Experimental study of the interactions of nuclear waste with potential waste package components from Hanford site, WA

The Basalt Waste Isolation Project has begun a program to investigate the interactions of actual spent fuel with groundwater, both alone and in the presence of site-specific waste package components, in evaluating the Columbia River basalt of the Pasco Basin, Washington, as a possible high-level nuclear waste repository site. The experiments are run in Dickson autoclaves for up to six months; fluid is extracted at intervals during each run to analyze concentrations of species in solution. This allows the authors to monitor the dissolution of the components and their interactions, which commonly result in the formation of secondary minerals. It is anticipated that these secondary minerals will incorporate radionuclides, thus restricting their mobility and limiting their release from the waste package. Some radionuclides show markedly lower concentrations in basalt-bearing runs. For example, Cs consistently attains a concentration of 8.9x10/sup -2/ mg/1 with basalt while remaining steady at 5.7x10/sup -1/ in spent fuel-only runs. Sr concentrations reach 7.8x10/sup -4/ mg/1 without basalt, remaining an order of magnitude lower with basalt present. Actinides also show lower concentrations with basalt. U concentrations drops to 0.002 mg/1 after 2000 hours with basalt present. Pu reaches a maximum of 1.9x10/sup -5/ with basalt, 5.8x10/sup -5/more » without basalt. These concentrations all lie well below the limits required to meet federal release criteria.« less