VOLATILE FISSION-PRODUCT BUBBLE BEHAVIOR IN URANIUM-DIOXIDE

The role of volatile fission products in the formation and migration of gas bubbles in the nuclear fuel UO2 has been investigated. The theoretical model used previously to study the behaviour of inert fission gas bubbles in oxide fuel has been applied in the interpretation of annealing experiments of uranium dioxide implanted with other volatile fission products (Cs, Rb, I, and Te). The coalescence of the randomly migrating equilibrium bubbles was considered as a main mechanism defining the development of fission product porosity and swelling. The model predictions are compared with measured bubble size distributions and differences in the behaviour of different fission products are highlighted. The calculational results are applied to discuss important aspects of the formation and the behaviour of fission product filled bubbles in oxide nuclear fuel.