The worlds most powerful fast neutron reactor called the BN-800, currently operating at unit 4 of the Beloyarsk nuclear power plant (NPP) in Russia, has been loaded with the first serial batch of MOX fuel made of depleted uranium and plutonium oxides, the Russian state atomic energy corporation Rosatom’s fuel arm TVEL announced earlier this week.
A TVEL Fuel Company statement said that the Beloyarsk NPP unit 4 has successfully resumed operation following an overhaul . The BN-800 fast neutron reactor is designed to use the MOX fuel as one of the stages on to the development of a closed nuclear fuel cycle. Where spent fuel from a reactor is reprocessed and partly reused, it is referred to as a “closed” nuclear fuel cycle, while fast reactors allow a more complete recycling of the plutonium fuel.
“Distinct from traditional nuclear fuel with enriched uranium, MOX fuel pellets are based on the mix of nuclear fuel cycle derivatives, such as oxide of plutonium bred in commercial reactors, and oxide of depleted uranium which is derived by defluorination of depleted uranium hexafluoride (UF6), the so-called secondary tailings of uranium enrichment facilities”, the statement said.
“The power plant engineers have loaded eighteen MOX fuel assemblies at the BN-800 reactor core, while Rosenergoatom and TVEL (i.e. power generation and nuclear fuel divisions, respectively, of Rosatom) are planning to load another batch of 180 fuel assemblies. By the end of 2021, Rosatom is committed to replace all remaining uranium-based fuel assemblies in the core with MOX fuel. Thus, for the first time in Russian history, a fast neutron reactor would start operations with a full load of MOX fuel only”, it added.
According to the statement, the Beloyarsk unit 4, operating for the last four years, has the twin tasks of not only producing electricity, but also to master a promising technology that is important for the future of nuclear power. Rosatom announced last year that the BN-800 fast neutron reactor of 789 MW capacity powering the fourth unit of the Beloyarsk NPP would be completely switched to uranium-plutonium MOX fuel in 2022. This reactor was initially fuelled by a “hybrid core” consisting of a mix of uranium and plutonium oxides arranged to produce new fuel material as it burns. The capacity of unit 4 exceeds that of the world’s second most powerful fast reactor – the 560 MW BN-600 Beloyarsk unit 3.
Rosatom strategy is aimed at the dual-component nuclear power system with both thermal neutron and fast neutron reactors, and closing nuclear fuel cycle, which would solve a number of highly important tasks. First, this would exponentially boost the feedstock for nuclear power plants. Second, this would enable to recycle spent nuclear fuel instead of storage. And third, we once again involve into nuclear fuel cycle and utilize the accumulated ground stocks of depleted uranium hexafluoride and plutonium, said TVEL Vice-President (Closed Nuclear Fuel Cycle Technologies) Vitaly Khadeev.
TVEL also announced earlier this month that it has signed the contracts for the manufacture and supply of the main equipment of the power unit with the BREST-OD-300 fast neutron reactor being constructed at the Siberian Chemical Combine (SCC) in Seversk, Russia. TVEL subsidiary SCC and Rosatom’s machine building arm CKBM have signed the contract for supply of equipment for the SCC refueling complex, as well as inked another agreement for the supply and installation of steam generators for the reactor by the ZiO-Podolsk Machine-Building Plant, according to a statement by Rosatom’s fuel division.
Both the fuel fabrication and the reactor units form part of the Pilot Demonstration Energy Complex being built at the Siberian Chemical Plant by the Rosatom subsidiary TVEL Fuel Company. The installation of equipment at this fuel fabrication-cum-refabrication unit called the Pilot Demonstration Energy Complex, which is a major landmark in the development of nuclear technology, started in June last year.
The Pilot Demonstration Energy Complex is underway as part of the strategic “Proryv” (‘Breakthrough’ in Russian) project. It will include three linked facilities, making up a closed nuclear fuel cycle at one site — the fuel fabrication/re-fabrication unit (FRU), the 300 MW nuclear power plant with the fast neutron BREST-OD-300 reactor, and the unit for spent fuel reprocessing.
According to Rosatom, the “Breakthrough” project targets creation of a new technology platform for the industry with the closed nuclear fuel cycle, as well as tackling the issues of spent nuclear fuel and radioactive waste. One of the project components is the construction of a lead-cooled BREST-OD-300 fast neutron reactor facility with an on-site closed nuclear fuel cycle.
“Most of the technical solutions for the BREST-OD-300 reactor installation itself and its main equipment are innovative and have never been applied at any nuclear facility so far. The equipment of the reactor must ensure operations during the entire service life at high temperatures, high fluxes of ionizing radiation, in the flows of heavy liquid-metal coolant. The structural materials must have high corrosion and radiation resistance, as well as high temperature resistance to ensure reliability”, TVEL said.
“Unlike NPPs (nuclear power plants) with light-water VVER reactors, where refueling is performed at the ‘cooled’ reactor, the BREST-OD-300 project provides that these operations will be carried out at the temperature of the liquid-lead coolant of the primary circuit over 400° C. Before loading into the core, the fuel assemblies will be heated up in a special chamber and then placed into the core filled with a melt of lead coolant”, the statement added.
“The special thing about all facilities of the Experimental Demonstration Energy Complex (EDEC) in Seversk is that all the key equipment, including the BREST reactor facility and the units for nuclear fuel fabrication and reprocessing, is absolutely unique at the global scale. The team of the “Breakthrough” project has to solve unconditional tasks, which are related not just to the facilities construction management, but also to a large program of R&D and technical design”, said TVEL President Natalia Nikipelova.
According to TVEL, the production of equipment for the reactor facility is supposed to take between three to five years, while installation of the main equipment is expected to be completed in 2025. In addition to the 300 MW power unit, the EDEC will include the on-site closed nuclear fuel cycle, embracing the unit for refabrication of mixed nitride uranium-plutonium fuel, as well as the unit for irradiated fuel reprocessing, the statement said.