Influence of high fluence irradiation on reference temperature of VVER-440 RPV surveillance specimens

Master curve (MC) testing of thermally aged and irradiated VVER-440 RPV surveillance specimens treated for 27 years (~200,000 hours) in a surveillance channel of Metsamor-NPP was performed to investigate the influence of long term high fluence irradiation on RPV embrittlement. The reference temperature (To) values obtained from irradiated specimens are compared with the results from thermal aged specimens to characterize irradiation induced shifts in To values for both base and weld metal specimens. It was found that the high fluence irradiation up to a nominal fluence of 3.2x1025 n.m-2 at E>0.5 MeV resulted large embrittlement with To shift values greater than 300C for both base and weld metal specimens. The obtained shifts in To values were used to check the validity of existing embrittlement trend curves (ETCs) for this type of material at high fluence values, namely PNAE procedure in the Russian regulatory guide. It was found that the measured shift in reference temperature for the weld metal was well below the predicted value while, the shift in reference temperature for base metal was largely under-predicted indicating that the base metal ETC is not valid at these high fluence values.

KOLLURI M.;  BREGMAN H.H.S.P.;  FRITH F.J.;  MARTIN Oliver;  PETROSYAN V.;  PETROSYAN A.;  SEVIKYAN G.; 

2024-07-05

ELSEVIER

JRC134828

0022-3115 (online),   

https://www.sciencedirect.com/science/article/pii/S0022311524003581?via%3Dihub,    https://publications.jrc.ec.europa.eu/repository/handle/JRC134828,   

10.1016/j.jnucmat.2024.155256 (online),