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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 dioxide matrix in contact with groundwater could be enhanced by alpha-radiolysis, which could create oxidizing conditions at the fuel surface. The radioactivity (hence the radiolysis) 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. UO(2) containing ~ 0.1 and ~ 10 wt. % of (238)PuO(2) was fabricated and leached. Previous results of static (batch and sequential) leaching tests on monoliths at room temperature in demineralized water under anoxic atmosphere showed that the amounts of U released were higher in the case of UO(2) containing (238)Pu than in the case of undoped UO(2). This work presents results of leaching experiments performed under similar conditions on materials of the same composition, but crushed to give samples with two different particle size distributions to investigate the effects of different surface areas. The U release data, normalized to the geometric surface area, showed enhanced U dissolution from alpha-doped UO(2) also in the case of crushed materials, except for the initial release after 1 hour of leaching. Under these experimental conditions, the concentration of U measured in the leachate for the two doped materials did not show a clear dependence on alpha-activity. .

Additional information

Authors: RINDINELLA V.V, EC-JRC, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe (DE);MATZKE H, EC-JRC, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe (DE);WISS T, EC-JRC, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe (DE);COBOS J, CIEMAT, Av. Da Complutense 22, E-28040 Madrid (ES)
Bibliographic Reference: An oral report given at: 7th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere (Migration 99) Incline Village, California, 26 Sept - 1 Oct 1999 Also an article published i
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