Assessment of thermal aging embrittlement in a cast stainless steel valve and its effect on the structural integrity

This paper analyzes the thermal aging embrittlement occurred in a cast stainless steel valve, which is part of the reactor water clean-up (RWCU) system of a Spanish boiling water reactor (BWR) nuclear power plant. The aim is to estimate the current and future state of the material and the corresponding structural integrity of the valve. Given that there is no data available for the experimental characterization of the material, the evolution of the mechanical properties (fracture toughness, yield stress, flow stress and Ramberg–Osgood parameters) has been estimated using the ANL procedure.

With the obtained estimations, the critical crack size has been calculated using the European procedure FITNET FFS and the ASME Code.

This analysis considers not only the evolution of the mechanical properties up to now but also its future evolution in case there is a life extension of the plant until year 2029.