Ion irradiation and finite element analysis to assess the effect of swelling on Cr-coated cladding

Abstract

By combining ion irradiation and finite element analysis, the effect of irradiation-induced swelling on the structural integrity of nuclear reactor components can be assessed. In this study, ion irradiation is used to obtain the void swelling as a function of damage level in pure chromium (Cr). Cr swells easily and exhibits almost no incubation period for swelling. The experimentally obtained swelling curve is then used as input for finite element analysis to evaluate the interfacial stress buildup in Cr-coated zircaloy tubes at reactor operation temperatures. As one accident-tolerant fuel design currently under evaluation by the nuclear industry, Cr coating can improve the oxidation resistance of zircaloy fuel cladding under abnormal conditions. However, the likelihood of debonding of the Cr coating from Zircaloy tubes needs to be evaluated. The stress evolution, after considering the contributions from thermal expansion, differential void swelling, and creep relaxation, is modeled as a function of time. The study shows that the highest probability of debonding occurs when the fuel cladding cools down when the reactor is shut down for refueling. The methodology presented in this study can be applied to other coating systems to evaluate their tolerance to radiation and accident scenarios.