Rates and Mechanisms of the Loss of Fission Products from Uranium-Graphite Fuel Materials

Experimental evidence indicates that diffusion through the porous matrix and evaporation from the geometric surface are the rate-limiting processes in the loss of some fission products from uranium-graphite fuel. The loss of other fission products is rate-limited by unidentified processes which do not include those macroscopic diffusion or evaporation processes, but which may include diffusion or evaporation on the microscopic or granular scale.