A method for determining the inertial flow test of a nuclear reactor coolant pump

Abstract

This invention relates to a method for determining the inertia flow rate of nuclear reactor coolant pumps. The method includes the following steps: Step 1: Collect the flow rate and pump speed of the three loops; Step 2: Simultaneously shut down all reactor coolant pumps; Step 3: Taking the simultaneous shutdown of the three reactor coolant pumps as the zero point, record the flow rate and pump speed of the three loops at different times; Step 4: Based on the heat balance calculation of the reactor coolant flow rate test report, determine the flow rates of the three loops as Q1, Q2, and Q3 during the stable operation of the reactor coolant system in the previous fuel cycle; Step 5: Preliminarily determine whether the flow rate of each loop meets the requirements; Step 6: Preliminarily determine whether the total flow rate of the reactor core coolant in the primary loop meets the requirements; Step 7: Compare the decrease in pump speed of each loop with the design curve; Step 8: Finally determine the test results. This invention is used to determine whether the inertia flow rate test of the coolant pumps in Generation II or Generation II Plus pressurized water reactors is qualified.

Description

Technical Field

[0001] This invention relates to a method for determining the inertial flow rate of a nuclear reactor coolant pump, applicable to second-generation or second-generation plus pressurized water reactors such as M310 and CPR1000, to determine whether the reactor coolant pump inertial flow rate test is qualified, that is, whether the pump's inertial performance can meet nuclear safety requirements after a sudden power loss. Background Technology

[0002] The safety-critical periodic test, the "Pressed Water Reactor Coolant Pump Inert Flow Test," aims to verify whether the Neutral State Suspension Flow Rate (NSSS) can remain in a safe state before reaching the minimum Density Circulation Base (DNBR) after the complete loss of forced circulation flow of the reactor coolant. This periodic test is conducted on the hot shutdown platform during each major overhaul startup phase. For Generation II or Generation II Plus units such as the M310 and CPR1000 units, the method for determining the test's validity involves measuring the flow rate data of each loop using the reactor primary loop flow meter. The flow meter measures percentage values, and the actual flow rate data is obtained by substituting the flow rate of each loop in the reactor primary loop calculated from the annual primary and secondary loop heat balance test into the percentage flow meter. Finally, this data is compared with nuclear safety guidelines to confirm the test's compliance.

[0003] For second-generation or second-generation plus reactors such as the M310 and CPR1000 units, this method is problematic because their primary loop design uses elbow flow meters for each loop, displaying percentage values. These flow meters are primarily used for reference and indication when measuring the reactor's primary coolant flow, and their measurement accuracy is not high. Furthermore, with these flow meters, after all three reactor coolant pumps lose power, the primary loop pressure fluctuates significantly, leading to substantial uncertainty and display delay in the differential pressure measured by the elbow flow meters. This means that even after the reactor coolant pumps have returned to shutdown status, the flow meter may still show an increase in flow or irregular fluctuations, which, based on experience, last for approximately 0.5 seconds. This is sufficient to affect the determination of pass or fail in this test.

[0004] In summary, due to design limitations of second-generation or second-generation plus reactors such as the M310 and CPR1000 units, the existing methods for determining the inertial flow rate of reactor coolant pumps suffer from numerous drawbacks, including inaccuracy, untimely flow meter response with abnormal fluctuations, and poor feasibility. Therefore, there is an urgent need to research a more accurate, intuitive, simple, and safe (without requiring additional equipment that could compromise nuclear safety) testing method. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the inertia flow rate of a nuclear reactor coolant pump, which, while ensuring the safe and stable operation of the unit and accurate determination, addresses the shortcomings in the current determination process of this test for second-generation or second-generation plus units.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for determining the inertial flow rate of a nuclear reactor coolant pump, when the primary coolant system has three loops, includes the following steps:

[0008] Step 1: Collect the flow rate of the three loops and the rotational speed of the reactor coolant pumps in the three loops;

[0009] Step 2: Simultaneously shut down all reactor coolant pumps;

[0010] Step 3: Taking the simultaneous shutdown of the three reactor coolant pumps as the zero point, record the flow rate and pump speed of the three loops at different times;

[0011] Step 4: Based on the heat balance calculation of the reactor coolant flow test report, the flow rates of the three loops during the stable operation of the reactor coolant system in the previous fuel cycle are Q1, Q2, and Q3, respectively.

[0012] Step 5: Initially determine whether the flow rate of each loop meets the requirements;

[0013] Step Six: Preliminary determination of whether the total flow rate of the primary coolant in the reactor core meets the requirements;

[0014] Step 7: Compare the speed drop of each loop pump with the design curve;

[0015] Step 8: Final determination of the test results.

[0016] Step 3: Collect a set of data every 0.1 seconds.

[0017] Step 5: The preliminary determination method is as follows: The reactor coolant pump inert flow test requires that the minimum flow rate 4 seconds after the pump is stopped in each loop must not be lower than the flow rate Q. 准则t =4.0, the uncertainty of the speed measuring instrument along with the instrument channel is η, then the corresponding speed Δn = η × n 额定 n 额定 Given the rated flow rates of the three loop reactor coolant pumps, whether the flow rate of one loop meets the test criteria is determined by the following formula:

[0018]

[0019] Q 1t =4.0 is the flow rate of the loop after the pump stops for 4.0 seconds, n 1t＝4.0n is the pump speed 4 seconds after the first loop pump stops. 1t＝0.0 The pump speed is 0 seconds after the pump stops in the loop, such as Q. 1t =4.0>Q 准则t =4.0, then the traffic flow of the first ring road is considered to initially meet the requirements; otherwise, it does not meet the requirements. For the second ring road:

[0020]

[0021] Q 2t =4.0 is the flow rate of the second loop after the pump stops for 4.0 seconds, n 2t＝4.0 n is the pump speed 4 seconds after the pump stops on the second ring road. 2t＝0.0 The pump speed is 0 seconds after the pump stops on the second loop, such as Q. 2t =4.0>Q 准则t =4.0, then the traffic flow on the Second Ring Road is considered to initially meet the requirements; otherwise, it does not. For the Third Ring Road:

[0022]

[0023] Q 3t =4.0 represents the flow rate of the three-loop system 4.0 seconds after the pump stops, n 3t＝4.0 n is the pump speed 4 seconds after the pump stops on the third ring road. 3t＝0.0 The pump speed is 0 seconds after the pump stops on the third ring road, such as Q. 3t =4.0>Q 准则t If the traffic flow is 4.0, then the traffic flow on the Third Ring Road is considered to meet the requirements initially; otherwise, it does not meet the requirements.

[0024] Step Six: Calculate the flow rate at 4.1 seconds after pump shutdown for each loop based on Step Five. For one loop:

[0025]

[0026] Q 1t =4.1 represents the flow rate of the loop after the pump stops for 4.1 seconds, n 1t＝4.1 The pump speed is 4.1 seconds after the pump stops in the first loop.

[0027] The Second Ring Road is:

[0028]

[0029] Q 2t =4.1 represents the flow rate of the second loop after the pump stops for 4.1 seconds, n 2t＝4.1 The pump speed is 4.1 seconds after the pump stops on the second ring road.

[0030] The Third Ring Road is:

[0031]

[0032] Q3t =4.1 represents the flow rate of the three-loop system 4.1 seconds after the pump stops, n 3t＝4.1 The pump speed is 4.1 seconds after the three-loop pump is shut down. The reactor coolant pump inertial flow test requires that the core flow rate must not be lower than the flow rate Q 4.1 seconds after the pump is shut down. 准则t =4.1, then the following comparison is possible:

[0033] Q1t=4.1+Q2t=4.1+Q3t=4.1>Q 准则t =4.1

[0034] If the above formula is satisfied, the total core flow rate is considered to have initially met the requirements.

[0035] Step 7: According to upstream documentation requirements, the evaluation requirements for the speed drop curve during the reactor primary coolant pump inertia flow test are as follows: Speed ​​ratio:

[0036]

[0037] And so on:

[0038] In the formula Ω 1t n represents the pump speed ratio at time t in the loop. 1t The pump speed at time t after the pump in the loop stops;

[0039] If:

[0040] Ω 1t＝0.0 ≥Ω 曲线t＝0.0

[0041] Ω 1t＝0.5 ≥Ω 曲线t＝0.5

[0042] Ω 1t＝1.0 ≥Ω 曲线t＝1.0

[0043] And so on Ω 1t＝5.0 ≥Ω 曲线t＝5.0

[0044] In the formula Ω 曲线t Let t represent the pump speed ratio at time t in each loop; then it is considered that the pump speed decrease in one loop meets the curve. If any of the above sets does not meet the curve, then it is considered that the pump speed decrease does not meet the curve.

[0045] The Second Ring Road and the Third Ring Road were calculated and compared using the same method as the First Ring Road.

[0046] Step 8: If all requirements are met according to Steps 5 to 7, the test is considered preliminarily qualified, and subsequent unit power increase operations can be carried out. After the unit reaches full power again, the reactor coolant flow test calculated based on heat balance will be repeated, and the measured flow rates Q of the three loops of the reactor coolant system will be used.1n Q 2n Q 3n If the comparison results of steps five and six are still met, and Q1, Q2, and Q3 are replaced respectively in steps five and six, then the test is considered to have met the requirements and is considered to be qualified.

[0047] Step 8: If the flow rate of any loop or the total flow rate in Step 5 or Step 6 is not met, the test is considered unqualified.

[0048] Step 8: If the flow rates in Step 5 or Step 6 meet the requirements, but any one or more sets of data in Step 7 do not meet the requirements, the test is preliminarily considered qualified but defective. Once the unit reaches full power again, the reactor coolant flow rate test calculated based on heat balance will be repeated, and the measured flow rates Q of the three loops of the reactor coolant system will be used. 1n Q 2n Q 3n If Q1, Q2, and Q3 in steps five and six are replaced respectively, and the test flow rate still meets the requirements of steps five and six, then the test is considered to be qualified, but there is a defect.

[0049] The beneficial effects achieved by this invention are as follows:

[0050] This invention combines the accuracy of actual instrument measurements on-site, the execution methods of relevant tests for domestically produced third-generation nuclear power units, and the judgment principles of the original method to comprehensively develop a more accurate, convenient, and safer test judgment method that can better ensure the nuclear safety of the unit and ensure its stable operation.

[0051] The present invention can more accurately determine whether the reactor coolant pump inert flow test meets the requirements. It is consistent with the original design in principle and is simpler in terms of data acquisition, zero point determination, calculation and evaluation at the implementation level. At the same time, it is more conservative than the original method and will not introduce more nuclear safety risks. It is more scientific than the original method and uses flow data of the reactor primary coolant system in two different cycles for verification, which is safer. Detailed Implementation

[0052] The present invention will now be described in detail with reference to specific embodiments.

[0053] A method for determining the inertial flow rate of a nuclear reactor coolant pump, comprising the following steps:

[0054] When the primary coolant system has three loops:

[0055] Step 1: Data Acquisition Setup: Pre-set the data acquisition points in the unit test data acquisition system. The acquired data includes: flow rates in the three loops and reactor coolant pump speeds in the three loops. There are three coolant pumps in total for the three loops; if there are two loops, then two coolant pumps are used.

[0056] Step Two: Simultaneously Shut Down All Reactor Coolant Pumps: Since the unit is in a hot shutdown condition following a refueling overhaul, all reactor coolant pumps will be simultaneously shut down according to the requirements of the upstream test documents. This involves three coolant pumps for three loops; if there are two loops, then two coolant pumps will be shut down.

[0057] Step 3: Data Acquisition: Data is collected every 0.1 seconds, with the simultaneous shutdown of all three reactor coolant pumps as time zero. Flow rate and pump speed data for the corresponding three loops at different times are recorded. The letters used are as follows: the flow rate 0.5 seconds after loop 1 pumps stop is denoted as Q. 1t =0.5; similarly, the flow rate 1.2s after the pump in the 3rd loop stops is set as Q. 3t =1.2; The pump speed 0.4s after the second loop pump stops is set to n. 2t＝0.4 Similarly, the pump speed 4.2 seconds after the pump in loop 3 stops is n. 3t＝4.2 The following letters will all follow this pattern.

[0058] Step 4: Initial flow rate: Based on the heat balance calculation and the test report record of the reactor coolant flow rate, the flow rates of the three loops during the stable operation of the reactor coolant system in the previous fuel cycle are Q1, Q2, and Q3, respectively.

[0059] Step 5: Preliminary determination of whether the flow rate of each loop meets the requirements: According to the safety guidelines for reactor coolant systems, the reactor coolant pump inert flow test requires that the minimum flow rate 4 seconds after each loop pump is stopped must not be lower than the flow rate Q. 准则t =4.0. The corresponding situation for each loop is as follows:

[0060]

[0061]

[0062] If the uncertainty of the speed measuring instrument along with the instrument channel is η, then the corresponding speed Δn is: Δn = η × n 额定 Note: n 额定 This refers to the rated flow rate of the three loop reactor coolant pumps.

[0063] Whether the flow rate of the first loop meets the test criteria is determined by the following formula:

[0064]

[0065] In the formula Q1t =4.0 represents the flow rate of the reactor coolant system's first loop at 4.0 seconds after pump shutdown, n 1t＝4.0 n is the pump speed 4 seconds after the first loop pump stops. 1t＝0.0 The pump speed is 0 seconds after the pump stops in the loop, such as Q. 1t =4.0>Q 准则t =4.0, then the traffic flow of the first ring road is considered to initially meet the requirements; otherwise, it does not. The same applies to the second ring road:

[0066]

[0067] In the formula Q 2t =4.0 is the flow rate of the reactor coolant system's second loop when the pump is stopped for 4.0 seconds, n 2t＝4.0 n is the pump speed 4 seconds after the pump stops on the second ring road. 2t＝0.0 The pump speed is 0 seconds after the pump stops on the second loop, such as Q. 2t =4.0>Q 准则t =4.0, then the traffic flow on the Second Ring Road is considered to initially meet the requirements; otherwise, it does not. The same applies to the Third Ring Road:

[0068]

[0069] In the formula Q 3t =4.0 represents the flow rate of the reactor coolant system's three-loop circuit 4.0 seconds after pump shutdown, n 3t＝4.0 n is the pump speed 4 seconds after the pump stops on the third ring road. 3t＝0.0 The pump speed is 0 seconds after the pump stops on the third ring road, such as Q. 3t =4.0>Q 准则t If the traffic flow is 4.0, then the traffic flow on the Third Ring Road is considered to meet the requirements initially; otherwise, it does not meet the requirements.

[0070] Step Six: Preliminary determination of whether the total flow rate of the primary coolant in the reactor core meets the requirements:

[0071] Based on the calculation method in step five, calculate the flow rate at 4.1 seconds after the pump stops in each loop. Then, one loop is:

[0072]

[0073] In the formula Q 1t =4.1 represents the flow rate of the reactor coolant system loop 4.1 seconds after pump shutdown, n 1t＝4.1 The pump speed is 4.1 seconds after the pump stops in the first loop; for the second loop:

[0074]

[0075] In the formula Q 2t =4.1 represents the flow rate of the reactor coolant system's second loop at 4.1 seconds after pump shutdown, n2t＝4.1 The pump speed is 4.1 seconds after the pump stops on the second ring road; for the third ring road:

[0076]

[0077] In the formula Q 3t =4.1 represents the flow rate of the reactor coolant system's three-loop circuit at 4.1 seconds after pump shutdown, n 3t＝4.1 The pump speed is 4.1 seconds after the three-loop pump is shut down. The reactor coolant pump inertial flow test requires that the core flow rate must not be lower than the flow rate Q 4.1 seconds after the pump is shut down. 准则t =4.1. Then the following comparison exists:

[0078] Q1t=4.1+Q2t=4.1+Q3t=4.1>Q 准则t =4.1

[0079] If the above formula is satisfied, the total core flow rate is considered to have initially met the requirements.

[0080] Step 7: Compare the speed drop of each loop pump with the design curve.

[0081] According to upstream documentation, the reactor primary coolant pump inertial flow test includes an evaluation of the speed drop curve, and the evaluation requires the following curve:

[0082] 0.0 <![CDATA[Ω 曲线t＝0.0 ]]> 0.5 <![CDATA[Ω 曲线t＝0.5 ]]> 1.0 <![CDATA[Ω 曲线t＝1.0 ]]> 1.5 <![CDATA[Ω 曲线t＝1.5 ]]> ...... ...... 4.5 <![CDATA[Ω 曲线t＝4.5 ]]> 5.0 <![CDATA[Ω 曲线t＝5.0 ]]>

[0083] The pump speed ratio at different times in each loop is expressed as follows (taking one loop as an example):

[0084]

[0085]

[0086] Speed ​​ratios in the table above:

[0087]

[0088] And so on.

[0089]

[0090] In the formula Ω 1t n represents the pump speed ratio at time t in the loop. 1t The pump speed at time t after the pump in the loop stops;

[0091] If:

[0092] Ω 1t＝0.0 ≥Ω 曲线t＝0.0

[0093] Ω 1t＝0.5 ≥Ω 曲线t＝0.5

[0094] Ω 1t＝1.0 ≥Ω 曲线t＝1.0

[0095] And so on.

[0096] Ω 1t＝5.0 ≥Ω 曲线t＝5.0

[0097] In the formula Ω 曲线t This represents the pump speed ratio at time t in each loop; it is assumed that the pump speed decrease in the first loop conforms to the curve. If any of the above sets does not conform, then the pump speed decrease is considered not to conform to the curve. Similarly, the second and third loops are calculated and compared in the same way.

[0098] Step 8: Final Judgment of Test Results: Based on the calculations and comparisons performed in Steps 5 to 7, if all requirements are met, the test is considered preliminarily qualified, and subsequent operations such as increasing the unit's power output can proceed. Once the unit reaches full power again, the reactor coolant flow rate test calculated based on heat balance will be performed again, and the measured flow rates Q in the three loops of the reactor coolant system will be used. 1n Q 2n Q 3n Replace Q1, Q2, and Q3 in steps five and six respectively. If the comparison results of steps five and six are still met, the test is considered to have ultimately met the requirements and is considered qualified. If any loop flow or total flow in step five or six is ​​not met, the test is considered unqualified. If the flow rates in steps five or six are all met, but any set or multiple sets of data in step seven do not meet the curve requirements, the test is initially considered qualified, but has defects. Once the unit reaches full power again, the reactor coolant flow rate test calculated based on heat balance is repeated, and the measured flow rates Q in the three loops of the reactor coolant system are used. 1n Q 2n Q 3n If Q1, Q2, and Q3 in steps five and six are replaced respectively, and the test flow rate still meets the requirements of steps five and six, then the test is considered to be qualified, but there is a defect.

Claims

1. A method for determining the inertial flow rate of a nuclear reactor coolant pump, characterized in that: When the primary coolant system has three loops, the following steps are included: Step 1: Collect the flow rate of the three loops and the rotational speed of the reactor coolant pumps in the three loops; Step 2: Simultaneously shut down all reactor coolant pumps; Step 3: Taking the simultaneous shutdown of the three reactor coolant pumps as the zero point, record the flow rate and pump speed of the three loops at different times; Step 4: Based on the test report record of reactor coolant flow rate calculation according to heat balance calculation, the flow rates of the three loops of the reactor coolant system during the stable operation of the previous fuel cycle reactor are Q1, Q2, and Q3, respectively; Step 5: Preliminary determination of whether the flow rate of each loop meets the requirements; the preliminary determination method is as follows: the reactor coolant pump inert flow test requires that the minimum flow rate 4 seconds after the pump is stopped in each loop must not be lower than the flow rate Q. 准则t=4.0 If the uncertainty of the speed measuring instrument along with the instrument channel is η, then the corresponding speed Δn = η × n 额定 n 额定 Given the rated flow rates of the three loop reactor coolant pumps, whether the flow rate of one loop meets the test criteria is determined by the following formula: Q 1t=4.0 n represents the flow rate of the loop after the pump stops for 4.0 seconds. 1t=4.0 n is the pump speed 4 seconds after the first loop pump stops. 1t=0.0 The pump speed is 0 seconds after the pump stops in the loop, such as Q. 1t=4.0 >Q 准则t=4.0 If the traffic flow on the first ring road is high, it is considered to initially meet the requirements; otherwise, it does not. For the second ring road: Q 2t=4.0 n represents the flow rate of the second ring road 4.0 seconds after the pump stops. 2t=4.0 n is the pump speed 4 seconds after the pump stops on the second ring road. 2t=0.0 The pump speed is 0 seconds after the pump stops on the second loop, such as Q. 2t=4.0 >Q 准则t=4.0 If the traffic flow on the Second Ring Road is high, it is considered to initially meet the requirements; otherwise, it does not. For the Third Ring Road: Q 3t=4.0 n represents the flow rate of the third ring road when the pump stops for 4.0 seconds. 3t=4.0 n is the pump speed 4 seconds after the pump stops on the third ring road. 3t=0.0 The pump speed is 0 seconds after the pump stops on the third ring road, such as Q. 3t=4.0 >Q 准则t=4.0 If the traffic flow is high, it is considered that the traffic flow on the Third Ring Road initially meets the requirements; otherwise, it does not meet the requirements. Step Six: Preliminary determination of whether the total flow rate of the reactor core coolant in the primary loop meets the requirements; based on the calculation in Step Five, the flow rate at 4.1 seconds after the pumps in each loop are stopped is as follows: Q 1t=4.1 Let n be the flow rate of the loop at 4.1 seconds after pump shutdown. 1t=4.1 The pump speed is 4.1 seconds after the pump stops in the first loop. The Second Ring Road is: Q 2t=4.1 n represents the flow rate of the second ring road 4.1 seconds after the pump stops. 2t=4.1 The pump speed is 4.1 seconds after the pump stops on the second ring road. The Third Ring Road is: Q 3t=4.1 n represents the flow rate of the third ring road at 4.1 seconds after the pump stops. 3t=4.1 The pump speed is 4.1 seconds after the three-loop pump is shut down. The reactor coolant pump inertial flow test requires that the core flow rate must not be lower than the flow rate Q 4.1 seconds after the pump is shut down. 准则t=4.1 Then the following comparison can be made: Q 1t=4.1 +Q 2t=4.1 +Q 3t=4.1 >Q 准则t=4.1 If the above formula is satisfied, the total core flow rate is considered to have initially met the requirements. Step 7: Compare the speed drop of each loop pump with the design curve; the evaluation requirements for the speed drop curve in the reactor primary coolant pump inert flow test are as follows: Speed ​​ratio: And so on: In the formula Ω 1t n represents the pump speed ratio at time t in the loop. 1t The pump speed at time t after the pump in the loop stops; If: Oh 1t=0.0 ≥Ω 曲线t=0.0 Oh 1t=0.5 ≥Ω 曲线t=0.5 Oh 1t=1.0 ≥Ω 曲线t=1.0 And so on Ω 1t=5.0 ≥Ω 曲线t=5.0 In the formula Ω 曲线t Let t represent the pump speed ratio at time t in each loop; then it is assumed that the pump speed decrease in one loop satisfies the curve. If any of the above formulas is not true, then it is assumed that the pump speed decrease does not satisfy the curve. Step 8: Final judgment of test results. Based on steps 5 to 7, if all requirements are met, the test is considered preliminarily qualified, and subsequent unit power increase operations are carried out. After the unit reaches full power again, the reactor coolant flow test calculated based on heat balance is repeated, and the measured flow rates Q of the three loops of the reactor coolant system are used. 1n Q 2n Q 3n Replace Q1, Q2, and Q3 in steps five and six respectively. If the comparisons in steps five and six are still satisfied, the test is considered to have met the final requirements and is considered qualified. If any loop flow or total flow in step five or six is ​​not met, the test is considered unqualified. If the flow in step five or six is ​​met, but any set or multiple sets of data in step seven are not met, the test is initially considered qualified. Once the unit reaches full power again, the reactor coolant flow test calculated based on heat balance is repeated, and the measured flow rates Q in the three loops of the reactor coolant system are used. 1n Q 2n Q 3n Replace Q1, Q2, and Q3 in steps five and six respectively. If the comparison in steps five and six is ​​still satisfied, the test flow rate is considered to meet the requirements and the test is qualified.

2. The method for determining the inertia flow rate of a nuclear reactor coolant pump according to claim 1, characterized in that: Step 3: Collect a set of data every 0.1 seconds.

3. The method for determining the inertia flow rate of a nuclear reactor coolant pump according to claim 1, characterized in that: The Second Ring Road and the Third Ring Road were calculated and compared using the same method as the First Ring Road.

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