The first batch of innovative uranium-plutonium Remix fuel was loaded into the VVER-1000 reactor at unit 1 of Russia’s Balakovo NPP, Rosatom’s fuel company TVEL said on 21 December.
Six fuel assemblies with Remix fuel were loaded into the reactor core during a regular maintenance outage. Each of the fuel assemblies of the standard TVS-2M design is fully equipped with fuel elements comprising a uranium-plutonium fuel (312 fuel elements in total), which is produced from used nuclear fuel.
Earlier in 2021, at Balakovo 3, a programme was completed for pilot operation of three experimental fuel assemblies, including six experimental Remix fuel rods involving a total of three irradiation cycles of 18 months. TVEL said the programme was fully consistent with the world practice for the development and implementation of innovative nuclear fuel, in which the first several experimental assemblies with experimental fuel rods are loaded into a reactor (lead test rods). The next stage involves several cassettes entirely consisting of fuel rods containing the new fuel (lead test assemblies or LTA).
“The LTA programme, that is, the operation of complete Remix assemblies, is a prerequisite for the commercialisation and wider introduction of uranium-plutonium fuel for VVER reactors,” said Alexander Ugryumov, Vice President of TVEL JSC for Scientific and Technical Activities and Quality. “Thus, we will be able to obtain both the necessary data for licensing for full refuelling of the core, and the reference experience, which is important for potential customers.”
Remix fuel comprises reprocessed used nuclear fuel, which, after enrichment, is recycled back to the reactor,” explained Andrey Filonenko, head of Balakovo NPP’s laboratory for nuclear safety and reliability. “This technology was developed in order to close the nuclear fuel cycle using thermal reactors.”
The pilot assembly plant Remix-TVS for VVER-1000 was established in 2021 at the Siberian Chemical Plant in Seversk, Tomsk Region (part of TVEL) in cooperation with the Mining and Chemical Combine in Zheleznogorsk (Krasnoyarsk Territory), which made fuel pellets using a uranium-plutonium mixture.
Full-scale fuel assemblies with Remix fuel will be used at Balakovo 1 for three cycles - about five calendar years, during which specialists of the Balakovo NPP will monitor the neutron-physical and resource characteristics of the assemblies.
Remix (regenerated mixture) fuel is an innovative Russian development for light-water thermal reactors, which is expected to become the basis of nuclear energy. Its fuel composition is made from a mixture of reprocessed uranium and plutonium, which is formed during the reprocessing of used nuclear fuel, with the addition of enriched uranium. Compared with uranium-plutonium fuel for fast reactors (MNUP and mixed oxide), Remix has a lower plutonium content.
Because its neutron spectrum does not differ from standard enriched uranium fuel, its behaviour in the reactor core and the amount of plutonium generated from uranium as a result of irradiation are generally identical. For NPP operators, this means that Remix fuel can be introduced without changes to the design of the reactor and additional safety measures. The use of such fuel will make it possible to multiply the resource base of the nuclear power industry by closing the nuclear fuel cycle, as well as to reuse the irradiated fuel instead of storing it.
Photo: Each REMIX fuel assembly contains 312 fuel rods with a mixture of uranium and plutonium recovered from spent nuclear fuel (Credit: TVEL)