Radiochemical Analysis of CANDU Used Fuel Stored in Concrete Canisters in Moist Air at 150 degrees C

Abstract

The analysis of storage water used to provide a moist environment in two stainless-steel pressure vessels containing defected used CANDU fuel bundles showed that the major fission product released was 137Cs after an interim storage period of up to 3.3 years. In the pressure vessel containing two in-reactor defected fuel elements, -50% more fission products were released compared to the first interim examination, The higher release was attributed to the presence of in-reactor defected fuel. The results from the second pressure vessel showed lower releases, and represented less than half the radioisotope activities found in the first interim examination. All the fission products showed releases of less than 0.1% of the calculated inventory, except 3H, which was measured for the first time with a release of 1%.