An update of the status of the joint SKB/Studsvik fuel leaching programme is given. High burnup BWR fuel has been leached for up to 5.5 years cumulated contact time. Data for leaching of PWR fuel are also presented. The present results confirm earlier results from the programme, i.e., in groundwater and deionized water under oxidizing conditions uranium rapidly attains saturation at about 1 mg/l and 10 μg/l, respectively.
Under reducing conditions, the uranium saturation levels are below 1μg/l. The plutonium saturation level under oxidizing conditions is at about 0.3 μg/l. Under reducing conditions, the plutonium concentrations in solution appear to be controlled by the solubility of the fuel matrix.
Most of the detected fission products appear to be released through selective leaching of fuel/cladding gap, fuel cracks and fissures, and grain boundaries.