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 role in the transport of heat through the pores of UO2 fuel. This possibility was investigated computationally, and the contribution of radiative 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 using finite element analysis. Conduction through both the solid fuel matrix and pore gas, and radiative exchange within the pore were modeled. Several pore compositions were investigated. Porosity, pore size, shape and orientation, temperature, and temperature gradient were parametrically studied to determine their influence on the radiative transfer mechanism.