Perspective on fission gas release from spent fuel rods during geologic disposal

Release of pressurization gas, fission product gases and fission product volatiles contained within light water reactor (LWR) spent fuel rods is of concern relative to pressurization of fuel rod cladding, waste package components and the repository geology. Pressurization effects on each of these spent fuel repository barriers were analyzed considering three different spent fuel waste forms and three hypothetical gas release scenarios. No adverse pressurization effects were evident for the cases analyzed, which considered packages containing single pressurized water reactor (PWR) spent fuel assemblies. The method of analysis is generally applicable to other canister and spent fuel configurations. As part of the analysis, calculations of fission product and gas inventories as a function of burnup and storage time were made using the ORIGEN2 code.