State nuclear fuel company Tvel said each Remix assembly contains only fuel rods with a mixture of uranium and plutonium recovered from spent nuclear fuel, with 312 fuel rods in each assembly.
Since 2016, three fuel assemblies, each containing six experimental Remix fuel rods, have been undergoing pilot operation at Unit 3 at Balakovo, about 900km southeast of Moscow. The third 18-month cycle of their irradiation began in 2020 and was completed earlier this year.
Remix fuel is made from uranium and plutonium recovered from used fuel. It is topped up with low-enriched uranium to give a fuel that performs within the same parameters as fuel made only from fresh low-enriched uranium. Remix can be used in existing reactors without changes to their design or additional safety measures.
The cycle of reprocessing, recycling and top-up can be repeated as many as five times, with waste fission products removed each time and vitrified in glass ready for permanent geological disposal. In theory, a new reactor could operate for its whole design life of 60 years on just three Remix fuel loads, circulating them continuously.
The test programme is a prerequisite for the commercialisation and wider introduction of VVER uranium-plutonium fuel. The Remix assemblies will be operated at Balakovo for about five years while engineers monitor their behaviour.
“Remix fuel is spent nuclear fuel that was reprocessed and then returned back to the reactor,” said Andrey Filonenko of Balakovo NPP. “The purpose of the technology is to close the nuclear fuel cycle.”
Remix fuel is manufactured at the Mining and Chemical Combine in Zheleznogorsk, but the fuel pellets themselves are made at the Siberian Chemical Combine in Seversk, 640 km to the east, where Russia has a large storage facility for used VVER-1000 fuel.
