Transition of Spent Nuclear Fuel to Dry Storage: Modeling activities concerning aluminum spent nuclear fuel cladding integrity
In 2017, a report was prepared by the Spent Nuclear Fuel Working Group in 2017 and titled “Technical Considerations and Challenges for Extended (>50 Years) Dry Storage” [1-2]. In this report several key scientific issues were identified pertaining to the problem of aluminum spent nuclear fuel (ASNF) and its safe removal from wet storage with subsequent drying and transfer to dry storage at the Department of Energy (DOE) Idaho National Laboratory (INL). This report outlines two modeling analyses performed for aluminum and aluminum oxides. The first analysis examined the solubility of aluminum oxides as a function of temperature and pH. This report presents existing literature produced as far back as the 1950’s and including significant analysis and reporting performed at Alcoa in the 1980’s. The primary technical gap was the lack of solubility data beyond that reported at standard temperature (25°C). The analysis examined these solubility curves as a function of temperature as well as phase type. The pH value of minimum solubility shifted with temperature but was insensitive to the oxide phase type. The solubility increases with temperature as would be expected, where an order of magnitude increase was observed from 25°C and 90°C. This data provides greater information to understand the various conditions experiences by ASNF including in dry storage in cases where water filming may occur. A second thermodynamic analysis was performed to examine the aluminum phase behavior as a function of temperature. This was performed to understand limitations and possible problems with fuel drying at elevated temperatures. Based on what has been established in previous reports, water remains chemically entrained within boehmite until temperatures exceeding 400°C. Analysis showed that significant phase changes occurred with highly alloyed AA6061 and AA5052 while the more pure aluminum (AA1100) showed nearly ideal behavior (i.e. limited phase changes). In the case of the more alloyed AA5052 and AA6061, the phase changes could take place at relatively low temperatures (100°C to 250°C), and thus may have already experienced some of these phase changes in service. As results are thermodynamic in nature, assessment of kinetics will be examined to determine if the phase changes are a concern for the relatively short fuel drying step.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE Office of Environment, Health, Safety and Security (AU)
- DOE Contract Number:
- AC07-05ID14517
- OSTI ID:
- 1492831
- Report Number(s):
- INL/EXT-18-51694-Rev000
- Country of Publication:
- United States
- Language:
- English
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