Evaluation of the potential for spent fuel oxidation under tuff repository conditions
The status of the spent fuel oxidation data base has been reviewed. Although there are a number of shortcomings in the data base, the expected performance of breached fuel in a tuff repository has been analyzed. This analysis tried to determine whether, during a number of different repository time frames, the cladding would further degrade due to fuel oxidation, and which higher oxides of UO{sub 2} would be expected to form. Above 230{sup 0}C, oxides at least as high as U{sub 3}O{sub 8} form in a rather short time in a "dry" air atmosphere with resultant cladding splitting. The rate of oxidation is not firmly established, but it is high enough to cause problems in an early high temperature repository time frame. For this reason, storage in an air-filled canister is not recommended. In all likelihood, spent fuel can be sucessfully stored in an inert atmosphere, even if there is water in the canister from rods initially containing water. There is some uncertainty though, whether radiolysis of the H{sub 2}O might cause fuel oxidation. When long times and lower temperatures are considered, there is evidence that even at room temperature, UO{sub 2} will convert to UO{sub 3} . 2H{sub 2}O. Once the canister breaches and air is the storage atmosphere, oxidation of the UO{sub 2} to a higher state is expected to occur, even at the low tuff repository temperatures, given enough time. The rate of oxidation after canister breach is expected to be low enough during the first 10,000 yrs, that cladding splitting won`t occur, but the higher oxides, which might have a greater leach rate than UO{sub 2}, might form. Cladding credit can be maintained and leach rates evaluated only if the rates of oxidation and the composition of subsequently formed products are determined. Areas for additional work are indicated.
- Research Organization:
- Hanford Engineering Development Lab., Richland, WA (United States)
- DOE Contract Number:
- AC06-76FF02170
- OSTI ID:
- 59937
- Report Number(s):
- HEDL-7452; ON: DE86015889
- Resource Relation:
- Other Information: PBD: Mar 1985
- Country of Publication:
- United States
- Language:
- English
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