Miniature CT Fracture Toughness Testing of Harvested Materials From an Aged PWR Pressurizer

Abstract Thermal ageing of low alloy steels for the higher temperature pressurized water reactor (PWR) components has been raised as an industry concern as the PWRs prepare to operate beyond 60 years. Thermal ageing embrittlement was identified as a potential degradation mechanism and therefore a review was conducted of available long-term aged material samples that could bring the highest value to the industry for the study of thermally aged low alloy steel. Following this review, the Indian Point Unit 2 pressurizer was identified as having the best available materials based on several criteria evaluated. Samples were harvested from the closed Indian Point Unit 2 pressurizer and tested for ductile-brittle transition region fracture toughness testing. This pressurizer operated at 343°C for approximately 35 effective full power years (307,000 hours). Samples harvested included material from the A302B shell plate, A216 WCC bottom head casting, joining weldment and heat affected zones (HAZ). Due to the limited amount of material, 4.2 mm thick compact fracture toughness (mini-CT) specimens were tested to determine T0 according to ASTM E1921. Testing process, observations, learned lessons and test results will be presented for this test program. The results will be compared to prior published evaluations (PVP2022-85520) of the pressurizer with assumed amounts of thermal aging embrittlement.