The evolution of hydrated lime-based cementitious waste forms during leach testing leading to enhanced technetium retention.

Autor: Bourchy A; Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA., Saslow SA; Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA., Williams BD; Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA., Avalos NM; Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA., Um W; Pohang University of Science and Technology, Pohang, South Korea., Canfield NL; Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA., Sweet L; Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA., Smith GL; Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA., Asmussen RM; Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA. Electronic address: matthew.asmussen@pnnl.gov.
Jazyk: angličtina
Zdroj: Journal of hazardous materials [J Hazard Mater] 2022 May 15; Vol. 430, pp. 128507. Date of Electronic Publication: 2022 Feb 17.
DOI: 10.1016/j.jhazmat.2022.128507
Abstrakt: The interaction between radionuclides and cementitious material phases is crucial in the prediction of the long-term disposal behavior of cementitious waste forms. This work focuses on the behavior of technetium-99 (Tc) within a hydrated-lime based waste form developed as a candidate to immobilize high-sulphate containing liquid wastes known to inhibit cement solidification when using a fly ash based formulation. In leach testing, the hydrated-lime based formulation demonstrated improvement in Tc retention over a fly ash containing formulation beginning after 14 d leaching. The mineralogical evolution of the hydrated-lime samples during leach testing showed a decrease in portlandite content and reduction capacity at the onset of the Tc retention improvement. Leach testing upwards of 400 days showed the improved Tc retention was sustained. Samples cured for different lengths of time (28 days vs 60 days) confirmed that the improved Tc retention and mineralogic change was caused by cement - leachant interactions and not the sample curing time. The Tc observed diffusivities in the hydrated-lime samples are amongst the lowest measured in a cement waste form tested for development at the US Department of Energy Hanford site, leading to a possible pathway to improved cement conditioning where contaminants can be retained for long disposal times.
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Databáze: MEDLINE
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