Nondestructive characterization of reactor pressure vessel steels: A feasibility study. Technical note (Final)

Radiation damage to the walls of reactor pressure vessels (RPVs) causes the steel to become more brittle and less able to withstand the thermal stresses of start-up and shut-down procedures. Current methods of monitoring the degree of embrittlement are based on measurements of the ductile-to-brittle transition temperature (DBTT) of surveillance specimens subjected to severe radiation damage inside the reactor itself. In order to improve on this conservative approach and extend the useful life of vessels that have been in service for many years, NIST undertook a feasibility study to investigate nondestructive techniques for inferring the DBTT of the pressure vessel wall itself. The approach used was based on the hypothesis that the changes in microstructure that accompany embrittlement could be detected by accurate measurements of the physical properties of the steel in the pressure vessel wall.