Mekanismer och kinetik för upplösning av utbränt kärnbränsle
Forskare:
For UO₂ based nuclear fuel, the innermost barrier protecting the fission products and heavier actinides from escaping the deep repository is the fuel matrix itself. After use in the nuclear reactor, the spent nuclear fuel still contains more than 95 % UO₂. UO₂ has very low solubility under the reducing conditions prevailing in a potential deep repository in granitic bedrock (e.g., in Sweden) and could thus be considered to be an efficient barrier. However, the inherent radioactivity of the spent nuclear fuel will induce radiolysis of groundwater in contact with the fuel. Radiolysis of water produces equal amounts of oxidants and reductants. For kinetic reasons, the oxidants will have the largest impact on the local environment. The net effect will be oxidation of U(IV) to the significantly more soluble U(VI). Hence, radiolysis will induce oxidative dissolution of the fuel matrix.
In this project we study the mechanism and kinetics of elementary processes of importance in spent nuclear fuel dissolution. Parallel with the experimental studies, a predictive model describing the dynamics of spent nuclear fuel dissolution is developed.
Funding: SKB and EURATOM
