Thermodynamic stability of actinide pyrochlore minerals in deep geologic repository environments
Crystalline phases of pyrochlore (e.g., CaPuTi{sub 2}O{sub 7}, CaUTi{sub 2}O{sub 7}) have been proposed as a durable ceramic waste form for disposal of high level radioactive wastes including surplus weapons-usable plutonium. In this paper, the authors use a linear free energy relationship to predict the Gibbs free energies of formation of pyrochlore phases (CaMTi{sub 2}O{sub 7}). The Pu-pyrochlore phase is predicted to be stable with respect to PuO{sub 2}, CaTiO{sub 3}, and TiO{sub 2} at room temperatures. Pu-pyrochlore is expected to be stable in a geologic repository where silica and carbonate components are absent or limited. The authors suggest that a repository in a salt formation be an ideal environment for disposal of high level, pyrochlore-based ceramic wastes. In such environment, adding CaO as a backfill will make pyrochlore minerals thermodynamically stable and therefore effectively prevent actinide release from these mineral phases.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandia National Labs., Livermore, CA (US) (US)
- Sponsoring Organization:
- US Department of Energy (US) (US)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 752158
- Report Number(s):
- SAND2000-0505C; ISSN 0148-7191; TRN: US0200757
- Resource Relation:
- Conference: Material Research Society Annual Meeting, Boston, MA (US), 11/28/2000--12/02/2000; Other Information: Supercedes report DE00752158; PBD: 14 Mar 2000; PBD: 14 Mar 2000
- Country of Publication:
- United States
- Language:
- English
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