Comparative Life Cycle Assessment of MOX and REMIX Fuels in Fast Reactors: Environmental Benefits of Closing the Nuclear Fuel Cycle

The transition toward sustainable nuclear energy systems requires optimizing the nuclear fuel cycle to min- imize environmental burdens and maximize resource utilization. Conventional once-through light water re- actors (LWRs) utilize less than 1% of the total energy potential of natural uranium, as only a small portion of U-235 and some plutonium bred from U-238 are fissioned before discharge. In contrast, fast reactors (FRs) op- erating under closed fuel cycles with mixed oxide (MOX) or regenerated mixture (REMIX) fuels can enhance uranium utilization, reduce long-term radiotoxicity, and contribute to decarbonization objectives aligned with the IAEA’s Atoms4NetZero initiative.