Methods for conducting zero-power physics experiments using intermediate ranges of off-core nuclear instrumentation systems

Abstract

This invention belongs to the field of nuclear power plant reactor physics technology, specifically relating to a method for conducting zero-power physics tests using the intermediate range of an external nuclear instrumentation system. The method includes: Measurement of the critical boron concentration for full control rod extraction: the maximum reactivity introduction is 70 pcm, and the intermediate range current value is controlled within the range of 5E-8 to 5E-7 A; Measurement of the isothermal temperature coefficient: the reactivity introduction range is -20 to 20 pcm, and the intermediate range current value is controlled within the range of 5E-8 to 5E-7 A; Measurement of the control rod value: the maximum reactivity in the dynamic rod test is -1200 to 60 pcm, and the highest power of the reactor core in the dynamic rod test should reach the Doppler heating point. The corresponding intermediate range current values ​​are 1.5E-6 A for the M310 unit and 2.5E-7 A for the Hualong One unit, and are not limited by the range of zero-power physics tests. By using the intermediate range of the external nuclear instrumentation system to conduct zero-power physics tests, the test can be completed during critical zero-power physics tests even when the reactivity meter is not connected to the power range channel or when the reactivity meter experiences a sudden failure.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power plant reactor physics technology, specifically relating to a method for conducting zero-power physics tests using the intermediate range of an off-core nuclear instrumentation system. Background Technology

[0002] After refueling, nuclear power plants need to conduct zero-power physics tests to verify the consistency between the actual core operating conditions and the design predictions. Typically, the startup physics tests after refueling include: critical boron concentration measurement, isothermal temperature coefficient measurement, and control rod assembly integral value measurement.

[0003] Currently, when nuclear power units perform initial criticality and zero-power physics tests, the power range channel current signal of the external nuclear instrumentation system needs to be connected to the reactivity meter via a data line for reactivity measurement, thereby enabling relevant operating condition verification tests. However, connecting the power range signal to the reactivity meter triggers a power range unavailable signal, causing the unit shutdown logic to change from a 2-out-of-4 logic to a 1-out-of-3 logic, increasing the risk of unit shutdown. Simultaneously, because the intermediate range current chamber is a gamma-supplement current chamber, its output current is a compensated and corrected current, and the influence of the background current can be largely ignored. Therefore, using the intermediate range for zero-power physics tests also increases the test range. Summary of the Invention

[0004] The purpose of this invention is to provide a method for conducting zero-power physics tests using the intermediate range of an off-core nuclear instrumentation system. By using the intermediate range of the off-core nuclear instrumentation system to conduct zero-power physics tests, the test can be completed during critical zero-power physics tests even when the reactivity meter is not connected to the power range channel or when the reactivity meter suddenly fails.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for conducting zero-power physics experiments using the intermediate range of an off-core nuclear instrumentation system.

[0007] Measurement of critical boron concentration for full extraction using control rods: maximum reactivity is introduced at 70 pcm, and the intermediate range current value is controlled within the range of 5E-8 to 5E-7 A.

[0008] Isothermal temperature coefficient measurement: The reactivity introduction range is -20 to 20 pcm, and the intermediate range current value is controlled within the range of 5E-8 to 5E-7A;

[0009] Control rod value measurement: The maximum reactivity of the dynamic rod test is -1200 to 60 pcm, and the highest power of the reactor core in the dynamic rod test should reach the Doppler heating point. The corresponding intermediate range current values ​​are 1.5E-6A for M310 unit and 2.5E-7A for Hualong One unit, which is not limited by the zero power physics test range.

[0010] The value of the measuring rod is measured by the rod replacement method: the reactivity range is from -100pcm to 40pcm, and the intermediate range current value is controlled within the range of 5E-8 to 5E-7A.

[0011] The core power distribution measurement is a quasi-steady-state test, and the corresponding intermediate range current value is 5E-6A for M310 unit. It is not limited by the zero-power physical test range, and the reactivity variation range is -2pcm to 2pcm.

[0012] Measurement of critical boron concentration for full extraction using control rods: maximum reactivity was introduced at 70 pcm, corresponding to a doubling period of 50 s.

[0013] Isothermal temperature coefficient measurement: The reactivity introduction range is -20 to 20 pcm, corresponding to a doubling period of 230 s.

[0014] Control rod value measurement: The maximum reactivity of the dynamic etched rod test is -1200 to 60 pcm, corresponding to a doubling period of 65 s.

[0015] The value of a rod is measured by the rod replacement method: the reactivity range is -100 pcm to 40 pcm, and the corresponding doubling period is 105 s.

[0016] The beneficial effects achieved by this invention are as follows:

[0017] This method can be used to conduct zero-power physics experiments. The method for conducting zero-power physics experiments is stable, reliable, and simple, and can be widely used. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments.

[0019] The physics tests for startup after refueling of a nuclear power plant include: measurement of the critical boron concentration of the All-Rise Control Rods (ARO), measurement of the isothermal temperature coefficient of the All-Rise Control Rods (ARO), measurement of the integral value of the control rod assembly, and measurement of the core power distribution.

[0020] I. Experimental Process Control

[0021] During reactor criticality and zero-power physics tests, the reactor shutdown protection signal settings are generated by the intermediate range of the external nuclear instrumentation system. The shutdown protection setting for the Hualong One unit is 2%FP, and for the M310 unit, it is 2.5%FP. During the tests, the intermediate range current value is typically required to not exceed 1%FP (approximately: M310 unit: 1.5E-5A, Hualong One unit: 2.5E-6A). During the reactor criticality and zero-power physics tests, the power plant computer information and control system (KIC) in the main control room can display the range current values ​​between the external nuclear instrumentation systems and their corresponding doubling periods in real time (the doubling period corresponds to reactivity). During the tests, zero-power physics tests can be performed by controlling the intermediate range current value within the range of 5E-8–5E-7A and ensuring a minimum stable doubling period of no less than 50 seconds (corresponding to a positive reactivity of approximately 70 pcm). The test process is safe, and the data processing results are relatively accurate.

[0022] The specific experimental reactivity is introduced as follows:

[0023] 1. The maximum reactivity of the control rod total extraction (ARO) critical boron concentration measurement is 70 pcm (corresponding to a doubling period of approximately 50 s), and the intermediate range current value is controlled within the range of 5E-8 to 5E-7 A;

[0024] 2. Isothermal temperature coefficient measurement: The reactivity introduction range is -20 to 20 pcm (corresponding to a doubling period of approximately 230 s), and the intermediate range current value is controlled within the range of 5E-8 to 5E-7 A;

[0025] 3. Control rod value measurement: The maximum reactivity of the dynamic rod test is -1200 to 60 pcm (corresponding to a doubling period of approximately 65 s), and the highest core power in the dynamic rod test should reach near the Doppler heating point. The corresponding intermediate range current values ​​are 1.5E-6A for M310 unit and 2.5E-7A for Hualong One unit, and are not limited by the zero-power physical test range.

[0026] 4. The value response range of the measuring rod using the rod replacement method is -100pcm to 40pcm (corresponding to a doubling period of approximately 105s), and the intermediate range current value is controlled within the range of 5E-8 to 5E-7A.

[0027] 5. Core power distribution measurement is a quasi-steady-state test. The corresponding intermediate range current value is 5E-6A for M310 unit. It is not limited by the zero-power physical test range, and the reactivity varies within the smallest possible range: -2pcm to 2pcm.

[0028] II. Data Processing

[0029] The specific experimental data processing was based on solving the inverse dynamic neutron kinetic equations.

[0030] The intermediate range current values ​​during the critical zero-power physics experiment were derived using the experimental data acquisition system and based on the point pile inverse dynamic neutron kinetic equations:

[0031]

[0032]

[0033] In the formula,

[0034] The rate of change of neutron density over time, n / (cm²) 3 . s);

[0035] ρ(t) refers to reactivity (pcm);

[0036] β eff The effective share of delayed-emission neutrons;

[0037] The mean generation time of a transient neutron, in seconds;

[0038] λi refers to the decay constant of the i-th group of slow-emitting neutrons;

[0039] ci refers to the precursor nuclear density of the i-th delayed neutron group, n / cm3;

[0040] β i，eff The effective share of the i-th delayed neutron group.

[0041] From equation (1) we get

[0042]

[0043] Equation (2) is a first-order linear differential equation, and its solution is in the form of:

[0044]

[0045] Substituting (4) into (1) yields the solution for the reactivity ρ(t).

[0046]

[0047] This is the inverse dynamic equation. Given the reactor power change n(t), this equation reveals the form in which reactivity changes over time. By combining the intermediate-range current values ​​recorded in real-time by the experimental data acquisition system with the point reactor dynamics equations, the reactivity can be solved, thus enabling the processing of critical and zero-power physics experimental data. Because the experimental data acquisition system has good stability, this method is stable and effective for critical and zero-power physics experiments.

[0048] This method involves controlling the intermediate range current of the external nuclear instrumentation system displayed in the main control room (KIC) to be within the range of 5E-8–5E-7A, and ensuring the minimum stable doubling period of the intermediate range is no less than 50 seconds (corresponding to a positive reactivity of approximately 70 pcm) to perform zero-power physics tests. (During the test, if the stable doubling period of the intermediate range is less than 50 seconds, the unit power is increased by inserting control rods to ensure unit safety.) The reactivity is then calculated inversely using the real-time measured current values ​​of the intermediate range of the external nuclear instrumentation system during the critical and zero-power physics tests, thus enabling data processing during these tests. Verification using the initial data from the first critical zero-power physics test of the Fuqing Nuclear Power Plant's Hualong One unit showed that the data processing results met the acceptance criteria. This demonstrates that using the intermediate range of the external nuclear instrumentation system for zero-power physics tests is applicable to nuclear power plants. Specifically, the verification was conducted using data from the first zero-power physics test of the Fuqing Nuclear Power Plant's Hualong One unit.

Claims

1. A method for conducting zero-power physics experiments using the intermediate range of an off-core nuclear instrumentation system, characterized in that: Measurement of critical boron concentration for full extraction using control rods: maximum reactivity is introduced at 70 pcm, and the intermediate range current value is controlled within the range of 5E-8 to 5E-7 A. Isothermal temperature coefficient measurement: The reactivity introduction range is -20 to 20 pcm, and the intermediate range current value is controlled within the range of 5E-8 to 5E-7A; Control rod value measurement: The maximum reactivity of the dynamic rod test is -1200 to 60 pcm, and the highest power of the reactor core in the dynamic rod test should reach the Doppler heating point. The corresponding intermediate range current values ​​are 1.5E-6A for M310 unit and 2.5E-7A for Hualong One unit, which is not limited by the zero power physics test range. The value of the measuring rod is measured by the rod replacement method: the reactivity range is from -100pcm to 40pcm, and the intermediate range current value is controlled within the range of 5E-8 to 5E-7A. The core power distribution measurement is a quasi-steady-state test, and the corresponding intermediate range current value is 5E-6A for M310 unit. It is not limited by the zero-power physical test range, and the reactivity variation range is -2pcm to 2pcm. The intermediate range current values ​​during the critical zero-power physics experiment were derived using the experimental data acquisition system and based on the point pile inverse dynamic neutron kinetic equations: In the formula, The rate of change of neutron density over time, n / (cm²) 3 . s); ρ(t) refers to reactivity (pcm); β eff The effective share of delayed-emission neutrons; l refers to the mean generation time of a transient neutron, in seconds; λi refers to the decay constant of the i-th group of slow-emitting neutrons; ci refers to the precursor nuclear density of the i-th delayed neutron group, n / cm² 3 ; β i,eff The effective share of the i-th delayed neutron group. From equation (1) we get Equation (2) is a first-order linear differential equation, and its solution is in the form of: Substituting (4) into (1) yields the solution for the reactivity ρ(t).

2. The method for conducting zero-power physics experiments using the intermediate range of an off-core nuclear instrumentation system according to claim 1, characterized in that: Measurement of critical boron concentration for full extraction using control rods: maximum reactivity was introduced at 70 pcm, corresponding to a doubling period of 50 s.

3. The method for conducting zero-power physics experiments using the intermediate range of an off-core nuclear instrumentation system according to claim 1, characterized in that: Isothermal temperature coefficient measurement: The reactivity introduction range is -20 to 20 pcm, corresponding to a doubling period of 230 s.

4. The method for conducting zero-power physics experiments using the intermediate range of an off-core nuclear instrumentation system according to claim 1, characterized in that: Control rod value measurement: The maximum reactivity of the dynamic etched rod test is -1200 to 60 pcm, corresponding to a doubling period of 65 s.

5. The method for conducting zero-power physics experiments using the intermediate range of an off-core nuclear instrumentation system according to claim 1, characterized in that: The value of a rod is measured by the rod replacement method: the reactivity range is -100 pcm to 40 pcm, and the corresponding doubling period is 105 s.

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