Oxidative alteration of spent fuel in a silica-rich environment: SEM/AEM investigation and geochemical modeling
Correctly identifying the possible alteration products and accurately predicting their occurrence in a repository-relevant environment are the key for the source-term calculation in a repository performance assessment. Uraninite in uranium deposits has long been used as a natural analog to spent fuel in a repository because of their chemical and structural similarity. In this paper, a SEM/AEM investigation has been conducted on a partially alternated uraninite sample from a uranium ore deposit of Shinkolobwe of Congo. The mineral formation sequences were identified: uraninite {yields} uranyl hydrates {yields} uranyl silicates {yields} Ca-uranyl silicates or uraninite {yields} uranyl silicates {yields} Ca-uranyl silicates. Reaction-path calculations were conducted for the oxidative dissolution of spent fuel in a representative Yucca Mountain groundwater. The predicted sequence is in general consistent with the SEM observations. The calculations also show that uranium carbonate minerals are unlikely to become major solubility-controlling mineral phases in a Yucca Mountain environment. Some discrepancies between model predictions and field observations are observed. Those discrepancies may result from poorly constrained thermodynamic data for uranyl silicate minerals.
- 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:
- 752105
- Report Number(s):
- SAND2000-0504C; ISSN 0148-7191; TRN: US0200756
- Resource Relation:
- Conference: Materials Research Society Annual Meeting, Boston, MA (US), 11/28/2000--12/02/2000; Other Information: Supercedes report DE00752105; PBD: 14 Mar 2000; PBD: 14 Mar 2000
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
DISSOLUTION
HYDRATES
PERFORMANCE
SILICATES
SPENT FUELS
THERMODYNAMICS
URANINITES
URANIUM CARBONATES
URANIUM DEPOSITS
URANIUM ORES
URANYL SILICATES
YUCCA MOUNTAIN
GEOCHEMISTRY
RADIOACTIVE WASTE DISPOSAL