Progress in evaluation of radionuclide geochemical information developed by DOE high-level nuclear waste repository site projects. Report for April-June 1985. Volume 3

Geochemical information relevant to the potential mobility of radionuclides at the Hanford Site and the Yucca Mountain site, candidate sites for high-level nuclear waste geologic repositories being developed by Department of Energy projects, is being evaluated by Oak Ridge National Laboratory (ORNL) for the US Nuclear Regulatory Commission. Neptunium(V) sorption isotherms in three different basalt/synthetic groundwater systems were initiated this quarter. Uranium(VI) sorption isotherms were completed with McCoy Canyon basalt and synthetic groundwater GR-2. The control of U(VI) solutions at a level of {similar_to}10{sup -4} mol/L is apparently dominated by the precipitation of sodium boltwoodite. Different apparent concentration limits for uranium were obtained with GR-2 and GR-4 solutions. The results suggest that uranium sorption/solubility behavior could be substantially different in the various basalt units likely to be encountered by groundwater during migration from the waste package to the accessible environment. The EQ3/6 software package was implemented and tested on the ORNL computer system. 13 refs., 2 figs., 1 tab