Based on the results of the research - using the BFS-1 critical test facility - "Rosatom scientists intend to justify the neutron-physical characteristics and safety of operation in various modes of reactor units with VVER-type MOX fuel (including future advanced units)".
The VVER-S is a 600 MWe water-cooled reactor under development. The fundamental difference for VVER-S compared with other VVER reactors is in spectral regulation "of the change in the reactivity margin of the core during fuel burnout due to a change in the water-uranium ratio and the complete rejection of liquid boron regulation during reactor operation at power. In the VVER-S, excess neutrons, instead of being absorbed in boric acid, are absorbed by uranium-238" which produces plutonium, a new fissile fuel. The first two units are planned as part of Kola 2 in the Murmansk region, with construction due to begin in 2028 with a commissioning target for 2035.
In Russia, MOX (mixed oxide) fuel is currently produced for fast neutron reactors, notably the BN-800 fast reactor at Beloyarsk. MOX fuel is manufactured from plutonium recovered from used reactor fuel, mixed with depleted uranium. Uranium-plutonium REMIX fuel has been developed for VVER reactors. Rosatom says that, if the proposed VVER-S reactors can use a full load of MOX fuel, it will cut its use of natural uranium by 50% and, over its lifetime - with high uranium prices - could save about the same amount as the capital cost of a unit.
Alexander Zhukov, head of the BFS complex, said: "In anticipation of the physical launch, a mock-up of the critical assembly without nuclear materials inside was fully formed and presented to the nuclear safety commission, which checked the readiness of all critical stand systems and personnel, the programme for the control physical launch, and authorised the control physical launch. After receiving permission, the mock-ups were replaced in portions with real fuel elements with energy plutonium."
Rosatom sees the project as helping towards a balanced fuel cycle, which it sees as having economic and environmental benefits, by reducing future fuel requirements while also minimising waste.
