JP7202984B2 - Nuclear property prediction method and nuclear property prediction device - Google Patents

Description

The present invention relates to a nuclear property prediction method and a nuclear property prediction device for predicting the nuclear property of a nuclear reactor.

Conventionally, in a core analysis (nuclear design calculation) of a core including fuel assemblies, the calculation is performed in two stages, an assembly calculation as the first stage and a core calculation as the latter stage. In the assembly calculation, the homogenized nuclear constants (macroscopic cross sections) are obtained by performing various calculations with the microscopic cross sections of various nuclides as input values and considering the detailed spatial and energy dependence of the neutron flux. Calculated as an output value. In the core calculation, the nuclear constants calculated in the assembly calculation are used as input values, and the core fuel system is taken into account to calculate the nuclear characteristics of the core as output values. When predicting the nuclear properties of the core, the nuclear properties of the core are predicted by performing core calculations using the nuclear constants.

In such a core analysis, in order to improve the prediction accuracy of the nuclear characteristics, the nuclear characteristics as the analysis result are approximated to the measurement results of the nuclear characteristics measured by the measuring device provided in the core, and the reproducibility is improved. A technique (data assimilation technique) for adjusting nuclear constants is known (see, for example, Non-Patent Document 1). In this adjustment method, since the micro cross-sectional area, which is the input value for the assembly calculation, is adjusted, the core calculation is performed after the assembly calculation is performed using the adjusted micro cross-sectional area. Characteristics will be calculated. In addition, in this adjustment method, by adjusting the micro-cross section, the micro-covariance data, which is data related to the uncertainty of the micro-cross section, is also adjusted. Uncertainty can be evaluated.

In addition, in the core analysis, in order to improve the accuracy of analysis of nuclear characteristics, past plant data and analysis results using it are stored, the relationship between them is analyzed using regression analysis, etc., and the analysis results are used. Therefore, there is known a reactor core performance calculation apparatus that corrects nuclear constants using measurement data (see, for example, Patent Document 1).

Tomoaki Watanabe, 5 others, “Cross section adjustment method based on random sampling technique”, Journal of Nuclear Science and Technology, Atomic Energy Society of Japan, 2014, vol.51, p.590-599, [February 2, 2018 Search date], Internet <URL: http://www.tandfonline.com/doi/abs/10.1080/00223131.2014.882801>

JP-A-10-335290

However, in the adjustment method of Non-Patent Document 1, since it is necessary to perform an enormous aggregate calculation, the calculation cost increases by the amount of the aggregate calculation. In particular, since the assembly calculation considers the detailed spatial and energy dependence of the neutron flux, the calculation load is large and the calculation cost is large compared to the core calculation.

Moreover, in the method of Patent Document 1, the uncertainty of the nuclear constant cannot be taken into account because the analysis is performed using regression analysis or the like.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a nuclear property prediction method and a nuclear property prediction apparatus capable of improving the accuracy of nuclear property prediction while considering the uncertainty of nuclear constants.

A method for predicting nuclear properties of the present invention comprises the steps of: measuring nuclear properties of the reactor that change due to core power fluctuation operation of the reactor, obtaining a measured value of the change in the nuclear properties; a step of calculating the calculated value of the nuclear characteristic to be calculated by performing a core calculation using the nuclear constant before correction; obtaining a plurality of the nuclear properties by perturbing the nuclear constants and performing a core calculation, and calculating sensitivity data based on the obtained plurality of the nuclear properties; a step of calculating a correction amount of the nuclear constant based on the sensitivity data; and using the nuclear constant corrected by the correction amount, a change in the nuclear characteristic of the reactor that changes due to the next core power fluctuation operation. and predicting.

Further, the nuclear characteristic prediction apparatus of the present invention is a nuclear characteristic prediction apparatus comprising a control section for predicting the nuclear properties of a nuclear reactor that change due to a core power fluctuation operation of the nuclear reactor, wherein the control section comprises: obtaining a measured value of the change in the nuclear property by measuring the nuclear property of the reactor that changes due to the power fluctuation operation; and performing core calculation by perturbing the nuclear constant using the perturbation data of the nuclear constant created based on macro covariance data prepared in advance. and calculating sensitivity data based on a plurality of the obtained nuclear characteristics; and a correction amount of the nuclear constant based on the sensitivity data so that the calculated value reproduces the measured value. and predicting changes in the nuclear characteristics of the reactor that will change due to the next core power variation operation, using the nuclear constant corrected by the correction amount.

According to the present invention, it is possible to improve the accuracy of predicting nuclear properties while considering the uncertainty of nuclear constants.

FIG. 1 is a schematic configuration diagram schematically showing a covariance data creation device according to this embodiment. FIG. 2 is a schematic configuration diagram schematically showing the reactor core analysis apparatus according to this embodiment. FIG. 3 is an explanatory diagram relating to prediction of nuclear characteristics according to this embodiment. FIG. 4 is a flow chart for creating macrocovariance data. FIG. 5 is a flow chart for correction of nuclear constants. FIG. 6 is a graph of nuclear characteristics for N-1 months. FIG. 7 is a graph of nuclear characteristics for N months.

EMBODIMENT OF THE INVENTION Below, embodiment which concerns on this invention is described in detail based on drawing. In addition, this invention is not limited by this embodiment. In addition, components in the following embodiments include components that can be easily replaced by those skilled in the art, or components that are substantially the same. Furthermore, the components described below can be combined as appropriate, and when there are multiple embodiments, each embodiment can be combined.

[This embodiment]
In the nuclear property prediction method and nuclear property prediction device according to the present embodiment, the nuclear property of a nuclear reactor is predicted periodically. When predicting the nuclear properties of a nuclear reactor, macrocovariance data are created in advance, and nuclear constant perturbation data are created based on the macrocovariance data. The macro covariance data is created by the covariance data creation device shown in FIG. First, with reference to FIG. 1, the covariance data generation device will be described.

(Covariance data creation device)
FIG. 1 is a schematic configuration diagram schematically showing a covariance data creation device according to this embodiment. The covariance data creation device 10 includes a first computing unit 11 capable of performing computations by executing various programs, a first storage unit 12 storing various programs and data, and a first input device composed of an input device such as a keyboard. It has a unit 13 and a first output unit 14 configured by an output device such as a monitor. The covariance data generation device 10 may be configured as a single device, may be configured as a device integrated with the core analysis device 20 described later, or may be configured as a plurality of devices combining an arithmetic device and a data server. It is not particularly limited.

The first storage unit 12 stores various programs such as a nuclear constant calculation code C1 used to calculate a nuclear constant (macro cross section), a covariance data creation program used to create macro covariance data, P1 is stored. In the first storage unit 12, as data, for example, a cross-sectional area library that summarizes cross-sectional areas, macro cross-sectional areas calculated by aggregate calculation, and macro covariance data calculated based on macro cross-sectional areas and are stored.

FIG. 2 is a schematic configuration diagram schematically showing a reactor core analysis apparatus. As shown in FIG. 1, the core analysis device 20 functions as a nuclear property prediction device that predicts the nuclear properties of the core by performing core analysis using macrocovariance data. The core analysis apparatus 20 includes a second computing unit 21 capable of performing computations by executing various programs, a second storage unit 22 storing various programs and data, and a second input unit 23 composed of an input device such as a keyboard. and a second output unit 24 configured by an output device such as a monitor. Like the covariance data generation device 10, the core analysis device 20 may be configured as a single device, or may be integrated with the covariance data generation device 10, or may be an arithmetic device, a data server, or the like. may be configured by a plurality of devices in combination, and is not particularly limited.

In the second storage unit 22, as various programs, for example, a core calculation code C2 used to calculate the nuclear characteristics, a A number correction program P2 is stored. The second storage unit 22 stores, as data, for example, sensitivity data, which is data relating to changes in nuclear properties accompanying changes in the macroscopic cross-sectional area, and nuclear property measurement data measured by a measurement device that measures nuclear properties. , and data on the amount of correction for correcting the nuclear constant.

Now, with reference to FIG. 3, prediction of nuclear properties will be described. FIG. 3 is an explanatory diagram relating to prediction of nuclear characteristics according to this embodiment. Prediction of nuclear properties is performed periodically, for example, as shown in FIG. 3, every month. Here, when predicting the nuclear properties for the Nth month, the prediction is performed using the measured values and the calculated values of the nuclear properties for the N-1 month, which is one month before the Nth month (previous month).

In January N-January, stem-free operation will be performed to confirm plant function. In the stem-free operation, core power fluctuation operation is performed by inserting and withdrawing control rods from the core, and nuclear property measurements are obtained. The nuclear characteristic is, for example, the power distribution in the axial direction of the core (the axial direction of the control rods), specifically, the power deviation (ΔI) in the axial direction. The nuclear characteristic may be the power distribution in the radial direction of the core.

In month N-1, the nuclear characteristic ΔI, which fluctuates due to the stem-free operation being performed, is measured by a measuring device (not shown), and the measured values are stored in the second storage unit 22 of the reactor core analysis device 20 as nuclear characteristic measurement data. memorize to Also, in month N-1, core calculations are performed using nuclear constants before correction to calculate values of the nuclear characteristic ΔI corresponding to the measured values. That is, a core state in which stem-free operation is performed is simulated, and the core characteristic ΔI at that time is calculated using the nuclear constants before correction.

Then, based on the nuclear characteristic ΔI as the measured value in month N−1 and the nuclear characteristic ΔI as the calculated value, the correction amount of the nuclear constant is calculated, and the nuclear constant corrected based on the calculated correction amount is used. By performing core calculation with

Next, the nuclear constant calculation code C1 and core calculation code C2 used for nuclear design calculation will be described. The nuclear constant calculation code C1 is a calculation code used for assembly calculation, and the core calculation code C2 is a calculation code used for core calculation.

The nuclear constant calculation code C1 uses as input values the specification data on the fuel assembly and the micro cross-sectional area obtained from the cross-sectional area library stored in the first storage unit 12 of the covariance data creation device 10, and this micro cross section Various calculations such as resonance calculation, neutron transport calculation, burnup calculation and assembly (nuclear constant) calculation are performed based on the area. The specification data includes, for example, the radius of the fuel rod, the gap between assemblies, the fuel composition, the fuel temperature, the moderator temperature, and the like.

The nuclear constant calculation code C1 uses a quadrangular geometric shape as a cross section obtained by cutting the fuel assembly perpendicular to the axial direction as a two-dimensional analysis target area, and the nuclear constant including the macro cross-sectional area in this analysis target area is calculated. It is a computable code. The nuclear constants are the input values used in the core calculation code C2. and so on. That is, by performing assembly calculation using the nuclear constant calculation code C1, the nuclear constants, which are the input values for core calculation, are generated.

The core calculation code C2 performs core calculation by setting the calculated nuclear constants to fuel nodes (not shown) each having a rectangular parallelepiped small volume by dividing the fuel assembly into a plurality of pieces in the axial direction. Multiple fuel nodes represent the core, and the core calculation code C2 can evaluate the nuclear characteristics (core characteristics) in the core, such as power distribution, critical boron concentration, and reactivity coefficient, by performing core calculations. code.

The covariance data creation device 10 causes the first computation section 11 to execute the nuclear constant calculation code C1 stored in the first storage section 12 based on the input parameters input from the first input section 13 . Then, the covariance data creation device 10 calculates the nuclear constant in the analysis target region of the fuel assembly by performing the assembly calculation using the nuclear constant calculation code C1. Further, the core analysis apparatus 20 causes the second calculation unit 21 to execute the core calculation code C2 stored in the second storage unit 22 based on the calculated nuclear constants. Then, the core analysis device 20 derives the nuclear properties of the core 5 by performing core calculations using the core calculation code C2. Then, the core analysis apparatus 20 corrects the nuclear constants and predicts the nuclear properties based on the derived nuclear properties. In other words, the core analysis apparatus 20 has a function of correcting nuclear constants and a function of predicting nuclear characteristics. Note that the core analysis device 20 may be a separate device that has a function of correcting nuclear constants and a device that has a function of predicting nuclear characteristics, and is not particularly limited.

Next, with reference to FIG. 4, processing for generating macro covariance data by the covariance data generation device 10 will be described. FIG. 4 is a flow chart for creating macrocovariance data. The covariance data generation device 10 executes a process of generating macro covariance data by executing the covariance data generation program P1.

In the covariance data generation device 10, the first calculation unit 11 first acquires micro-covariance data, which is data relating to the uncertainty of the micro cross-sections contained in the cross-section library stored in the first storage unit 12. (Step S11). Next, the first calculation unit 11 calculates N perturbation amounts of the micro cross-sectional area by a random sampling (random sampling) method using the micro covariance data. Calculating perturbations in the microscopic cross section by random sampling method makes it possible to take into account the significant thermal-hydraulic and combustion feedback effects in the core of light water reactors. Then, the first calculation unit 11 generates the calculated perturbation amounts of the L micro-sectional areas as micro-perturbation data (step S12). The first calculation unit 11 then stores the generated micro-perturbation data in the first storage unit 12 .

Next, the first calculation unit 11 performs aggregate calculation based on the generated micro-perturbation data, that is, based on each micro-cross-sectional area that is a perturbation amount from 1 to L, and calculates from 1 to L L nuclear constants (macro cross sections) corresponding to the perturbation amounts of are derived (step S13). Here, as a calculation condition for executing the assembly calculation, a predetermined representative parameter is selected in advance as a representative parameter from among the parameters relating to the core state of the core including the fuel assemblies. Then, in step S13, aggregate calculation based on the micro-perturbation data is performed using the selected representative parameter as a calculation condition. Therefore, by selecting parameters, the number of combinations of parameters can be reduced, and the load of aggregate calculation can be reduced. As the representative parameter, a parameter highly dependent on the generated macrocovariance data is selected. After that, the first calculation unit 11 generates macrocovariance data, which is data relating to the uncertainty of the nuclear constants, based on the calculated L nuclear constants (step S14). The macrocovariance data is, for example, standard deviations of the calculated L nuclear constants. The first calculation unit 11 then stores the generated macro covariance data in the first storage unit 12 .

Subsequently, the first calculation unit 11 calculates M perturbation amounts of nuclear constants by a random sampling (random sampling) method using the generated macro covariance data. The first calculation unit 11 generates the calculated perturbation amounts of the M nuclear constants as macro perturbation data (step S15). The first calculation unit 11 then stores the generated macro perturbation data in the first storage unit 12 and outputs the same to the core analysis device 20 .

In this way, the covariance data generation device 10 executes the process of generating macro covariance data, expands the uncertainty of the nuclear constant as the uncertainty of the macro cross section, and converts the macro constant based on the uncertainty of the nuclear constant into Generate perturbation data.

Next, referring to FIG. 5, the process of correcting the nuclear constants by the core analysis system 20 will be described. FIG. 5 is a flow chart for correction of nuclear constants. The core analysis apparatus 20 executes the process of correcting the nuclear constant by executing the nuclear constant correction program P2. In the core analysis device 20, the macro perturbation data output from the covariance data creation device 10 is stored in the second storage unit 22 in advance.

In the reactor core analysis apparatus 20, the second calculation unit 21 first, based on the macro perturbation data stored in the second storage unit 22, that is, based on the nuclear constants that are perturbation amounts from 1 to M, Each core calculation is executed to derive M nuclear characteristics corresponding to perturbation amounts from 1 to M (step S21). After that, the second calculation unit 21 calculates the relationship between the changes in the M nuclear constants and the changes in the M nuclear properties accompanying the changes in the M nuclear constants, based on the calculated M nuclear properties. , is derived and acquired as sensitivity data (step S22). This sensitivity data may be stored in the second storage unit 22 .

Next, the second calculation unit 21 acquires the nuclear characteristic ΔI measured by the measuring device for measuring the nuclear characteristic of the core as core characteristic measurement data (step S23). This core characteristic measurement data is the nuclear characteristic ΔI measured during stem-free operation in N months, and is stored in the second storage unit 22 . Specifically, in step S23, the measured value is measured (see Figure 6). Here, the point S2 is, for example, the lower limit of the nuclear characteristic ΔI. In step S23, during period H, measured values are measured at a plurality of arbitrary measurement points.

In addition, the second calculation unit 21 simulates the core state in which the stem-free operation is performed, performs core calculation based on the macro perturbation data, that is, based on the nuclear constant before correction, and calculates the nuclear characteristic ΔI. (step S24). In step S24, the nuclear characteristic ΔI, which is a calculated value corresponding to the measured value, is acquired. That is, in step S24, the nuclear characteristic ΔI is acquired at points corresponding to a plurality of arbitrary measurement points.

When the second calculation unit 21 acquires the sensitivity data, the nuclear characteristic ΔI as the measured value, and the nuclear characteristic ΔI as the calculated value, based on the acquired sensitivity data, the nuclear constant is calculated (step S24).

Here, the formula (1) is as follows.
ΔT _ADJ : Nuclear constant correction amount ΔT: Nuclear constant perturbation amount (input value) ΔR ^T : Nuclear property perturbation amount (output value) due to nuclear constant perturbation ΔR: Nuclear constant difference (R _e - R _c (T ₀ ))
V _e : Uncertainty of the nuclear properties used as the measured value V _m : Uncertainty due to the calculation method (m) of the nuclear properties used as the calculated value R _e : Nuclear properties used as the measured value (ΔI)
R _c (T ₀ ): Nuclear characteristic calculated based on unadjusted (before correction) nuclear constant T ₀ (nuclear characteristic ΔI as a calculated value)

The second calculation unit 21 adjusts the unadjusted nuclear constant (T ₀ ) based on the correction amount (ΔT _ADJ ) calculated by the formula (1), and converts the corrected nuclear constant T into " T=T ₀ +ΔT _ADJ " (step S26). Here, the nuclear constants corrected based on the correction amount (ΔT _ADJ ) are at least the fuel macro constant, the xenon micro constant, and the control rod macro constant. In this embodiment, the fuel macro constant, the xenon micro constant, and the control rod macro constant are corrected as nuclear constants, but the fuel temperature may be corrected.

Then, the second calculation unit 21 executes the core calculation based on the corrected nuclear constants and derives the nuclear characteristics for N months (step S27). As described above, in step S27, the second calculation unit 21 acquires the nuclear properties calculated by the corrected nuclear constant T, which is calculated so as to reproduce the measured values of the nuclear properties.

In this way, the core analysis apparatus 20 executes the process of correcting the nuclear constants so that the calculated values of the nuclear properties are approximated to the measured values of the nuclear properties in month N-1, and uses the corrected nuclear constants. By performing the core calculations for N months, the nuclear characteristics with high prediction accuracy for the measured values for N months are calculated.

Next, with reference to FIGS. 6 and 7, the nuclear characteristics of N-1 month and N month will be described. FIG. 6 is a graph of nuclear characteristics for N-1 months. FIG. 7 is a graph of nuclear characteristics for N months. In FIGS. 6 and 7, the horizontal axis is time, and the vertical axis is nuclear characteristics. Line T1 in FIGS. 6 and 7 is the nuclear characteristic ΔI as the measured value, line T2 is the nuclear characteristic ΔI calculated from the nuclear constant before correction, and line T3 is the nuclear constant after correction. is the nuclear characteristic ΔI calculated by

As shown in FIG. 6, in month (N-1), line T1 and line T2 have different values, but line T1 and line T3 have similar values. Therefore, the nuclear characteristic ΔI calculated from the corrected nuclear constant accurately reproduces the nuclear characteristic ΔI as the measured value. In other words, the corrected nuclear constant is a value that can accurately reproduce the nuclear characteristic ΔI, which is the measured value.

As shown in FIG. 7, in month N, as in month (N-1), there is a difference between line T1 and line T2, but line T1 and line T3 have similar values. In other words, the nuclear characteristic ΔI predicted by the nuclear constant before correction differs from the nuclear characteristic ΔI as the measured value, so there is room for improvement in the prediction accuracy. On the other hand, it can be seen that the nuclear characteristic ΔI predicted from the corrected nuclear constant accurately reproduces the nuclear characteristic ΔI as the measured value.

As described above, according to the present embodiment, it is possible to improve the prediction accuracy of the nuclear characteristic ΔI by performing the core calculation using the corrected nuclear constants. In addition, since core calculations based on nuclear constants can be performed using macrocovariance data, core calculations can be performed in consideration of uncertainties of nuclear constants.

Further, according to this embodiment, since the fuel macro constant, the control rod macro constant, and the xenon micro constant are applied as the nuclear constants to be corrected, the nuclear constants that affect the power distribution (nuclear characteristic ΔI) of the core are appropriately set. can be corrected to Similarly, the fuel temperature may also be applied as a nuclear constant to be corrected, and in this case as well, the nuclear constant affecting the core power distribution (nuclear characteristic ΔI) can be appropriately corrected.

Further, according to the present embodiment, the power distribution of the core in the axial direction of the reactor can be accurately predicted as the nuclear characteristic ΔI. As a nuclear characteristic, it is also possible to accurately predict the power distribution of the core in the radial direction of the reactor.

Further, according to the present embodiment, the measured value can be measured during the period from the change start point at which the change in the core power of the nuclear reactor starts due to the stem-free operation to the time when the differential value of the change in the nuclear characteristic becomes almost zero. can. Therefore, it is possible to calculate the correction amount of the nuclear constant using the measurement value measured during the period in which the change in the nuclear properties is large. Therefore, it is possible to calculate the correction amount with high accuracy that can reproduce the measurement value. .

It should be noted that, in the present embodiment, nuclear characteristics are predicted in the order of steps S22 to S24, but the order of these steps may be changed as appropriate. For example, step S23 or step S24 may be performed before step S22.

10 covariance data creation device 11 first calculation unit 12 first storage unit 13 first input unit 14 first output unit 20 core analysis device (nuclear property prediction device)
21 second calculation unit 22 second storage unit 23 second input unit 24 second output unit C1 nuclear constant calculation code C2 core calculation code P1 covariance data creation program P2 nuclear constant correction program

Claims (6)

measuring a nuclear property of the reactor that changes due to a core power perturbation operation of the reactor to obtain a measurement of the change in the nuclear property;
calculating the calculated values of the nuclear properties corresponding to the measured values by performing a core calculation using the nuclear constants before correction;
Using perturbation data of the nuclear constant created based on macrocovariance data prepared in advance, the nuclear constant is perturbed and a core calculation is performed to obtain the plurality of the nuclear characteristics, and the obtained plurality of the nuclear calculating sensitivity data based on the properties;
calculating a correction amount of the nuclear constant based on the sensitivity data such that the calculated value reproduces the measured value;
and a step of predicting changes in the nuclear properties of the reactor that will change due to the next core power fluctuation operation, using the nuclear constants corrected by the correction amounts. 2. The method of predicting nuclear properties according to claim 1, wherein said nuclear constants include fuel macro constants, control rod macro constants, and xenon micro constants. 3. The method of predicting nuclear properties according to claim 2, wherein said nuclear constants further include fuel temperature. 4. The nuclear property prediction method according to claim 1, wherein the nuclear property is a power distribution in the axial direction of the nuclear reactor or a power distribution in the radial direction of the nuclear reactor. 5. The method of claims 1 to 4, wherein the measured value is measured in a period from a change start point at which a change in the core power of the nuclear reactor starts due to the core power fluctuation operation and a differential value of the change in the nuclear characteristic becomes zero. A method for predicting nuclear properties according to any one of claims 1 to 3. A nuclear property prediction device comprising a control unit for predicting nuclear properties of a nuclear reactor that change due to core power fluctuation operation of the nuclear reactor,
The control unit
measuring a nuclear property of the reactor that changes due to a core power perturbation maneuver of the reactor to obtain a measurement of the change in the nuclear property;
calculating the calculated values of the nuclear properties corresponding to the measured values by performing a core calculation using the nuclear constants before correction;
Using perturbation data of the nuclear constants created based on macrocovariance data prepared in advance, the nuclear constants are perturbed and a core calculation is performed to obtain the plurality of the nuclear characteristics, and the obtained plurality of the nuclear calculating sensitivity data based on the properties;
calculating a correction amount of the nuclear constant based on the sensitivity data such that the calculated value reproduces the measured value;
and a step of predicting changes in the nuclear properties of the reactor that will change due to the next core power fluctuation operation, using the nuclear constants corrected by the correction amounts.

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