Development of simplified beam model of a spent nuclear fuel rod

Abstract

The integrity of spent nuclear fuel during handling operations or transportation became an important issue as the storage period extends due to the failure of timely installation of final disposal site. This is an issue especially for the high burn up fuels with burnup higher than 45,000 GWd/MTU which is more fragile than the low burn-up fuel to many degradation mechanisms such as hydride reorientation and so on. A lot of efforts have been made to quantify and model the degradation of fuel cladding as a function of relevant parameters including time and to evaluate the integrity of fuel assemblies during transportation accidents [1]. In many references, it is deemed impractical to model the whole fuel assembly with solid finite elements and many of them use a simplified beam element to represent a single fuel rod. However, the procedure to find an appropriate set of properties of the beam element has not been investigate much. In this paper, a procedure to find the material properties of a beam element which considers the interfacial bonding between the fuel pellets and cladding. During the reactor operation, there occur complicated mechanical and chemical interaction between the pellets and cladding, and it is known that a chemical bond can form between them. The effect of such bonding is investigated in this paper with the aim of building an equivalent beam model of single, irradiated fuel rod