Rosatom’s Fuel Company TVEL said that VVER-1000 fuel assemblies (FAs) containing experimental fuel elements with REMIX fuel, had been operated in the reactor at unit 3 of Russia’s Balakovo NPP for three fuel campaigns - about five calendar years.
The FAs were unloaded from the reactor during a recent scheduled preventive maintenance outage. REMIX fuel is designed to reduce the consumption of natural uranium in the nuclear power industry and to reuse the components of already irradiated fuel. The main advantage of a closed nuclear fuel cycle is the possibility of using plutonium formed during irradiation of uranium-238.
“The pilot industrial operation of the innovative fuel at the Balakovo NPP was successful,” noted Yury Ryzhkov, Deputy Chief Engineer for Safety and Reliability at the plant. “In total, three fuel assemblies were loaded into the reactor of unit 3 along with standard fuel assemblies, each of which contained six fuel elements with REMIX fuel. During all five years of testing, our specialists monitored the neutronic and life characteristics of experimental fuel assemblies - there were no deviations from normal operation, which confirms the design properties of the new nuclear fuel."
After being unloaded, the assemblies were moved to the used fuel pool to remove activity and residual heat to allow its transportation. In 2023, they will be sent to the Research Institute of Atomic Reactors (NIIAR - Dimitrovgrad) for post-reactor research.
In 2021, Rosatom established pilot production of full-scale fuel assemblies with REMIX fuel in cooperation with the Mining and Chemical Combine in Krasnoyarsk, where REMIX tablets are manufactured, and the Siberian Chemical Combine (SCC, part of TVEL) where fuel elements are manufactured and REMIX-TVS are assembled.
“Experimental fuel assemblies with REMIX fuel at SCC are manufactured in the TVS-2M design - the design is used in the VVER-1000 reactors at the Balakovo NPP. We expect that the next step in the implementation of the programme for the development and commercialisation of Russian uranium-plutonium fuel for VVERs should be the pilot operation of several fuel assemblies with all REMIX fuel rods,” noted TVEL Vice President for Science and Technology Alexander Ugryumov.
REMIX fuel (REMIX - regenerated mixture) is an innovative Russian development for light-water thermal reactors. Its is composed of a mixture of reprocessed uranium and plutonium, which is formed during the reprocessing of used nuclear fuel, with the addition of enriched uranium. Unlike uranium-plutonium fuel for fast reactors (MNUP and MOX), REMIX fuel is characterised by a lower plutonium content (up to 5%). Its neutron spectrum does not differ from standard enriched uranium fuel, so the behaviour of the fuel in the reactor core and the amount of plutonium generated from uranium as a result of irradiation are generally identical.
For nuclear power plant operators, this means that in future, REMIX fuel can be introduced without changes in the design of the reactor and additional safety measures. The use of such fuel will make it possible to expand the resource base of the nuclear power industry many times over by closing the nuclear fuel cycle, as well as to reuse the irradiated fuel instead of storing it. The strategic objective of the prospective introduction of REMIX fuel is to close the nuclear fuel cycle using thermal reactors.