Predictive calculations to assess the long-term effect of cementitious materials on the pH and solubility of uranium(VI) in a shallow land disposal environment
- Pacific Northwest Lab., Richland, WA (United States)
- Westinghouse Hanford Company, Richland, WA (United States)
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.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 374121
- Report Number(s):
- PNNL-11182; ON: DE96014977; TRN: 96:028347
- Resource Relation:
- Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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