Finite element analysis of local overheating within plutonium enriched U02 fuel rods caused by Pu02 islands

Abstract

Within natural UO2 fuel elements enriched with plutonium, this last material should form Pu02 solid solutions inside the UO2 pellets, in a wide range of concentrations. If the solutions are obtained by mechanical mixing o f the oxides, Pu02 islands are formed in the U02 matrix. These islands may be the source o f several problems in the fuel behavior, the most important being the overheating o f the matrix in the neighbourhood o f the particles. It is caused by the large fission cross section of plutonium compared with that of uranium.