Lysimeter study of commercial reactor waste forms: waste form acquisition characterization and full-scale leaching

This report describes work conducted at Brookhaven National Laboratory (BNL) as part of a joint program with Savannah River Laboratory. Typical full-scale (55-gallon drum size) waste forms were acquired by BNL from a boiling water reactor (BWR) and a pressurized water reactor (PWR). Liquid waste stream activity concentrations were analyzed by gamma spectroscopy. This information was used to determine the waste from activity inventory, providing the necessary source term for lysimeter and leaching experiments. Predominant radionuclides of interest include 60Co, 137Cs, 134Cs, and 54Mn. A full-scale leaching experiment was initiated by BNL encompassing four representative waste stream-solidification agent combinations. Waste streams tested include PWR evaporator concentrate (boric acid waste), BWR evaporator concentrate (sodium sulfate waste) and BWR evaporator concentrate plus ion exchange resins. Solidification agents include masonry cement, portland type III cement, and vinyl ester-styrene (Dow polymer). Analyses of leachates indicate measurable leach rates of 137Cs, 134Cs, and 60Co from both BWR and PWR cement waste forms. The leach rates for both cesium isotopes in cement are at least two orders of magnitude greater than those for cobalt. Leachates from the BWR Dow polymer waste form include the same isotopes present in cement leachates, with the addition of 54Mn. Cesium leach rates from the Dow polymer waste form are approximately one order of magnitude lower than from an equivalent cement waste form. The 60Co cumulative fraction release, however, is approximately three times greater for the Dow polymer waste form