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After a few hundred years in a geologic repository, alpha-emissions will dominate the radiation field in and around spent nuclear fuel. In the event of a failure of the spent fuel container, the dissolution of the uranium matrix contact with groundwater could be enhanced by alpha-radiolysis, which could create oxidizing conditions at the fuel surface. The radioactivity of the irradiated fuel available nowadays is characterized by strong beta and gamma contributions, which are not representative of aged fuel in a repository. A possible way to single out the effects of alpha-radiolysis on the dissolution behaviour of irradiated fuel is to study unirradiated UO2 doped with a short-lived alpha-emitter. UO2 containing ~0.1 and ~10 wt. % of 238 PuO2 was fabricated and leached. Previous results of static leaching tests on monoliths at room temperature in dimineralized water under anoxic atmosphere showed that the amounts of U released were higher in the case of UO2 containing 238Pu than in the case of undoped UO2. The present work presents results of leaching experiments performed under similar conditions on the same materials crushed with two different particle size distributions to investigate the effects of different surface areas. Enhanced U dissolution from alpha-doped UO2 was observed also in the case of crushed materials, except for the initial release after 1 hour of leaching. No significant differences were observed as a function of alpha-activity between the two doped materials. The released amounts of U after 1000 hours were higher for the crushed materials than those previously measured in the leachates of monoliths after similar leaching times. However, the surface area effect was more pronounced in the case of undoped UO2, especially after the shortest leaching time, than for materials containing alpha-emitters.

Additional information

Authors: RONDINELLA V V, ITU Karlsruhe, Karlsruhe (DE);MATZKE H, ITU Karlsruhe, Karlsruhe (DE);COBOS J, CIEMAT Madrid (ES);WISS T, CIEMAT Madrid (ES)
Bibliographic Reference: Paper presented: 7th International Conference on the Chemistry and Migration Behaviour Actinides and Fission Products in the Geosphere, California (US), 26 September- 1st October (1999)
Availability: Available free of charge from the Public Relations and Publications Unit, Ispra (IT)
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