The role of secondary mineral precipitates on radionuclide sequestration at the Hanford Site

摘要

The effects of secondary mineral precipitates on radionuclide sequestration at the Hanford Site were investigated by reacting quartz and Hanford sediment (Warden soil) with caustic solution of high ionic strength (2 M NaNO_3), high pH (～13), high temperature (～90°C), and dissolved Al (0.01 M Al(NO_3)_3). Continuous Si dissolution and concomitant secondary mineral precipitation were the principal reactions observed. Nitrate-cancrinite was the dominant secondary precipitate on mineral surfaces after 3-10 d reaction time. The presence of dissolved Al in the simulated tank fluid was found to depress the net Si dissolved concentration. Based on batch equilibrium sorption results, secondary precipitates (cancrinite) at the primary mineral surfaces enhanced the sorption capacity of typical Hanford sediment for radionuclides of major concern at the Hanford Site such as ~(129)I, ~(79)Se, ~(99)Tc, and ~(90)Sr.