Open AccessPredictive calculations to assess the long-term effect of cementitious materials on the pH and solubility of uranium(VI) in a shallow land disposal environment
Author(s) -
Louise Criscenti,
R. Jeffrey Serne,
Kenneth M. Krupka,
M.I. Wood
Publication year - 1996
Language(s) - English
Resource type - Reports
DOI - 10.2172/374121
Subject(s) - uranium , radioactive waste , cement , cementitious , leaching (pedology) , dispose pattern , environmental chemistry , uranium ore , solubility , actinide , environmental science , chemistry , waste management , geology , mineralogy , nuclear chemistry , metallurgy , materials science , soil science , soil water , organic chemistry , engineering
One proposed method of low-level radioactive waste (LLW) disposal is to mix the radioactive waste streams with cement, place the mixture in steel barrels, and dispose of the barrels in near-surface unsaturated sediments. Cement or concrete is frequently used in burial grounds, because cement porewaters are buffered at high pH values and lanthanides and actinides; are very insoluble in highly alkaline environments. Therefore, leaching of these contaminants from the combined cement/low-level radioactive waste streams will at least initially be retarded. The calculations performed in this study demonstrate that the pH of cement porewaters will be maintained at a value greater than 10 for 10,000 years under Hanford specific hydrogeochemical conditions. Ten thousand years is the period generally studied in longterm performance assessments per regulatory guidance. The concentrations of dissolved hexavalent uranium [U(VI)], the valence form of dissolved U usually present in oxidizing surface and groundwaters, are also constrained by the high pH and predicted solution compositions over the 10,000-year period, which is favorable from a long-term performance perspective