Critical proximity monitoring device, critical proximity monitoring method, and program

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

Technical Field

[0001] The present disclosure relates to a critical proximity monitoring device, a critical proximity monitoring method, and a program.

Background Art

[0002] In the nuclear reactor physics inspection of a nuclear power plant, there is a process of starting up the nuclear reactor to reach a critical state. In this process, the operator performs critical operations (insertion / extraction of control rods, enrichment / dilution of boron) while monitoring the value of 1 / M (inverse multiplication factor) defined by the following formula (1). 1 / M = (Neutron detection value in the source region in the reference state) / (Neutron detection value in the source region at the measurement time) ··· (1) The "neutron detection value in the source region in the reference state" in the numerator of formula (1) is the neutron detection value in the source region before the start of critical operation in the nuclear reactor physics inspection, and the "neutron detection value in the source region at the measurement time" in the denominator is the neutron detection value in the source region at each time point until the nuclear reactor reaches the critical state by performing critical operations. The neutron detection value in the source region is measured by an out-of-core detector provided outside the nuclear reactor. The value of formula (1) becomes "1" at the start of critical operation and "0" at criticality.

[0003] Patent Document 1 discloses a method of detecting a neutron flux by an out-of-core detector during the critical operation of a nuclear reactor, calculating 1 / M at at least three different time points by the above formula (1), and estimating the transition of 1 / M until the nuclear reactor reaches the critical state from the calculated 1 / M values by solving a predetermined set of simultaneous equations.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the conventional critical approach monitoring method, a 1 / M prediction line indicating the transition of 1 / M during critical operation is calculated in advance, and based on the calculated 1 / M prediction line, prediction of the critical operation amount (e.g., dilution amount) required to achieve criticality is performed. However, in an actual scenario, a deviation occurs between the measured value of 1 / M measured during critical operation and the 1 / M indicated by the 1 / M prediction line obtained by prior analysis. Even if a critical operation is performed based on the 1 / M prediction line, there is a possibility that criticality cannot be achieved, or criticality may be achieved earlier than expected. There is a need for a technology to accurately calculate the operation amount required to achieve criticality.

[0006] The present disclosure provides a critical approach monitoring device, a critical approach monitoring method, and a program that can solve the above problems.

Means for Solving the Problems

[0007] The critical approach monitoring device of the present disclosure includes an inverse multiplication rate calculation unit that measures the out-of-core detector response with respect to the dilution amount of boron and calculates the inverse multiplication rate, and a correction unit that calculates a prediction line indicating the transition of the inverse multiplication rate with respect to the dilution amount based on the inverse multiplication rate calculated by the inverse multiplication rate calculation unit, and a stop instruction unit that gives a stop instruction for the dilution operation when the inverse multiplication rate reaches the dilution stop target set based on the prediction line. , the correction unit generates a plurality of analysis lines showing the transition of the inverse multiplication factor with respect to the dilution amount by adjusting the reactivity of the core and the secondary neutron source intensity as parameters, and calculates, from among the plurality of analysis lines, the analysis line closest to the transition of the inverse multiplication factor calculated by the inverse multiplication factor calculation unit as the prediction line.

[0008] The critical approach monitoring method of the present disclosure A critical proximity monitoring method implemented by a computer, includes a step of measuring the out-of-core detector response with respect to the dilution amount of boron and calculating the inverse multiplication rate, a step of calculating a prediction line indicating the transition of the inverse multiplication rate with respect to the dilution amount based on the inverse multiplication rate calculated in the calculating step, and a step of giving a stop instruction for the dilution operation when the inverse multiplication rate reaches the dilution stop target set based on the prediction line. and in the step of calculating the prediction line, a plurality of analysis lines showing the transition of the inverse multiplication factor with respect to the dilution amount are generated by adjusting the reactivity of the core and the secondary neutron source intensity as parameters, and the analysis line closest to the transition of the inverse multiplication factor calculated in the step of calculating the inverse multiplication factor is calculated as the prediction line from among the plurality of analysis lines.

[0009] The program of the present disclosure causes a computer to perform steps of measuring an in-core detector response with respect to the dilution amount of boron and calculating an inverse multiplication factor, calculating a prediction line showing the transition of the inverse multiplication factor with respect to the dilution amount based on the inverse multiplication factor calculated in the calculating step, and issuing a stop instruction for the dilution operation when the inverse multiplication factor reaches a dilution stop target set based on the prediction line. having, in the step of calculating the prediction line, a process of generating a plurality of analysis lines showing the transition of the inverse multiplication factor with respect to the dilution amount by adjusting the reactivity of the core and the secondary neutron source intensity as parameters, and calculating, from among the plurality of analysis lines, the analysis line closest to the transition of the inverse multiplication factor calculated in the step of calculating the inverse multiplication factor as the prediction line to execute.

Advantages of the Invention

[0010] According to the above-described critical proximity monitoring device, critical proximity monitoring method, and program, the critical operation amount required for achieving criticality can be accurately calculated.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0012] <Embodiment> Hereinafter, the critical proximity monitoring method of the present disclosure will be described with reference to FIGS. 1 to 6. (Configuration) FIG. 1 is a block diagram showing an example of a nuclear reactor physics inspection apparatus according to an embodiment. The nuclear reactor physics inspection apparatus 10 accurately calculates the control amount (dilution amount) of critical operation necessary for achieving criticality in the process of achieving a critical state in nuclear reactor physics inspection.

[0013] The nuclear reactor physics inspection apparatus 10 is communicably connected to a nuclear power plant 20. The nuclear power plant 20 includes a control rod insertion / withdrawal operation panel 21, a boron dilution / enrichment operation panel 22, and an ex-core detector 23. When an operator gives an instruction such as withdrawal to the control rod insertion / withdrawal operation panel 21, a control rod insertion / withdrawal signal based on the instruction is transmitted from the nuclear power plant 20 to the nuclear reactor physics inspection apparatus 10. When an operator gives an instruction such as dilution to the boron dilution / enrichment operation panel 22, a boron dilution / enrichment signal based on the instruction is transmitted from the nuclear power plant 20 to the nuclear reactor physics inspection apparatus 10. The ex-core detector 23 measures a neutron detection value in the source range (ex-core detector response measurement value) and transmits the value to the nuclear reactor physics inspection apparatus 10. The nuclear reactor physics inspection apparatus 10 acquires from the nuclear power plant 20 during nuclear reactor physics inspection a control rod insertion / withdrawal signal including the control rod step position, a boron dilution / enrichment signal including boron concentration and dilution amount / enrichment amount, and an ex-core detector response measurement value.

[0014] The nuclear reactor physics inspection apparatus 10 includes a timer 11, a data recording / control device 12, a 1 / M measurement value calculation device 13, a 1 / M prediction line correction device 14, an ex-core detector response analysis device 15, an operator console 16, and a display device 17. Among these, the data recording / control device 12, the 1 / M measurement value calculation device 13, the ex-core detector response analysis device 15, the 1 / M prediction line correction device 14, and the operator console 16 are constituted by a computer such as a PC (personal computer) or a server terminal device.

[0015] The timer 11 measures time. The data recording and control device 12 records and stores the data acquired from the nuclear power plant 20 (control rod insertion / extraction signals, boron dilution / concentration signals, out-of-core detector response measurement values), and the data calculated by the nuclear physics inspection device 10 (1 / M measurement values, out-of-core detector response prediction values, 1 / M analysis lines, 1 / M prediction lines, etc.). Further, the data recording and control device 12 performs control of critical approach monitoring processing, display control of the display device 17, etc.

[0016] The 1 / M measurement value calculation device 13 calculates 1 / M (inverse multiplication factor). The 1 / M measurement value calculation device 13 uses the out-of-core detector response measurement value measured by the out-of-core detector 23 at the start point (reference state) of the critical operation as the numerator, and the out-of-core detector response measurement value measured by the out-of-core detector 23 at each time point during the critical operation as the denominator, and calculates 1 / M during the critical operation according to the above formula (1). The 1 / M calculated by the 1 / M measurement value calculation device 13 is called the "1 / M measurement value". Further, the 1 / M measurement value calculation device 13 acquires the control rod step position, boron dilution amount / concentration amount, and creates a "1 / M curve diagram" in which the 1 / M measurement value is plotted on the vertical axis and the control amount (control rod extraction amount / dilution amount) of the critical operation is plotted on the horizontal axis as exemplified in FIGS. 2 to 4 later.

[0017] Each time the 1 / M measurement value calculation device 13 calculates the 1 / M measurement value, the 1 / M prediction line correction device 14 calculates a 1 / M prediction line that predicts the transition of 1 / M based on the 1 / M measurement values calculated so far. The 1 / M prediction line correction device 14 previously performs sensitivity analysis using parameters such as the reactivity of the reactor core, etc., and based on the predicted values of 1 / M obtained by simulating various reactor core states (sensitivity analysis, simulation of reactor core states, calculation of predicted values of 1 / M, etc. are executed by the out-of-core detector response analysis device 15 described below), creates a plurality of 1 / M analysis lines showing the transition of 1 / M by fitting (such as 6th-order polynomial approximation) of the 1 / M prediction values, and selects the 1 / M analysis line that is closest to the actual transition of the 1 / M measurement value from among the 1 / M analysis lines. The selected 1 / M analysis line is the 1 / M prediction line.

[0018] The ex-core detector response analysis device 15 simulates the in-core state corresponding to various reactivity levels, etc., using parameters such as the reactivity of the nuclear reactor, and calculates the predicted value of the ex-core detector response at that time through analysis. The ex-core detector response analysis device 15 has an in-core neutron flux analysis device 151 and an ex-core detector response calculation device 152.

[0019] The in-core neutron flux analysis device 151 has a core model that simulates the state of the core. The in-core neutron flux analysis device 151 uses the core model to analyze the distribution of neutron flux in the nuclear reactor under various boron concentrations by adjusting and varying the boron concentration. For example, the in-core neutron flux analysis device 151 sets a certain boron concentration in the initial state and then analyzes the distribution of neutron flux in the reactor at each moment when boron is diluted at a certain speed. The in-core neutron flux analysis device 151 creates a plurality of "sensitivity analysis scenarios (hereinafter referred to as scenarios)" in which the reactivity of the core in the initial state, the secondary neutron source intensity, etc., and the reactivity of the core after the start of dilution, the secondary neutron source intensity, etc., are varied in various ways according to the dilution amount, and for each scenario, analyzes the in-core neutron flux according to the reactivity of the core, the secondary neutron source intensity, etc. The in-core neutron flux analysis device 151 outputs the information on the in-core neutron flux of the analysis results for each scenario to the ex-core detector response calculation device 152. Also, the in-core neutron flux analysis device 151 calculates the reactivity (withdrawal value) corresponding to the position of the control rod.

[0020] The ex-core detector response calculation device 152 acquires the information on the in-core neutron flux for each scenario analyzed by the in-core neutron flux analysis device 151, and calculates the measured value of the ex-core detector response measured by the ex-core detector 23 when the core is in the state indicated by the analysis results of the scenario. This value is called the predicted value of the ex-core detector response. The ex-core detector response calculation device 152 records data (a data set combining the boron concentration at each time point and the predicted value of the ex-core detector response) including the transition of the predicted value of the ex-core detector response with the progress of dilution for each scenario in the data recording and control device 12. Note that the calculation codes (programs) that exhibit the functions of the in-core neutron flux analysis device 151 and the ex-core detector response calculation device 152 are known in the field of nuclear power.

[0021] The operator console 16 is a terminal device used by an operator to give various instructions to the nuclear physics inspection device 10. For example, the operator uses the operator console 16 to give instructions on the flow rate and addition amount of water and boron regarding the dilution and enrichment of boron.

[0022] The display device 17 is a liquid crystal display or an organic EL display, etc. The display device 17 displays the 1 / M curve diagram illustrated in FIGS. 2 to 4, the control amount necessary for achieving criticality, information indicating the stop of dilution, etc.

[0023] Figure 2 shows the 1 / M curve diagram. The vertical axis in Figure 2 is 1 / M, and the horizontal axis is the dilution amount and the control rod withdrawal amount. L1 in Figure 2 is the 1 / M prediction line showing the transition of 1 / M obtained by pre-analysis, and points M0 to M11 are the 1 / M measured values measured during the critical operation. In the process of achieving the critical state of the reactor physics inspection, before the start of the critical operation, the control rod is withdrawn to the position of X steps, and boron dilution is started in this state. Then, after dilution to a certain target point, the critical state is achieved by further withdrawing the control rod by Y steps from the position of X steps. Conventionally, the 1 / M prediction line L1 showing the transition of 1 / M when dilution is performed at a desired speed is estimated by pre-analysis, and in order to achieve the critical state by withdrawing the control rod by Y steps after dilution, the 1 / M measured value is monitored with the uncritical point P0 corresponding to the withdrawal of Y steps as the target, compared to the point P1 where the value of this 1 / M prediction line L1 becomes 0 (critical achievement), and dilution is performed until the 1 / M measured value becomes the "dilution stop 1 / M" which is the 1 / M value corresponding to the target point P0. However, in this method, as in the example of Figure 2, when there is a difference between the 1 / M measured values M0 to M11 measured during the actual critical operation and the 1 / M prediction line L1 obtained by pre-analysis, if dilution is performed until the 1 / M measured value becomes the "dilution stop 1 / M", there is a possibility of reaching the critical state with a withdrawal amount smaller or larger than Y steps in the subsequent control rod withdrawal process. Different withdrawal amounts after dilution will affect the subsequent processes of the reactor physics inspection. Therefore, it is desirable to be able to achieve the critical state with the planned withdrawal of Y steps. For this purpose, it is necessary to accurately calculate the 1 / M prediction line L1 that matches the 1 / M measured value measured during the reactor physics inspection. Therefore, the 1 / M measured value calculation device 13 calculates 1 / M every time the out-of-core detector 23 measures the out-of-core detector response during the critical operation, and the 1 / M prediction line correction device 14 updates and corrects the 1 / M prediction line every time the 1 / M measured value is calculated to calculate an accurate 1 / M prediction line.

[0024] (Update and correction of the 1 / M prediction line) With reference to FIG. 3, the calculation of the prediction line according to the embodiment will be described. The 1 / M prediction line correction device 14 reads out the predicted values of the out-of-core detector responses for each scenario, which have been previously analyzed by the out-of-core detector response analysis device 15, from the data recording / control device 12, calculates the predicted values of the out-of-core detector responses in the reference state based on the boron concentration of the reactor before the critical operation in the actual reactor physics inspection by linear interpolation or the like, calculates the value of 1 / M associated with the progress of dilution by Equation (1), and generates a plurality of "1 / M analysis lines" by fitting (such as 6th-order polynomial approximation) to the 1 / M predicted values for each scenario. At this time, by performing fitting by linear interpolation or a predetermined curve (such as an approximation curve of a 6th-order polynomial) using the 1 / M predicted values in the subcritical state, the 1 / M analysis line up to near criticality achievement is calculated. As a result, a highly accurate 1 / M analysis line can be obtained. FIG. 3 shows the 1 / M analysis lines L1 to L4.

[0025] The 1 / M prediction line correction device 14 selects, from among the 1 / M analysis lines L1 to L4, the 1 / M analysis line that is closest to the locus indicated by the 1 / M measurement values M0 to M5 measured during the nuclear physics inspection, and sets the selected 1 / M analysis line as the "most likely" 1 / M prediction line at that time. In the case of the example in FIG. 3, the 1 / M prediction line correction device 14 sets the 1 / M analysis line L3 as the 1 / M prediction line. There are, for example, the following methods for selecting the 1 / M prediction line from among a plurality of 1 / M analysis lines based on the predicted values of the out-of-core detector responses analyzed in advance. That is, the 1 / M prediction line correction device 14 calculates the distances between each of the 1 / M measurement values M0 to M5 and each of the 1 / M analysis lines L1 to L4, and selects, as the 1 / M prediction line, the 1 / M analysis line for which the sum of the squares of the distances from each of the 1 / M measurement values M0 to M5 is the smallest. Alternatively, the 1 / M prediction line correction device 14 may select a part of the 1 / M measurement values M0 to M5, for example, a predetermined number (for example, the measurement values M3 to M5) traced back from the latest 1 / M measurement value, and select, as the 1 / M prediction line, the 1 / M analysis line for which the sum of the squares of the distances from each of the selected 1 / M measurement values to each of the 1 / M analysis lines L1 to L4 is the smallest. Alternatively, for example, with respect to the 1 / M analysis line L1, the 1 / M prediction line correction device 14 may calculate an evaluation value D1 regarding the difference between the 1 / M measurement value and the 1 / M analysis line L1 using the following formula (2) with arbitrary weighting factors A1 to A5 assigned to each 1 / M measurement value. 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 (distance between 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 (distance between 1 / M measurement value M5 and 1 / M analysis line L1) 2 ···(2) The 1 / M prediction line correction device 14 similarly calculates evaluation values D2 to D4 for the other 1 / M analysis lines L2 to L4, and selects, as the 1 / M prediction line, the 1 / M analysis line for which the values of the evaluation values D1 to D4 are the smallest. Also, regarding 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.

[0026] (Dilution stop 1 / M) When calculating the 1 / M prediction line, the 1 / M prediction line correction device 14 calculates the 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. Using the core model of the in-core neutron flux analyzer 151, the reactivity corresponding to the position of the control rod can be calculated. Utilizing this property, for example, the increase in reactivity when the control rod is withdrawn by Y steps from the state where it is at the X-step position can be calculated. The 1 / M prediction line correction device 14 calculates the increase in reactivity (withdrawal value) corresponding to the Y-step withdrawal using the in-core neutron flux analyzer 151. The 1 / M prediction line correction device 14 calculates a point P0 where the 1 / M prediction line L3 is returned in the subcritical direction by an amount of dilution corresponding to the withdrawal value from the critical point P1 predicted by the 1 / M prediction line L3, and calculates the value of 1 / M at the intersection P2 of the perpendicular line passing through the point P0 and the prediction line L3. This value is the dilution stop 1 / M. When dilution is performed until the value of the 1 / M measurement value calculated by the 1 / M measurement value calculation device 13 during critical operation becomes the dilution stop 1 / M, the remaining can achieve criticality by withdrawing the control rod by Y steps.

[0027] (Operation) Next, with reference to FIG. 5, the flow of the critical approach monitoring process during critical operation will be described. FIG. 5 is a flowchart showing an example of the critical approach monitoring process according to the embodiment. In advance, the out-of-core detector response analysis device 15 performs a sensitivity analysis using parameters such as the reactivity of the core and the intensity of the secondary neutron source, performs in-core neutron flux analysis and out-of-core detector response evaluation, and calculates the predicted value of the out-of-core detector response for each scenario (step S1). The out-of-core detector response analysis device 15 records the predicted value of the out-of-core detector response in the data recording / control device 12.

[0028] Next, the operator starts the critical operation (step S2). From the nuclear power plant 20, the boron concentration before the start of the critical operation (reference state) is transmitted to the nuclear physics inspection device 10. Also, when the critical operation is started, from the nuclear power plant 20, the control rod insertion / withdrawal signal, boron dilution / concentration signal, and out-of-core detector response measurement values are transmitted to the nuclear physics inspection device 10 periodically or when a signal is output. These pieces of information are recorded in the data recording / control device 12.

[0029] When the 1 / M measurement value calculation device 13 acquires the measurement value of the out-of-core detector response with respect to the amount of boron dilution, it calculates the 1 / M measurement value (step S3). When the 1 / M measurement value calculation device 13 calculates the 1 / M measurement value, it plots the value on the 1 / M curve diagram. Also, the 1 / M prediction line correction device 14 calculates the out-of-core detector response prediction value at the boron concentration before the actual start of the critical operation (reference state) from the previously created out-of-core detector response prediction values by linear interpolation or the like, and creates a plurality of 1 / M analysis lines by fitting (such as 6th-order polynomial approximation) to the 1 / M prediction values for each scenario as the dilution progresses according to Equation (1).

[0030] Next, the 1 / M prediction line correction device 14 calculates the error between the 1 / M measurement value and the 1 / M analysis lines (step S4). For example, the 1 / M prediction 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 prediction line correction device 14 selects the 1 / M analysis line with the smallest error as the 1 / M prediction line (step S5). For example, the 1 / M prediction line correction device 14 selects the 1 / M analysis line for which the sum of the squares of the distances between the 1 / M measurement value at each time measured during the critical operation and the 1 / M analysis line is the smallest as the 1 / M prediction line. The 1 / M prediction line correction device 14 displays the selected 1 / M prediction line on the 1 / M curve diagram.

[0031] When the 1 / M prediction line can be calculated, the 1 / M prediction line correction device 14 calculates the dilution stop 1 / M based on the 1 / M prediction line and the extracted amount after dilution (for example, Y step) (step S6). The 1 / M prediction line correction device 14 calculates a point P0, which is a position returned to the subcritical side by the amount of dilution corresponding to the extraction value of the Y step from the critical point P1 indicated by the 1 / M prediction line in the 1 / M curve diagram, obtains the value of 1 / M corresponding to the amount of dilution of the point P0 on the 1 / M prediction line, and calculates that value as the dilution stop 1 / M. The 1 / M prediction line correction device 14 displays the calculated dilution stop 1 / M on the 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.

[0032] Further, the data recording / control device 12 may display the time until the dilution amount reaches the intersection point P2 (= point P0) of the dilution stop 1 / M and the 1 / M prediction line. Specifically, since the data recording / control device 12 acquires the dilution amount from the nuclear power plant 20, it can detect the current boron concentration and dilution amount in the reactor. Also, from the change in the dilution amount in the time series so far, the data recording / control device 12 can calculate the dilution speed. The data recording / control device 12 calculates the difference between the current dilution amount and the dilution amount indicated by the point P2 on the 1 / M prediction line, and divides the difference by the dilution speed, thereby calculating the time until the dilution amount reaches the intersection point P2 (= point P0) of the dilution stop 1 / M and the 1 / M prediction line (the time until the 1 / M measurement value during dilution becomes the dilution stop 1 / M), and outputs the calculated time, the current dilution amount, and the dilution amount at the intersection point P2 (= point P0) to the display device 17 together with the 1 / M curve diagram. The display device 17 displays the time until the 1 / M measurement value reaches the dilution stop 1 / M together with the most probable 1 / M prediction line and the 1 / M measurement value. Thereby, the user can grasp how much more dilution should be performed, and how much time will remain until the 1 / M measurement value becomes the dilution stop 1 / M assuming that the current dilution speed is maintained.

[0033] 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 last calculated by the 1 / M measurement value calculation device 13 with the dilution stop 1 / M. When the latest 1 / M measurement value reaches the dilution stop 1 / M or the difference between the two is within a predetermined range, it is determined that the 1 / M measurement value has reached the dilution stop 1 / M. Otherwise, it is determined that the 1 / M measurement value has not reached the dilution stop 1 / M. When the 1 / M measurement value reaches the dilution stop 1 / M (step S7; Yes), the data recording / control device 12 outputs information instructing the stop of the dilution operation to the display device 17. The display device 17 displays, for example, that the 1 / M measurement value of the monitoring target has reached the dilution stop 1 / M and the text indicating the content instructing the stop of the dilution operation (step S8). The operator stops the dilution operation and withdraws the Y step of the control rod to achieve criticality. The data recording / control device 12 may display the text indicating the content instructing the stop of the dilution operation a predetermined time before the 1 / M measurement value reaches the dilution stop 1 / M so that the operator can operate with a margin. Alternatively, the data recording / control device 12 may display the text indicating that the 1 / M measurement value will reach the dilution stop 1 / M in a little while a predetermined time before the 1 / M measurement value reaches the dilution stop 1 / M. The operator performs the dilution operation so that the dilution can be stopped at the target point while confirming these notifications and the 1 / M curve diagram on which the time when the 1 / M measurement value reaches the dilution stop 1 / M is displayed. On the other hand, when the 1 / M measurement value does not reach the dilution stop 1 / M (step S7; No), the process from step S3 is repeated.

[0034] As described above, according to this embodiment, during critical operation, the 1 / M prediction line is corrected based on the 1 / M measurement value to calculate an accurate 1 / M prediction line. Then, the 1 / M prediction line is updated each time the 1 / M measurement value is measured. As a result, the point P1 (FIG. 2, FIG. 4) representing the operation amount (dilution amount) when reaching criticality by dilution can be accurately calculated. Also, based on the amount of control rod withdrawal planned after dilution, the withdrawal value (reactivity before Y-step withdrawal when criticality is just achieved after Y-step withdrawal) is calculated, and the point P0 in front of point P1 (the point where dilution has not advanced by the amount of the withdrawal value) is calculated by the amount of the withdrawal value, and the dilution stop 1 / M corresponding to the dilution amount at that time is calculated. Thereby, the control amounts (dilution amount, withdrawal amount) of critical operation required for reaching criticality can be accurately calculated. By improving the prediction accuracy of critical operation, criticality can be achieved as planned with the planned critical operation, so the safety is improved. For example, unexpected criticality due to a rapid decrease in the 1 / M measurement value can be prevented, so the safety is improved. Also, by displaying the time until the 1 / M measurement value reaches the dilution stop 1 / M together with the corrected and accurate 1 / M prediction line and the dilution stop 1 / M, the time margin and dilution amount necessary for ensuring safety can be grasped.

[0035] Also, by suppressing the variation in dilution stop, the variation in the amount of control rod withdrawal can be reduced, and criticality can be achieved by the planned Y-step withdrawal, so there is no need to perform unnecessary dilution / concentration operations in subsequent processes. Therefore, not only the process of achieving the critical state in the reactor physics inspection but also the time of related subsequent processes can be shortened.

[0036] FIG. 6 is a diagram showing an example of the hardware configuration of the reactor physics 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 and control device 12, 1 / M measurement value calculation device 13, 1 / M prediction line correction device 14, out-of-furnace detector response analysis device 15, and operator console 16 are implemented in computer 900. And each of the above-described functions is stored in auxiliary storage device 903 in the form of a program. CPU 901 reads the program from auxiliary storage device 903, expands it in main storage device 902, and executes the above processing according to the program. Also, CPU 901 secures a storage area in main storage device 902 according to the program. Further, CPU 901 secures a storage area in auxiliary storage device 903 for storing data during processing according to the program.

[0037] A program for realizing all or part of the functions of data recording and control device 12, 1 / M measurement value calculation device 13, 1 / M prediction line correction device 14, out-of-furnace detector response analysis device 15, and operator console 16 may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed to perform the processing by each functional unit. Here, the "computer system" is assumed to include hardware such as an OS and peripheral devices. Also, the "computer system" includes a homepage providing environment (or display environment) if it uses the WWW system. Also, the "computer-readable recording medium" refers to a portable medium such as a CD, DVD, USB, or a storage device such as a hard disk built into a computer system. Also, when this program is distributed to computer 900 via a communication line, the receiving computer 900 may expand the program in main storage device 902 and execute the above processing. Also, the above program may be for realizing a part of the above-described functions, or may be a combination with a program already recorded in the computer system for realizing the above-described functions.

[0038] As described above, some embodiments according to the present disclosure have been described. However, all of 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, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and its equivalent scope.

[0039] <Appendix> The critical proximity monitoring device, critical proximity monitoring method, and program described in each embodiment are understood as follows, for example.

[0040] (1) The critical proximity monitoring device (reactor physics inspection device 10) according to the first aspect measures the out-of-core detector response (neutron flux output value) with respect to the dilution amount of boron, and calculates the inverse multiplication factor (1 / M measurement value). It includes an inverse multiplication factor calculation unit (1 / M measurement value calculation device 13), a correction unit (1 / M prediction line correction device 14) that calculates a prediction line indicating the transition of the inverse multiplication factor based on the inverse multiplication factor calculated by the inverse multiplication factor calculation unit, and a stop instruction unit (data recording / control device 12) that issues a stop instruction for the dilution operation when the inverse multiplication factor reaches the dilution stop target (dilution stop 1 / M) set based on the prediction line. Thereby, an accurate 1 / M prediction line can be calculated, and the dilution amount required to achieve criticality can be accurately calculated.

[0041] (2) The critical proximity monitoring device (reactor physics inspection device 10) according to the second aspect is the critical proximity monitoring device of (1), wherein the inverse multiplication factor calculation unit (1 / M measurement value calculation device 13) calculates the inverse multiplication factor each time the out-of-core detector response is measured, and the correction unit (1 / M prediction line correction device 14) calculates the prediction line based on the calculated inverse multiplication factor each time the inverse multiplication factor is calculated by the inverse multiplication factor calculation unit. Thereby, an accurate 1 / M prediction line corresponding to the reactivity in the nuclear reactor that changes due to dilution can be calculated, and the prediction accuracy of the time until criticality and the dilution amount required to achieve criticality can be maintained.

[0042] (3) The critical proximity monitoring device (reactor physics inspection device 10) according to the third aspect is the critical proximity monitoring device of (1) to (2), and the correction unit (1 / M prediction line correction device 14 and out-of-core detector response analysis device 15) uses parameters such as the reactivity of the reactor core and the secondary neutron source intensity, and by adjusting the reactivity of the reactor core, the secondary neutron source intensity, etc., generates analysis lines showing the transitions of a plurality of the inverse multiplication factors, and calculates, as the prediction line, the analysis line closest to the calculated transition of the inverse multiplication factor from among the plurality of analysis lines. In advance, sensitivity analysis is performed using parameters such as the reactivity of the reactor core and the secondary neutron source intensity to create a plurality of out-of-core detector response prediction values, and the out-of-core detector response prediction value at the boron concentration before the actual critical operation starts (reference state) is calculated by linear interpolation or the like, and a plurality of 1 / M analysis lines are created by formula (1). Thereby, the accuracy of the 1 / M prediction line can be maintained.

[0043] (4) The critical proximity monitoring device (reactor physics inspection device 10) according to the fourth aspect is the critical proximity monitoring device of (3), and the correction unit (out-of-core detector response analysis device 15) analyzes the neutron flux distribution in the reactor with respect to the dilution amount (critical operation amount) using, as parameters, the reactivity of the reactor core and the secondary neutron source intensity among the parameters of the reactor core model of the nuclear reactor, and calculates a predicted value of the out-of-core detector response (out-of-core detector response prediction value) based on the analyzed neutron flux distribution, and generates a predicted value of the out-of-core detector response corresponding to the change in the dilution amount. Using a reactor core model, perform sensitivity analysis with parameters such as the reactivity of the reactor core and the secondary neutron source intensity to create predicted values of out-of-core detector responses in various patterns, whereby it is possible to correspond to the 1 / M measurement value measured in the actual critical operation scenario, and the accuracy of the prediction line can be maintained.

[0044] (5) The critical proximity monitoring device (reactor physics inspection device 10) according to the fifth aspect is the critical proximity monitoring device of (4), and the correction unit performs fitting on the predicted value of the out-of-core detector response corresponding to the change in the dilution amount with a predetermined curve (for example, a curve represented by a sixth-order polynomial) to generate a plurality of the analysis lines. Accordingly, an analysis line can be generated from the predicted value of the out-of-core detector response.

[0045] (6) The critical proximity monitoring device (reactor physics inspection device 10) according to the sixth aspect is the critical proximity monitoring device of (3) to (5), and calculates the error between the inverse multiplication factor calculated by the inverse multiplication factor calculation unit and the analysis line, and selects the analysis line with the minimum error as the prediction line. Accordingly, a prediction line that matches the actual 1 / M measurement value can be calculated.

[0046] (7) The critical proximity monitoring device (reactor physics inspection device 10) according to the seventh aspect is the critical proximity monitoring device of (1) to (6), and the correction unit (1 / M prediction line correction device 14) calculates the change amount (withdrawal value, reactivity value) of the reactivity when the control rod is controlled from a predetermined initial position (X step) to a predetermined target position (X+Y step), and calculates the dilution stop target based on the change amount and the dilution amount when the prediction line indicates reaching the critical state. Accordingly, the dilution stop target can be calculated in consideration of the withdrawal amount after dilution.

[0047] (8) The critical proximity monitoring device (reactor physics inspection device 10) according to the eighth aspect is the critical proximity monitoring device of (1) to (7), and further includes a display device that displays the prediction line. Accordingly, the operator can predict the change in 1 / M due to dilution.

[0048] (9) The critical proximity monitoring device (reactor physics inspection device 10) according to the ninth aspect is the critical proximity monitoring device of (8), and the display device displays a stop target line indicating the dilution stop target and the time until the dilution amount reaches the intersection of the stop target line and the prediction line. Accordingly, the stop position of the dilution amount and the time until dilution stops can be grasped.

[0049] (10) The critical proximity monitoring method according to the tenth aspect includes: measuring the out-of-core detector response with respect to the dilution amount of boron and calculating the inverse multiplication factor; calculating a prediction line indicating the transition of the inverse multiplication factor based on the calculated inverse multiplication factor; and when the inverse multiplication factor reaches the dilution stop target set based on the prediction line, giving an instruction to stop the dilution operation.

[0050] (11) The program according to the eleventh aspect causes the computer 900 to execute: measuring the out-of-core detector response with respect to the dilution amount of boron and calculating the inverse multiplication factor; calculating a prediction line indicating the transition of the inverse multiplication factor based on the calculated inverse multiplication factor; and when the inverse multiplication factor reaches the dilution stop target set based on the prediction line, giving an instruction to stop the dilution operation.

Explanation of Signs

[0051] 10 ··· Reactor physics inspection device 11 ··· Timer 12 ··· Data recording and control device 13 ··· 1 / M measurement value calculation device 14 ··· 1 / M prediction line correction device 15 ··· Out-of-core detector response analysis device 151 ··· In-core neutron flux analysis device 152 ··· Out-of-core detector response calculation device 16 ··· Operator console 17 ··· Display device 20 ··· Nuclear power plant 21 ··· Control rod insertion / extraction operation panel 22 ··· Boron dilution / concentration operation panel 23 ··· Out-of-core detector 900 ··· Computer 901 ··· CPU 902 ··· Main memory device 903 ··· Auxiliary storage device 904 ··· Input / output interface 905 ··· Communication interface

Claims

1. An inverse multiplication factor calculation unit that measures the response of an ex-core detector with respect to the dilution amount of boron and calculates an inverse multiplication factor; A correction unit that calculates a prediction line indicating the transition of the inverse multiplication factor with respect to the dilution amount based on the inverse multiplication factor calculated by the inverse multiplication factor calculation unit; A stop instruction unit that issues a stop instruction for the dilution operation when the inverse multiplication factor reaches a dilution stop target set based on the prediction line; Comprising: The correction unit generates a plurality of analysis lines indicating the transition of the inverse multiplication factor with respect to the dilution amount by adjusting the reactivity of the core and the intensity of the secondary neutron source as parameters, and selects, from among the plurality of analysis lines, the analysis line closest to the transition of the inverse multiplication factor calculated by the inverse multiplication factor calculation unit as the prediction line; A critical approach monitoring device.

2. The inverse multiplication factor calculation unit calculates the inverse multiplication factor each time the response of the ex-core detector is measured; The correction unit calculates the prediction line based on the inverse multiplication factor calculated each time the inverse multiplication factor is calculated by the inverse multiplication factor calculation unit; The critical approach monitoring device according to Claim 1.

3. Among the parameters of the core model of the nuclear reactor, the correction unit analyzes the neutron flux distribution in the nuclear reactor with respect to the dilution amount, using the reactivity of the core and the intensity of the secondary neutron source as parameters, calculates a predicted value of the ex-core detector response based on the analyzed neutron flux distribution, and generates the analysis line based on the predicted value of the ex-core detector response corresponding to the change in the dilution amount; The critical approach monitoring device according to Claim 1 or Claim 2.

4. The correction unit performs fitting on the predicted value of the ex-core detector response corresponding to the change in the dilution amount with a predetermined curve to generate the analysis line; The critical approach monitoring device according to Claim 3.

5. The correction unit calculates the error between the inverse multiplication factor calculated by the inverse multiplication factor calculation unit and the analysis line, and selects the analysis line with the minimum error as the prediction line; The critical approach monitoring device according to any one of Claims 1 to 4.

6. The correction unit calculates the change amount of reactivity when the control rod is controlled from a predetermined initial position to a predetermined target position, and calculates the dilution stop target based on the change amount and the dilution amount when the criticality indicated by the prediction line is achieved; The critical approach monitoring device according to any one of Claims 1 to 5.

7. A display device that displays the prediction line The critical proximity monitoring device according to any one of claims 1 to 6, further comprising

8. The display device displays a stop target line indicating the dilution stop target and the time until the dilution amount reaches the intersection of the stop target line and the prediction line. The critical proximity monitoring device according to claim 7.

9. A critical proximity monitoring method implemented by a computer, comprising: measuring the out-of-core detector response with respect to the boron dilution amount and calculating the inverse multiplication factor; calculating a prediction line showing the transition of the inverse multiplication factor with respect to the dilution amount based on the inverse multiplication factor calculated in the calculating step; when the inverse multiplication factor reaches the dilution stop target set based on the prediction line, issuing an instruction to stop the dilution operation; having In the step of calculating the prediction line, by adjusting the reactivity of the core and the secondary neutron source intensity as parameters, a plurality of analysis lines showing the transition of the inverse multiplication factor with respect to the dilution amount are generated, and from among the plurality of analysis lines, the analysis line closest to the transition of the inverse multiplication factor calculated in the step of calculating the inverse multiplication factor is calculated as the prediction line. Critical proximity monitoring method.

10. A computer is caused to measure the out-of-core detector response with respect to the boron dilution amount and calculate the inverse multiplication factor; calculate a prediction line showing the transition of the inverse multiplication factor with respect to the dilution amount based on the inverse multiplication factor calculated in the calculating step; when the inverse multiplication factor reaches the dilution stop target set based on the prediction line, issue an instruction to stop the dilution operation; having In the step of calculating the prediction line, by adjusting the reactivity of the core and the secondary neutron source intensity as parameters, a plurality of analysis lines showing the transition of the inverse multiplication factor with respect to the dilution amount are generated, and from among the plurality of analysis lines, the analysis line closest to the transition of the inverse multiplication factor calculated in the step of calculating the inverse multiplication factor is calculated as the prediction line, a program to execute.

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