Progress in evaluation of radionuclide geochemical information developed by DOE high-level nuclear waste repository site projects: report for January-March 1985. Volume 2

Geochemical information relevant to the retention of radionuclides by the Hanford Site (in basalt) and the Yucca Mountain site (in tuff), candidate high-level nuclear waste geologic repositories being developed by US Department of Energy (DOE) projects, is being evaluated by Oak Ridge National Laboratory (ORNL) for the US Nuclear Regulatory Commission (NRC). Our evaluation of the sorption of technetium by basalt/groundwater systems was essentially completed this quarter and the results summarized; we conclude that the experimental methodology and results reported by the DOE for the Hanford Site have not conclusively established that significant retardation of technetium migration may be provided by phases present in the basalts of the Hanford Site. We have shown that sodium boltwoodite is the saturating uranium solid phase in two basalt/groundwater systems. Because thermodynamic data are not available for sodium boltwoodite, calculated solubilities for uranium are erroneous in these systems. Results of radionuclide solubility/speciation calculations, published by the DOE for the Yucca Mountain site, were evaluated this quarter under our geochemical modeling task. We express concerns relative to the inherent limitations of such calculations. Samples of Yucca Mountain tuff and J-13 well water were received for use in our planned radionuclide sorption/solubility experiments. These Yucca Mountain materials will be used to evaluate radionuclide sorption and apparent concentration limit values published by the Nevada Nuclear Waste Storage Investigations (NNWSI) project. 40 refs., 5 figs., 16 tabs.