A report on the status of hydrothermal testing of fully radioactive waste forms and basalt repository waste package components

Initial experiments to investigate the hydrothermal behavior to basalt repository constitutents including fully radioactive waste forms have been terminated. Solutions from these three experiments have been analyzed to gather data on the concentrations of radionuclides carried in solution as a function of time through the duration of each run. Two runs contained ATM-6 glass with groundwater; one of these with basalt, one without. Turkey Point spent fuel and groundwater comprised the third experiment. In the glass experiments, which allow comparison to demonstrate the effect of basalt, several trends were noted. Dissolved silica was lower with basalt than without; pH increased slightly in the presence of basalt; concentrations in the water of {sup 99}T{sub c}, {sup 75}{sub Se}, {sup 137}Cs were less with basalt than without, actinide concentration in water was lower than the calculated value. The latter two imply that these radionuclides were either adsorbed or precipitated in secondary phases. The experiment using spent fuel also demonstrates that radionuclide concentrations in solution are much less than calculated by the amount of the waste form dissolved. Again this implies that radionuclides released from the waste form are removed from the water and immobilized.