Solidification and leaching of boric acid and resin LWR wastes

Leach testing was conducted on two types of reactor wastes (resin beads from a BWR and boric acid concentrate from a PWR) solidified in cement. In these wastes, Cs-14,137 isotopes were the most mobile constituents followed by Sr-90. Co-60 was found to be the least mobile. Effective diffusivities of these radionuclides were approx. 10-9 cm2/s for Cs-isotopes, approx. 10-11 cm2/s for Sr-90, and approx. 10-13 cm2/s for Co-60. A comparison of the release of Cs-137 from these wastes and the results of a previous study in which simulated counterparts of these reactor wastes were solidified and leached under identical conditions show a general correspondence in their release behavior. Radionuclide release data generated at EG and G, Idaho, in which test specimens from the same batch of the PWR boric acid waste were solidified in-plant employing a commercial proprietary process, exhibited significantly higher releases of Cs-137, Sr-90, and Co-60 (approximately two to four orders of magnitude difference in effective diffusivity values) in comparison to those observed at BNL. Greater radionuclide releases in the EG and G data set were attributed to higher waste-to-cement ratio and variance in the solidification agent used. Leachability index (LI) values were calcualted for determining regulatory compliance of waste forms