Fission product diffusion in ZrC coated fuel particles

The diffusion behavior of 137Cs, 90Sr and 144Ce in CVD-ZrC was studied by measuring concentration profiles in ZrC and inner PyC layers of the coated particles, and the release from the particles during post-irradiation annealing. 90Sr diffusion in ZrC is found to be controlled by a volume diffusion mechanism at 16000C; this is found also for 137Cs although it is influenced by micro-pores. The diffusion coefficient of 137Cs obtained from the analysis of the concentration profiles in ZrCsub(1.3) is D = 2.3 x 10-3exp(-3.18 x 105/RT) (cm2/s), where D is the diffusion coefficient, R the gas constant (8.314 J/mol x K ) and T the temperature (K). In case of 144Ce, the volume diffusion is not so remarkable as 90Sr. (orig.)