Meta-Autunite Solubility as Related to Uranium Minerals in Concrete Waste Forms
- Pacific Northwest National Laboratory, Richland, WA, 99354 (United States)
- Colorado School of Mines, Golden, CO, 80401 (United States)
- Fluor Hanford Inc., Richland, WA, 99354 (United States)
Previous in situ examination of U(VI) spiked concrete indicated that uranyl-oxyhydroxide phases that were initially formed, later led to the formation of mixed uranyl-oxyhydroxide/ silicates, which subsequently transformed into uranyl-silicates, and finally altered into mixed uranyl-silicate/phosphate and uranyl-phosphate phases. We conducted solubility studies of the identified final uranyl-phosphate phase (calcium meta-autunite) in phosphate solutions ranging in concentration from 0.001 - 0.1 M as a function of pH. These studies indicated a secondary phosphate phase that formed during the solubility of meta-autunite regulated the uranium concentrations at relatively low levels under high pH conditions (>12) typically encountered in cement pore waters. The importance of uranyl-phosphate minerals in concrete waste forms has, to date, been neglected because of the minimal amount of phosphorus present in most concrete compositions. However, because concrete is a continuously reacting solid, the thermodynamic stability of uranyl minerals that form at the later stages of reaction may have a substantial impact on the long-term fate of uranium in the waste forms. This study suggests that any future investigations should consider the potential benefit of including phosphorus in concrete waste forms. (authors)
- Research Organization:
- Materials Research Society, 506 Keystone Drive, Warrendale, PA, 15086-7573 (United States)
- OSTI ID:
- 21091546
- Resource Relation:
- Conference: Symposium Actinides 2008 - Basic Science, Applications and Technology, San Francisco, CA (United States), 24-28 Mar 2008; Other Information: Country of input: France; 20 refs.; Full text available at: http://www.mrs.org/s{sub m}rs/bin.asp?CID=12409&DID=212490&DOC=FILE.PDF; Related Information: In: Proceedings of the symposium Actinides 2008 - Basic Science, Applications and Technology, by Chung, B.; Thompson, J.; Shuh, D.; Albrecht-Schmitt, T.; Gouder, T. (eds.), v. 1104, [260] pages.
- Country of Publication:
- United States
- Language:
- English
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