the present invention corrects delayed gamma rays in real time with respect to the detection signals from the self-powered gamma ray detector and the self-powered gamma ray detector. It is equipped with a delayed gamma ray correction device. It is also provided with a data collection device that detects the start and end of the power change of the nuclear reactor and collects the detection signal from the self-powered gamma ray detector during the power fluctuation and in the constant power state after the power fluctuation.

The reactor power monitoring device of the present invention includes a self-powered gamma-ray detector, a delayed gamma-ray correction device that corrects delayed gamma-rays in real time, and a data collection device that collects detection signals from the self-powered gamma-ray detector. And a delayed gamma ray ratio calculation device that calculates a delayed gamma ray ratio based on a detection signal collected by the data collection device.
The self-powered gamma ray detector includes a metal emitter that emits electrons by irradiation with gamma rays, and a metal collector that electrically insulates and contains the emitter.
The data collection device includes an output operation signal input device to which an output operation signal is input by an operator or a control device. Then, the data collection device detects the start and end of the output fluctuation of the reactor based on the output operation signal, and the detection signal from the self-output type gamma ray detector in the state of constant output during and after the output fluctuation. To collect.
The delayed gamma ray correction device uses the delayed gamma ray ratio calculated by the delayed gamma ray ratio calculation device, and actually applies the detection signal from the self-output type gamma ray detector in the constant output state collected by the data collection device. Correct late gamma rays with time.

In the above-mentioned reactor output monitoring device, the data collection device can further be configured to use one or both signals of the control rod operation signal and the recirculation flow rate operation signal as the output operation signal.

In the above reactor power monitoring device, the delayed gamma ray correction device further groups the delayed gamma rays into a group of a plurality of decay time constants from a minimum of less than 1 second to a maximum of 1 day or more, and contributes to each of the total delayed gamma rays. A model formula calculated as the sum of contributions from the group can be used to correct the delayed gamma rays.

In the above reactor output monitoring device, the data collection device further detects the start and end of the reactor output fluctuation based on the output operation signal, and self-output gamma rays in a constant output state after the output fluctuation from the start of the output. The detection signal of the detector is collected and sent to the delayed gamma ray ratio calculation device, and the late gamma ray ratio calculation device calculates the late gamma ray ratio according to a predetermined process and sends it to the late gamma ray correction device. The delayed gamma ray correction device can be configured to update the value stored at that time according to the transmitted delayed gamma ray ratio.

The above-mentioned reactor power monitoring device may further include a reactor protection device that generates a scram signal of the reactor based on the output from the delayed gamma ray correction device.

In the above reactor power monitoring device, the core performance calculation device further corrects the calculation of the core three-dimensional simulator based on the output from the delayed gamma ray correction device, and calculates the maximum line output density and the minimum limit output ratio. Can be configured to include.

The reactor power monitoring device of the present invention can be applied to a nuclear reactor such as a boiling water reactor (BWR).

In the above reactor power monitoring device, the self-powered gamma ray detector has a configuration including a metal emitter that emits electrons by irradiation with gamma rays and a metal collector that electrically insulates and contains the emitter. is there.
In the self-powered gamma ray detector having this configuration, electrons are emitted from the emitter irradiated with gamma rays, and a current is generated between the emitter and the collector. Then, this current can be detected as a detection signal.
With this configuration of the self-powered gamma ray detector, a gamma thermometer can detect relatively large changes over a short period of time that cannot be separated from the effects of thermal response, and is used to evaluate the percentage of delayed gamma rays. can do.

In the self-powered gamma ray detector, for example, lead metal can be used for the emitter, and for example, stainless steel can be used for the collector.
In the above-mentioned reactor power monitoring device, as the self-powered gamma-ray detector, for example, a conventionally known self-powered gamma-ray detector disclosed in Patent Document 4 or the like can also be adopted.

A plurality of self-powered gamma ray detectors are preferably arranged three-dimensionally in the core.
When, for example, four or more self-output type gamma ray detectors are installed in the height direction of the core, the rod block performance can be sufficiently ensured.

The delayed gamma ray correction device preferably groups the delayed gamma rays into a group of a plurality of decay time constants having a minimum of less than 1 second and a maximum of 1 day or more, and calculates the contribution of all delayed gamma rays as the sum of the contributions from each group. The late gamma ray is corrected by using the model formula.
As described above, by setting the time constant of the group having the shortest decay time constant to less than 1 second among the group of model formulas, the accuracy and responsiveness of correction of delayed gamma rays can be improved. Further, if the configuration is further provided with a reactor protection device that generates a scram signal of the reactor based on the output from the delayed gamma ray correction device, the accuracy and responsiveness of the scram signal can be improved.

According to the reactor power monitoring device having the above configuration, a self-powered gamma ray having a metal emitter that emits electrons by irradiation with gamma rays and a metal collector that electrically insulates and contains the emitter. Equipped with a detector. Since this self-powered gamma ray detector has a small sensitivity deterioration due to neutrons, it is possible to reduce the sensitivity deterioration due to neutrons as compared with the conventional fixed neutron detector.
Further, since the delayed gamma ray correction device corrects the delayed gamma ray in real time with respect to the detection signal from the self-output type gamma ray detector, it is possible to measure the reactor output with a quick response.
This makes it possible to accurately correct the delay from the reactor output when the output changes, even if there is not necessarily an adjacent fixed neutron detector.
In addition, the costly scanning neutron detector can be abolished, and by substituting a part or all of the fixed neutron detector, the detector can be rationalized and the cost can be reduced.
Furthermore, since a self-powered gamma-ray detector with less sensitivity deterioration due to neutrons can replace the fixed neutron detector, the life of the detector can be extended, and cost reduction and waste volume reduction can be achieved. Can be done.

In addition, the data collection device detects the start and end of the output fluctuation of the reactor based on the output operation signal input to the output operation signal input device by the operator or the control device, and outputs during and after the output fluctuation. The detection signal from the self-output type gamma ray detector in a constant state is collected.
Furthermore, it is provided with a delayed gamma ray ratio calculation device that calculates a delayed gamma ray ratio based on a detection signal collected by the data collection device. Then, using the delayed gamma ray ratio calculated by this delayed gamma ray ratio calculation device, the delayed gamma ray correction device corrects the delayed gamma ray for the detection signal in the constant output state collected by the data collection device.
Therefore, since the data collection device can accurately grasp the constant output state of the reactor, the delayed gamma ray correction device can accurately and in real time correct the delayed gamma ray. As a result, the reactor can be started and stopped in accordance with the output state of the reactor with high accuracy, and the operability of the reactor can be improved.

Further, when the data collection device is configured to use one or both of the control rod operation signal and the recirculation flow rate operation signal as the output operation signal, the rate of prompt gamma rays and the delayed gamma ray ratio that change during operation The gamma ray ratio can be calculated from the output signal when the reactor output is constant. As a result, delayed gamma rays can be corrected with higher accuracy.

In addition, the delayed gamma ray correction device groups the delayed gamma rays into a group of a plurality of decay time constants from a minimum of less than 1 second to a maximum of 1 day or more, and calculates the contribution of all delayed gamma rays as the sum of the contributions from each group. When the late-onset gamma-ray is corrected by using the model formula, a signal in which the late-onset component is sequentially corrected can be calculated from the detection signal of the self-output type gamma-ray detector.

In addition, the data collection device detects the start and end of the output fluctuation of the reactor based on the output operation signal, and collects the detection signal of the self-output type gamma ray detector in the constant output state after the output fluctuation from the start of the output. When the configuration is set to send to the delayed gamma ray ratio calculation device, the output fluctuation of the reactor can be detected accurately based on the output operation signal.
Further, the delayed gamma ray ratio calculation device calculates the delayed gamma ray ratio according to a predetermined process and sends it to the delayed gamma ray correction device, and the delayed gamma ray correction device determines the time point according to the transmitted delayed gamma ray ratio. When the value stored in is updated, the delayed gamma ray ratio can be calculated by accurately following the output fluctuation of the reactor. Then, in the delayed gamma ray correction device, the delayed gamma ray can be corrected by accurately following the output fluctuation of the nuclear reactor. In particular, it is possible to accurately follow fluctuations in the output of a nuclear reactor in a short time and correct delayed gamma rays.

In addition, when the configuration is equipped with a reactor protection device that generates a scram signal of the reactor based on the output from the delayed gamma ray correction device, the delayed gamma ray correction device that accurately corrects the delayed gamma ray correction device A scram signal can be generated based on the output of. As a result, the scrum signal can be generated accurately according to the output of the reactor, so that it is possible to prevent the scrum signal from being generated even when the output does not need to stop the reactor in an emergency. However, the operability of the reactor can be improved.

In addition, when the configuration is equipped with a core performance calculation device that corrects the calculation of the core three-dimensional simulator based on the output from the delayed gamma ray correction device and calculates the maximum line output density and the minimum limit output ratio, it is delayed. It is possible to supply a highly responsive and highly accurate output signal from the emission gamma ray correction device to the core performance calculation device. Therefore, the core performance calculation can be performed quickly and accurately, the core performance can be monitored quickly and accurately, and the operability and safety of the reactor can be improved.

Next, an embodiment of the reactor power monitoring device will be described in detail with reference to the drawings.

(Example 1)
The overall configuration diagram of the reactor power monitoring device of the first embodiment is shown in FIG.
As shown in FIG. 1, the reactor output monitoring device of this embodiment includes an in-reactor instrumentation tube 3 and a self-powered gamma ray detector 4 inserted in a reactor pressure vessel 1 containing a core 2. ing.
Further, the reactor output monitoring device of this embodiment has a delayed gamma ray correction device 6, a data collection device 7, a reactor protection system 8, a control rod drive control device 12, and a recirculation flow rate outside the reactor pressure vessel 1. A control device 13 and a delayed gamma ray ratio calculation device 15 are provided.

The self-powered gamma ray detector 4 is included in the in-core instrumentation tube 3 in order to measure the internal output of the core 2. A cable 5 is connected to the self-output type gamma ray detector 4, and a delayed gamma ray correction device 6 and a data collection device 7 are connected to the other end of the cable 5.
The delayed gamma ray correction device 6 is connected to the reactor protection system 8.
The data collection device 7 has a built-in output operation signal input device 14. The data collection device 7 is connected to the delayed gamma ray ratio calculation device 15.
The reactor protection system 8 generates a scrum signal to stop the reactor in an emergency.

The control rod drive control device 12 transmits an operation signal to the control rod 9 and the control rod drive device 10 attached to the reactor pressure vessel 1.
The recirculation flow rate control device 13 transmits an operation signal to the recirculation pump 11.
The control rod 9, control rod drive device 10, recirculation pump 11, control rod drive control device 12, and recirculation flow rate control device 13 have a configuration conventionally used for controlling a nuclear reactor.

In particular, the output operation signal input device 14 built in the data collection device 7 is connected to the control rod drive control device 12 and the recirculation flow rate control device 13.
As a result, the control signal of the control rod drive control device 12 and the control signal of the recirculation flow rate control device 13 can be input to the output operation signal input device 14 as an output operation signal.

Next, a structural diagram of an example of the self-output type gamma ray detector 4 of FIG. 1 is shown in FIG.
The self-output gamma ray detector 4 shown in FIG. 2 has a lead metal emitter 17 in the center and a stainless steel collector 19 on the outside, and is insulated from each other by an alumina insulating material 18.
The emitter 17 is connected to the core wire 20 of the metal sheath cable, and the emitter 17 and the core wire 20 are conductive. The core wire 20 of the metal sheath cable is covered with a metal sheath 21, and is insulated from the metal sheath 21 by an insulating material 22 made of alumina.
Further, both ends of the collector 19 have a structure in which the inside is airtight due to the metal end plugs 23.
In the self-output type gamma ray detector 4 having this configuration, electrons are emitted from the emitter 17 irradiated with gamma rays, and a current is generated between the emitter 17 and the collector 19. Then, this current can be detected as a detection signal.

Further, a configuration diagram of an example of the delayed gamma ray correction device 6 of FIG. 1 is shown in FIG.
The delayed gamma ray correction device 6 shown in FIG. 3 is connected to the self-output type gamma ray detector 4 of FIG. 1 by a cable 5, and is a weak current measuring device 25, an arithmetic device 26, a storage device 27, a transmitter 28, and an input device 29. , The initialization switch 30 is provided.

The weak current measuring instrument 25 is connected to the cable 5 and receives a signal from the cable 5.
The weak current measuring device 25 is connected to the arithmetic unit 26.
The arithmetic unit 26 is connected to the storage device 27, the initialization switch 30, and the transmitter 28, respectively.
An input device 29 is connected to the storage device 27.

Here, an example of the interface screen of the input device 29 of FIG. 3 is shown in FIG.
_{The decay constant λ j} and the ratio a _j of each component j (j = 1 to 10 in this screen) of _{the prompt gamma ray ratio a 0} and the delayed gamma ray on the left side of the screen in FIG. 4 are set by the direction buttons and variables on the right side of the screen. Select with the select button and change with the number button and change execution button.
The meaning of these constants will be described later.

Further, a configuration diagram of an example of the data collection device 7 of FIG. 3 is shown in FIG.
The data collection device 7 shown in FIG. 5 includes an output operation signal input device 14, a weak current measuring device 32, an arithmetic device 33, a storage device 34, and a transmitter 35.

The output operation signal input device 14 receives the operation signals from the control rod drive control device 12 and the recirculation flow rate control device 13.
The weak current measuring device 32 is connected to the cable 5 and receives a signal from the cable 5.
The weak current measuring device 32 is further connected to the arithmetic unit 33.
The arithmetic unit 33 is connected to the storage device 34 and the transmitter 35, respectively.

Next, the operation of the reactor power monitoring device configured as described above will be described below.

When the operation of the reactor is started, the generated gamma rays are irradiated to the self-powered gamma ray detector 4 by the fission reaction of the core 2 held in the reactor pressure vessel 1.
In the self-output type gamma ray detector 4, electrons are emitted from the emitter 17 irradiated with gamma rays, so that a current is generated between the emitter 17 and the collector 18. This current is sent as a detection signal to the delayed gamma ray correction device 6 and the data collection device 7.

In the delayed gamma ray correction device 6, the current received every moment is measured by the weak current measuring device 25, converted into an output signal, and sent to the arithmetic unit 26 as a digital value.
_{The arithmetic unit 26 calls the prompt gamma ray ratio a 0} and the decay constants λ _j and the ratio a _j of the delayed gamma ray held in the storage device 27, and corrects the delayed gamma ray component according to the correction model built in in advance. To generate.
As the correction model, as shown in the following equation (1), a model is used in which the transmutation that emits delayed gamma rays is grouped into several time constant components and the delayed gamma rays are calculated as the sum of each component.

ここで、G(t)はガンマ線測定値であり、GC(t)は遅発成分を補正したガンマ線測定値である。
また、前述したように、λ_jは第ｊ群の遅発ガンマ線の崩壊定数であり、ａ_０は全ガンマ線に占める即発ガンマ線の割合であり、ａ_ｊは全ガンマ線に占める第ｊ群の遅発ガンマ線の割合である。

Here, G (t) is a gamma ray measurement value, and GC (t) is a gamma ray measurement value corrected for a delayed component.
Further, as described above, λ _j is the decay constant of the delayed gamma rays of the j group, a ₀ is the ratio of the prompt gamma rays to the _{total gamma rays, and a j} is the delayed gamma rays of the j group to the total gamma rays. The percentage of gamma rays.

As the collapse time constant (the reciprocal of the collapse constant), 10 pieces (N = 10) from an order of less than 1 second to more than 1 day are used.
Using this equation (1), it is possible to calculate an output signal in which the delayed component is sequentially corrected from the output signal obtained at a fixed cycle.
The sequential formula used for calculating this output signal is shown in the following formula (2).

In this equation (2), G _k represents the output signal at time k, GC ^j _k represents the contribution from the delayed γ-rays of the j-th group, and GC _k represents the corrected output signal.
The time is discretized at intervals of the current sampling cycle Δt of the self-output gamma ray detector, where k represents the current time and k-1 represents the time one cycle before.
In the formula (2), the contribution of all delayed gamma rays is calculated as the sum of the contributions from the delayed gamma rays of each group (j = 1 to N), and the delayed gamma ray component is corrected.

In the delayed gamma ray correction processing procedure using this equation (2), first, the output signal G _k at the current time k is read.
Next, it is confirmed whether or not the corrected output signal GC _k and the delayed γ-ray contribution GC ^j _{k of each component are initialized.}
Then, if it is not initialized, it is initialized on the assumption that the output signal is always constant until the current time.
On the other hand, if it has been initialized, the output signal GC _k corrected at the current time and the delayed γ-ray contribution GC ^j _k of each component are calculated in this order according to the equation (2).

The corrected output signal GC _k and the delayed γ-ray contribution GC ^j _k of each component are automatically initialized when the reactor output monitoring device is started, and the operator also initializes the initialization switch if necessary. It is assumed that the output signal is always constant until the current time at the time when 30 is pressed.
The initialization of the output signal GC _k and the delayed γ-ray contribution GC ^j _k of each component is carried out according to the following equations (3) and (4).

As described above, the output signal generated by correcting the delayed gamma ray component according to the correction model built in in advance is transmitted to the reactor protection system 8 by the transmitter 28 of the delayed gamma ray correction device 6, and is a scrum signal. Used to generate.

On the other hand, in the data collecting device 7, similarly to the delayed gamma ray correction device 6, the current received every moment is measured by the weak current measuring device 32, converted into an output signal, and sent to the arithmetic unit 33 as a digital value.
An output operation signal input device 14 is connected to the arithmetic unit 33, and the control rod operation signal from the control rod drive control device 12 and the recirculation flow rate operation signal from the recirculation flow rate control device 13 are input to the arithmetic unit 33. Enter in 33.
In the arithmetic unit 33, the output signal from the time when the output of the reactor starts to change by the control rod drive device 12 or the recirculation flow rate control device 13 until a certain time elapses after the output operation satisfying a predetermined condition is performed. Is stored in the storage device 34.
Then, after the storage of all the data is completed, this data is transmitted to the delayed gamma ray ratio calculation device 15 by the transmitter 35.

Here, FIG. 6 shows a flowchart of processing based on the output operation signal performed by the arithmetic unit 33 of the data collection device 7 shown in FIG.

In the flowchart shown in FIG. 6, when the arithmetic unit 33 starts processing, first, in step S1, the initial value P0 of the output signal is initialized to the current output signal P until there is a control rod operation or a recirculation flow rate operation. .. Further, in step S2, the initial value t1 of the first timer is reset to the current time t.
In this state, in step S3, it is detected whether or not the control rod operation or the recirculation flow rate operation has been performed. Then, when the control rod operation or the recirculation flow rate operation is performed, the process proceeds to step S4, and the storage of the output signal in the storage device 34 is started. On the other hand, when neither the control rod operation nor the recirculation flow rate operation is performed, the process returns to step S1 and the initial value P0 of the output signal is initialized to the current output signal P.

After starting the storage of the output signal in the storage device 34 in step S4, it is detected in step S5 whether or not the control rod operation or the recirculation flow rate operation is performed. Then, when neither the control rod operation nor the recirculation flow rate operation is performed (Yes), it is determined that the operation has been completed, and the process proceeds to step S6. On the other hand, when the control rod operation or the recirculation flow rate operation is performed (No), it is determined that the operation has not been completed, and the process returns to the step S5.

After the operation is completed, in step S6, it is detected whether or not the output change | P−P0 | due to the control rod operation or the recirculation flow rate operation is equal to or greater than the predetermined value ΔP1 (for example, 5% of the rated output). When the output change | P−P0 | is ΔP1 or more, it is determined that the output change is sufficient, and the process proceeds to step S9. On the other hand, when the output change | P−P0 | is less than ΔP1, it is determined that the output change is insufficient, and the process proceeds to step S7.

In step S7, it is detected whether or not the elapsed time t−t1 from the start of the operation is less than the predetermined value Δt1 (for example, 2 minutes). If the elapsed time t−t1 is less than Δt1, it is determined that the elapsed time is not sufficient, the process returns to the front of step S6, and then the output change | P−P0 | of step S6 is detected again. On the other hand, when the elapsed time t−t1 is Δt1 or more, it is determined that the output change is still insufficient even after a sufficient time has elapsed, and the process proceeds to step S8.
In step S8, it is determined that the output change is insufficient and accurate evaluation cannot be performed, the output signal stored in the storage device 34 is erased, and the process returns to the step S1.

In step S9, the initial value t2 of the second timer is initialized to the current time t.
Then, in step S10, it is detected whether the elapsed time t−t2 in the state without operation is equal to or more than the predetermined value Δt2 (for example, 5 minutes). If the elapsed time t−t2 is Δt2 or more, it is determined that the elapsed time is sufficient, and the process proceeds to step S12. On the other hand, when the elapsed time t−t2 is less than Δt2, it is determined that the elapsed time is insufficient, and the process proceeds to step S11.

In step S11, since the elapsed time without operation is short and the output may still change, it is determined that accurate evaluation cannot be performed. Then, as in the process of step S8, the output signal stored in the storage device 34 is erased, and the process returns to the step S1.

In step S12, the storage of the output signal in the storage device 34 is completed, and the process proceeds to step S13.
In step S13, the data stored in the storage device 34 is transmitted to the delayed gamma ray ratio calculation device 15.
After that, the process in the data collection device 7 is terminated. Further, the process returns to the previous step S1, and in the next process, initialization is performed again.

In the delayed gamma ray ratio calculation device 15 that has received the output signal data after the core output has been changed, the model is applied to the received data, and the parameters a of equations (1) and (2) that change during the operation of the reactor. _{Find 0} and a _j and the true output change ΔP.
However, the method of determining the contribution of a component having a short decay time constant from short-time data is not accurate.
Therefore, giving priority to the response accuracy in a short time, _{only the parameter a 0} (or 1-a ₀ ) to be changed is used, and the sum is set to 1 as shown in the following equation (5) accordingly. A _{method of restandardizing a j} is used (λ _j is also constant).

Here, FIG. 7 shows a schematic diagram of the fitting for calculating the prompt gamma ray ratio and the delayed gamma ray ratio.
_{As shown in FIG. 7, a 0} and a so that the sum of squares of the difference between the fitting values calculated based on the above equation (1) is the smallest for each time value of the received output signal data. _{Determine j} and ΔP. _{At this time, a 0} and a _j and ΔP are determined on the assumption that the output is constant before and after the true output change ΔP.
The a ₀ and a _j thus determined are sent to the delayed gamma ray correction device 6.

In delayed gamma ray correction device 6, or the value of the stored a ₀ and a _j in the storage device 27 automatically rewritten, or to confirm whether the rewriting of the values of a ₀ and a _j to the operator Display the screen.

As described above, by inputting the control rod operation signal and the recirculation flow rate operation signal as the core output operation signal, the operation is performed from the output signal in a constant state of the reactor output even if there is no reference neutron flux signal. It is possible to calculate the ratio of delayed gamma rays that change during the process, and it is possible to accurately correct the delayed gamma rays.
In addition, since about half of the delayed gamma rays are saturated by the first minute, by using the self-output gamma ray detector 4, a relatively large change in the period that cannot be separated from the influence of the thermal response by the gamma thermometer. Can be used to evaluate the percentage of late-onset gamma rays. As a result, it is possible to evaluate with data for a short time, and it is possible to improve the accuracy of correction immediately after the output change.

According to the configuration of the present embodiment described above, a self-output gamma ray detector 4 having a lead metal emitter 17 and a stainless steel collector 19 in which the emitter 17 is insulated by an insulating material (alumina) 18 and contained therein is provided. I have.
In the self-output type gamma ray detector 4 having this configuration, electrons are emitted from the emitter 17 irradiated with gamma rays, and a current is generated between the emitter 17 and the collector 19. Then, this current can be detected as a detection signal.
By adopting the self-output gamma ray detector 4 in such a configuration, a relatively large change in a short period of time that cannot be separated from the influence of the thermal response by the gamma thermometer can be detected, and the delayed gamma ray ratio can be evaluated. Can be used.
Since the self-powered gamma-ray detector 4 having this configuration is provided with the self-powered gamma-ray detector 4, the sensitivity deterioration due to neutrons is smaller than that of the conventional fixed neutron detector. Can be reduced.

According to the configuration of the present embodiment described above, the delayed gamma ray correction device 6 can correct the delayed gamma ray in real time with respect to the detection signal from the self-output type gamma ray detector 4, and the response is quick. Can measure reactor power.
As a result, even if there is not necessarily a fixed neutron detector adjacent to the self-powered gamma ray detector 4, it is possible to accurately correct the delay from the reactor power when the power changes.
In addition, the costly scanning neutron detector can be abolished, and by substituting a part or all of the fixed neutron detector, the detector can be rationalized and the cost can be reduced.
Furthermore, since the self-powered gamma ray detector 4 with less sensitivity deterioration due to neutrons can replace the fixed neutron detector, the life of the detector can be extended, and cost reduction and waste volume reduction can be achieved. be able to.

According to the configuration of the present embodiment described above, the data collection device 7 detects the start and end of the output change of the reactor based on the output operation signal input to the output operation signal input device 14 by the operator or the control device. Then, the detection signal from the self-output type gamma ray detector 4 is collected during the output fluctuation and in the constant output state after the output fluctuation. Further, a delayed gamma ray ratio calculation device 15 for calculating the delayed gamma ray ratio based on the detection signal collected by the data collection device 7 is provided, and the delayed gamma ray ratio calculated by the delayed gamma ray ratio calculation device 15 is provided. Is used to correct the delayed gamma ray for the detection signal in the delayed gamma ray correction device 6.
Therefore, since the data collection device 7 can accurately grasp the constant output state of the reactor, the delayed gamma ray correction device 6 can accurately and in real time correct the delayed gamma rays. As a result, the reactor can be started and stopped in accordance with the output state of the reactor with high accuracy, and the operability of the reactor can be improved.

According to the configuration of the present embodiment described above, the output operation signal input device 14 built in the data collection device 7 is connected to the control rod drive control device 12 and the recirculation flow rate control device 13.
Therefore, one or both of the control rod operation signal from the control rod drive control device 12 and the recirculation flow rate operation signal from the recirculation flow rate control device 13 can be used as the output operation signal. .. As a result, the ratio of prompt gamma rays and the ratio of delayed gamma rays that change during operation can be calculated from the output signal in a state where the furnace output is constant, and the delayed gamma rays can be corrected more accurately.

According to the configuration of the present embodiment described above, since the reactor protection device 8 that generates the scram signal of the reactor based on the output from the delayed gamma ray correction device 6 is provided, the delayed gamma ray correction is performed with high accuracy. , A scram signal can be generated based on the output from the delayed gamma ray correction device 6.
As a result, the scrum signal can be generated accurately according to the output of the reactor, so that it is possible to prevent the scrum signal from being generated even when the output does not need to stop the reactor in an emergency. However, the operability of the reactor can be improved.

(Example 2)
The overall configuration diagram of the reactor power monitoring device of the second embodiment is shown in FIG.
In this embodiment, the core performance monitoring device 37 is added to the configuration of the reactor output monitoring device of the first embodiment shown in FIG.
The core performance monitoring device 37 is connected to the delayed gamma ray correction device 6.

The self-output type gamma ray detector 4 (only one is described in FIGS. 1 and 8) is three-dimensionally arranged in the core 2, and the weak current output from the self-output type gamma ray detector 4 is slow. It is sent to the gamma ray correction device 6 and the data collection device 7.

The delayed gamma ray correction device 6 converts the current received every moment into an output signal, and generates an output signal corrected with the delayed gamma ray component according to the correction models shown in the equations (1) and (2).

The data collection device 7 converts a weak current into an output signal, and delays the output signal from the time when the output of the reactor starts to change until a certain time elapses after performing an output operation satisfying a predetermined condition. It is sent to the emission gamma ray ratio calculation device 15.
_{Then, the latest a0} and _aj calculated by the delayed gamma ray ratio calculation device 15 are sent to the delayed gamma ray correction device 6, and the output signal corrected by the gamma ray correction device 6 is the core performance. It is sent to the computing device 37.

The core performance calculation device 37 adjusts (corrects the calculation) the built-in core calculation program (core three-dimensional simulator) based on the output signal considering the ratio of prompt gamma rays during reactor operation, and adjusts the output distribution and maximum line. Outputs core management information such as output density and minimum limit output ratio.
Examples of the output destination of the core management information from the core performance calculation device 37 include a display unit for displaying numerical values, a monitor for displaying information, a storage device for storing information, and the like.

According to the configuration of the present embodiment described above, the core calculation program is adjusted based on the output from the delayed gamma ray correction device 6, and the core management information such as the output distribution, the maximum line output density, and the minimum limit output ratio is output. The core performance calculation device 37 is provided.
As a result, the delayed gamma ray correction device 6 can supply the core performance calculation device 37 with a highly responsive and highly accurate output signal, so that the core performance calculation can be performed quickly and accurately, and the core performance can be monitored quickly and accurately. Therefore, the operability and safety of the nuclear reactor can be improved.

(Modification example)
In the first and second embodiments, the output operation signal is input from the control rod drive control device 12 and the recirculation flow rate control device 13 to the output operation signal input device 14, but the output operation signal is input by the operator. The output operation signal may be input to the device 14.

Further, in the first and second embodiments, both the control rod operation signal and the recirculation flow rate operation signal are used as output operation signals, but either the control rod operation signal or the recirculation flow operation signal is used. Only the signal may be used as the output signal.

The present invention is not limited to the above-described embodiments and examples, and includes various modifications. For example, the above-described embodiments and examples have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations.

1 Reactor pressure vessel, 2 Reactor core, 3 In-reactor instrumentation tube, 4 Self-powered gamma ray detector, 5 Cable, 6 Delayed gamma ray correction device, 7 Data collection device, 8 Reactor protection system, 9 Control rod, 10 Control rod drive device, 11 Recirculation pump, 12 Control rod drive control device, 13 Recirculation flow control device, 14 Output operation signal input device, 15 Delayed gamma ray ratio calculation device, 17 Emitter, 18 Insulation material, 19 Collector, 20 Core wire, 21 metal sheath, 22 insulation, 23 end plug, 25 weak current measuring device, 26 arithmetic device, 27 storage device, 28 transmitter, 29 input device, 30 initialization switch, 32 weak current measuring instrument, 33 arithmetic Equipment, 34 storage equipment, 35 transmitter, 37 core performance calculation equipment

Claims (6)

A self-output gamma ray detector provided with a metal emitter that emits electrons by irradiation with gamma rays and a metal collector that electrically insulates and encloses the emitter.
A delayed gamma ray correction device that corrects delayed gamma rays in real time,
A data collection device that collects detection signals from the self-output gamma ray detector, and
A delayed gamma ray ratio calculation device for calculating a delayed gamma ray ratio based on the detection signal collected by the data collection device is provided.
The data collection device includes an output operation signal input device to which an output operation signal is input by an operator or a control device, detects the start and end of the output fluctuation of the reactor based on the output operation signal, and outputs the output fluctuation. The detection signal from the self-output type gamma ray detector in the medium and constant output state after the output fluctuation is collected, and the detection signal is collected.
The delayed gamma ray correction device uses the delayed gamma ray ratio calculated by the delayed gamma ray ratio calculation device, and the self-output type gamma ray detector from the self-output type gamma ray detector in the constant output state collected by the data collection device. Reactor output monitoring device that corrects delayed gamma rays in real time for detection signals. The reactor output monitoring device according to claim 1, wherein the data collection device uses one or both signals of a control rod operation signal and a recirculation flow rate operation signal as the output operation signal. The delayed gamma ray correction device groups the delayed gamma rays into a group of a plurality of decay time constants having a minimum of less than 1 second and a maximum of 1 day or more, and calculates the contribution of all delayed gamma rays as the sum of the contributions from each of the groups. The reactor power monitoring device according to claim 1, wherein the delayed gamma ray is corrected by using a model formula. The data collection device detects the start and end of the output fluctuation of the reactor based on the output operation signal, and collects the detection signal of the self-output type gamma ray detector in a constant output state after the output fluctuation from the start of the output. Then, it is sent to the delayed gamma ray ratio calculation device.
The delayed gamma ray ratio calculation device calculates the delayed gamma ray ratio according to a predetermined process and sends it to the delayed gamma ray correction device.
The reactor output monitoring device according to claim 1, wherein the delayed gamma ray correction device updates a value stored at that time according to the transmitted delayed gamma ray ratio. The reactor output monitoring device according to claim 1, further comprising a reactor protection device that generates a scram signal of the reactor based on the output from the delayed gamma ray correction device. The first aspect of claim 1, further comprising a core performance calculation device that corrects the calculation of the core three-dimensional simulator based on the output from the delayed gamma ray correction device and calculates the maximum line output density and the minimum limit output ratio. Reactor output monitoring device.

Images