Fractional release behavior of volatile and semivolatile fission products during a voloxidation and oreox treatment of spent PWR fuel

Quantitative analysis of the fission gas release characteristics during the voloxidation and oxidation and reduction of oxide fuel (OREOX) processes of spent pressurized water reactor (PWR) fuel was carried out by spent PWR fuel in a hot cell of the DUPIC Fuel Development Facility. The release characteristics of Kr-85 and C-14 fission gases during voloxidation process at 500'C are closely linked to the degree of conversion efficiency Of UO2 to U3O8 powder, and it can be interpreted that the release from grain boundary would be dominated during this step. Volatile fission gases of C-14 and Kr-85 were released to near completion during the OREOX process. Both the C-14 and Kr-85 have similar release characteristics under the voloxidation and OREOX process conditions. A higher burnup spent fuel showed a higher release fraction than that of a low burnup fuel during the voloxidation step. It was also observed that the release fraction of semivolatile Cs was similar to 16% during a reduction at 1000 degrees C of the oxidized powder, but over 90% during the voloxidation at 1250 degrees C.