Recriticality calculations for uraniumdioxide-water systems with MCNP

With the aim of generating a certain feeling for the general dependencies of the multiplication factor k∞ the first section provides some results for two classes of deformations of the original fuel pins. The main part examines UO2-structures of increasing disorder, beginning with the hexagonal close package of fuel spheres and ending up with stochastic geometries. Among these structures the worst case, i.e. the one with the highest k∞ but preserving mechanical stability is identified. The composition and geometric parameter of this case is used to calculate the critical thickness of a slab and critical radius of a sphere. (orig.)