Thermohydraulic Aspects of Deep Burnup of Nuclear Fuel in Fast Reactors

The results of thermomechanical and thermohydraulic studies showing the relative effect of the deformation of fuel-element claddings and lattices in fast-reactor fuel assemblies on their temperature regimes are presented. It is shown that the temperature nonuniformities in fuel assemblies largely determine the deformation of fuel assemblies and, in turn, the operating efficiency and, correspondingly, the degree of burnup of nuclear fuel in fast reactors. The increase in the efficiency of the fuel assemblies is largely due to temperature smoothing, including smoothing of local temperature nonuniformities. Various solutions to technical and structural problems can accomplish this.