Method for calculating primary loop leakage rate during VVER reactor power operation

Abstract

The invention belongs to the technical field of reactor primary loop leakage rate calculation, and particularly relates to a primary loop leakage rate calculation method during VVER reactor power operation. The water filling amount supplemented to the primary loop through the volume and boron control system is equal to the sum of recognizable leakage and unrecognizable leakage of the primary loop, namely Q = V recognizable + V unrecognizable; the water replenishing Q for the primary loop of the reactor is composed of two parts, the primary loop chemical dosing amount V1 and the volume and boron control system water replenishing amount V2 for the primary loop, namely Q = V1 + V2; the primary circuit recognizable leakage V recognizable comprises the following parts: V recognizable = V3 + V4 + V5: the variation V3 of the primary circuit passing through the final stage shaft seal leakage of the four main pumps; the leakage rate of the first loop to the pressure relief box is V4; the leakage rate V5 of a first loop passing through an automatic sampling system; and the leakage rate V unidentifiable of the final primary loop is calculated through the following formula: V unidentifiable = (V1 + V2)-(V3 + V4 + V5). And the leakage rate of the primary loop can be quickly and effectively calculated by using the existing instrument and equipment parameters on the unit.

Description

Technical Field

[0001] The invention belongs to the technical field of reactor primary loop leakage rate calculation, and in particular relates to a method for calculating the primary loop leakage rate during power operation of a VVER reactor. Background Art

[0002] VVER units have clear requirements for the primary coolant leakage limit when the reactor is in power operation, that is, if the leak location is known, the leakage is required to be no more than 2t / h, if the leak location is unknown, the leakage is required to be no more than 0.7t / h, and there must be no leakage at the pressure boundary. During power operation, the radiation monitoring system and the leakage monitoring system can confirm that there is no leakage at the pressure boundary. At the same time, it is necessary to calculate the primary coolant balance in the steady state every day to monitor the unrecognizable leakage of the primary circuit.

[0003] During the power operation period of Tianwan Units 3 and 4, the primary circuit leakage rate shall be calculated every day when the primary circuit temperature, pressure and stabilizer liquid level are stable. When the unrecognizable primary circuit leakage rate exceeds 0.1t / h, it needs to be calculated every 8 hours. When the unrecognizable primary circuit leakage rate is between 0.7t / h and 2.0t / h, personnel need to be quickly organized to check for leaks. When the unrecognizable primary circuit leakage rate exceeds 2.0t / h, it needs to be retreated according to the requirements of the technical specifications.

[0004] By regularly calculating the primary loop leakage rate and monitoring the changes in the primary loop leakage rate, small leaks in the primary loop can be discovered in advance to prevent the leakage from expanding and affecting the safe and stable operation of the unit. Therefore, through a scientific and effective primary loop leakage rate calculation method, the reactor primary loop leakage rate can be calculated more accurately. Summary of the invention

[0005] The object of the present invention is to provide a method for calculating the primary loop leakage rate during power operation of a VVER reactor, which can quickly and effectively calculate the primary loop leakage rate by using existing instruments and equipment parameters on the unit.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for calculating the primary loop leakage rate during power operation of a VVER reactor, wherein all leakages in the primary loop are calculated by balancing the primary loop coolant, i.e., the amount of water added to the primary loop by the volume and boron control system is equal to the sum of the identifiable leakage and the unidentifiable leakage in the primary loop, i.e., Q = V 可识别 +V 不可识别 ; The water supply Q to the reactor primary circuit consists of two parts, one is the chemical dosage V1 of the primary circuit, and the other is the water supply V2 of the volume and boron control system to the primary circuit, that is, Q = V1 + V2; the primary circuit can identify the leakage V 可识别 It includes the following parts, namely V可识别 =V3+V4+V5: the change in leakage of the first circuit through the final shaft seal of the four main pumps V3; the leakage of the first circuit to the pressure relief box V4; the leakage of the first circuit through the automatic sampling system V5; the final leakage of the first circuit V 不可识别 It is calculated by the following formula: V 不可识别 =(V1+V2)-(V3+V4+V5).

[0008] V1=(L2-L1)*2.5 / (T2-T1), V1 represents the chemical dosage of the first circuit, unit is m 3 / h; L2 represents the liquid level of the primary ammonia supply tank at time T2, both in m; L1 represents the liquid level of the primary ammonia supply tank at time T1, both in m; T1 and T2 represent two time points selected for calculating the primary leakage rate, with an interval of at least 1h, both in h; 2.5 represents the volume of the primary ammonia supply tank corresponding to each 1m liquid level, both in m 3 / m.

[0009] V2=(L4-L3)*6.89 / (T2-T1), V2 represents the volume and the amount of water added to the primary circuit by the boron control system, unit: m 3 / h; L4 represents the volume and liquid level of the degasser in the boron control system at time T2, in m; L3 represents the volume and liquid level of the degasser in the boron control system at time T1, in m; T1 and T2 represent two time points selected for calculating the leakage rate of a circuit, with an interval of at least 1h, both in h; 6.89 represents the volume corresponding to each 1m liquid level of the degasser, in m 3 / m.

[0010] V3=F4+F3+F2+F1-F0, V3 represents the change in leakage of the final shaft seal of the four main pumps in one circuit, unit: m 3 / h; F4, F3, F2, F1 represent the final stage shaft seal leakage of the four main pumps at time T2, the unit is m 3 / h; F0 represents the flow rate of the four main pumps after the last adjustment of the final boron flushing, which is a known data, the unit is m 3 / h.

[0011] V4=(L6-L5)*14.5658 / (T2-T1), V4 represents the leakage of the primary circuit pressure relief box, unit is m 3 / h; L6 represents the liquid level of the pressure relief tank at time T2, in m; L5 represents the liquid level of the pressure relief tank at time T1, in m; T1 and T2 represent two time points selected for calculating the leakage rate of a circuit, with an interval of at least 1h, both in h; 14.5658 represents the volume of the pressure relief tank corresponding to each 1m liquid level, in m 3 / m.

[0012] V5=(F5+F6+F7+F8+F9) / 10 3 , V5 represents the leakage of a circuit through the automatic sampling system, unit: m 3 / h; F9, F8, F7, F6, and F5 represent the average sampling flow rate of a single-loop automatic sampling system between time T1 and T2.

[0013] The sampling flow rate at time T2 represents the average flow rate in l / h.

[0014] The beneficial effects achieved by the present invention are:

[0015] Wide application: This calculation method is a convenient, fast and accurate calculation method for the primary circuit leakage rate designed based on the experience of the unit operation since the operation of the Tianwan Phase II project, based on the primary circuit coolant balance when the pressurizer liquid level is stable and the primary circuit temperature is stable. At present, the domestic Tianwan Nuclear Power Plant Units 1-4 and Units 7 and 8, and Xudabao Nuclear Power Plant Units 3 and 4 all use the same VVER reactor design. This calculation method can be widely used by the nuclear power industry to improve the overall operation stability of China's nuclear power units.

[0016] Economic benefits: By regularly calculating the primary circuit leakage rate and monitoring the changes in the primary circuit leakage rate, small leaks in the primary circuit can be discovered in advance to prevent the leakage from expanding and causing a primary circuit rupture, which can lead to an unexpected shutdown of the unit and maintain safe and stable operation of the unit. If an unexpected shutdown occurs, it will take at least one day to restore the unit to full power operation, and one unit can avoid economic losses of 19.92 million yuan.

[0017] Practical and efficient: This calculation method fully uses the existing system and instrument parameters of the unit, and does not require the addition of new equipment or devices. Using this method to calculate the leakage rate of a circuit is more economical and efficient.

[0018] Safety improvement: By regularly calculating the leakage rate of the primary circuit, small leaks in the primary circuit can be discovered in advance and eliminated in time. This measure will improve the operating stability and economy of the units of Tianwan Nuclear Power Plant and its peers, and effectively avoid unplanned shutdowns.

[0019] The calculation results are accurate and fast: This calculation method accurately divides the systems and media entering and leaving the reactor's primary circuit, so the leakage rate of the primary circuit can be accurately calculated, and the calculation results are more accurate than other methods. This calculation method can calculate the leakage rate of the primary circuit simply and quickly, and the formula can be solidified into Excel. You only need to enter the relevant data to calculate the result. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1A schematic diagram of a method for calculating the primary loop leakage rate during power operation of a VVER reactor;

[0021] V1 represents the chemical dosage of the primary circuit;

[0022] V2 represents the amount of water added to the primary circuit by the volume and boron control system;

[0023] V3 represents the change in leakage of the final shaft seal of the four main pumps in one circuit;

[0024] V4 represents the leakage of the primary circuit pressure relief tank;

[0025] V5 represents the leakage of a circuit through the automatic sampling system;

[0026] V 不可识别 Represents the leakage amount of a circuit (a circuit cannot identify leakage). DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] By utilizing the existing system instruments and system equipment parameters of the VVER unit, all leakages in the first circuit, as well as identifiable leakages and unidentifiable leakages, can be calculated through the first-circuit coolant balance without adding additional equipment or devices. Then, by calculating the identifiable leakages in the first circuit, the unidentifiable leakage amount of the first circuit can be obtained, and finally the leakage rate of the first circuit can be calculated.

[0029] In order to ensure the simplicity and effectiveness of the calculation formula, the temperature, pressure and stabilizer liquid level of the primary circuit are required to be stable during the calculation period. At the same time, it is necessary to avoid manual sampling of the primary circuit, radioactive analysis sampling, main pump independent circuit exhaust and other calculation operations that may affect the identifiable leakage of the primary circuit. Finally, after a period of use, the reliability of the calculation formula was determined. This calculation method has been well verified in Tianwan Units 3 and 4 and achieved the expected effect.

[0030] The specific steps of the present invention are as follows:

[0031] 1. All leakages in a circuit can be calculated through the balance of the primary coolant, that is, the amount of water added to the primary circuit through the volume and boron control system is equal to the sum of the identifiable leakage and the unidentifiable leakage in the primary circuit, that is, Q = V 可识别 +V 不可识别 .

[0032] The water replenishment Q to the primary circuit of the reactor is composed of two parts, one is the chemical dosage V1 of the primary circuit, and the other is the water replenishment V2 of the volume and boron control system to the primary circuit, that is, Q=V1+V2.

[0033] One circuit can identify the leakage V 可识别It includes the following parts, namely V 可识别 =V3+V4+V5:

[0034] The change in leakage of the final shaft seal of the four main pumps in the primary circuit is V3;

[0035] Leakage volume V4 of the primary circuit pressure relief tank;

[0036] The leakage volume of a circuit through the automatic sampling system is V5.

[0037] The final leakage of the first circuit is V 不可识别 It can be calculated by the following formula:

[0038] V 不可识别 =(V1+V2)-(V3+V4+V5)

[0039] 2. The calculation method of each part is introduced one by one below

[0040] 1. V1 = (L2-L1)*2.5 / (T2-T1)

[0041] in:

[0042] V1 represents the amount of chemical dosing in one circuit (daily continuous addition of ammonia water), unit: m 3 / h;

[0043] L2 represents the liquid level of the primary ammonia supply tank at time T2, in m;

[0044] L1 represents the liquid level of the primary ammonia supply tank at time T1, in m;

[0045] T1 and T2 represent two time points selected for calculating the leakage rate of a circuit, generally with an interval of at least 1 hour, both in h;

[0046] 2.5 represents the volume of the primary ammonia supply tank per 1m of liquid level, in m 3 / m.

[0047] 2. V2 = (L4-L3)*6.89 / (T2-T1)

[0048] in:

[0049] V2 represents the volume and amount of water added to the primary circuit by the boron control system, in m 3 / h;

[0050] L4 represents the volume and liquid level of the degasser in the boron control system at time T2, in m;

[0051] L3 represents the volume and liquid level of the degasser in the boron control system at time T1, in m;

[0052] T1 and T2 represent two time points selected for calculating the leakage rate of a circuit, generally with an interval of at least 1 hour, both in h;

[0053] 6.89 represents the volume of the degasser corresponding to every 1m of liquid level, in m 3 / m.

[0054] 3. V3=F4+F3+F2+F1-F0

[0055] in:

[0056] V3 represents the change in leakage of the final shaft seal of the four main pumps in one circuit, in m 3 / h;

[0057] F4, F3, F2, F1 represent the final stage shaft seal leakage of the four main pumps at time T2, the unit is m 3 / h;

[0058] F0 represents the total flow rate of the four main pumps after the last adjustment of the final boron flushing, which is a known data in m 3 / h.

[0059] 4. V4=(L6-L5)*14.5658 / (T2-T1)

[0060] in:

[0061] V4 represents the leakage of the primary circuit pressure relief box, unit: m 3 / h;

[0062] L6 represents the liquid level of the pressure relief tank at time T2, in m;

[0063] L5 represents the liquid level of the pressure relief tank at time T1, in m;

[0064] T1 and T2 represent two time points selected for calculating the leakage rate of a circuit, generally with an interval of at least 1 hour, both in h;

[0065] 14.5658 represents the volume of the pressure relief tank corresponding to each 1m liquid level, in m 3 / m.

[0066] 5. V5 = (F5 + F6 + F7 + F8 + F9) / 10 3

[0067] in:

[0068] V5 represents the leakage of a circuit through the automatic sampling system, unit: m 3 / h;

[0069] F9, F8, F7, F6, and F5 represent the average sampling flow rate of a single-loop automatic sampling system between T1 and T2. The sampling flow rate generally does not change, and the sampling flow rate at T2 can be taken to represent the average flow rate in l / h.

Claims

1. A method for calculating the primary loop leakage rate during power operation of a VVER reactor, characterized in that: All leakages in a circuit are calculated through the balance of the coolant in a circuit, that is, the amount of water added to the circuit through the volume and boron control system is equal to the sum of the identifiable leakage and the unidentifiable leakage in the circuit, that is, Q = V 可识别 +V 不可识别 ; The water supply Q to the reactor primary circuit consists of two parts, one is the chemical dosage V1 of the primary circuit, and the other is the water supply V2 of the volume and boron control system to the primary circuit, that is, Q = V1 + V2; the primary circuit can identify the leakage V 可识别 It includes the following parts, namely V 可识别 =V3+V4+V5: the change in leakage of the first circuit through the final shaft seal of the four main pumps V3; the leakage of the first circuit to the pressure relief box V4; the leakage of the first circuit through the automatic sampling system V5; the final leakage of the first circuit V 不可识别 It is calculated by the following formula: V 不可识别 =(V1+V2)-(V3+V4+V5).

2. The method for calculating the primary loop leakage rate during power operation of a VVER reactor according to claim 1, characterized in that: V1=(L2-L1)*2.5 / (T2-T1), V1 represents the chemical dosage of the first circuit, unit is m 3 / h; L2 represents the liquid level of the primary ammonia supply tank at time T2, both in m; L1 represents the liquid level of the primary ammonia supply tank at time T1, both in m; T1 and T2 represent two time points selected for calculating the leakage rate of a circuit, with an interval of at least 1 hour, both in h; 2.5 represents the volume of the primary ammonia supply tank per 1m of liquid level, in m 3 / m.

3. The method for calculating the primary loop leakage rate during power operation of a VVER reactor according to claim 1, characterized in that: V2=(L4-L3)*6.89 / (T2-T1), V2 represents the volume and the amount of water added to the primary circuit by the boron control system, unit: m 3 / h; L4 represents the liquid level of the degasser in the volume and boron control system at time T2, in m; L3 represents the liquid level of the degasser in the volume and boron control system at time T1, in m; T1 and T2 represent two time points selected for calculating the leakage rate of a circuit, with an interval of at least 1 hour, both in h; 6.89 represents the volume of the degasser corresponding to every 1m of liquid level, in m 3 / m.

4. The method for calculating the primary loop leakage rate during power operation of a VVER reactor according to claim 1, characterized in that: V3=F4+F3+F2+F1-F0, V3 represents the change in leakage of the final shaft seal of the four main pumps in one circuit, unit: m 3 / h; F4, F3, F2, F1 represent the final stage shaft seal leakage of the four main pumps at time T2, the unit is m 3 / h; F0 represents the flow rate of the four main pumps after the last adjustment of the final boron flushing, which is a known data, the unit is m 3 / h.

5. The method for calculating the primary loop leakage rate during power operation of a VVER reactor according to claim 1, characterized in that: V4=(L6-L5)*14.5658 / (T2-T1), V4 represents the leakage of the primary circuit pressure relief box, unit is m 3 / h; L6 represents the liquid level of the pressure relief tank at time T2, in m; L5 represents the liquid level of the pressure relief tank at time T1, in m; T1 and T2 represent two time points selected for calculating the leakage rate of a circuit, with an interval of at least 1 hour, both in h; 14.5658 represents the volume of the pressure relief tank corresponding to each 1m liquid level, in m 3 / m.

6. The method for calculating the primary loop leakage rate during power operation of a VVER reactor according to claim 1, characterized in that: V5=(F5+F6+F7+F8+F9) / 10 3 , V5 represents the leakage of a circuit through the automatic sampling system, unit: m 3 / h; F9, F8, F7, F6, and F5 represent the average sampling flow rate of a single-loop automatic sampling system between time T1 and T2.

7. The method for calculating the primary loop leakage rate during power operation of a VVER reactor according to claim 6, characterized in that: The sampling flow rate at time T2 represents the average flow rate in l / h.

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