Methods for monitoring and evaluating radiation damage of reactor pressure vessel steel in nuclear power plants

Abstract

The invention discloses a method for monitoring and evaluating the irradiation damage of reactor pressure vessel steel in a nuclear power station. The method comprises the following steps: determining and recording the upper limit of the upper limit critical value of the nil-ductility temperature (RTNDT) and the lower limit of the lower limit critical value of the upper platform energy (USE) of a reactor pressure vessel; measuring to obtain a magnetic suspectibility x of a monitored part, subjected to irradiation damage, of the reactor pressure vessel at any point in time; computing the real-time nil ductility temperature RTNDT, real-time upper platform energy, real-time tensile strength Rm and real-time yield strength Rp0.2 of the reactor pressure vessel during the process of irradiation damage; performing analysis and evaluation on the irradiation damage degree of steel of the reactor pressure vessel according to the lowering speed of the magnetic suspectibility and the obtained RTNDT, USE, Rm and Rp0.2. According to the method, real-time and multiple nondestructive measurements can be performed, the data is accurate, the testing operation is good in safety, and further the irradiation damage degrees of multiple positions of the reactor pressure vessel can be monitored at the same time.

Description

technical field [0001] The invention belongs to the technical field of nuclear power, and more specifically, the invention relates to a method for monitoring and evaluating radiation damage of reactor pressure vessel steel in a nuclear power plant. Background technique [0002] The reactor pressure vessel is one of the most critical large-scale equipment in the nuclear island of a nuclear power plant. Its main function is to contain and support the steel pressure vessel of the core nuclear fuel assembly, control assembly, reactor internals and reactor coolant. It has served in strong irradiation, high temperature, and high pressure environments for a long time, and neutron irradiation damage is one of its main failure modes, which is specifically manifested in the increase in strength, decrease in toughness, and material hardening during the irradiation embrittlement of reactor pressure vessel steel. [0003] In order to ensure the safety of reactor pressure vessel operation...

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Problems solved by technology

[0008] (1) Due to the limitation of the internal space of the reactor pressure vessel, the number of loaded irradiation supervision tubes is very limited. Since the existing technology cannot realize the installation of radiation supervision tubes after a period of operation, it must be installed once before the first fuel loading operation. This method cannot fully meet the requirements for radiation supervision of reactor pressure vessels during the life extension of nuclear power plants in the future;

[0009] (2) At present, there are only two hot cell institutions in Sichuan and Beijing in China. After the radiation supervision tube is extracted from the reactor pressure vessel, it must be transported from the nuclear power plant to the designated hot cell institution over long distances across provinces. It has very high radioactivity, so the security requirements during transportation are very high, the transportation cost is very high, and the cycle is long;

[0010] (3) Since the mechanical performance test of the irradiation supervision sample is a destructive test, a large amount of radioactive waste will be generated after the test is completed, and the subsequent treatment of the three wastes will be large and costly;

[0011] (4) Since the radiation monitoring samples come from the rest of forgings in the core area, this method can only monitor the damage degree of the reactor pressure vessel core area as a whole, and does not have the ability to monitor other parts of the reactor pressure vessel. , especially the degree of radiation damage at a specific location;

[0012] (5) It does not have the ability to monitor the radiation damage of reactor pressure vessel steel, and can only obtain the radiation damage degree of reactor pressure vessel steel at certain specific time points (depending on the extraction time of the radiation supervision tube)

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