Analysis on Transmutation of Long-Lived Fission Products from PWR Spent Fuel Using the 30-MW(thermal) RSG-GAS Reactor

The use of the RSG-GAS research reactor as a transmutation reactor is analyzed to study its effectiveness for transmuting long-lived fission products (LLFPs), particularly ¹²⁹I and ⁹⁹Tc. Both radionuclides selected are assumed as discharged from of a 1000-MW(electric) pressurized water reactor (PWR) spent fuel. If these radionuclides are stored in sustainable geologic disposal, they will require high-cost handling due to their special shielding. In one cycle of PWR1000 operation, the ⁹⁹Tc produced is 43.7 kg and ¹²⁹I is 9.5 kg in its spent fuel. Considering reactor safety, the maximum target mass permitted to be transmuted in the RSG-GAS is 3.0 kg for the ⁹⁹Tc and 5.0 kg for the ¹²⁹I. In 1 year of (five cycles) operation, the ⁹⁹Tc and ¹²⁹I targets would be reduced by 126 and 290 g, respectively. Although it has the potentiality to safely transmute LLFP targets in its core, RSG-GAS requires longer irradiation time (about 20 years) to entirely transmute the targets.