Method and device for estimating power distribution in a nuclear reactor

Abstract

To provide a method and device for estimation power distribution in nuclear reactors, capable of highly precisely estimating power distribution.SOLUTION: A method for estimating power distribution in nuclear reactors includes the steps of: calculating a detector response coefficient Cnm; calculating a power correlation coefficient between fuels Fmk; using Cnm and Fmk and calculating a power distribution-dependent detector response matrix TCC with a power distribution-dependent detector response coefficient CCnk defined as an element, for converting power distribution vector with power Rm defined as an element into measurement vector with a detector measurement value Dnr defined as an element; using the power distribution-dependent detector response matrix TCC to calculate calculated measurement values Dnc and estimating power distribution based on each of the detector measurement values Dnr and each of the calculated measurement values Dnc; and compensating the power distribution-dependent detector response matrix TCC based on each of the detector measurement values Dnr with respect to the known power distribution of the power Rm and each of the calculated measurement values Dnc.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a method for estimating power distribution in a nuclear reactor and an apparatus for estimating power distribution in a nuclear reactor. [Background technology]

[0002] Nuclear instrumentation for estimating the power distribution of a nuclear reactor is generally installed inside the reactor core, and even when using nuclear instrumentation outside the reactor, the power distribution of the core as a whole is estimated using information from the nuclear instrumentation installed inside the reactor core (Patent Documents 1 and 2). In conventional commercial nuclear reactors, fuel changes and regular inspections are performed once every 1 to 2 years, so if a malfunction occurs in the nuclear instrumentation, it can be repaired or replaced at that time.

[0003] On the other hand, some small modular reactors (SMRs) that have been developed in various countries around the world in recent years include a type called a microreactor that does not require refueling for 10-20 years. Such microreactors have the problem that the nuclear instrumentation installed inside the reactor cannot be easily replaced. In addition, when evaluating the power distribution inside the reactor core from the nuclear instrumentation installed outside the reactor, and especially when trying to quickly detect abnormalities that occur inside the reactor core, there is a problem that it is not possible to grasp power abnormalities inside the reactor core because most of the information inside the core is lost due to scattering, etc., while neutrons are traveling from the reactor core to the nuclear instrumentation installed outside the reactor.

[0004] Against this background, Non-Patent Document 1 proposes a method for evaluating the power distribution inside the core from nuclear instrumentation installed outside the reactor by using information on the detector response and the power correlation between fuel regions, which is obtained in advance, as the detector response coefficient and the power correlation coefficient between fuel regions.

[0005] On the other hand, the method described in Non-Patent Document 1 requires that the steady-state core and the environment around the detector be known with high accuracy in advance, and there is a problem that the accuracy of power distribution estimation decreases when, for example, there is a difference between the drawing and the actual construction situation, or when the burnup of the core progresses. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 2096594 [Patent Document 2] Patent No. 5443901 [Non-patent literature]

[0007] [Non-Patent Document 1] R. Kimura, Y. Nakai, S. Wada, “Reactor Core Power Distribution Reconstruction Method by Ex-Core Detectors Based on the Correlation Effect Between Fuel Regions”, Nucl. Sci. Eng., publish online (2021) Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, the conventional technology had a problem that the accuracy of power distribution estimation decreased when there was a difference between the information obtained in advance regarding the steady-state core and the environment around the detector and the actual situation.

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide a method and an apparatus for estimating power distribution in a nuclear reactor, which are capable of estimating power distribution with greater accuracy than conventional methods. [Means for solving the problem]

[0010] In the embodiment, the method for estimating the power distribution in a nuclear reactor is carried out by dividing the fuel in the core into M fuel regions and estimating the power distribution R m The power distribution, which is the relative ratio of (m=1,…,M), is calculated by the detector measurement values ​​D nr (n=1, . . . , N),m The detector measurement value D nr The detector response factor C is the ratio of nm and a detector response evaluation and coefficient calculation step for calculating the output R m The fuel power correlation coefficient F is the ratio of the number of neutrons generated in the m-th fuel region to the number of neutrons generated in the m-th fuel region. mk A step of calculating the fuel power correlation evaluation coefficient, nm and the fuel power correlation coefficient F mk Using the output R m The detector measurement value D nr The power distribution dependent detector response coefficient CC is converted into a measurement vector with elements nm The power distribution dependent detector response matrix T with elements CC and a power correlation dependent response coefficient calculation step of calculating the power distribution dependent detector response matrix T CC Calculate the measured value D using nc Calculate the detector measurement value D nr and the calculated measurement value D nc and a power distribution estimation step of estimating the power distribution based on each of the outputs R m The detector measurements D for a known power distribution for nr and the calculated measurement value D nc Based on each of the power distribution dependent detector response matrix T CC and a coefficient adjustment step of correcting Effect of the Invention

[0011] According to the present invention, it is possible to provide a method for estimating power distribution in a reactor and an apparatus for estimating power distribution in a reactor, which are capable of estimating power distribution with high accuracy even when there is a discrepancy between the actual situation and information on the steady-state core and the environment around the detector obtained in advance. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of an embodiment. [Diagram 2] FIG. 2 is a flow chart showing a schematic configuration of a main part of the embodiment. [Diagram 3] FIG. 2 is a flow chart showing a schematic configuration of a main part of the embodiment. [Figure 4] FIG. 2 is a flow chart showing a schematic configuration of a main part of the embodiment. [Diagram 5] 4 is a graph showing a result of estimating power distribution in a nuclear reactor in the embodiment. [Figure 6] 13 is a graph showing the results of estimating the power distribution in a nuclear reactor in a conventional example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a method for estimating power distribution in a reactor and an apparatus for estimating power distribution in a reactor according to an embodiment will be described with reference to the drawings.

[0014] FIG. 1 is a block diagram showing a schematic configuration of an in-reactor power distribution estimation device 100 according to an embodiment.

[0015] The reactor power distribution estimation device 100 receives outputs from a plurality of neutron detectors and estimates the power distribution in the reactor, that is, the power ratio of the fuel regions.

[0016] The reactor power distribution estimation device 100 includes a response characteristic evaluation unit 110, a power distribution estimation unit 120, and an input unit .

[0017] The input unit 130 accepts as external inputs data relating to the reactor core, data relating to the characteristics of the neutron detectors, and detector measurements which are outputs from each neutron detector.

[0018] The response characteristic evaluation unit 110 evaluates the characteristics of the measurement value of the neutron detector depending on the power of the reactor. The response characteristic evaluation unit 110 has a detector response evaluation / coefficient calculation unit 111, an inter-fuel power correlation evaluation / coefficient calculation unit 112, a power distribution dependent detector response coefficient calculation unit 113, and a power distribution dependent detector response coefficient adjustment unit 114.

[0019] The power distribution estimation unit 120 uses the response characteristics obtained by the response characteristic evaluation unit 110 to estimate the power distribution, that is, the power ratio of the fuel region, from the outputs of the multiple neutron detectors.

[0020] Here, a method for estimating the power distribution in a nuclear reactor in this embodiment will be described. It is assumed that the region having fissile material that generates neutrons in the core of a nuclear reactor is divided into M fuel regions. The fuel regions are numbered i=1 to M, and their respective powers are denoted by R1 to R2. M Let us assume that.

[0021] The N neutron detectors are numbered j=1 to N, and their measurements are D1 to D N Let us assume that.

[0022] R in the mth fuel region m The neutrons generated when the output of is generated are d nm Only d nm If, the detector response factor C nm is defined by the following equation (1). Detector response factor C nm =d nm / R m (1)

[0023] The measured value D of the nth neutron detector n is the measured value d nm m is the sum of 1 to M.

[0024] The detector response evaluation and coefficient calculation unit 111 calculates the amount of neutrons arriving at the nth neutron detector from the mth fuel region, and calculates the output R of each fuel region based on the characteristics of the neutron detector. m Measured value of neutron detector by d nm The neutron amount can be calculated by, for example, the Monte Carlo method or the method of characteristics (MOC) transport calculation. Next, the output R m and the measured value of the neutron detector d nmUsing equation (1), the detector response coefficient C nm Calculate.

[0025] The kth fuel region has output R k The rate at which one neutron generated in the fuel region causes fission in the mth fuel region is called the fission rate r mk In this case, the fuel power correlation coefficient F mk is defined by the following equation (2). Fuel power correlation coefficient F mk =r mk / ν k (2)

[0026] In addition, ν k is the fission neutron generation rate in the kth fuel zone. Here, the fission neutron generation rate ν k may, for example, use the average value for each fissile nuclide and energy region across the kth fuel region.

[0027] The fuel power correlation evaluation and coefficient calculation unit 112 calculates the fission occurrence rate r mk In this case, the power distribution of each fuel zone can be assumed by the detector response evaluation and coefficient calculation unit 111. In addition, the fission occurrence rate r mk The calculation of the fission rate r can be done by, for example, the Monte Carlo method or the method of characteristics (MOC) transport calculation. mk and the number of fission neutrons produced ν k Using the above, the fuel power correlation coefficient F mk Calculate.

[0028] The power distribution dependent detector response coefficient calculation unit 113 calculates the detector response coefficient C nm (n=1~N, m=1~M) and the fuel power correlation coefficient F mk Based on (k=1~M), the power distribution dependent detector response coefficient CC nm(n=1 to N, m=1 to M).

[0029] First, from the neutron detector side, the measurement value D of the nth neutron detector n is the mth output R m Measured value d by neutrons from the fuel region (m=1~M) nm m is the sum of 1 to M.

[0030] From the above equation (1), the measured value d nm is expressed as the output R m The detector response factor C nm The value is multiplied by . Measurement value d nm =C nm ·R m (3)

[0031] Therefore, the measurement value D of the nth neutron detector n is the measured value d nm m is the sum of 1 to M, and is calculated using the following formula (4). Measurement value D n =d n1 +d n2 +···+d nM =C n1 R1+C n2 ·R2+···+C nM ·R M (4)

[0032] On the other hand, when viewed from the fuel area side, the output R k The fission rate in the mth fuel region due to one neutron emitted in the kth fuel region of mk is obtained from the above formula (2) by the following formula (5). Fission rate r mk =F mk ·ν k ·R k (5)

[0033] Here, the power output of the mth fuel region R mis the fission fraction r mk where k is the sum from 1 to M. Output R m =r m1 +r m2 +···+r mM =F m1 ν1 R1+F m2 ν2 R2+ +F mM ·ν M ·R M (6)

[0034] Therefore, by combining equation (4) viewed from the neutron detector side and equation (6) viewed from the fuel region side, we obtain the following equation (7). Measurement value D n =C n1 R1+C n2 ·R2+···+C nM ·R M =C n1 R1 +C n2 R2 +··· +C nM ·R M =C n1 (F 11 ν1 R1+F 12 ν2 R2+ +F 1M ·ν M ·R M ) +C n2 (F 21 ν1 R1+F 22 ν2 R2+ +F 2M ·ν M ·R M ) +··· +C nM (F M1 ν1 R1+F M2 ν2 R2+ +F mM ·ν M ·R M ) =(C n1 F11 ν1+C n2 F 21 ν1+···+C nM F M1 ν1)·R1 +(C n2 F 12 ν2+C n2 F 22 ν2+···+C nM F M2 ν2)·R2 +··· +(C nM F 1M ν M +C nM F 2M ν M +···+C nM F MM ν M )·R M (7)

[0035] The measurement vector DD is expressed as the measurement values ​​D1, D2, . . . , D N The output vector RR is an N-dimensional vertical vector with elements R1, R2, . . . , R M Assuming that the elements of the vector are M-dimensional columns, the power distribution dependent detector response matrix T CC The relationship between the two is expressed by the following equation (8). The power distribution dependent detector response coefficient calculation unit 113 calculates the power distribution dependent detector response matrix T CC Calculate the elements of . DD=T CC RR (8)

[0036] where the power distribution dependent detector response matrix T CC is the power distribution dependent detector response coefficient CC defined by the following equation (9): nm It is an N row, M column matrix with elements (n=1 to N, m=1 to M). Power distribution dependent detector response coefficient CC nm =C nm F nm ν m (9)

[0037] In this way, the power distribution dependent detector response coefficient CC nm By using n (n=1~N) is the output of the fuel region R m (m=1 to M).

[0038] The power distribution dependent detector response coefficient adjustment unit 114 calculates a power distribution dependent detector response matrix T CC Power distribution dependent detector response coefficient CC nm In this case, the power distribution dependent detector response coefficient CC nm Adjust the detector measurement value D nr Calculated measurement value D nc In this case, the optimization method may be the minimum gradient method, the steepest descent method, the Newton method, the conjugate gradient method, etc., but since various methods can be applied as long as the optimization objective is achieved, this is not limited to these. This adjustment can be performed in the following cases, for example, in addition to the coefficient adjustment at the beginning of operation.

[0039] When burnup in the reactor core progresses, a known power distribution is obtained by core analysis under the conditions at that time, and the effects of the burnup are corrected. When detector response changes over time as the reactor operates, a known power distribution is obtained by core analysis under the conditions at that time, and the effects of the change in detector response over time are corrected. When the position of a control rod in the reactor is changed, a known power distribution is obtained by core analysis under the conditions at that time, and the effects of the control rod are corrected. When a temperature change occurs in the reactor core, a known power distribution is obtained by core analysis under the conditions at that time, and the effects of the temperature change are corrected. When a detector is replaced, a known power distribution is obtained by core analysis under the conditions at that time, and the effects of the detector replacement are corrected. These cases may also be combined.

[0040] Then, the power distribution estimation unit 120 calculates the power distribution-dependent detector response coefficient CC generated by the power distribution-dependent detector response coefficient calculation unit 113 and adjusted by the power distribution-dependent detector response coefficient adjustment unit 114. nm The power distribution dependent detector response matrix T using CC The core power distribution is estimated from the measurements of the neutron detector.

[0041] At this time, although the above explanation assumes the use of neutron detection data from ex-core instrumentation, the derived evaluation formula does not distinguish between detectors inside and outside the core, and since more accurate power distribution estimation is possible by placing detectors inside the core, the location of the detector should be such that it can detect neutrons generated inside the core, and is not limited to that of the ex-core instrumentation.

[0042] In this embodiment configured as described above, even if there is a difference between the information on the steady-state core and the environment around the detector obtained in advance and the actual situation, it is possible to estimate the power distribution with high accuracy.

[0043] 2 and 3 are flow charts showing the procedure of the in-reactor power distribution estimation method according to the embodiment. The in-reactor power distribution estimation method according to the embodiment includes a response evaluation step shown in FIG. 2 and a power distribution estimation step shown in FIG.

[0044] First, the response evaluation step shown in FIG. 2 includes detector response evaluation and coefficient calculation steps (151 to 153), inter-fuel power correlation evaluation and coefficient calculation steps (161 to 163), and a power distribution dependent detector response coefficient calculation step (170) performed after these steps.

[0045] The detector response evaluation and coefficient calculation step includes a power distribution assumption step (151), a detector response evaluation step (152), and a detector response coefficient calculation step (153). The power distribution assumption step (151) and the detector response evaluation step (152) can be performed in any order. These steps are performed by the detector response evaluation and coefficient calculation unit 111 shown in FIG. 1.

[0046] In the power distribution assumption step (151), the power distribution, i.e., the power R m Set the assumed value (m=1 to M).

[0047] In the detector response evaluation step (152), a detector response evaluation is performed based on the power distribution assumed in the power distribution assumption step (151). Specifically, the amount of neutrons reaching the nth neutron detector from the mth fuel region is calculated, and the output R of each fuel region is calculated based on the characteristics of the neutron detectors stored in advance. m Measured value of neutron detector by d nm In calculating the amount of neutrons, as described above, for example, the Monte Carlo method, the method of characteristics (MOC) transport calculation, etc. can be used.

[0048] In the detector response coefficient calculation step (153), the output R m and the measured value of the neutron detector d nm Using the above equation (1), the detector response coefficient C nm Calculate.

[0049] The fuel power correlation evaluation and coefficient calculation step includes a power correlation evaluation step (161), an average fission neutron generation rate calculation step (162), and a fuel power correlation calculation step (163). These steps are performed by the fuel power correlation evaluation and coefficient calculation unit 112 shown in FIG. 1.

[0050] In the power correlation evaluation step (161), the fission occurrence rate r is calculated based on the power distribution assumed in the power distribution assumption step (151). mk The behavior of neutrons in this case can be evaluated by transport calculations using the Monte Carlo method, the method of characteristics (MOC), or the like, as described above.

[0051] In the step (162) of calculating the average fission neutron generation number,k For example, the average value for each fission nuclide and energy region over the k-th fuel region is calculated as k When used as a fission neutron number, the value input from the memory is read out and the fission neutron number ν k The output is as follows:

[0052] In the fuel power correlation coefficient calculation step (163), the fission occurrence rate r obtained in the detector response coefficient calculation step (153) is mk and the fission neutron generation number ν obtained in the average fission neutron generation calculation step (162) k Using the above, the fuel power correlation coefficient F mk Calculate.

[0053] In the power distribution dependent detector response coefficient calculation step (170), the power distribution dependent detector response coefficient calculation unit 113 shown in FIG. 1 calculates the detector response coefficient C nm (n=1~N, m=1~M) and the fuel power correlation coefficient F mk Based on (k=1 to M), the power distribution dependent detector response matrix T CC Power distribution dependent detector response coefficient CC nm Calculate (n=1 to N, m=1 to M) and store.

[0054] Then, calculate and store the power distribution dependent detector response coefficients CC nm If adjustment is required for (n=1 to N, m=1 to M) (Yes in 171), an adjustment step (172) of the power distribution-dependent detector response coefficients is performed by the power distribution-dependent detector response coefficient adjustment unit 114 shown in FIG. 1. On the other hand, if adjustment is not required (No in 171), the power distribution-dependent detector response coefficients CC calculated and stored in the power correlation-dependent response coefficient calculation step (170) are calculated. nm (n=1 to N, m=1 to M) are used in the power distribution estimation step described below.

[0055] Next, a description will be given of each step of the power distribution estimation shown in Fig. 3. These steps are performed by the power distribution estimation unit 120 shown in Fig. 1.

[0056] First, in the power distribution dependent detector response coefficient input step (181), the power distribution dependent detector response coefficients CC calculated and stored in the step shown in FIG. nm (n=1 to N, m=1 to M) is entered.

[0057] Next, in the power distribution estimation value setting step (182), the initial value of the power distribution of the reactor is set. That is, the power R m A value of (m=1 to M) or a relative value is set. As the initial value of the power distribution, for example, the power distribution during steady operation may be used.

[0058] In the detector measurement value calculation step (183), the output of each neutron detector, i.e., the calculated measurement value D nc Calculate the output R of each fuel region. m The power distribution dependent detector response factor CC is used to calculate the neutron detector measurements based on the distribution (m = 1 to M). nm is used.

[0059] Next, in the detector measurement difference calculation step (184), the calculated measurement value D calculated as described above is nc and the detector measurement value D nr The sum of all neutron detectors is normalized to 1 for each of the neutron detectors. The normalized value is called the normalized detector measurement value ND nr and the standardized calculated measurement value ND nc Let us assume that.

[0060] That is, according to the following equations (10) and (11). N.D. nr =D nr / (ND 1r +ND 2r +···+ND Nr ) ···(10) N.D. nc=D nc / (ND 1c +ND 2c +···+ND Nc ) ···(11)

[0061] In addition, the normalized detector measurement value ND nr and the standardized calculated measurement value ND nc Difference ΔND n Calculate.

[0062] In the objective function value calculation step (185), the value of the objective function (objective function value) G is calculated based on the measurement value difference. For example, the objective function value G is calculated by the following formula (12): nr and the standardized calculated measurement value ND nc Difference ΔND n Calculate the sum of the absolute values ​​of Objective function value G = |ΔD1|+|ΔD2|+···+|ΔD N | (12)

[0063] In the step of determining whether the objective function value is at a minimum (186), it is determined whether the objective function value G has reached a minimum value. Specifically, for example, it is determined whether the objective function value G is equal to or smaller than a predetermined value ε.

[0064] If it is determined in the objective function value minimum determination step (186) that the objective function value G has reached the minimum value (Yes), the procedure ends.

[0065] On the other hand, if it is not determined that the objective function value G has reached the minimum value (No), the process proceeds to an output distribution estimate updating step (187).

[0066] In the power distribution estimate updating step (187), the process returns to the power distribution estimate setting step (182), where the power distribution estimate is set to a new estimate, and the above steps are repeated.

[0067] The algorithm for repeating the steps from the objective function value minimum determination step (186) to the output distribution estimate value update step (187) and the output distribution estimate value setting step (182) can use a general optimization algorithm or a recursion algorithm.

[0068] Furthermore, since formula (7) or formula (8) is formally a linear formula, specifically, a linear algorithm such as the IMPLEX method can be used. Alternatively, when it is difficult to treat it as a completely linear formula, such as when an element such as the sum of absolute values ​​is introduced as the objective function value G, it may be treated as a nonlinear formula.

[0069] Next, an example of comparing the power distribution estimated value according to this embodiment with the power distribution estimated value according to a conventional method not including the power distribution dependent detector response coefficient adjustment unit 114 in this embodiment is shown. The graph in FIG. 5 shows the relationship between the power distribution estimated value according to this embodiment (shown by a dotted line in the figure) and the true value (shown by a solid line in the figure), and the graph in FIG. 6 shows the relationship between the power distribution estimated value according to the conventional method (shown by a dotted line in the figure) and the true value (shown by a solid line in the figure). In these examples, an attempt was made to estimate the core power distribution when the balance of the power distribution changed using a coefficient obtained when a detector was placed outside a certain reactor core, but as shown in FIG. 6, the power distribution estimation according to the conventional method had a large difference from the true value and did not provide an accurate estimated value. On the other hand, as shown in FIG. 5, the power distribution estimation according to this embodiment can reduce the difference from the true value and provide an accurate estimated value.

[0070] Furthermore, in this embodiment, the accuracy of the power distribution reconstruction can be improved by adjusting the coefficients not only to the environment around the detector but also to changes in burnup and control rod position. In this case, in actual operation, as shown in FIG. 4, the power distribution dependent detector response matrix T CC Power distribution dependent detector response coefficient CC nm Request.

[0071] Next, the influence of the environment around the detectors can be adjusted in the coefficient adjustment phase 193 at the beginning of operation based on the detector count when the detectors are actually placed. Furthermore, the influence of burnup change, time-dependent change in detector response, change in control rod position, change in core temperature, replacement of neutron detectors, and change in the position of other structures are appropriately adjusted in the coefficient evaluation phase 194 during operation, and this is repeated until the end of operation (Yes in 195). As a result, the power distribution-dependent detector response matrix T CC Power distribution dependent detector response coefficient CC nm Even if the power distribution changes with operation, the estimation accuracy of the power distribution can be maintained by repeating fine adjustments.

[0072] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0073] 100...in-reactor power distribution estimation device, 110...response characteristic evaluation unit, 111...detector response evaluation / coefficient calculation unit, 112...inter-fuel power correlation evaluation / coefficient calculation unit, 113...power distribution dependent detector response coefficient calculation unit, 114...power distribution dependent detector response coefficient adjustment unit, 120...power distribution estimation unit, 130...input unit.

Claims

1. The fuel portion in the core is divided into M fuel regions, and the power R of each fuel region is ｍ The power distribution, which is the relative ratio of the neutron detectors (m=1, ..., M), is expressed as the detector measurement value D ｎｒ A method for estimating a power distribution in a nuclear reactor based on (n=1, ..., N), The output R ｍ The detector measurement value D ｎｒ The detector response coefficient C is the ratio of ｎｍ A detector response evaluation and coefficient calculation step for calculating The output R of the number of fissions in the k-th fuel zone ｍ The fuel power correlation coefficient F is the ratio of the number of neutrons generated in the m-th fuel region to the number of neutrons generated in the m-th fuel region. ｍｋ A fuel output correlation evaluation and coefficient calculation step for calculating The detector response coefficient C ｎｍ and the fuel output correlation coefficient F ｍｋ Using the output R ｍ The detector measurement value D ｎｒ The power distribution dependent detector response coefficient CC converts the measured value vector into a vector with elements ｎｍ A power distribution dependent detector response matrix T with elements ＣＣ An output correlation dependent response coefficient calculation step of calculating The power distribution dependent detector response matrix T ＣＣ Calculated measurement value D ｎｃ Calculate the detector measurement value D ｎｒ and the calculated measurement value D ｎｃ a power distribution estimation step of estimating the power distribution based on each of the above; The output R ｍ The detector measurements D for a known power distribution for ｎｒ and the calculated measurement value D ｎｃ , the power distribution dependent detector response matrix T ＣＣ A coefficient adjustment step for correcting A method for estimating power distribution in a nuclear reactor, comprising:

2. In the coefficient adjustment step, when the burnup of the reactor core progresses, the known power distribution is obtained by a core analysis under the conditions at that time, and the influence of the burnup is corrected. The method for estimating power distribution in a nuclear reactor according to claim 1 .

3. In the coefficient adjustment step, when the detector response changes over time due to the operation of the reactor, the known power distribution is obtained by a core analysis under the conditions at that time, and the effect of the change over time of the detector response is corrected. The method for estimating power distribution in a nuclear reactor according to claim 1 .

4. In the coefficient adjustment step, when the control rod position in the reactor is changed, the known power distribution is obtained by a core analysis under the conditions at that time, and the influence of the control rod is corrected. The method for estimating power distribution in a nuclear reactor according to claim 1 .

5. In the coefficient adjustment step, when a temperature change occurs in the reactor core, the known power distribution is obtained by a core analysis under the conditions at that time, and the effect of the temperature change is corrected. The method for estimating power distribution in a nuclear reactor according to claim 1 .

6. In the coefficient adjustment step, when the detector is replaced, the known power distribution is obtained by a core analysis under the conditions at that time, and the influence of the detector replacement is corrected. The method for estimating power distribution in a nuclear reactor according to claim 1 .

7. In the coefficient adjustment step, when any two or more of the following occurs: when the burnup of the reactor core progresses, when the detector response changes over time with the operation of the reactor, when the control rod position in the reactor is changed, when a temperature change occurs in the reactor core, and when the detector is replaced, the known power distribution is obtained by core analysis under the conditions at that time, and the influence of the known power distribution is corrected. The method for estimating power distribution in a nuclear reactor according to claim 1 .

8. The fuel portion in the core is divided into M fuel regions, and the power R of each fuel region is ｍ The power distribution, which is the relative ratio of the neutron detectors (m=1, ..., M), is expressed as the detector measurement value D ｎｒ (n=1, ..., N), The detector measurement value D, which is the output from each of the neutron detectors ｎｒ an input section for receiving The output R ｍ The detector measurement value D ｎｒ The detector response coefficient C is the ratio of ｎｍ A detector response evaluation and coefficient calculation unit for calculating The output R of the number of fissions in the k-th fuel zone ｍ The fuel power correlation coefficient F is the ratio of the number of neutrons generated in the m-th fuel region to the number of neutrons generated in the m-th fuel region. ｍｋ A fuel output correlation evaluation and coefficient calculation unit for calculating The detector response coefficient C ｎｍ and the fuel output correlation coefficient F ｍｋ Using the output R ｍ The detector measurement value D ｎｒ The power distribution dependent detector response coefficient CC converts the measured value vector into a vector with elements ｎｍ A power distribution dependent detector response matrix T with elements ＣＣ A power distribution dependent detector response coefficient calculation unit for calculating The power distribution dependent detector response matrix T ＣＣ Calculated measurement value D ｎｃ Calculate the detector measurement value D ｎｒ and the calculated measurement value D ｎｃ a power distribution estimation unit that estimates the power distribution based on each of the above; The output R ｍ The detector measurements D for a known power distribution for ｎｒ and the calculated measurement value D ｎｃ , the power distribution dependent detector response matrix T ＣＣ A coefficient adjustment unit that corrects A reactor power distribution estimation device comprising:

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