RADIATIVE HEAT-TRANSFER IN POROUS URANIUM-DIOXIDE

Due to the low thermal conductivity and high emissivity of UO2, it has been suggested that radiative heat transfer may play a nontrivial rol e in the transport of heat through the pores of UO2 fuel. This possibi lity was investigated computationally, and the contribution of radiati ve heat transfer through pores to the overall heat transport in porous UO2 was quantified. A two-dimensional unit cell model was employed to approximate a porous UO2 fuel system. The heat transfer through unit cells representing a wide variety of fuel conditions was calculated us ing finite element analysis. Conduction through both the solid fuel ma trix and pore gas, and radiative exchange within the pore were modeled . Several pore compositions were investigated. Porosity, pore size, sh ape and orientation, temperature, and temperature gradient were parame trically studied to determine their influence on the radiative transfe r mechanism.