Release rates of radionuclides into dripping groundwater

Packages of high-level waste are to be emplaced in unsaturated tuff at the proposed Yucca Mountain repository. Each cylindrical waste package is separated from surrounding rock by a 2-cm air gap. A possible mechanism for release of radionuclides is the dripping of groundwater onto waste packages. Drips are assumed to penetrate cracks in a failed container and to dissolve radionuclides as the partly failed container fills and overflows. For this wet-drip scenario, with assumed constant drip rate, the authors have developed analytical solutions for the time-dependent release rates of radionuclides to the surrounding rock. Release rates have been calculated for key radionuclides. The calculated results are constructive to the extent that barriers from fuel cladding have not been considered. Also, repository-average release rates can be lower if the expected statistical distribution of container failures is included