Rosatom has been pursuing verification of REMIX fuel use of VVER-1000 reactors as a strategic investment project since 2014. A key facet of the program envisions integrating reprocessed uranium and plutonium from SNF into Russia’s nuclear energy ecosystem. An explicit goal is to close the nuclear fuel cycle for derivatives of the VVER-1000, a pressurized water reactor (PWR) design that forms the cornerstone of Russia’s flagship Generation II+ nuclear power fleet and is a key export product for Rosatom.

Traditional efforts to reuse SNF have focused heavily on mixed oxide (MOX) fuel, which combines regenerated plutonium with depleted uranium to produce a viable fuel for thermal and fast reactors. While MOX fuel has been widely deployed in Europe and Japan and has proven effective, its approach inherently requires separate recycling streams for uranium and plutonium, adding processing steps and specialized infrastructure.

REMIX fuel (REgenerated MIXture of uranium and plutonium oxides) introduces an innovative approach to closing the nuclear fuel cycle by enabling multiple recycling of reprocessed uranium and plutonium into a single fuel type for thermal reactors. “Its fuel composition is produced from a mixture of reprocessed uranium and plutonium, which is formed during the processing of spent nuclear fuel, with the addition of enriched uranium,” TVEL explained.

The enriched uranium correction, containing about 16–17% uranium-235, ensures that REMIX fuel matches the energy potential of fresh uranium fuel. That capability allows for the repeated recycling of all recovered uranium and plutonium. After irradiation, the fuel undergoes a cooling period of five years in a storage pool before being reprocessed. Each cycle produces fuel containing approximately 4% uranium-235 and 1–2% plutonium, which could enable five to seven recycling iterations with fresh additions of natural or reprocessed uranium.