JPH06186380A - Performance calculator for reactor core - Google Patents

Abstract

PURPOSE:To provide a performance calculator for reactor core in which calculation time of three-dimensional neutron flux distribution and the like can be shortened while allowing high monitoring calculation or predictive calculation. CONSTITUTION:Calculation of a first calculating means 2 is performed intermittently by a first nuclear thermal hydraulic calculation means 2 having an assembly as one node in horizontal direction, a second calculation means 3 having four assemblies as one node, and means 6 correcting the difference of calculation results between the first and second means 2, 3. When current condition monitoring is requested, correction results are displayed while taking account of the difference of preserved calculation results of the second means 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor core performance calculation device for calculating or monitoring a reactor power distribution and the like.

[0002]

2. Description of the Related Art Conventionally, for monitoring and predicting the core of a nuclear reactor,
TIP (Traversing In-Core Probe), LPRM (Local P
ower range monitor) and other nuclear neutron counters are used, and at the same time, nuclear thermohydraulic characteristics such as eigenvalues of reactor, three-dimensional power distribution, neutron flux distribution, and margin from thermal limit value are obtained. Therefore, it is equipped with a three-dimensional core simulator based on a physical model. The physical model classifies neutrons into high-speed groups, out-heat groups, heat groups, etc. according to energy, derives a diffusion equation that neutron flux of each group follows, and
A nuclear calculation model that solves a grouped so-called modified one-group diffusion equation is often used.

[0003]

The diffusion equation is usually
Several hundred fuel assemblies in the horizontal direction are integrated into one lattice, which is divided into a lattice of ten-odd nodes to twenty-odd nodes in the axial direction and discretized for solving. This nuclear calculation model includes nuclear constants determined by the void distribution and burnup distribution in the core and the presence or absence of control rods as coefficients. By the way, when the neutron flux distribution changes, the power distribution also changes, and the void distribution in the reactor also changes, so the nuclear constant changes. For this reason, in order to find a neutron flux distribution and a void distribution that are consistent with each other, it is necessary to repeatedly replace variables on the grid and calculate iteratively, especially when performing online monitoring and prediction. There is a problem that it takes time.

An object of the present invention is to provide a reactor core performance calculation device which executes monitoring and prediction calculation in a short time.

[0005]

In order to achieve the above object, the present invention provides a control rod in addition to the conventional three-dimensional calculation means (first calculation means) in which the aggregates are integrated into one lattice in the horizontal direction. A three-dimensional calculation means (2nd unit) that uses four surrounding aggregates as one grid
Calculation means), means for storing an index indicating the difference between the calculation result of the second calculation means and the calculation result of the first calculation means, and the index stored in the storage means is input to correct the second calculation result. A means is provided, and the monitoring by the first calculation means is intermittently executed, and the monitoring and prediction during that time are executed by the second calculation means.

Further, the above-mentioned means and means for inputting the above-mentioned correction result to the first calculating means are provided, and an initial calculation result is given to the first calculating means.

[0007]

Since the second calculating means calculates with a smaller number of grid points than the first calculating means, the calculation time is short. Further, by saving the difference between the calculation result of the second calculation means and the calculation result of the first calculation means and correcting the second calculation result, the error caused by substituting the second calculation means is reduced. it can. Therefore, the calculation by the first calculation means may be intermittently executed to reduce the error by the second calculation means, and the calculation time can be shortened by performing the calculation mainly by the second calculation means.

Further, when the calculation error by the second calculating means is not sufficiently corrected, the correction result of the calculation by the second calculating means is used and the input to the first calculating means is performed.
It can be used as the initial value of the calculation by the first calculation means.
As a result, the number of iterations in the first calculation means is reduced, and the total calculation time can be shortened.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the operation plan creating apparatus of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a reactor core performance calculation device, 2 is first nuclear thermal-hydraulic calculation means, 3 is second nuclear-thermal-hydraulic calculation means, 4 is a measured value input unit, 5 is a storage device, 6 Is a compensator, 10 is a reactor, 11 is a core, 12
Is a process data processing unit, and 13 is a display device. The operation of each calculator will be described in detail below.

From core 11 of reactor 10 to TIP, LPR
When the neutron flux measurement positive data φ _T0 , φ _L0 by M etc. are obtained, the process data processing unit 12 causes the core performance calculation device 1 equipped with the measured value input device 4 to measure the TIP measured values φ _T , LPRM.
It is sent as the measured value φ _L.

The input device 4 uses the first calculation means 1 and the data obtained after the failure of LPRM and TIP is judged by a statistical method or the like, and the data judged to be normal or replaced with the most probable value. Transfer to the second calculation means 2.
Here, the TIP measured value and the LPRM measured value after such processing are also shown as φ _T and φ _L.

The first calculation means 2 uses the modified first group neutrons based on operating parameters such as reactor heat output, core flow rate, control rod pattern, etc. obtained as core data at the time of monitoring calculation, and operating parameters desired by the user at the time of prediction calculation. Implement nuclear thermal-hydraulic calculation means based on diffusion model. In this calculation, the aggregate of the aggregates is one calculation grid (node), and the nuclear constants representing the nuclear characteristics of each aggregate are the functions of the void fraction, burnup, fuel temperature, etc. for each node. At the time of this calculation, the first calculation means corrects the neutron flux and output distribution calculation results so as to match the measured values φ _T and φ _L obtained from the input device 4. Alternatively, a correction parameter is prepared for the modified first group neutron diffusion equation, and the neutron flux and output distribution are calculated while correcting this parameter. The obtained neutron flux distribution,
The output distribution, the correction parameters and the like (x ₁ , hereinafter, also simply referred to as results) are displayed on the display device 13 as needed when the first calculation means is executed, and are sent to the storage device 5.

The calculation by the first calculating means is performed every time the TIP is running, but when the actual measurement value of LPRM is obtained and the monitoring calculation is requested, the calculation is not performed for all but is performed once every several times. It

The second calculation means 3 uses the modified first group neutrons based on operating parameters such as reactor heat output, core flow rate, control rod pattern, etc. obtained as core data at the time of monitoring calculation, and operating parameters desired by the user at the time of prediction calculation. Implement nuclear thermal-hydraulic calculation means based on diffusion model. In this calculation, four aggregates around the control rod are set as one calculation grid (node), and a nuclear constant representing the nuclear characteristic of each aggregate is used as a function of operating parameters, burnup, fuel temperature and the like. As the nuclear constant representing the nuclear characteristic of the aggregate around the control rod, a neutron flux weighted average of four nuclear constants used in the first calculation means can be used.

At the time of this calculation, the second calculation means corrects the neutron flux and the output distribution calculation result so as to match the measured values φ _T and φ _L obtained from the input device 4. Or fix 1
A correction parameter is prepared for the group neutron diffusion equation, and the neutron flux and power distribution are calculated while correcting this parameter. The obtained neutron flux distribution, output distribution, correction parameters, etc. (x ₂ , hereinafter these are also simply referred to as results) are displayed on the display device 13 as necessary when executing the second calculation means, and the storage device 5 Sent to. If there is no calculation by the first calculation means, the result is also sent to the correction device 6.

The calculation by the second calculating means is executed every time when the actual measurement value of LPRM is obtained during the TIP traveling and the monitoring calculation is requested.

The second calculating means 3 is the same program as the first calculating means 2, and only the usage may be changed, such as changing the constants used.

In the storage device 5, the result x _{2 obtained} by the second calculation means 3 when the calculation by the first and second calculation means is executed,
Index α representing the difference in the result x _{1 obtained} by the first calculation means 2
(For example, a difference or a ratio between x ₂ and x ₁ , etc., hereinafter referred to as a stored value) is calculated and stored. As a result, the number of storage points is required to store at least information corresponding to the number of calculation grids of the first calculation means.

In the correction device 6, when only the calculation by the second calculation means is executed, the stored value α is taken out from the storage device 5 and stored backward in the latest calculation result x ₂ by the second calculation means (back calculation ( For example, the correction result x'is calculated by applying (sum, product) of α and x ₂ . It is needless to say that x ₂ is the result of being integrated with the four aggregates, whereas x ₁ and x ′ are the results of being integrally with the aggregate.

The obtained correction result x'is displayed on the display device 13 at the time of request. Since the error due to the use of the calculation means 2 is corrected by the first calculation result at the time of the previous calculation, this result is in good agreement with the result calculated by using only the calculation means 1 at the time of requesting all monitoring calculations. This is especially effective when the fuel core characteristics of the four bodies around the assembly are similar. According to this embodiment, the number of calculation points is 1 / for the first calculation means.
The second calculation means of 4 reduces the three-dimensional nuclear thermal-hydraulic calculation time to about 1/4.

Next, a second embodiment of the operation plan creating apparatus of the present invention will be described with reference to FIG. FIG. 2 shows a configuration in which the correction result x ′ calculated by the second calculation means is transferred from the correction device 6 in the first embodiment to the first calculation means 3. The other device configurations are similar to those of the first embodiment. The first calculation device uses this result, replaces the result of the previous calculation as the initial value of the calculation, and then calculates the calculated value x _{1 of} this time and displays it on the display device 13.

When the nuclear characteristics of the four fuel assemblies around the control rod are quite different from each other, if the second calculation means is allowed to perform the monitoring calculation and the prediction calculation as in the first embodiment, Although the result is corrected using the calculation result of the first calculating means, the error may increase. Therefore, in this embodiment, the calculation result by the second calculation means is
After being corrected by the first calculation result of the previous time, it is used as the initial value of the first calculation result, and the current monitoring prediction result is calculated by the first calculation means. The correction value of the second calculation result is the first
Compared with the previous calculation result of the calculation means of 1, the initial value for the first calculation means is a good value, so that the number of times of repetition of calculation by the first calculation means can be reduced.

At this time, the calculation by the first calculation means is started by providing means for judging that the error has become large by the knowledge processing method, or simply by increasing the number of times as compared with the first embodiment. Can be started by.

According to this embodiment, an initial value close to a convergent solution can be given to the first calculating means by the second calculating means which is ¼ of the number of calculation points, and the three-dimensional kernel of the first calculating means can be given. This has the effect of reducing the number of iterations in thermal-hydraulic calculation and shortening the calculation time.

[0025]

According to the present invention, it is possible to shorten the time required for three-dimensional nuclear thermal-hydraulics calculation in the core performance calculation, and to shorten the overall monitoring and prediction calculation time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an operation plan creation device of the present invention.

FIG. 2 is an explanatory diagram showing a fragmentary diagram of a second embodiment of the operation plan creation device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor core performance calculation device, 2 ... 1st nuclear thermal-hydraulic calculation means, 3 ... 2nd nuclear-thermal-hydraulic calculation means, 4 ... Measurement value input part, 5 ... Storage device, 6 ... Correction device, 10 ... Reactor, 11
... Reactor core, 12 ... Process data processing unit, 13 ... Display device.

Claims (4)

[Claims] 1. Reactor eigenvalues, three-dimensional output distributions, which are input with parameters representing core state such as reactor heat output, core flow rate, control rod pattern, etc., and in-core neutron detector count values, In a nuclear reactor performance calculation device that calculates nuclear thermal hydraulic characteristics such as neutron flux distribution and margin from thermal limit value,
A first calculation means for calculating a two-dimensional tetragonal system surrounding a region occupied by the fuel assemblies integrally loaded in the core of the nuclear reactor as one horizontal grid in the three-dimensional nuclear thermal-hydraulic characteristic calculation; Surround the area occupied by adjacent fuel assemblies 2
The second calculation means for calculating the three-dimensional tetragonal system as one horizontal grid in the three-dimensional nuclear thermal-hydraulic characteristic, and the difference between the calculation result by the first calculation means and the result by the second calculation means The calculation means includes means for storing the index for the number of calculation grid points of the first calculation means, and means for inputting the storage result and correcting the calculation result of the second calculation means, and the calculation interval of the first calculation means. Is a calculation interval of the second calculation means or more, the reactor core performance calculation device. 2. The nuclear reactor core performance calculation device according to claim 1, wherein the lattice used in the second calculation means is a tetragonal system surrounding four assembly bodies around a control rod. 3. The first calculation means, the second calculation means, and the index representing the difference between the calculation result of the first calculation means and the result of the second calculation means according to claim 1. The first calculation means comprises means for storing the number of calculation grid points of the first calculation means, and means for inputting the storage result and correcting the calculation result of the second calculation means. Reactor core performance calculation device having means for inputting into the reactor. 4. The reactor core performance calculation method according to claim 3, wherein the correction result of the second calculation means is used as an initial value for the calculation of the first calculation means.