JP2023135895A - Critical approach monitor device, method for monitoring critical approach, and program - Google Patents

Abstract

To provide a critical approach monitoring device which can accurately calculate the amount of dilution necessary to achieve a criticality in an operation of the criticality of a nuclear reactor.SOLUTION: The critical approach monitoring device includes: a reverse duplation rate calculation unit for measuring an outside-of-reactor detector response to the amount of dilution of boron and calculating a reverse duplation rate; a correction unit for calculating a prediction line showing the shift of the reverse duplation rate on the basis of the reverse duplation rate calculated by the reverse duplation rate calculation unit; and a stop instruction unit for issuing a stop instruction of a dilution operation when the revere duplation rate reaches the dilution stop target set on the basis of the prediction line.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a critical proximity monitoring device, a critical proximity monitoring method, and a program.

Reactor physical inspection of a nuclear power plant involves the process of starting up the reactor and reaching a critical state. In this process, operators perform critical operations (insertion and withdrawal of control rods, concentration and dilution of boron) while monitoring the value of 1/M (inverse multiplication factor) defined by the following equation (1). )I do.
1/M=(Detection value of neutrons in the source area in the reference state)/(Detection value of neutrons in the source area at the time of measurement)...(1)
The numerator of Equation (1), ``source area neutron detection value in the reference state'', is the source area neutron detection value before the start of critical operation in reactor physical inspection, and the denominator, ``source area neutron detection value at the time of measurement'', is the source area neutron detection value at the time of measurement. The ``neutron detection value'' is the neutron detection value in the source region at each point in time until the nuclear reactor reaches a critical state after performing critical operation. The source region neutron detection value is measured by an ex-core detector installed outside the reactor. The value of equation (1) is "1" at the start of critical operation and "0" at critical time.

Patent Document 1 discloses that during critical operation of a nuclear reactor, neutron flux is detected by an ex-core detector, and 1/M at at least three different times is calculated by the above equation (1). A method is disclosed for estimating the transition of 1/M from the value of /M until the reactor reaches a critical state by solving predetermined simultaneous equations.

Special Publication No. 04-069759

In the conventional criticality approach monitoring method, a 1/M prediction line indicating the transition of 1/M during criticality operation is calculated in advance, and based on the calculated 1/M prediction line, the criticality operation amount required to achieve criticality is calculated. (for example, the amount of dilution). However, in actual situations, there is a discrepancy between the 1/M measured value measured during critical operation and the 1/M predicted line obtained by preliminary analysis, and the 1/M predicted line Even if criticality operations are carried out based on this, there is a possibility that criticality cannot be achieved or that criticality is achieved sooner than expected. There is a need for technology to accurately calculate the amount of operation necessary to achieve criticality.

The present disclosure provides a critical proximity monitoring device, a critical proximity monitoring method, and a program that can solve the above problems.

The criticality proximity monitoring device of the present disclosure includes an inverse doubling factor calculating section that measures an ex-core detector response to the dilution amount of boron and calculates an inverse doubling factor, and the inverse doubling factor calculated by the inverse doubling factor calculating section. a correction unit that calculates a predicted line indicating the transition of the inverse doubling rate with respect to the dilution amount based on the dilution amount; A stop instruction unit that issues a stop instruction.

The criticality proximity monitoring method of the present disclosure includes a step of measuring an ex-core detector response to the dilution amount of boron and calculating an inverse doubling factor, and based on the inverse doubling factor calculated in the calculating step, calculating a predicted line indicating the transition of the inverse doubling rate with respect to the dilution amount; and instructing to stop the dilution operation when the inverse doubling rate reaches a dilution stop target set based on the predicted line. , has.

The program of the present disclosure includes a step of having a computer measure an ex-core detector response to the amount of dilution of boron and calculating an inverse doubling factor, and based on the inverse doubling factor calculated in the calculating step, calculating a predicted line indicating the transition of the inverse doubling rate with respect to the dilution amount; and instructing to stop the dilution operation when the inverse doubling rate reaches a dilution stop target set based on the predicted line. , is executed.

According to the above-described criticality proximity monitoring device, criticality proximity monitoring method, and program, it is possible to accurately calculate the criticality operation amount required to achieve criticality.

FIG. 1 is a block diagram showing an example of a reactor physical inspection apparatus according to an embodiment. It is a figure explaining a 1/M prediction line. It is a figure explaining calculation of a 1/M prediction line concerning an embodiment. It is a figure explaining calculation of dilution stop 1/M concerning an embodiment. It is a flow chart which shows an example of critical approach monitoring processing concerning an embodiment. 1 is a diagram illustrating an example of a hardware configuration of a reactor physical inspection apparatus according to an embodiment.

<Embodiment>
The criticality approach monitoring method of the present disclosure will be described below with reference to FIGS. 1 to 6.
(composition)
FIG. 1 is a block diagram showing an example of a reactor physical inspection apparatus according to an embodiment. The reactor physical inspection device 10 accurately calculates the control amount (dilution amount) of the criticality operation necessary to achieve criticality in the process of achieving a critical state in the reactor physical inspection.

The reactor physical inspection device 10 is communicatively connected to the nuclear power plant 20. The nuclear power plant 20 includes a control rod insertion/extraction operation panel 21, a boron dilution/concentration operation panel 22, and an external detector 23. When an operator instructs the control rod insertion/withdrawal operation panel 21 to withdraw, etc., a control rod insertion/withdrawal signal based on the instruction is transmitted from the nuclear power plant 20 to the reactor physical inspection device 10 . When an operator issues an instruction such as dilution to the boron dilution/concentration operation panel 22, a boron dilution/concentration signal based on the instruction is transmitted from the nuclear power plant 20 to the reactor physical inspection device 10. . The ex-core detector 23 measures a source region neutron detection value (ex-core detector response measurement value) and transmits the value to the reactor physical inspection device 10. The reactor physical inspection device 10 receives control rod insertion/withdrawal signals including control rod step positions, boron dilution/concentration signals including boron concentration and dilution/concentration amounts, from a nuclear power plant 20 undergoing a reactor physical inspection. Obtain ex-core detector response measurements.

The reactor physical inspection device 10 includes a timer 11, a data recording/control device 12, a 1/M measurement value calculation device 13, a 1/M predicted line correction device 14, an external detector response analysis device 15, and an operator. It includes a console 16 and a display device 17. Of these, the data recording/control device 12, the 1/M measured value calculation device 13, the external detector response analysis device 15, the 1/M predicted line correction device 14, and the operator console 16 are connected to a PC ( It consists of computers such as personal computers and server terminal devices.

The timer 11 measures time.
The data recording/control device 12 uses data acquired from the nuclear power plant 20 (control rod insertion/withdrawal signals, boron dilution/concentration signals, measured response values of external detectors) and the reactor physical inspection device 10 to perform calculations. Record and store the data (1/M measured values, predicted responses of ex-core detectors, 1/M analysis lines, 1/M predicted lines, etc.). Further, the data recording/control device 12 controls the criticality approach monitoring process, the display control of the display device 17, and the like.

The 1/M measurement value calculation device 13 calculates 1/M (inverse multiplication factor). The 1/M measurement value calculation device 13 converts the ex-core detector response measurement value measured by the ex-core detector 23 at the start point (reference state) of the critical operation into a numerator, and calculates the ex-core detector response measurement value measured by the ex-core detector 23 at each point during the critical operation. 1/M during critical operation is calculated using the above equation (1) using the measured ex-core detector response measured by as the denominator. The 1/M calculated by the 1/M measurement value calculation device 13 is referred to as a "1/M measurement value." In addition, the 1/M measurement value calculation device 13 acquires the control rod step position, the boron dilution amount/concentration amount, and later plots the 1/M measurement value on the vertical axis as illustrated in FIGS. 2 to 4. , create a "1/M curve chart" in which the 1/M measured values are plotted on a graph with the control amount of critical operation (control rod withdrawal amount/dilution amount) on the horizontal axis.

Each time the 1/M measurement value calculation device 13 calculates a 1/M measurement value, the 1/M prediction line correction device 14 calculates the change in 1/M based on the 1/M measurement values calculated so far. Calculate a 1/M prediction line that predicts . The 1/M predicted line correction device 14 is based on the predicted value of 1/M obtained by simulating various core states, which is obtained in advance by sensitivity analysis using the reactivity of the reactor core as a parameter. (Sensitivity analysis, simulation of core state, calculation of predicted value of 1/M, etc. are executed by the ex-core detector response analysis device 15, which will be explained next.), and a 1/M analysis line showing the transition of 1/M is calculated. Create multiple 1/M analysis lines by fitting 1/M predicted values (sixth-order polynomial approximation, etc.), and select the 1/M analysis line closest to the actual 1/M measurement value transition from among the 1/M analysis lines. . The selected 1/M analysis line is the 1/M prediction line.

The ex-core detector response analysis device 15 uses the reactivity of the reactor as a parameter to simulate the state inside the reactor core according to various reactivities, and analyzes the predicted value of the ex-core detector response at that time. calculate. The ex-core detector response analysis device 15 includes an in-core neutron flux analyzer 151 and an ex-core detector response calculation device 152.

The in-core neutron flux analysis device 151 has a core model that simulates the state of the reactor core. The in-core neutron flux analysis device 151 analyzes the distribution of neutron flux in the reactor under various boron concentrations by adjusting and varying the boron concentration using a reactor core model. For example, the in-core neutron flux analysis device 151 analyzes the moment-by-moment distribution of neutron flux in the reactor when a certain boron concentration is set in the initial state and the boron is then diluted at a certain rate. do. The in-core neutron flux analyzer 151 variously calculates the core reactivity, secondary neutron source strength, etc. in the initial state, and the core reactivity, secondary neutron source strength, etc. after the start of dilution, depending on the amount of dilution. Multiple "sensitivity analysis scenarios" (hereinafter referred to as scenarios) with varying changes are created, and for each scenario, the neutron flux within the core is analyzed according to the reactivity of the reactor core, the strength of the secondary neutron source, etc. The in-core neutron flux analysis device 151 outputs information on the in-core neutron flux as an analysis result for each scenario to the out-of-core detector response calculation device 152. Further, the in-core neutron flux analysis device 151 calculates the reactivity (withdrawal value) according to the position of the control rod.

The out-of-core detector response calculation device 152 acquires information on the in-core neutron flux for each scenario analyzed by the in-core neutron flux analysis device 151, and performs out-of-core detection when the reactor core is in the state indicated by the analysis result of the scenario. The measured value of the ex-core detector response measured by the detector 23 is calculated. This value is called the ex-core detector response predicted value. The ex-core detector response calculation device 152 stores data including the transition of the predicted ex-core detector response value as dilution progresses for each scenario (data that combines the boron concentration at each time point and the predicted ex-core detector response value). set) is recorded in the data recording/control device 12. Note that the calculation code (program) that performs the functions of the in-core neutron flux analysis device 151 and the out-of-core detector response calculation device 152 is well known in the field of nuclear power.

The operator console 16 is a terminal device used by an operator to issue various instructions to the reactor physical inspection apparatus 10. For example, an operator uses the operator console 16 to instruct the flow rate and addition amount of water and boron regarding dilution and concentration of boron.

The display device 17 is a liquid crystal display, an organic EL display, or the like. The display device 17 displays 1/M curve diagrams illustrated in FIGS. 2 to 4, control amounts necessary to achieve criticality, information instructing to stop dilution, and the like.

FIG. 2 shows a 1/M curve diagram. The vertical axis in FIG. 2 is 1/M, and the horizontal axis is the dilution amount and control rod withdrawal amount. L1 in FIG. 2 is a 1/M prediction line showing the transition of 1/M obtained by preliminary analysis, and points M0 to M11 are 1/M measurement values measured during critical operation. In the process of achieving a critical state for reactor physical inspection, the control rod is pulled out to the X step position before the start of critical operation, and boron dilution is started in that state. After dilution has been carried out to a certain target point, criticality is achieved by withdrawing the control rod further Y steps from the X step position. Conventionally, criticality could be achieved by estimating the 1/M prediction line L1, which shows the 1/M transition when dilution is performed at a desired rate, through preliminary analysis, and then withdrawing the control rod in Y steps after dilution. , monitor the 1/M measurement value with a target of point P0, which is subcritical by the amount corresponding to the Y step extraction, from the point P1 where the value of this 1/M prediction line L1 becomes 0 (criticality achieved), Dilution is performed until the 1/M measurement value reaches "dilution stop 1/M" which is the 1/M value corresponding to the target point P0. However, with this method, as shown in the example in Fig. 2, there is a difference between the 1/M measured values M0 to M11 measured during actual critical operation and the 1/M predicted line L1 obtained by preliminary analysis. In this case, if dilution is performed until the 1/M measurement value becomes "dilution stop 1/M", there is a possibility that criticality will be reached in the subsequent control rod withdrawal process with a withdrawal amount smaller or larger than the Y step. be. Different withdrawal amounts after dilution will affect the subsequent process of furnace physical inspection. Therefore, it is desirable to be able to achieve criticality by drawing Y steps as planned. For this purpose, it is necessary to accurately calculate the 1/M prediction line L1 that matches the 1/M measurement value measured during the reactor physical inspection. Therefore, the 1/M measurement value calculation device 13 calculates 1/M every time the extra-core detector 23 measures the extra-core detector response during critical operation, and the 1/M predicted line correction device 14 Every time a 1/M measurement value is calculated, the 1/M predicted line is updated and corrected to calculate an accurate 1/M predicted line.

(Update/correction of 1/M prediction line)
Calculation of the predicted line according to the embodiment will be described with reference to FIG. 3. The 1/M predicted line correction device 14 reads out the predicted ex-core detector response values for each scenario, analyzed in advance by the ex-core detector response analysis device 15, from the data recording/control device 12, and calculates the actual reactor physics. Calculate the predicted response of the ex-core detector response in the reference state based on the boron concentration of the reactor before critical operation in the inspection by linear interpolation, etc., and calculate the value of 1/M as dilution progresses using equation (1). Then, a plurality of "1/M analysis lines" are generated by fitting (such as sixth-order polynomial approximation) to the 1/M predicted value for each scenario. At this time, by performing linear interpolation or fitting using a predetermined curve (approximate curve of a sixth-order polynomial, etc.) using the 1/M predicted value of the subcritical state, a 1/M analytical line close to achieving criticality can be drawn. Calculate. As a result, a highly accurate 1/M analysis line can be obtained. FIG. 3 shows 1/M analysis lines L1 to L4.

The 1/M predicted line correction device 14 selects the 1/M analytical line closest to the trajectory indicated by the 1/M measured values M0 to M5 measured during the reactor physical inspection from among the 1/M analytical lines L1 to L4. The selected 1/M analysis line is then set as the "most likely" 1/M prediction line. In the example of FIG. 3, the 1/M predicted line correction device 14 sets the 1/M analysis line L3 as the 1/M predicted line. Examples of methods for selecting a 1/M prediction line from among a plurality of 1/M analysis lines based on predicted ex-core detector response values analyzed in advance include the following method. That is, the 1/M predicted line correction device 14 calculates the distance between each of the 1/M measured values M0 to M5 and each of the 1/M analysis lines L1 to L4, and calculates the distance between each of the 1/M measured values M0 to M5. The 1/M analysis line with the minimum sum of squares of distances is selected as the 1/M prediction line. Alternatively, the 1/M predicted line correction device 14 selects some of the 1/M measured values M0 to M5, for example, a predetermined number (for example, measured values M3 to M5) starting from the latest 1/M measured value. Select the 1/M analysis line that has the minimum sum of squares of distances from each of the 1/M analysis lines L1 to L4 calculated for each of the selected 1/M measurement values as the 1/M prediction line. Good too. Alternatively, for example, the 1/M predicted line correction device 14 calculates the 1/M analysis line L1 using the following equation (2) with arbitrary weighting coefficients A1 to A5 added to each 1/M measurement value. An evaluation value D1 regarding the difference between the M measurement value and the 1/M analysis line L1 may be calculated.
D1=A1 (distance between 1/M measurement value M0 and 1/M analysis line L1) ² +A2 (distance between 1/M measurement value M1 and 1/M analysis line L1) ² +A3 (1/M measurement value M2 and 1 /M analysis line L1) ² +A4 (distance between 1/M measurement value M3 and 1/M analysis line L1) ² +A5 (distance between 1/M measurement value M4 and 1/M analysis line L1) ² +A6 (1 /Distance between measured value M5 and 1/M analysis line L1) ² ...(2)
The 1/M predicted line correction device 14 similarly calculates the evaluation values D2 to D4 for the other 1/M analysis lines L2 to L4, and selects the 1/M analysis line for which the evaluation values D1 to D4 are the smallest. Select as the 1/M predicted line. Further, for the distance between the 1/M measurement value and the 1/M analysis line, the distance itself (absolute value) may be used instead of the square of the distance.

(Dilution stop 1/M)
After calculating the 1/M predicted line, the 1/M predicted line correction device 14 calculates a dilution stop 1/M, which is the value of 1/M when dilution is stopped. FIG. 4 shows a method for calculating the dilution stop 1/M according to the embodiment. By using the core model of the in-core neutron flux analysis device 151, it is possible to calculate the reactivity according to the position of the control rod. By utilizing this property, for example, it is possible to calculate the increase in reactivity when the control rod is further pulled out by Y steps from the position of X steps. The 1/M predicted line correction device 14 uses the in-core neutron flux analysis device 151 to calculate the amount of increase in reactivity (withdrawal value) corresponding to the Y-step withdrawal. The 1/M predicted line correction device 14 calculates a point P0 that is returned to the subcritical direction from the critical point P1 predicted by the 1/M predicted line L3 by the amount of dilution corresponding to the extraction value, and returns the point P0 The value of 1/M of the intersection P2 between the perpendicular line passing through and the predicted line L3 is calculated. This value is the dilution stop 1/M. During criticality operation, dilution is performed until the value of the 1/M measurement value calculated by the 1/M measurement value calculation device 13 reaches the dilution stop 1/M, and then criticality is achieved by withdrawing the control rod in Y steps. be able to.

(motion)
Next, with reference to FIG. 5, the flow of processing for criticality approach monitoring during criticality operation will be described.
FIG. 5 is a flowchart illustrating an example of criticality approach monitoring processing according to the embodiment.
In advance, the ex-core detector response analysis device 15 performs a sensitivity analysis using parameters such as the reactivity of the reactor core and secondary neutron source strength, and performs an in-core neutron flux analysis and an ex-core detector response evaluation. A predicted response value for the outside core detector is calculated for each scenario (step S1). The out-of-core detector response analysis device 15 records the predicted out-of-core detector response value to the data recording/control device 12 .

Next, the operator starts critical operation (step S2). From the nuclear power plant 20, the boron concentration before the start of critical operation (reference state) is transmitted to the reactor physical inspection device 10. In addition, when the criticality operation starts, the nuclear power plant 20 periodically or signals are outputted, such as control rod insertion/withdrawal signals, boron dilution/concentration signals, and external detector response measurement values. It is transmitted to the reactor physical inspection device 10 when the These pieces of information are recorded in the data recording/control device 12.

The 1/M measurement value calculation device 13 calculates the 1/M measurement value after acquiring the measurement value of the response of the outside reactor detector to the dilution amount of boron (step S3). After calculating the 1/M measurement value, the 1/M measurement value calculation device 13 plots the value on a 1/M curve diagram. In addition, the 1/M predicted line correction device 14 adjusts the predicted ex-core detector response value at the boron concentration before the start of the actual criticality operation (reference state) from the ex-core detector response predicted value created in advance to within a linear range. A plurality of 1/M analysis lines are created by fitting (such as sixth-order polynomial approximation) to the 1/M predicted value for each scenario as the dilution progresses using equation (1).

Next, the 1/M predicted line correction device 14 calculates the error between the 1/M measured value and the 1/M analysis line (step S4). For example, the 1/M predicted line correction device 14 calculates the distance between the 1/M measurement value at each time measured during the critical operation and each of the plurality of 1/M analysis lines. Next, the 1/M predicted line correction device 14 selects the 1/M analysis line with the smallest error as the 1/M predicted line (step S5). For example, the 1/M predicted line correction device 14 performs a 1/M analysis in which the sum of the squares of the distances of the 1/M measurement values at each time measured during the critical operation and the 1/M analysis line is the minimum. Select the line as the 1/M predicted line. The 1/M predicted line correction device 14 displays the selected 1/M predicted line on a 1/M curve diagram.

Once the 1/M predicted line can be calculated, the 1/M predicted line correction device 14 calculates the dilution stop 1/M based on the 1/M predicted line and the amount of extraction after dilution (for example, Y step). (Step S6). The 1/M predicted line correction device 14 is located at a position in the 1/M curve diagram that returns to the subcritical side by a dilution amount corresponding to the extraction value of the Y step from the critical point P1 indicated by the 1/M predicted line. A certain point P0 is calculated, the value of 1/M corresponding to the dilution amount of point P0 on the 1/M prediction line is found, and that value is calculated as the dilution stop 1/M. The 1/M predicted line correction device 14 displays the calculated dilution stop 1/M on a 1/M curve diagram. The data recording/control device 12 outputs a 1/M curve diagram as illustrated in the left diagram 400 of FIG. 4 to the display device 17.

Further, the data recording/control device 12 may display the time until the dilution amount reaches the intersection P2 (=point P0) of the dilution stop 1/M and the 1/M predicted line. Specifically, since the data recording/control device 12 obtains the dilution amount from the nuclear power plant 20, it can detect the current boron concentration and dilution amount in the nuclear reactor. Furthermore, the data recording/control device 12 can calculate the dilution speed from the past changes in the dilution amount over time. The data recording/control device 12 calculates the difference between the current dilution amount and the dilution amount indicated by point P2 on the 1/M prediction line, and divides the difference by the dilution speed to determine the dilution amount. Calculate the time it takes to reach the intersection P2 (= point P0) of the 1/M and 1/M predicted lines (the time it takes for the 1/M measurement value during dilution to reach the dilution stop 1/M), and calculate the calculated time. , the current dilution amount and the dilution amount at the intersection P2 (=point P0) are output to the display device 17 together with the 1/M curve diagram. The display 17 displays the most probable 1/M prediction line and the 1/M measurement as well as the time at which the 1/M measurement reaches the dilution stop 1/M. This allows the user to know how much more dilution is required, and how much time it will take until the 1/M measurement value becomes 1/M, the dilution stop, assuming the current dilution speed is maintained. can do.

Next, the data recording/control device 12 determines whether the 1/M measurement value has reached the dilution stop 1/M (step S7). The data recording/control device 12 compares the latest 1/M measurement value calculated last by the 1/M measurement value calculation device 13 with the dilution stop 1/M, and the latest 1/M measurement value is the dilution stop. When it reaches 1/M or when the difference between the two falls within a predetermined range, it is determined that the 1/M measurement value has reached the dilution stop level of 1/M, and if not, the 1/M measurement value is determined to be 1/M. It is determined that the dilution stop 1/M has not been reached. When the 1/M measurement value reaches the dilution stop 1/M (step S7; Yes), the data recording/control device 12 outputs information to the display device 17 instructing to stop the dilution operation. The display device 17 displays, for example, a message indicating that the 1/M measurement value of the monitored object has reached the dilution stop value of 1/M and an instruction to stop the dilution operation (step S8). The operator stops the dilution operation and withdraws the control rod in Y steps to achieve criticality. The data recording/control device 12 displays text instructing the operator to stop the dilution operation a predetermined time before the 1/M measurement value reaches the dilution stop 1/M value so that the operator can operate the operation with sufficient time. You may also do so. Alternatively, the data recording/control device 12 sends a notification that the 1/M measurement value will soon reach the dilution stop 1/M, a predetermined time before the 1/M measurement value reaches the dilution stop 1/M. You may also display the following text. The operator performs the dilution operation so that the dilution can be stopped at the target point while checking these notifications and the 1/M curve diagram showing the time when the 1/M measurement value reaches the dilution stop value of 1/M. On the other hand, if the 1/M measurement value does not reach the dilution stop 1/M (step S7; No), the process from step S3 is repeated.

As described above, according to the present embodiment, the 1/M predicted line is corrected during critical operation based on the 1/M measured value, and an accurate 1/M predicted line is calculated. Then, each time a 1/M measurement value is measured, the 1/M prediction line is updated. Thereby, it is possible to accurately calculate the point P1 (FIGS. 2 and 4) representing the manipulated variable (dilution amount) when achieving criticality by dilution. In addition, the withdrawal value (the reactivity before Y-step withdrawal when criticality is exactly achieved after Y-step withdrawal) based on the planned control rod withdrawal amount after dilution is calculated, and the withdrawal value is calculated from point P1 by the amount of withdrawal value. The near point P0 (the point in time when dilution has not progressed by the amount of withdrawal value) is calculated, and the dilution stop 1/M corresponding to the dilution amount at that time is calculated. Thereby, it is possible to accurately calculate the control amount (dilution amount, withdrawal amount) of criticality operation required to achieve criticality. By improving the prediction accuracy of criticality operations, criticality can be achieved as planned with planned criticality operations, improving safety. For example, it is possible to prevent unexpected criticality due to a sudden drop in the 1/M measurement value, thereby improving safety. In addition, by displaying the corrected accurate 1/M prediction line and dilution stop 1/M, as well as the time until the 1/M measurement value reaches the dilution stop 1/M, the time required to ensure safety is displayed. You can understand the margin and dilution amount.

In addition, by suppressing variations in dilution stoppage, variations in the amount of control rods withdrawn can be reduced, and criticality can be achieved with the scheduled Y-step withdrawal, so unnecessary dilution and concentration operations are unnecessary in subsequent processes. There's no need. Therefore, it is possible to shorten the time not only for the process of achieving a critical state in the reactor physical inspection but also for related post-processes.

FIG. 6 is a diagram illustrating an example of the hardware configuration of the reactor physical inspection apparatus according to the embodiment. The computer 900 includes a CPU 901, a main storage device 902, an auxiliary storage device 903, an input/output interface 904, and a communication interface 905.
The above-described data recording/control device 12, 1/M measured value calculation device 13, 1/M predicted line correction device 14, external detector response analysis device 15, and operator console 16 are implemented in the computer 900. Ru. Each of the above-mentioned functions is stored in the auxiliary storage device 903 in the form of a program. The CPU 901 reads the program from the auxiliary storage device 903, expands it to the main storage device 902, and executes the above processing according to the program. Further, the CPU 901 reserves a storage area in the main storage device 902 according to the program. Further, the CPU 901 secures a storage area in the auxiliary storage device 903 to store the data being processed according to the program.

Realizes all or part of the functions of the data recording/control device 12, the 1/M measured value calculation device 13, the 1/M predicted line correction device 14, the external detector response analysis device 15, and the operator console 16. It is also possible to record a program for doing this on a computer-readable recording medium, and to cause the computer system to read and execute the program recorded on the recording medium, thereby performing processing by each functional unit. The "computer system" here includes hardware such as an OS and peripheral devices. Furthermore, the term "computer system" includes the homepage providing environment (or display environment) if a WWW system is used. Furthermore, the term "computer-readable recording medium" refers to portable media such as CDs, DVDs, and USBs, and storage devices such as hard disks built into computer systems. Further, when this program is distributed to the computer 900 via a communication line, the computer 900 that received the distribution may develop the program in the main storage device 902 and execute the above processing. Further, the above program may be one for realizing a part of the above-mentioned functions, and further may be one that can realize the above-mentioned functions in combination with a program already recorded in the computer system. .

As described above, several embodiments according to the present disclosure have been described, but all these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

<Additional notes>
The critical proximity monitoring device, critical proximity monitoring method, and program described in each embodiment can be understood, for example, as follows.

(1) The criticality proximity monitoring device (reactor physical inspection device 10) according to the first aspect measures the response of the external detector (neutron flux output value) to the dilution amount of boron, and measures the inverse doubling factor (1/M a prediction indicating the transition of the inverse doubling rate based on the inverse doubling rate calculated by the inverse doubling rate calculating unit (1/M measured value calculating device 13) and the inverse doubling rate calculating unit A correction unit (1/M predicted line correction device 14) that calculates the line and a stop of the dilution operation when the inverse doubling rate reaches the dilution stop target (dilution stop 1/M) set based on the predicted line. It includes a stop instruction section (data recording/control device 12) that issues instructions.
This makes it possible to calculate an accurate 1/M prediction line and accurately calculate the amount of dilution required to achieve criticality.

(2) The criticality proximity monitoring device (reactor physical inspection device 10) according to the second aspect is the criticality proximity monitoring device of (1), which includes the inverse doubling factor calculation unit (1/M measurement value calculation device 13). calculates the inverse doubling factor each time the ex-core detector response is measured, and the correction unit (1/M predicted line correction device 14) calculates the inverse doubling factor by the inverse doubling factor calculation unit. Each time the prediction line is calculated, the predicted line is calculated based on the calculated inverse doubling factor.
Thereby, it is possible to accurately calculate a 1/M prediction line according to the reactivity in the reactor that changes due to dilution, and maintain prediction accuracy of the time to reach criticality and the amount of dilution required to achieve criticality.

(3) The criticality proximity monitoring device (reactor physical inspection device 10) according to the third aspect is the criticality proximity monitoring device of (1) to (2), which includes the correction unit (1/M predicted line correction device 14). The external detector response analysis device 15) adjusts the reactivity of the reactor core, the strength of the secondary neutron source, etc. using the reactivity of the core, the strength of the secondary neutron source, etc. as parameters. An analytic line indicating a change in the inverse doubling rate is generated, and from among the plurality of analytic lines, the analytic line closest to the calculated change in the inverse doubling rate is calculated as the predicted line.
In advance, sensitivity analysis was performed using the reactor core reactivity and secondary neutron source strength as parameters, and multiple ex-core detector response prediction values were created. The predicted response value of the external detector is calculated by linear interpolation or the like, and a plurality of 1/M analysis lines are created using equation (1). Thereby, the accuracy of the 1/M prediction line can be maintained.

(4) The criticality proximity monitoring device (reactor physical inspection device 10) according to the fourth aspect is the criticality proximity monitoring device of (3), in which the correction section (ex-core detector response analysis device 15) Among the parameters of the reactor core model, the neutron flux distribution in the reactor for the dilution amount (critical operation amount) is analyzed using the reactivity of the reactor core, secondary neutron source strength, etc. as parameters, and the analyzed neutron A predicted value of the ex-core detector response (ex-core detector response predicted value) is calculated based on the flux distribution, and a predicted value of the ex-core detector response according to the change in the dilution amount is generated.
Using a core model, sensitivity analysis is performed using parameters such as core reactivity and secondary neutron source strength, and various patterns of predicted ex-core detector response values are created. It is possible to correspond to the 1/M measurement value measured in the operation scene, and the accuracy of the predicted line can be maintained.

(5) The criticality proximity monitoring device (reactor physical inspection device 10) according to the fifth aspect is the criticality proximity monitoring device according to (4), in which the correction section adjusts the Fitting is performed on the predicted value of the detector response using a predetermined curve (for example, a curve expressed by a sixth-order polynomial) to generate a plurality of analysis lines.
Thereby, an analytical line can be generated from the predicted response value of the out-of-core detector.

(6) The criticality proximity monitoring device (reactor physical inspection device 10) according to the sixth aspect is the criticality proximity monitoring device of (3) to (5), wherein the inverse The doubling rate and the error between the analysis line and the analysis line are calculated, and the analysis line with the minimum error is selected as the prediction line.
This makes it possible to calculate a predicted line that matches the actual 1/M measurement value.

(7) The criticality proximity monitoring device (reactor physical inspection device 10) according to the seventh aspect is the criticality proximity monitoring device of (1) to (6), which includes the correction unit (1/M predicted line correction device 14). ) calculates the amount of change in reactivity (pulling value, reactivity value) when controlling the control rod from a predetermined initial position (X step) to a predetermined target position (X+Y step), and calculates the amount of change and the above-mentioned amount of change. The dilution stop target is calculated based on the dilution amount at which the criticality indicated by the predicted line is achieved.
Thereby, the dilution stop target can be calculated in consideration of the amount of withdrawal after dilution.

(8) The criticality proximity monitoring device (reactor physical inspection device 10) according to the eighth aspect is the criticality proximity monitoring device of (1) to (7), further comprising a display device that displays the predicted line. .
This allows the operator to predict the 1/M change due to dilution.

(9) The criticality proximity monitoring device (reactor physical inspection device 10) according to the ninth aspect is the criticality proximity monitoring device according to (8), wherein the display device includes a stop target line indicating the dilution stop target; The time required for the dilution amount to reach the intersection of the stop target line and the predicted line is displayed.
This makes it possible to know the stop position of the dilution amount and the time until the dilution stops.

(10) The criticality proximity monitoring method according to the tenth aspect includes the steps of: measuring the response of an ex-core detector to the dilution amount of boron and calculating an inverse doubling factor; and based on the calculated inverse doubling factor, The method includes the steps of calculating a predicted line indicating the transition of the inverse doubling rate, and instructing to stop the dilution operation when the inverse doubling rate reaches a dilution stop target set based on the predicted line.

(11) The program according to the eleventh aspect includes the step of causing the computer 900 to measure the response of the ex-core detector to the dilution amount of boron and calculating the inverse doubling factor, and to calculate the inverse doubling factor based on the calculated inverse doubling factor. , calculating a predicted line indicating the transition of the inverse doubling rate, and instructing to stop the dilution operation when the inverse doubling rate reaches a dilution stop target set based on the predicted line. let

10...Reactor physical inspection device 11...Timer 12...Data recording/control device 13...1/M measurement value calculation device 14...1/M predicted line correction device 15...Outside the reactor Detector response analysis device 151...In-core neutron flux analysis device 152...External detector response calculation device 16...Operator console 17...Display device 20...Nuclear plant 21...Control rod Insertion/extraction operation panel 22...Boron dilution/concentration operation panel 23...External detector 900...Computer 901...CPU
902... Main storage device 903... Auxiliary storage device 904... Input/output interface 905... Communication interface

Claims (11)

an inverse doubling factor calculation unit that measures an ex-core detector response to the dilution amount of boron and calculates an inverse doubling factor;
a correction unit that calculates a prediction line indicating a change in the inverse doubling rate with respect to the dilution amount based on the inverse doubling rate calculated by the inverse doubling rate calculation unit;
a stop instruction unit that instructs to stop the dilution operation when the reverse doubling rate reaches a dilution stop target set based on the predicted line;
A critical proximity monitoring device equipped with. The inverse doubling factor calculation unit calculates the inverse doubling factor each time the ex-core detector response is measured,
The correction unit calculates the prediction line based on the inverse doubling rate calculated each time the inverse doubling rate is calculated by the inverse doubling rate calculating unit.
The critical proximity monitoring device according to claim 1. The correction unit indicates the transition of the inverse doubling factor with respect to the dilution amount by adjusting the reactivity of the reactor core and the intensity of the secondary neutron source using the reactivity of the reactor core and the intensity of the secondary neutron source as parameters. generating a plurality of analytical lines, and calculating, from among the plurality of analytical lines, the analytical line closest to the transition of the inverse doubling rate calculated by the inverse doubling rate calculation unit as the predicted line;
The critical proximity monitoring device according to claim 1 or claim 2. The correction unit analyzes the neutron flux distribution in the reactor with respect to the dilution amount using the reactivity of the reactor core and the secondary neutron source strength as parameters among the parameters of the reactor core model, and calculating a predicted value of the out-of-core detector response based on the flux distribution, and generating the analytical line based on the predicted value of the out-of-core detector response in response to a change in the dilution amount;
The critical proximity monitoring device according to claim 3. The correction unit generates the analysis line by fitting a predicted value of the ex-core detector response according to a change in the dilution amount using a predetermined curve.
The critical proximity monitoring device according to claim 4. The correction unit calculates an error between the inverse doubling factor calculated by the inverse doubling factor calculation unit and the analytic line, and selects the analytic line with a minimum error as the predicted line.
The critical proximity monitoring device according to any one of claims 3 to 5. The correction unit calculates the amount of change in reactivity when controlling the control rod from a predetermined initial position to a predetermined target position, and calculates the amount of change and the dilution amount when achieving the criticality indicated by the predicted line. Calculating the dilution stop target based on
The critical proximity monitoring device according to any one of claims 1 to 6. a display device that displays the predicted line;
The critical proximity monitoring device according to any one of claims 1 to 7, further comprising: The display device displays a stop target line indicating the dilution stop target and a time until the dilution amount reaches the intersection of the stop target line and the predicted line.
The critical proximity monitoring device according to claim 8. measuring an ex-core detector response to a dilution amount of boron and calculating an inverse doubling factor;
Based on the inverse doubling rate calculated in the calculating step, calculating a prediction line indicating a change in the inverse doubling rate with respect to the dilution amount;
When the reverse doubling rate reaches a dilution stop target set based on the predicted line, instructing to stop the dilution operation;
A critical proximity monitoring method having to the computer,
measuring an ex-core detector response to a dilution amount of boron and calculating an inverse doubling factor;
Based on the inverse doubling rate calculated in the calculating step, calculating a prediction line indicating a change in the inverse doubling rate with respect to the dilution amount;
When the reverse doubling rate reaches a dilution stop target set based on the predicted line, instructing to stop the dilution operation;
A program to run.

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