On the Modelling of Thermal Aging through Neutron Irradiation and Annealing

Abstract

A new method predicting long-term thermal embrittlement of steel caused by P segregation is verified. e method is based on the results of impact strength or fracture toughness tests using specimens after relatively short-term neutron irradiation followed by annealing. 2Cr-Ni-Mo-V steel used in reactor pressure vessels of WWER-1000 type is investigated in four conditions: initial condition, after thermal aging, after neutron irradiation, and postirradiation annealing. e results of impact strength and tensile tests and SEM investigation are presented. e brittle fracture features are considered for different material conditions. Calculative estimation on neutron irradiation effect on P diffusion in steels is carried out. Experimental data are reported which confirm an intense P diffusion acceleration under neutron irradiation.

Non-hardening embrittlement mechanism of pressure vessel steel Ni-Cr-Mo-V welds during thermal aging

“…Thermal aging embrittlement mechanism Figure 5 shows the AES spectrum of the grain boundary and the transgranular fracture surface of samples No. 15,No. 3,and No.…”

“…The RPV will operate under high temperature, high pressure, corrosion, and strong radiation condition for a long time, and thermal aging embrittlement and irradiation embrittlement may occur. [12][13][14][15] In order to monitor the mechanical performance of Ni-Cr-Mo-V steel for RPV during service, a surveillance component with samples in the pressure vessel is placed in advance to be taken out for inspection and relevant data. At the same time, monitoring experimental data provides basis for reactor operation safety and lifetime extension.…”