Studies on the correlation between irradiation hardening and thermal conductivity of RPV steel irradiated with protons

Reactor pressure vessel (RPV) is a critical safety component in nuclear power plants, and irradiation embrittlement induced by hardening is its primary safety challenge. Developing a new method for evaluating hardening is an important safety management strategy. This study investigated a correlation between irradiation hardening and thermal conductivity of ion irradiated RPV steel and provides possible solutions. Specimens of RPV steel were irradiated with 240 keV proton. Four irradiation regions with damage levels of 0, 0.3, 1.0, and 1.6 dpa were prepared in the same specimen. The nano-indenter and time-domain thermoreflectance (TDTR) instrument were used to analyze the hardness and thermal conductivity variations. The hardness data array was obtained with hundreds of measurements and showed a significant hardening phenomenon. The thermal conductivity of irradiation damage layer was extracted and a decreasing tendency with increasing irradiation damage was observed. An approximate linear correlation between hardness and thermal conductivity was established. This correlation suggests a potential application of thermal conductivity as a significant hardening indicator for the non-destructive characterization of RPV during service.