VVER unit dynamic bar carving transient process current signal and reactivity verification method

Abstract

The invention discloses a VVER unit dynamic rod-carving transient process current signal and reactivity verification method. The method comprises the following steps: 1, recording a measured value of a current signal in a control rod moving process by adopting an out-of-pile detector in a VVER unit dynamic rod-carving test; 2, simulating a control rod moving process by a reactor core physical calculation program to obtain a calculated value responded by the out-of-core detector; thirdly, determining the sensitivity coefficient of the out-of-pile detector according to the measured value of the current signal at the initial moment and the calculated value of the response, and obtaining the calculated value of the current signal of the out-of-pile detector; fourthly, comparing the measured value of the current signal with the calculated value to realize verification of the current signal; 5, substituting the measured value of the current signal into the inverse point reactor equation to obtain a dynamic reactivity measured value, and substituting the calculated value of the current signal into the inverse point reactor equation to obtain a dynamic reactivity calculated value; and 6, comparing the measured value and the calculated value of the dynamic reactivity to realize the verification of the reactivity. The problem of engineering data missing in VVER unit transient neutronics verification is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of pressurized water reactor core physics calculation, and particularly relates to a method for verifying current signals and reactivity in the dynamic rod insertion transient process of a VVER unit. Background Art

[0002] VVER series units are pressurized water-cooled and water-moderated reactors (pressurized water reactors) with hexagonal fuel assemblies. As one of the important nuclear power technologies, the engineering construction of VVER units has been steadily advancing, marking the continuous development and innovation of the nuclear power industry in the country. In this context, the commercial operation safety and stability of VVER series hexagonal fuel assembly pressurized water reactors are particularly important. Generally, pressurized water reactors operate under steady-state conditions, but there is also a possibility of transient conditions such as control rod ejection and rod drop. Accurately simulating such conditions in advance is crucial for the safe and stable operation of pressurized water reactors.

[0003] Transient conditions generally require considering the delayed neutron effect on the order of seconds. To accurately simulate the transient conditions of VVER units, transient neutronics software is needed to solve the three-dimensional time-dependent neutron kinetics equation. Currently, most of the verification of transient neutronics software for VVER units is carried out using transient benchmark problems, but there are very few transient benchmark problems and they cannot reflect the engineering reality. Therefore, there is a lack of direct verification of transient neutronics software with engineering measured data for VVER units, and the accuracy and reliability of transient neutronics software in engineering applications cannot be guaranteed. Summary of the Invention

[0004] Aiming at the problem of lack of engineering data in the transient neutronics verification of VVER units, the purpose of the present invention is to provide a method for verifying current signals and reactivity in the dynamic rod insertion transient process of a VVER unit. During the dynamic rod insertion process of a VVER unit, the measured values of the current signals of the out-of-core detectors are collected, and the calculated values of the out-of-core detector responses are obtained by simulating the control rod movement process through a core physics calculation program. The sensitivity coefficient of the out-of-core detector is determined according to the measured value of the out-of-core detector current signal at the initial moment and the calculated value of the out-of-core detector response, and the sensitivity coefficient is used to obtain the calculated values of the out-of-core detector current signals at each moment. The calculated values of the out-of-core detector current signals are compared with the measured values of the out-of-core detector current signals to complete the verification of the current signals in the dynamic rod insertion transient process of the VVER unit. The measured value of the current signal is substituted into the inverse point reactor equation to obtain the measured value of the dynamic reactivity, and the calculated value of the current signal is substituted into the inverse point reactor equation to obtain the calculated value of the dynamic reactivity. The measured value of the dynamic reactivity and the calculated value of the dynamic reactivity are compared to complete the verification of the reactivity in the dynamic rod insertion transient process of the VVER unit.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions for implementation:

[0006] A method for verifying the current signal and reactivity of the transient process of dynamic rod insertion in a VVER unit, comprising the following steps:

[0007] Step 1: When measuring the worth of control rods by the dynamic rod insertion method during the startup physical test of the VVER unit, record the variation law of the measured values of the current signals of the out-of-core detectors with time during the movement of each group of control rods;

[0008] Step 2: According to the movement information of each group of control rods from the top of the core to the bottom of the core during the dynamic rod insertion process, use the core physics calculation program SPARK to perform transient numerical simulation calculations on the movement process of each group of control rods, and obtain the variation law of the calculated values of the responses of the out-of-core detectors with time during the movement of each group of control rods;

[0009] Step 3: According to the measured values of the current signals of the out-of-core detectors at the initial moment during the movement of each group of control rods in Step 1 and the calculated values of the responses of the out-of-core detectors at the initial moment during the movement of each group of control rods in Step 2, calculate the sensitivity coefficient of the out-of-core detectors, and use it to calculate the calculated values of the current signals of the out-of-core detectors during the movement of each group of control rods;

[0010] Step 4: Compare the measured values of the current signals of the out-of-core detectors during the movement of each group of control rods in Step 1 with the calculated values of the current signals of the out-of-core detectors during the movement of each group of control rods in Step 3 to verify the current signal of the transient process of dynamic rod insertion in the VVER unit;

[0011] Step 5: Input the variation of the measured values of the current signals of the out-of-core detectors with time during the movement of each group of control rods in Step 1 into the inverse point reactor equation to calculate the measured values of the control rod dynamic reactivity introduced during the movement of each group of control rods from the top of the core to the bottom of the core. Input the variation of the calculated values of the responses of the out-of-core detectors with time during the movement of each group of control rods in Step 2 into the inverse point reactor equation to calculate the calculated values of the control rod dynamic reactivity introduced during the movement of each group of control rods from the top of the core to the bottom of the core;

[0012] Step 6: Compare the measured values of the dynamic reactivity and the calculated values of the dynamic reactivity of each group of control rods in Step 5 to verify the reactivity of the transient process of dynamic rod insertion in the VVER unit.

[0013] The implementation process of Step 1 is as follows:

[0014] During the process of measuring the worth of control rods by the dynamic rod insertion method in the VVER unit, each group of control rods moves separately from the top of the core to the bottom of the core at a fixed driving speed, and record the measured values of the current signals of the out-of-core detectors during the movement of each group of control rods m represents the abbreviation of the English word "measurement", i represents the number of control rod groups, t represents time, and the measured values of the off-core detectors at the initial moment of the movement process of each group of control rods are denoted as

[0015] The implementation process of Step 2 is as follows:

[0016] 1) According to the geometric and material layout information of the VVER reactor core, a model from the in-core fuel assemblies to the off-core detectors is established. By solving the conjugate neutron transport equation, the off-core detector spatial response function ω j , j represents the grid number in three-dimensional space, and the off-core detector spatial response function characterizes the contribution of the fission neutron source in each grid in the three-dimensional space of the reactor core to the reading of the off-core detector;

[0017] 2) Use the core physics calculation program to simulate the entire process of each group of control rods moving from the top of the reactor core to the bottom of the reactor core, ensuring that the control rod positions and the control rod movement speeds are the same as the actual situation. Through transient neutronics calculations, obtain the three-dimensional power distribution P i,j (t) in the reactor core at each moment during the movement process of each group of control rods;

[0018] 3) According to the off-core detector spatial response function ω j and the three-dimensional power distribution P i,j (t) in the reactor core at each moment during the movement process of each group of control rods, obtain the calculated values of the off-core detector responses during the movement process of each group of control rods c represents the abbreviation of the English word "calculation";

[0019]

[0020] 4) Denote the calculated values of the off-core detector responses at the initial moment of the movement process of each group of control rods as

[0021] The implementation process of Step 3 is as follows:

[0022] 1) Calculate the off-core detector sensitivity coefficient ε for each group of control rods during the movement process based on the measured values of the off-core detector current signals at the initial moment of the movement process of each group of control rods and the calculated values i of the off-core detector responses at the initial moment of the movement process of each group of control rods:

[0023]

[0024] 2) Use the off-core detector sensitivity coefficient obtained from formula (2) to calculate the calculated values of the off-core detector responses during the movement process of each group of control rods Obtain the calculated values of the out-of-core detector current signals during the movement of each group of control rods

[0025]

[0026] The implementation process of Step 5 is as follows:

[0027] The basic principle of the reactivity meter is the inverse point reactor equation, and the reactivity is calculated through the current signal data of the power range detector; therefore, the measured values of the out-of-core detector current signals during the movement of each group of control rods The variation with time is input into the inverse point reactor equation to calculate the measured values of the dynamic reactivity introduced during the movement of each group of control rods The variation with time, where d is the abbreviation of the English word "dynamic"; the calculated values of the out-of-core detector current signals during the movement of each group of control rods The variation with time is input into the inverse point reactor equation to calculate the calculated values of the dynamic reactivity introduced during the movement of each group of control rods The variation with time.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. For VVER units, the present invention uses the measured data of dynamic rod calibration to realize the verification of current signals and reactivity during transient processes, ensuring the accuracy and reliability of transient neutronics software in engineering applications.

[0030] 2. The present invention gets rid of the limitations of traditionally relying only on benchmark problems for verifying three-dimensional space-time neutron dynamics, including the limitations of the extremely small number of benchmark problems and the limitations that benchmark problem verification cannot reflect engineering reality.

[0031] 3. The verification method adopted by the present invention can more comprehensively realize the transient neutronics verification of VVER units through a large amount of data. Currently, for VVER units, the dynamic rod calibration method is basically used to measure the worth of control rods in each fuel cycle, which can provide sufficient and rich data for more engineering-actual transient neutronics verification. Brief Description of the Drawings

[0032] Figure 1 is the verification flow of current signals and reactivity during the dynamic rod calibration transient process for VVER units;

[0033] Figure 2 is the axial arrangement of out-of-core detectors;

[0034] Figure 3 is the comparative verification result of the measured values and calculated values of the out-of-core detector current signals during the movement of control rods;

[0035] Figure 4The verification results of the comparison between the measured value and the calculated value of the dynamic reactivity during the movement of the control rod. Detailed implementation mode

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings and the detailed implementation mode:

[0037] The conjugate transport method is adopted in the present invention to calculate the response of the out-of-core detector of the VVER unit. The specific steps are as Figure 1 shown, including the following steps:

[0038] Step 1: When measuring the control rod worth by the dynamic rod calibration method in the physical start-up test of the VVER unit, record the measured value of the current signal of the out-of-core detector during the movement of each group of control rods m is the abbreviation of the English word "measurement", i represents the number of the control rod group, t represents time, and the measured value of the out-of-core detector at the initial moment during the movement of each group of control rods is recorded as

[0039] In this embodiment, the out-of-core detector of the VVER unit is divided into three sections axially. Among them, the third out-of-core detector is used to measure the control rod worth during the dynamic rod calibration test, as shown in the attached Figure 2 figure.

[0040] Step 2: According to the movement information of each group of control rods from the top of the core to the bottom of the core during the dynamic rod calibration process, use the core physical calculation program SPARK to perform transient numerical simulation calculations on the movement process of each group of control rods, and obtain the variation law of the calculated value of the response of the out-of-core detector during the movement of each group of control rods with time. This step is mainly refined into the following parts:

[0041] 1) According to the geometric and material layout information of the VVER unit core, establish a model from the core fuel assembly to the out-of-core detector, and obtain the spatial response function ω of the out-of-core detector by solving the conjugate neutron transport equation j , j represents the grid number in three-dimensional space, and the spatial response function of the out-of-core detector characterizes the contribution of the fission neutron source in each grid in the three-dimensional space of the core to the reading of the out-of-core detector;

[0042] 2) Use the core physical calculation program to simulate the whole process of each group of control plates moving from the top of the core to the bottom of the core, ensure that the control rod position and the control rod movement speed are the same as the actual situation, and obtain the three-dimensional power distribution P i,j (t) in the core at each moment during the movement of each group of control rods through transient neutronics calculations;

[0043] In this embodiment, the control rod is divided into 350 steps axially in the core. When the control rod is at the bottom of the core, it is recorded as step 0, and when it is at the top of the core, it is recorded as step 350. Additionally, during the dynamic rod calibration process, the moving speed of the control rod is 60 steps per minute.

[0044] 3) According to the spatial response function ω of the out-of-core detector j and the three-dimensional power distribution P in the core at each moment during the movement of each group of control rods i,j (t), the calculated values of the out-of-core detector response during the movement of each group of control rods are obtained c represents the abbreviation of the English word "calculation";

[0045]

[0046] 4) Denote the calculated values of the out-of-core detector response at the initial moment during the movement of each group of control rods as

[0047] Step 3: According to the measured values of the out-of-core detector current signals at the initial moment during the movement of each group of control rods in Step 1 and the calculated values of the out-of-core detector response at the initial moment during the movement of each group of control rods in Step 2 calculate the sensitivity coefficient ε of the out-of-core detector i :

[0048]

[0049] Use the sensitivity coefficient of the out-of-core detector obtained from formula (2) to calculate the calculated values of the out-of-core detector response during the movement of each group of control rods to obtain the calculated values of the out-of-core detector current signals during the movement of each group of control rods

[0050]

[0051] Step 4: Compare the measured values of the out-of-core detector current signals during the movement of each group of control rods in Step 1 with the calculated values of the out-of-core detector current signals during the movement of each group of control rods in Step 3 to verify the current signals during the dynamic rod calibration transient process of the VVER unit;

[0052] Step 5: Input the measured values of the out-of-core detector current signals during the movement of each group of control rods in Step 1 changing with time into the inverse point reactor equation to calculate the measured values of the control rod dynamic reactivity introduced during the movement of each group of control rods from the top of the core to the bottom of the core d represents the abbreviation of the English word "dynamic". Input the calculated values of the out-of-core detector current signals during the movement of each group of control rods in Step 2 Input the inverse point reactor equation over time, and calculate the calculated value of the control rod dynamic reactivity introduced by the movement of each group of control rods from the top to the bottom of the reactor core.

[0053] Step 6: Compare the measured values and calculated values of the dynamic reactivity of each group of control rods in Step 5 to verify the reactivity of the VVER unit during the dynamic rod calibration transient process.

[0054] In this embodiment, the comparison and verification results of the measured value and calculated value of the current signal of the out-of-core detector during the movement of a certain group of control rods in the VVER unit dynamic rod calibration test are as follows Figure 3 shown. It can be seen from the figure that the calculated value of the current signal of the out-of-core detector is in good agreement with the measured value of the current signal of the out-of-core detector; the comparison and verification results of the measured value and calculated value of the control rod dynamic reactivity introduced by the movement of a certain group of control rods from the top to the bottom of the reactor core are as follows Figure 4 shown. It can be seen from the figure that the calculated value of the control rod dynamic reactivity is highly consistent with the measured value of the control rod dynamic reactivity. Figure 3 and Figure 4 The comparison and verification results prove that the calculation results of transient neutronics are the same as the actual measurements. The present invention achieves the purpose of verifying transient neutronics using the measured data of the VVER unit. Currently, the dynamic rod calibration method is used to measure the control rod worth in basically each fuel cycle of the VVER unit. Therefore, sufficient and rich data can be provided for transient neutronics verification closer to engineering practice.

Claims

1. A method for verifying the current signal and reactivity of a VVER unit during dynamic rod cutting transient process, characterized in that: The steps include: Step 1: When the VVER unit uses the dynamic rod engraving method to measure the control rod value during the physical test of the start-up, the measured value of the current signal of the external detector during the movement of each group of control rods is recorded over time; Step 2: Based on the movement information of each group of control rods from the top of the core to the bottom of the core during the dynamic rod engraving process, the core physics calculation program SPARK is used to perform transient numerical simulation calculations on the movement process of each group of control rods, and the change law of the calculated value of the external detector response during the movement of each group of control rods over time is obtained; Step 3: According to the measured value of the current signal of the ex-core detector at the initial moment of the movement process of each group of control rods in step 1 and the calculated value of the response of the ex-core detector at the initial moment of the movement process of each group of control rods in step 2, the sensitivity coefficient of the ex-core detector is calculated and used to calculate the calculated value of the current signal of the ex-core detector during the movement process of each group of control rods; Step 4: Compare the measured value of the current signal of the out-of-core detector during the movement of each group of control rods in step 1 with the calculated value of the current signal of the out-of-core detector during the movement of each group of control rods in step 3, so as to verify the current signal of the transient process of dynamic rod cutting of the VVER unit; Step 5: Input the variation of the measured value of the current signal of the external detector during the movement of each group of control rods in step 1 with time into the inverse point reactor equation, and calculate the measured value of the dynamic reactivity of the control rods introduced in the movement process of each group of control rods from the top of the core to the bottom of the core; input the variation of the calculated value of the response of the external detector during the movement process of each group of control rods in step 2 with time into the inverse point reactor equation, and calculate the calculated value of the dynamic reactivity of the control rods introduced in the movement process of each group of control rods from the top of the core to the bottom of the core; Step 6: Compare the measured dynamic reactivity values ​​of each group of control rods in step 5 with the calculated dynamic reactivity values ​​to verify the reactivity of the VVER unit in the dynamic rod cutting transient process.

2. The method according to claim 1, characterized in that: The implementation process of step 1 is as follows: When the VVER unit uses the dynamic rod engraving method to measure the control rod value, each group of control rods moves from the top of the core to the bottom of the core at a fixed driving speed, and the measured value of the current signal of the external detector during the movement of each group of control rods is recorded. m represents the abbreviation of measurement, i represents the number of the control rod group, and t represents time. The measured value of the external detector at the initial moment of the movement process of each group of control rods is recorded as 3. The method according to claim 1, characterized in that: The implementation process of step 2 is as follows: 1) According to the geometry and material layout information of the VVER core, a model from the core fuel assembly to the external detector is established, and the spatial response function ω of the external detector is obtained by solving the conjugate neutron transport equation. j , j represents the grid number in the three-dimensional space, and the spatial response function of the ex-core detector characterizes the contribution of each grid fission neutron source in the three-dimensional space of the core to the reading of the ex-core detector; 2) The core physics calculation program is used to simulate the entire process of each group of control panels moving from the top of the core to the bottom of the core, ensuring that the control rod position and control rod movement speed are the same as the actual situation. The three-dimensional power distribution P in the core at each moment during the movement of each group of control rods is obtained through transient neutronics calculation. i,j (t); 3) According to the spatial response function ω of the off-pile detector j and the three-dimensional power distribution P in the core at each moment during the movement of each group of control rods i,j (t) Obtain the calculated value of the external detector response during the movement of each group of control rods c stands for the abbreviation of calculation; 4) The calculated value of the out-of-core detector response of each group of control rods at the initial moment of the movement process is recorded as 4. The method according to claim 1, characterized in that: The implementation process of step 3 is as follows: 1) According to the measured value of the current signal of the external detector of each group of control rods at the initial moment of the movement process and the calculated value of the external detector response of each group of control rods at the initial moment of the movement process Calculate the sensitivity coefficient ε of the out-of-core detector during the movement of each group of control rods i : 2) The sensitivity coefficient of the ex-core detector obtained by formula (2) is used to calculate the calculated value of the ex-core detector response during the movement of each group of control rods: Obtain the calculated value of the current signal of the external detector during the movement of each group of control rods 5. The method according to claim 1, characterized in that: The implementation process of step 5 is as follows: The basic principle of the reactivity meter is the inverse point reactor equation, which calculates the reactivity through the current signal data of the power range detector; therefore, the measured value of the current signal of the out-of-core detector during the movement of each group of control rods is The change over time is input into the inverse point reactor equation to calculate the measured value of dynamic reactivity introduced by the movement process of each group of control rods. The change over time, d represents the abbreviation of dynamic in English; the calculated value of the current signal of the external detector during the movement of each group of control rods The change over time is input into the inverse point reactor equation to calculate the dynamic reactivity calculation value introduced by the movement process of each group of control rods Changes over time.

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