JPS6021488A - Device for determining time of travelling of tip - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a core performance monitoring device for a nuclear reactor.

In particular, T to improve the monitoring accuracy of nuclear reactors during operation.
This invention relates to a device that determines IP travel timing. Determining such an optimal TIP running timing is important for efficiently operating a nuclear reactor.

[Background of the invention]

FIG. 1 is an example of a 1/4 core diagram of a boiling water reactor. The reactor core is composed of fuel assemblies 1 and control rods 2. Control rods are arranged at a ratio of one control rod to every four fuel assemblies, excluding the area around the core.

In addition, an IJ song is installed inside the reactor (one monitoring string for every 16 fuel assemblies, excluding the area around the core), and an LPRM that constantly measures the neutron flux is installed in the same string in the axial direction. Four of them are installed, and a guide tube is also arranged, through which the TIP travels when necessary to measure continuous neutron flux distribution in the axial direction.

Conventionally, in order to safely operate a nuclear reactor, the core has been monitored periodically (for example, every hour). As a method of calculating the power distribution during such periodic core monitoring, there is a method of calculating the power of each fuel assembly using a nuclear thermal hydraulic model (Japanese Patent Publication No. 53-22639). During cycle monitoring, in order to improve calculation accuracy, the LPII
, M measured values are fed back to the output distribution calculation value, and the output distribution calculation value is corrected.

Due to the progress of combustion, changes in control rod patterns, etc.
Its physical properties change. In order to accurately calculate the power distribution using a nuclear thermal-hydraulic model, the nuclear thermal-hydraulic model must represent the physical characteristics of the reactor core well. %TIP as a way to adapt nuclear thermal-hydraulic models to core conditions
A method of adjusting the model adjustment parameters so that the TIP measurement value obtained by running the nuclear thermal hydraulic model matches the TIP calculation value calculated by the nuclear thermal hydraulic model (Patent application No. 56-134165
) and methods to adjust the nuclear constants that represent the characteristics of the fuel assembly.

However, it takes three to four hours to travel on the TIP, and because it is necessary to maintain a constant output distribution while traveling on the TIP, control rods and the like cannot be operated. In order to operate a nuclear reactor efficiently, it is desirable to reduce the number of TIP runs.Currently, during steady operation,
I run TlPt about once a month. Conventionally, there were guidelines for determining 'I'IP driving, but there was no optimal index.

[Purpose of the invention]

The purpose of the present invention is to provide a device that determines the minimum required TIP travel timing and instructs operators to do so in order to maintain power distribution calculation accuracy at a target value, and to operate a nuclear reactor efficiently. It is in.

[Summary of the invention]

In the present invention, the LPRM measured value and the LPRM calculated value are compared, and the difference between the LPRM values exceeds the criterion, and the difference is found not to be due to a measurement error but to a calculation error. If this occurs, it is determined that the calculation accuracy of the nuclear thermal-hydraulic model has decreased, and the operator is instructed on the necessity of TIP driving.

First, the algorithm of the present invention will be explained.

FIG. 2 shows calculation errors when the TIP is run at the beginning of the cycle and a nuclear thermal hydraulic model with optimized adjustment parameters is used until the end of the cycle. Here, the calculation error refers to the output distribution measured value (TIP measurement value) and the output distribution calculation value (TI
P calculated value) indicates the root mean square of the difference. From FIG. 2, it can be seen that the calculation error increases as combustion progresses. now,
If the target calculation accuracy is 5% in mean square error, it is necessary to run the TIP at time T and adjust the adjustment parameters of the nuclear thermal hydraulic model again.

The algorithm of the present invention is shown in FIG. Judgment condition A and judgment condition B in FIG. 3 are shown in equations (1) and (2), respectively.

ΔA = l LPRMM (N, L) LPRMc (
N, L) l > ε... (1) LPRMM: LPRM measured value LPRMc: LPRM calculated value ε = 3σ.

σ0: Target calculation accuracy (mean square error) L: Monitoring string number N: LPRM number <ε... (2) LPRMM (N, L), LPRMc (N, L)
: LPR of height N, average value of M measured value and calculated value The calculation error shows a nearly normal distribution, and if the mean square error is less than the target value σ0, the calculation error exceeds 6=3σ0. I don't think so. In other words, the calculation error is ε
If there is an LPRM exceeding , it is determined that the calculation accuracy (mean square error) of the nuclear thermal-hydraulic model exceeds the target value. In determination A, first, it is determined whether the difference between the LPRM measurement value and the calculated value exceeds ε. Even if the difference between the two exceeds ε, it is necessary to further determine whether the difference is caused by a calculation error or a measurement error.

That is, only when the difference is due to a calculation error, it is determined that the calculation accuracy of the nuclear thermal-hydraulic model has decreased. Judgment B is based on the following idea.

(1) Measurement errors are caused by deterioration or failure of the LPRM, and are local and not systematic.

(2) Calculation errors are caused by the inability of nuclear thermal-hydraulic models to adapt to actual core conditions, and are widespread and systematic.

Judgment B determines whether the difference between the measured LPRM value and the calculated value is due to a calculation error or a measurement error. formula(
In 2), in order to reduce systematic calculation errors in the axial direction of the LPRM calculated values, the average calculated LPRM value in the radial direction at each height in the core is matched with the average value of the corresponding LPRM measured values. Calibrate the LP calculation value so that If the difference between the calibrated LPRM calculation value and the measured value exceeds ε, it is determined that the difference between the LPRM actual measurement value and the calculated value is due to a measurement error. That is, if the difference is large even after correcting the LPRM calculation value, it is determined that the difference is due to a measurement error. Conversely, if the difference is less than or equal to ε, it is determined that the difference is caused by a calculation error.

To summarize the above, 1 Judgment A: - The difference between the LPRM actual measurement value and the calculated value exceeds ε, and 1 Judgment B is made.

If the difference between the LPRM calculated value with calculation errors corrected and the actual measurement value is less than ε, then the LPRM calculation error is ε=3σ
It is determined that the value exceeds 0, that is, the calculation accuracy of the nuclear thermal hydraulic model nose exceeds the target value σ0, and a command for TIP travel is issued.

[Embodiments of the invention]

Next, examples of the present invention will be shown.

The configuration of the present invention is shown in FIG. The present invention comprises a power distribution calculation device 4 incorporating a nuclear thermal hydraulic model, an L PRM comparison device 5, a determination device 6, and a TIP travel command device 7. During period monitoring, the output distribution calculation device calculates 9LPRM.
Calculated value X2 is calculated, LPRM actual measurement value X1 and calculated value It is determined whether or not the limit is exceeded. If it is determined that TIP driving is necessary, the TIP driving command device 7 instructs the operator to perform TIP driving.

An example in which the present invention is applied to the cycle shown in FIG. 2 is shown.
The target calculation accuracy σ0 was set to 5chi. Table 1 shows the number of LPRMs whose LPRM calculation error was determined to exceed ε according to the determination of the present invention at each point from ■ to ■. L like this
If even one PRM exists, it is determined that the calculation accuracy of the nuclear thermal hydraulic model exceeds the target accuracy and an 'I' IP travel command is issued.

Table 2 shows the results for only determination A, that is, for simply comparing the LPRM measured values and calculated values. As can be seen from Table 1, when ε = 3σo = 15%, at points ■ and ■ when the calculation error of the nuclear thermal hydraulic model exceeds the target value of 5%,
The correct TIP driving command is issued. In contrast, 1 Table 2
In this case, even though the calculation error of the nuclear thermal-hydraulic model is smaller than the target value, an incorrect command for 'I' IP travel is issued.

Table 1 Case when judgment A and judgment B are used Case 2 Case when only judgment A is used [Effects of the invention] As explained above, according to the present invention, the TIP running timing is correctly determined and the number of TIP running is required. It is possible to keep this amount to a minimum, and it becomes possible to operate the nuclear reactor efficiently.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the core of a boiling water reactor. Figure 2 is a diagram showing the total n error. Figure 3 is a diagram showing the algorithm of the present invention.
FIG. 4 is a configuration diagram of an embodiment of the present invention. 4... Output distribution calculation device, 5... LP-M comparison device. 6... Determination device, 7... TIP travel command device. Agent Patent Attorney Akio Takahashi Figure 7/ 3rd day 4th session

Claims (1)

[Claims] 1. In order to improve the calculation accuracy of the nuclear thermal-hydraulic model in a reactor power distribution monitoring device that calculates the in-reactor power distribution of a nuclear reactor based on a nuclear thermal-hydraulic model, TIP (traveling type Decide when to run the neutron detector (neutron detector) by comparing the calculated value of the LPRM (fixed neutron detector) indication value calculated using the nuclear thermal hydraulic model with the actual value, and instruct the operator. A TIP travel timing determining device characterized by: 2. In claim 1, if the difference between the LPRM calculated value and the actual measured value exceeds the criterion, and the LPRM calculated value and the actual measured value corrected for calculation errors do not exceed the criterion, nuclear heat A TIP travel timing determining device that determines that the calculation accuracy of a hydraulic model does not satisfy a target value and issues a command for TIP travel.