MODELS FOR REACTOR FUEL ELEMENTS WHICH CONSIDER VOID DEPLOYMENT

Models for the composite fuel element behavior that are based on end-of-life performance (FIGRO), steady-state behavior (DEFORM), and pseudo-transient behavior (CYGRO), have been developed. The driving potential for the fuel element deformations in these models is the fission-induced swelling behavior of the fuel material. Theoretical models for the swelling behavior of the fuel material have received extensive study. Computer programs based on the system models incorporate some of the proposed swelling models into their methods of evaluating fuel element performance. Models for interactions between the fabricated voids and the fission induced gas bubbles have not been incorporated into these programs. Quantitative evaluations of microscopic void distributions can be obtained from micrographic studies on fuel materials from prototypical fuel element irradiations. These quantitative evaluations would provide the information required to evaluate and to validify the models for internal void redistribution. © 1969.