The first complete reloading of mixed oxide (mox) fuel for Russia’s BN-800 fast reactor at unit 4 of the Beloyarsk nuclear power plant has been manufactured at the Mining and Chemical Combine (MCC) in Zheleznogorsk.
It comprised 169 fuel assemblies, fuel company Tvel (part of state nuclear corporation Rosatom) said. The customer, nuclear utility Rosenergoatom, signed a certificate of acceptance relating to product development, and Zarubezhatomenergostroy (VPO ZNPP), which deals with quality control, issued a statement affirming the readiness of the fuel for shipment.
Tvel will supply the mox fuel to the Beloyarsk NPP at the end of 2020, and fuel loading is scheduled for January 2021.
Initially, the BN-800 reactor was launched with a hybrid core, comprising both uranium fuel produced by Mashinostroitelny Zavod in Elektrostal and experimental mox assemblies manufactured at the Research Institute of Atomic Reactors (NIIAR) in Dimitrovgrad. The first batch of mox fuel for BN-800, comprising 18 fuel assemblies, was loaded into the reactor at the end of 2019, the rest of the refuelling consisted of fuel assemblies with uranium fuel. Beloyarsk 4 resumed operation in January 2020 after the maintenance and refuelling outage.
“Starting from the next refuelling, the BN-800 core will be equipped with mox assemblies. At the same time, Tvel and MCC will continue to work on improving the mox fuel fabrication technology,” said Alexander Ugryumov, Tvel vice president for Scientific and Technical Activities. Completion of the transition to a full load of mox fuel is scheduled for 2022.
Russia’s mox is manufactured using depleted uranium and plutonium. The raw materials for the fuel pellets are plutonium oxide produced in power reactors and depleted uranium oxide (obtained by defluorination of depleted uranium hexafluoride - DUHF, the secondary tailings from enrichment production.
Rosatom's strategy to move to a two-component nuclear power industry with both thermal and fast neutron reactors, as well as to close the nuclear fuel cycle, will help to solve a number of important problems, Tvel said. First, it will increase the resource base of the nuclear power industry. Second, used fuel will be reprocessed and re-used instead of being stored. Third, it will utilise the DUHF stocks accumulated in warehouses. In addition, the development of recycling technologies in the nuclear industry is fully consistent with one of the UN Sustainable Development Goals - “Responsible Consumption and Production”. The industrial fabrication of mox fuel began at the end of 2018 at MCC.
The content of the uranium-238 isotope in natural uranium is about 99.3%, and uranium-235 (the main fissile isotope in thermal reactors) is only 0.7%. Thermal reactors use about 1% of natural uranium, the remaining 99% are sent for temporary storage or disposed of as radioactive waste. However, Fast neutron reactors, using a mixture of natural or depleted uranium and plutonium oxides as fuel, will be able to produce plutonium in an amount sufficient to provide themselves with new fuel and manufacture, if necessary, a certain amount of fuel for other reactors.