Development of deformation model for simulation of mechanical behaviors of coated-cladding

Abstract

A coated fuel cladding is one of the promising accident tolerant fuel (ATF) cladding concepts to enhance the fuel safety for accident conditions. In this study, a new analytical model called Fuel Rod and Cladding Analysis Subcode-Coated Cladding (FRACAS-CT), used to evaluate the mechanical behaviors of the ATF cladding, has been developed employing both thick-walled theory and some methodologies of the FRACAS. Based on the methodology of FRACAS, two different regimes of pellet-cladding mechanical interactions according to the gap status were considered as follows: one is an open-gap regime, and the other is a closed-gap regime. FRACAS-CT was developed within a limited scope of an elastic solution under the assumption of the prescribed creep, irradiation growth, and thermal deformation. To verify the FRACAS-CT model, an equivalent finite element (FE) model was proposed, and the mechanical behaviors of FRACAS-CT were compared with those of the equivalent FE model. As a result, it was determined that the stress results of FRACAS-CT are highly consistent with those of the equivalent FE model. Furthermore, FRACAS-CT was implemented into the FRAPCON4.0P1 code system to evaluate the mechanical behaviors of the ATF cladding using in-reactor conditions.