A transient neutronics verification method based on dynamic etched rod measured data

Abstract

A transient neutronics verification method based on measured data from dynamic rod etching is disclosed. This method verifies transient neutronics by utilizing real-time current data monitored by an external detector during the dynamic rod etching process. In the dynamic rod etching process of a pressurized water reactor, an external detector records the measured current signal values ​​during the control rod movement. The control rod movement process is simulated using transient neutronics software to obtain the calculated response of the external detector. The sensitivity coefficient of the external detector is determined by comparing the measured current signal value at the initial moment with the calculated response value, and this coefficient is used to obtain the calculated current signal value from the external detector. The measured and calculated current signal values ​​are then compared to verify the transient neutronics. This invention provides a novel transient neutronics verification method, addressing the long-standing problem of a lack of effective transient neutronics verification methods in the field, and ensuring the accuracy and reliability of transient neutronics software in engineering applications.

Description

Technical Field

[0001] This invention relates to the field of pressurized water reactor core physics calculation technology, specifically to a transient neutronics verification method based on dynamic etched rod measured data. Background Technology

[0002] The safe and stable operation of commercial pressurized water reactors (PWRs) has always been a crucial concern in the field of nuclear engineering. While PWRs typically operate under steady-state conditions, transient events such as control rod outages, rod ejection, and rod drop can occur. Accurately simulating these transient events in advance is essential for ensuring the control and safety of PWRs.

[0003] Transient operating conditions, typically on the order of seconds, require consideration of delayed neutron effects. Transient neutronics software needs to solve three-dimensional spacetime neutron dynamics equations to accurately simulate these conditions. Currently, most verification of transient neutronics software uses transient benchmark problems, but these benchmark problems are extremely limited and fail to reflect real-world engineering issues. Therefore, the lack of direct verification of transient neutronics software using actual engineering data cannot guarantee its accuracy and reliability in engineering applications. Summary of the Invention

[0004] To address the practical problem of missing engineering data in transient neutronics verification, this invention aims to provide a transient neutronics verification method based on measured data from dynamic rod etching in a pressurized water reactor (PWR). The method involves acquiring measured values ​​of the external detector current signal during the dynamic rod etching process, and obtaining calculated values ​​of the external detector response by simulating the control rod movement using transient neutronics software. The sensitivity coefficient of the external detector is determined based on the measured and calculated values ​​of the external detector current signal at the initial moment. This sensitivity coefficient is then used to obtain calculated values ​​of the external detector current signal at various time points. The calculated values ​​of the external detector current signal are compared with the measured values ​​to complete the transient neutronics verification. This invention provides a novel verification approach, solving the long-standing problem of missing engineering data in transient neutronics software verification, and ensuring the accuracy and reliability of PWR transient neutronics software in engineering applications.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A transient neutronics verification method based on measured data from dynamic etched rods in a pressurized water reactor includes the following steps:

[0007] Step 1: In the process of measuring the value of control rods using the dynamic rod-cutting method in pressurized water reactor nuclear power plants, each group of control rods moves individually from the top of the reactor core to the bottom of the reactor core at a fixed drive speed. The measured values ​​of the current signals of each section of the external detectors are recorded during the movement of each group of control rods. 'm' stands for the abbreviation of 'measurement,' 'i' represents the control rod group number, and the external detector is generally divided into multiple sections along the axial direction. 'j' represents the section number of each external detector. The measured values ​​of the current signals from each section of the upper part of the external detector are merged into the measured value of the upper current signal of the external detector." The measured values ​​of the current signals of each section at the bottom of the external detector were merged into a single measured value for the current signal at the bottom of the external detector. The measured values ​​of the upper and lower current signals of the external detectors at the initial moment of the movement of each group of control rods are recorded as follows: and

[0008] Step 2: The entire process of each set of control rods moving from the top of the reactor core to the bottom of the reactor core is simulated using transient neutronics software. Numerical calculations are then used to obtain the variation of the calculated values ​​of the external detector responses during the movement of each set of control rods over time. This step is mainly detailed into the following parts:

[0009] 1) Based on the geometry and material arrangement of the pressurized water reactor core, establish a model from the core fuel assemblies to the external detectors, and calculate the response function ω of each section of the external detectors. j,k , j represents the number of each section of the external detector, k represents the grid number in the three-dimensional space, and the response function of the external detector characterizes the contribution of the fission neutron source of each grid in the three-dimensional space of the core to the simulated value of the current signal of the external detector.

[0010] 2) The transient neutronics software was used to simulate the entire process of each group of control rods moving from the top of the core to the bottom of the core, ensuring that the position of the control rods and the moving speed of the control rods were the same as the actual situation. The three-dimensional power distribution Pi,k(t) in the core at each moment during the movement of each group of control rods was obtained by transient neutronics calculation.

[0011] 3) Based on the response function ω of each section of the external detector j,k The calculated values ​​of the external detector responses of each group of control rods during the movement of each group of control rods are obtained by using the three-dimensional power distribution Pi,k(t) within the core at each time point during the movement of each group of control rods. 'C' stands for the abbreviation of the English word 'calculation'.

[0012]

[0013] 4) Combine the calculated responses of each section of the external detector into a single calculated response value for the upper part of the external detector. The calculated responses of each section of the external detector are merged into a single calculated response value for the lower section of the external detector. The calculated values ​​of the upper and lower responses of the external detectors at the initial moment of the movement of each group of control rods are denoted as follows: and

[0014] Step 3: Based on the measured values ​​of the upper current signal of the external detector at the initial moment of the movement process of each group of control rods in Step 1. The calculated values ​​of the upper response of the external detector at the initial moment of each group of control rods moving in step 2. Calculate the sensitivity coefficient ε of the upper part of the external detector during the movement of each group of control rods. i,upper :

[0015]

[0016] Based on the measured values ​​of the lower current signal of the external detector at the initial moment of the movement process of each group of control rods. Calculated values ​​of the lower response of the external detectors at the initial moment of the movement of each group of control rods. Calculate the sensitivity coefficient ε of the lower part of the external detector during the movement of each group of control rods. i,lower :

[0017]

[0018] The sensitivity coefficient ε of the upper part of the off-site detector obtained by formula 2. i,upper The calculated response values ​​of the external detectors during the movement of each group of control rods in step 2 are applied to the calculation values. Calculated values ​​of the upper current signal of the external detector during the movement of each group of control rods.

[0019]

[0020] The sensitivity coefficient ε of the lower part of the off-site detector obtained by formula 3. i,lower The calculated response values ​​of the lower part of the external detector are applied to the movement of each group of control rods in step 2. Calculated values ​​of the current signal at the lower part of the external detector during the movement of each group of control rods.

[0021]

[0022] Step 4: Compare the measured values ​​of the external detector current signals during the movement of each group of control rods in Step 1 with the calculated values ​​of the external detector current signals during the movement of each group of control rods in Step 3 to verify the transient neutronics calculation results.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. This invention uses dynamic etched rod measured data to achieve direct verification of transient neutronics, ensuring the accuracy and reliability of transient neutronics software engineering applications, which is of great significance for reactor control and safety.

[0025] 2. This invention breaks through the limitations of traditional benchmark verification of transient neutronics, including the limitation of a very small number of benchmarks and the limitation that benchmark verification cannot reflect engineering practice.

[0026] 3. The verification method employed in this invention relies on abundant data, enabling more comprehensive verification of transient neutronics. Currently, most commercial pressurized water reactors use a dynamic bar marking method to measure the value of control rods during each fuel cycle, meaning that a large amount of data is available for transient neutronics verification, allowing for more comprehensive and practical verification of transient neutronics. Attached Figure Description

[0027] Figure 1 This is a transient neutronics verification process based on measured data from dynamic etched rods of a pressurized water reactor;

[0028] Figure 2 Axial arrangement for external detectors;

[0029] Figure 3 The results are verified by comparing the measured values ​​of the current signals from the external detectors during the control rod movement process with the calculated values. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0031] This invention utilizes measured data from an external detector during the dynamic bar etching process of a pressurized water reactor, along with simulation calculations using transient neutronics software, to complete transient neutronics verification. The specific steps are as follows: Figure 1 As shown, it includes the following steps:

[0032] Step 1: In the process of measuring the value of control rods using the dynamic rod-cutting method in pressurized water reactor nuclear power plants, each group of control rods moves individually from the top of the reactor core to the bottom of the reactor core at a fixed drive speed. The measured values ​​of the current signals of each section of the external detectors are recorded during the movement of each group of control rods. 'm' stands for the abbreviation of 'measurement,' 'i' represents the control rod group number, and the external detector is generally divided into multiple sections along the axial direction. 'j' represents the section number of each external detector. The measured values ​​of the current signals from each section of the upper part of the external detector are merged into the measured value of the upper current signal of the external detector." The measured values ​​of the current signals of each section at the bottom of the external detector were merged into a single measured value for the current signal at the bottom of the external detector. The measured values ​​of the upper and lower current signals of the external detectors at the initial moment of the movement of each group of control rods are recorded as follows: and

[0033] In this embodiment, the external detector is divided into six sections axially, with three sections in the upper part and three sections in the lower part, as shown in the attached diagram. Figure 2 As shown.

[0034] Step 2: The entire process of each set of control rods moving from the top of the reactor core to the bottom of the reactor core is simulated using transient neutronics software. The response values ​​of the external detectors during the movement of each set of control rods are obtained through numerical calculations. This step is mainly detailed into the following parts:

[0035] 1) Based on the geometry and material arrangement of the pressurized water reactor core, a model from the core fuel assemblies to the external detector is established using a discrete ordinate neutron transport program. The response function ω of each section of the external detector is obtained through conjugate neutron transport calculations. j,k , j represents the number of each external detector, k represents the grid number in the three-dimensional space, and the external detector response function characterizes the contribution of the fission neutron source of each grid in the three-dimensional space of the core to the simulated value of the external detector current signal.

[0036] 2) The transient neutronics software was used to simulate the entire process of each group of control rods moving from the top of the core to the bottom of the core, ensuring that the position of the control rods and the moving speed of the control rods were the same as the actual situation. The three-dimensional power distribution Pi,k(t) in the core at each moment during the movement of each group of control rods was obtained by transient neutronics calculation.

[0037] In this embodiment, the control rod is divided into a total of 225 steps along the core axis. Step 0 is defined as the control rod being at the bottom of the core, and step 225 is defined as the control rod being at the top of the core. Furthermore, during the dynamic marking process, the control rod moves at a speed of 72 steps per minute.

[0038] 3) Based on the response function ω of each section of the external detector j,k The calculated values ​​of the external detector responses of each group of control rods during the movement of each group of control rods are obtained by using the three-dimensional power distribution Pi,k(t) within the core at each time point during the movement of each group of control rods. 'C' stands for the abbreviation of the English word 'calculation'.

[0039]

[0040] 4) Combine the calculated responses of each section of the external detector into a single calculated response value for the upper part of the external detector. The calculated responses of each section of the external detector are merged into a single calculated response value for the lower section of the external detector. The calculated values ​​of the upper and lower responses of the external detectors at the initial moment of the movement of each group of control rods are denoted as follows: and

[0041] Step 3: Based on the measured values ​​of the upper current signal of the external detector at the initial moment of the movement process of each group of control rods in Step 1. The calculated values ​​of the upper response of the external detector at the initial moment of each group of control rods moving in step 2. Calculate the sensitivity coefficient ε of the upper part of the external detector during the movement of each group of control rods. i,upper :

[0042]

[0043] Based on the measured values ​​of the lower current signal of the external detector at the initial moment of the movement process of each group of control rods. Calculated values ​​of the lower response of the external detectors at the initial moment of the movement of each group of control rods. Calculate the sensitivity coefficient ε of the lower part of the external detector during the movement of each group of control rods. i,lower :

[0044]

[0045] The sensitivity coefficient ε of the upper part of the off-site detector obtained by formula 2. i,upper The calculated response values ​​of the external detectors during the movement of each group of control rods in step 2 are applied to the calculation values. Calculated values ​​of the upper current signal of the external detector during the movement of each group of control rods.

[0046]

[0047] The sensitivity coefficient ε of the lower part of the off-site detector obtained by formula 3. i,lower The calculated response values ​​of the lower part of the external detector are applied to the movement of each group of control rods in step 2. Calculated values ​​of the current signal at the lower part of the external detector during the movement of each group of control rods.

[0048]

[0049] Step 4: Compare the measured values ​​of the external detector current signals during the movement of each group of control rods in Step 1 with the calculated values ​​of the external detector current signals during the movement of each group of control rods in Step 3 to verify the transient neutronics calculation results.

[0050] In this example, the verification results of comparing the measured values ​​and calculated values ​​of the external detector current signals during the movement of a certain group of control rods are as follows: Figure 3 As shown in the figure, the calculated values ​​of the external detector current signal and the measured values ​​of the external detector current signal agree very well, proving that the calculated results of transient neutronics are the same as the actual measurements, thus achieving the goal of verifying transient neutronics using measured data from pressurized water reactors. Currently, most pressurized water reactors use a dynamic rod-cutting process to measure the control rod value; therefore, the measured data of the external detector current signal during the control rod movement process are abundant and comprehensive, enabling more comprehensive and practical verification of transient neutronics.

Claims

1. A transient neutronics verification method based on dynamic etched rod measured data, characterized in that: The ability to verify transient neutronics based on measured values ​​of the current signal from an external detector during the dynamic bar etching process of a pressurized water reactor includes the following steps: Step 1: When measuring the value of control rods in a pressurized water reactor using the dynamic rod-cutting method, record the variation of the measured values ​​of the current signals from the external detectors over time during the movement of each group of control rods. Step 2: Use transient neutronics software 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, and obtain the variation law of the calculated value of the external detector response during the movement of each group of control rods over time; Step 3: Based on the measured values ​​of the external detector current signals at the initial moment of each group of control rod movement in Step 1 and the calculated values ​​of the external detector responses at the initial moment of each group of control rod movement in Step 2, calculate the sensitivity coefficient of the external detector and use it to obtain the calculated values ​​of the external detector current signals during the movement of each group of control rods. Step 4: Compare the measured values ​​of the external detector current signals during the movement of each group of control rods in Step 1 with the calculated values ​​of the external detector current signals during the movement of each group of control rods in Step 3 to verify the transient neutronics. The implementation process of step 3 is as follows: 1) Based on the measured values ​​of the upper current signal of the external detector at the initial moment of the movement process of each group of control rods. Calculated values ​​of the upper response of the external detectors at the initial moment of the movement of each group of control rods. Calculate the sensitivity coefficient ε of the upper part of the external detector during the movement of each group of control rods. i,upper : Based on the measured values ​​of the lower current signal of the external detector at the initial moment of the movement process of each group of control rods. Calculated values ​​of the lower response of the external detectors at the initial moment of the movement of each group of control rods. Calculate the sensitivity coefficient ε of the lower part of the external detector during the movement of each group of control rods. i,lower : 2) The sensitivity coefficient ε of the upper part of the off-site detector obtained by formula 2 i,upper Calculated values ​​of the upper response of the external detectors during the movement of each group of control rods. Calculated values ​​of the upper current signal of the external detector during the movement of each group of control rods. The sensitivity coefficient ε of the lower part of the off-site detector obtained by formula 3. i,lower Calculated values ​​of the lower response of the external detectors during the movement of each group of control rods. Calculated values ​​of the current signal at the lower part of the external detector during the movement of each group of control rods.

2. The method according to claim 1, characterized in that: The implementation process of step 1 is as follows: In pressurized water reactor nuclear power plants, during the dynamic rod-cutting method for measuring the value of control rods, each group of control rods moves individually from the top of the reactor core to the bottom of the core at a fixed drive speed. The measured values ​​of the current signals from each section of the external detectors are recorded during the movement of each group of control rods. 'm' stands for the abbreviation of 'measurement,' 'i' represents the control rod group number, the external detector is divided into multiple sections along the axial direction, and 'j' represents the section number of each external detector; the measured values ​​of the current signals of each section in the upper part of the external detector are merged into the measured value of the current signal in the upper part of the external detector. The measured values ​​of the current signals of each section at the bottom of the external detector were merged into a single measured value for the current signal at the bottom of the external detector. The measured values ​​of the upper and lower current signals of the external detectors at the initial moment of the movement of each group of control rods are recorded as follows: and 3. The method according to claim 1, characterized in that: The implementation process of step 2 is as follows: 1) Based on the geometry and material arrangement of the pressurized water reactor core, a model is established from the core fuel assemblies to the external detectors. By solving the conjugate neutron transport equations, the response functions ω of each section of the external detectors are obtained. j,k , j represents the number of each external detector, k represents the grid number in the three-dimensional space, and the external detector response function characterizes the contribution of the fission neutron source of each grid in the three-dimensional space of the core to the simulated value of the external detector current signal. 2) The transient neutronics software was used to simulate the entire process of each group of control rods moving from the top of the core to the bottom of the core, ensuring that the position of the control rods and the moving speed of the control rods were the same as the actual situation. The three-dimensional power distribution Pi,k(t) in the core at each moment during the movement of each group of control rods was obtained by transient neutronics calculation. 3) Based on the response function ω of each section of the external detector j,k The calculated values ​​of the responses of each section of the external detector during the movement of each group of control rods are obtained by using the three-dimensional power distribution Pi,k(t) within the core at each moment during the movement of each group of control rods. 'C' stands for the abbreviation of the English word 'calculation'. 4) Combine the calculated responses of each section of the external detector into a single calculated response value for the upper part of the external detector. The calculated responses of each section of the external detector are merged into a single calculated response value for the lower section of the external detector. The calculated values ​​of the upper and lower responses of the external detectors at the initial moment of the movement of each group of control rods are denoted as follows: and

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