Research is underway to justify innovative nuclear fuel for Russia’s planned Generation IV BN-1200 sodium-cooled fast neutron reactors. The BN-1200 reactor has two possible cores with different types of uranium-plutonium nuclear fuel, which are simultaneously being investigated. These include a mixed oxide (MOX) fuel, similar to the smaller operating BN-800 reactor, as well as a dense nitride (SNUP) fuel, which will also be used by the Brest-OD-300 lead-cooled fast reactor nearing completion in Seversk.
Researchers at Rosatom’s Fuel Division TVEL have achieved new important milestones in the substantiation of both active zones. For testing in the “fast” reactor BN-600 at the Beloyarsk NPP, an OS-4 irradiation assembly with fuel rods based on SNUP fuel was manufactured. The peculiarity of this experimental assembly is the intended achievement of an increased level of nuclear fuel burnup, which will cover the needs of the developed core design with a significant margin. At the same time, special technical solutions were used in the assembly design to ensure the safety of testing in an operating power reactor.
In addition, three unique KETVS-MAK experimental assemblies with standard size BN-1200 fuel elements based on MOX fuel with an axial layer were manufactured. A design feature of these fuel rods, in contrast to traditional MOX fuel, is the introduction of a fragment with a breeding material into the composition of the fuel column. Together, these fragments form a horizontal layer in the reactor, axially dividing the active zone into two parts. This will significantly reduce radiation damage to fuel cladding while maintaining the required fuel burnup. This technical solution has been theoretically justified in several countries, but for the first time may be applied in practice in the Russian BN-1200 reactor. Reactor and post-reactor tests of these assemblies in the BN-600 will allow scientists to test nuclear fuel to the maximum design parameters, study the processes taking place in the fuel and subsequently conduct fuel licensing.
New fuel cassettes with SNUP and MOX fuel, manufactured at the Siberian Chemical Combine in Seversk, Tomsk Region, will have to undergo a test cycle in the BN-600 reactor at unit 3 of the Beloyarsk NPP. Loading into the core is planned for 2025. Reactor and post-reactor tests of these assemblies in the BN-600 will allow scientists to test nuclear fuel to maximum design parameters, study the processes occurring in the fuel rod and subsequently license the fuel.
The BN-1200 will become the world’s first serial fast neutron reactor. It continues the evolutionary line of Russian fast reactors with sodium coolant – the BN-600 and BN-800 at the Beloyarsk NPP – and will be built at the same site. Thee start of construction is scheduled for 2027.
“The BN-1200 reactor is designed to use any of the two possible types of fuel – SNUP and MOX,” said Alexander Ugryumov, Senior Vice President for Scientific and Technical Activities at TVEL. “Considerable experience has already been accumulated regarding traditional MOX fuel in its production and operation, and high-density SNUP fuel is attractive due to additional neutronic advantages that may be in demand in the future. Intensive work is currently underway to justify the choice of core design based on a comprehensive assessment of many different parameters.”
If SNUP fuel is chosen, the results of long-term tests conducted to justify SNUP fuel for the BN-1200M reactor (more than ten full-scale fuel assemblies tested in the BN-600 reactor since 2014) will also be used to justify the fuel.
