Abstract

In this work, we implemented a chemical rate theory model for the growth of nano-sized point defect clusters (PDCs) and copper- rich precipitates (CRPs) which can change the mechanical properties in the reactor pressure vessel material of a nuclear power plant. For the calculation of irradiation defect evolution, a number of time-dependent differential equations were established and numerically integrated. The concentration of mono-size vacancies and interstitials was saturated at an early stage of irradiation, and it was found that the vacancy concentration was higher than the interstitial concentration. The high concentration of vacancies induced a growth of the CRPs at the later stage. The concentration of PDCs and the size of CRPs were used to estimate the mechanical changes, and the calculation results were compared with the measured changes in yield strength and Charpy V-notch transition temperature shift obtained from the surveillance test data of Korean light water reactors (LWRs). It was observed that the estimated values were in fair agreement with the experimental results in spite of the uncertainty regarding the material property parameters and modeling method.

Keywords: Copper-rich precipitate, irradiation embrittlement, irradiation hardening, low alloy steel, point defect cluster, rate theory, reactor pressure vessel.