Oxidative Alteration of Spent Fuel in a Silica-Rich Environment: SEM/AEM Investigation and Geochemical Modeling.

Wang, Y. ; Xu, H.

Technical Information Center Oak Ridge Tennessee

关键词: Oxidative alteration;    Spent fuels;    Investigations;    Uraninite;    Geochemical modeling;   

RP-ID  :  DE2002752105

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

Correctly identifying the possible alteration products and accurately predicting their occurrence in a repository-relevant environment are the key for source-term calculations 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 SEIWAEM investigation has been conducted on a partially alterated 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 fiel 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 volubility-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.