Calculations Simulating Spent-Fuel Leaching Experiments

Calculations of UO₂-fuel corrosion and gas production from radiolysis of water have been carried out. The calculations simulated conditions of spent-fuel leaching experiments carried out within a European Union project. In some of these experiments, carried out by Forschungszentrum Karlsruhe, a fuel pellet was exposed in deionized water for 200 days, and fuel alteration and gas production rates were measured. A radiolysis model, developed previously, was used to calculate the oxidation of UO₂ caused by water radiolysis products. The calculated fuel alteration rate was 2.2 × 10^-8 mol UO₂(g U)^-1day^-1, about three times higher than the experimental rate, 6.3 × 10^-9 mol UO₂(g U)^-1day^-1.

The fair agreement between calculated and experimental corrosion rates shows that the model may be used for prediction of corrosion behavior of spent fuel in the repository. The calculated gas generation rates were 2 × 10^-8 and 1 × 10^-8 mol(g U)^-1day^-1 for hydrogen and oxygen, respectively, about six times lower than the experimental values.