Temperatures and thermo-elastic stress in spherically symmetric fuel elements with varying material properties

Abstract

In the thermo-elastic stress analysis of a spherically symmetric fuel element as used in a pebble bed reactor the problems of a radial variation in material properties and the temperature dependence of these properties can be unified into a single analysis. Such an analysis is developed for incorporation in a computer programme and applied, as an example, to a fuel element for a beryllia moderated reactor. The results give the effect of different material properties between surface and centre, a buffer layer between surface coating and centre, an increase in temperature of a fuel element composed of materials with different properties, and temperature dependance of the fuel element materials.