The Mechanical Behavior of Biso-Coated Fuel Particles During Irradiation. Part I: Analysis of Stresses and Strains Generated in the Coating of a Biso Fuel Particle During Irradiation

The stresses and strains generated in the outer pyrocarbon (PyC) coating of a two-layer Biso fuel particle coating during irradiation are analyzed to include very significant PyC property changes during irradiation. These property changes are not included in other analyses. The most significant change is in the anisotropy of the coating during irradiation and is related to irradiation-induced creep. A proposed method for calculating the effects of these anisotropy changes on irradiation-induced dimensional changes is supported by experimental data. Variations in Young’s modulus and the creep parameters of the coating during irradiation are also included in the analysis. Particle failure probability is calculated with an extension of Weibull’s analysis to the PyC coating.