Finite Element Analysis of Ring Compression Testing for Used Nuclear Fuel Cladding

Abstract

Abstract The performance of used nuclear fuel (UNF) (i.e., cladding integrity, fuel retrievability, transportability, and cladding embrittlement) is considered important to the safety of both extended long-term dry storage and subsequent transportation for final disposition. Analytical analysis for UNF structural performance under storage and transportation conditions requires mechanical property data for the cladding materials (e.g., stress-strain relationships and failure limits). However, currently available mechanical properties and correlations are not sufficient because they are primarily based on uniaxial tension tests and pressurized-tube tests of cladding materials with only circumferential hydrides and are not suitable for cladding materials with radial hydrides. Ring compression testing (RCT) has become a very useful method for measuring the relative ductility of cladding and determining the ductility transition temperature of cladding materials. The results of RCT can be used to assess the mechanical behavior of cladding materials and determine the effects of burnup, hydride orientation, and temperature to support the development of the technical basis for extended storage and transportation of high-burnup fuel. Finite element analysis (FEA) has been used to characterize the stress state associated with RCT and to facilitate a better understanding of the deformation and the failure mechanisms of the cladding ring during RCT. Three-dimensional finite element (3D FE) models have been constructed using the commercial FE computer code ABAQUS™; the FE models include RCT machine stiffness, elastic and anisotropic plastic stress-strain properties, and large strain capability, and these models are used to simulate cladding rings subjected to RCT hoop-bending loading. Useful information regarding the material properties and behavior can be extracted by FE simulation of cladding RCT. In this paper, applications of FEA to RCT are described, and the limitations are also discussed.