Method and system for monitoring water filling amount of primary loop in low operation mode

Abstract

The invention discloses a method and a system for monitoring the water loading capacity of a primary loop in a low operation mode, and the method comprises the steps: determining a reference source item and at least one dosage monitoring point of a nuclear power unit, and fitting a reference radiation dosage rate-water level relation formula of the dosage monitoring point through software; installing a dose rate monitoring instrument at the dose monitoring point, and calculating a dose rate correction factor k according to the formula k = Dfb / Dfr; monitoring the actual radiation dose rate of the dose monitoring point by using a dose rate monitoring instrument; correcting the actual radiation dose rate of the dose monitoring point into a reference radiation dose rate by using the dose rate correction factor k, substituting the reference radiation dose rate into a reference radiation dose rate-water level relation formula of the dose monitoring point, and calculating the water level of the pressure vessel; and the water level of the pressure container is displayed in the display device. Compared with the prior art, the device and the method have the advantages that continuous measurement of the water loading capacity of the primary loop in low operation modes such as maintenance cold shutdown or refueling cold shutdown can be realized, and an important basis is provided for monitoring the cooling state of a reactor core after an accident.

Description

technical field [0001] The invention belongs to the technical field of core cooling state monitoring after a nuclear power plant accident. More specifically, the invention relates to a method and system for monitoring the water content of a circuit in a low-operation mode of a pressurized water reactor nuclear power plant. Background technique [0002] The Three Mile Island nuclear accident made the industry realize the necessity of installing primary circuit water level monitoring instruments, especially pressure vessel water level monitoring instruments. The water level of the pressure vessel provides an important basis for monitoring the core cooling state after the accident, so as to ensure that the correct diagnosis of the core cooling state can be made in a timely, accurate and convenient manner, and then the appropriate accident operation strategy can be selected. According to the different types of instruments, different schemes have been formed. The most widely used...

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Problems solved by technology

[0003] However, whether the continuous monitoring of the water content of the pressure vessel is realized by measuring the differential pressure between the bottom and the top of the pressure vessel, or the water level is measured intermittently at a fixed height by using a thermocouple, in low operating modes (maintenance cold shutdown and refueling cold shutdown) ) can not be used when the top cover of the pressure vessel is removed: (1) For the water level measurement of the differential pressure pressure vessel, the upper pressure induction line is directly led from the exhaust line on the top cover of the pressure vessel, and is calculated based on the differential pressure Core outlet coolant temperature measurement required for pressure vessel water level Thermocouples are introduced into the core from pressure vessel roof instrumentation tubes that are removed during pressure vessel roof removal, differential pressure measurement and core outlet Coolant temperature measurement will be lost; (2) For the thermocouple intermittent measurement of water level at a fixed height, the thermocouple is introduced into the core from the instrument tube at the top of the pressure vessel and arranged at a fixed height. During the removal of the top of the pressure vessel , the gauge tubes will be removed and the thermocouple measurements will be lost

[0004] Therefore, during the period when the top cover of the pressure vessel is removed in the low operating mode, the monitoring of the water filling of the primary circuit can only rely on the loop water level gauge installed in the cold or hot section, but if figure 1 As shown, the pressure vessel carrying the core nuclear fuel is located at the bottom of the reactor pool, and the installed reactor pool loop water level gauge has a limited measurement range, and the lowest water level that can be measured is generally at the bottom of the cold and hot pipe sections; when the water level in the primary circuit continues to deteriorate (If the loss of waste heat discharge ability causes the coolant in the pressure vessel to continue boiling and evaporating, and at the same time, the recovery method of the water content of the primary circuit is not available), when the water level of the pressure vessel is lower than the bottom elevation of the heat pipe section, the monitoring of the water content of the primary circuit will be completely lost means

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