Investigation on reconstitution of reactor pressure vessel surveillance specimen

Since the reconstitution of surveillance specimens became an issue due to the shortage of surveillance test specimens for reactor pressure vessels (RPVs) for long-term operation of nuclear power plants, investigation research had been conducted for seven years until March 2006. As the standard Charpy and CT specimen reconstitution, minimum insert length was obtained from hardness distribution and twice of the sum of plastic zone width plus maximum of heat affected zone width and heat recovery zone width. Plastic zone width was correlated with absorbed energy (J) for Charpy impact test specimen (5.3 mm maximum) and J-integral (kJ/m²) for CT test specimen. Heat affected zone was checked by etching, and 1.2 mm for Charpy specimen of surface activated joining reconstitution and 1.6 mm for CT specimen of laser welding reconstitution. Heat recovery width was obtained by test measurement or thermal analysis of temperature history of inserts under the joining condition, and 1.9 mm for Charpy specimen of surface activated joining reconstitution and 2.5 mm for CT specimen of laser welding reconstitution. Standard surveillance specimen reconstitution could contribute to assessment of the integrity of aged RPVs. (T. Tanaka)