Leaching of Cesium and Uranium from Spent PWR fuel in the Gel-state Clays

The amounts of cesium and uranium released from crushed spent PWR fuel in the gel-state clays with a few ml of supernatant at hot cell temperature under Ar-atmosphere have been measured. The fractions of cesium dissolved from the fuel for 873 days were 0.29 and 0.25% in Boom clay/Boom-clay water and Ca-bentonite/synthetic granitic groundwater, respectively. These cesium fractions were very close to the gap inventory of cesium, which was determined to be around 0.30% in the previous experiment. The fraction of uranium released up to 193 days in the Boom clay media was 0.011% and this fraction has been retained until 873 days. Such this phenomenon was also obtained in the Ca-bentonite media even though the released fraction was higher than that in Boom clay. The increase of less than 0.001% in the dissolved uranium fraction between 193 and 873 days suggests that the long-term leach rate of uranium from spent fuel would be much less than 24 μg·m −2 ·day −1 .