Crack safety analysis of coating with plastic behavior in surface-coated Zircaloy cladding

Abstract

In this paper, consider the coupling of pressure, thermal flux and irradiation, the mechanical response of surface-coated Zircaloy cladding with different coating materials (Cr and Fe-Cr-Al), thickness and initial crack length has been investigated. The crack length and coating thickness determine whether the crack will propagate and whether the plastic zone will reach the interface of coating and cladding. The plastic zone size and energy release rate of different coating thickness are calculated in ABAQUS. Two failure modes of coating are determined, which are 1) the plastic zone reaches the interface of cladding and coating, 2) a crack channel connecting coolant and cladding formed in coating. According to the results, the second failure mode plays a decisive role in crack safety. Different crack lengths can be divided into three zones: safety zone, discussion zone and danger zone. Safe crack lengths under different conditions are calculated. Results show that the crack tolerance of Fe-Cr-Al is better than Cr and a relatively reasonable value should not exceed 40 μm. Meanwhile, the plastic behavior cannot be ignored in calculation. Conclusions in this paper have a positive impact on the actual engineering evaluation of structural safety. They can also provide reference for future experiments.