Pellet-cladding mechanical interaction analysis of Cr-coated Zircaloy cladding

The thermal-mechanical response of Cr-coated Zr cladding during power ramp condition is of critical importance for a better understanding of its reliability and security in ATF designing. The pellet-cladding mechanical interaction (PCMI) performance of Cr-coated Zircaloy cladding was analyzed in this study using multistep modeling strategy to capture the base-irradiation conditions of full-length fuel and the local transient PCMI responses during power ramp conditions. The traditional 1.5D fuel performance code, COPERNIC, and the commercial finite element (FE) code, ABAQUS, were combined to effectively reduce the computational demands while ensuring accuracy of local PCMI prediction. ABAQUS has been enhanced to support thermal, mechanical and irradiation behavior modeling of the coated cladding by adding a set of models representing fuel, cladding and coating in-pile behaviors using user-subroutines. Then, the PCMI responses of three Cr-coated claddings were analyzed under both steady and power ramp conditions. Parametric studies were carried out to demonstrate the effects of several key factors, such as coating thickness, burn-up level and transient power increment, etc., on PCMI behavior of the Cr-coated cladding, which may provide fuel designers and engineers a deeper understanding in thermal-mechanical responses of the Cr-coated cladding.