BN-1200 reactor  The BN-1200 reactor is a sodium-cooled fast breeder reactor project, under development by OKBM Afrikantov in Zarechny, Russia. The BN-1200 is based on the earlier BN-600 and especially BN-800, with which it shares a number of features. The reactor's name comes from its electrical output, nominally 1220 MWe. Originally part of an aggressive expansion plan including as many as eight BN-Reactors starting construction in 2012, plans for the BN-1200 were repeatedly scaled back until only two were ordered. The first was to begin construction at the Beloyarsk nuclear power plant in 2015, with initial commissioning in 2017, followed by a second unit at the same location. A possible new station known as South Ural would host another two BN-1200s at some future point. In 2015, after several minor delays, problems at the recently completed BN-800 indicated a redesign was needed. Construction of the BN-1200 was put on "indefinite hold", and Rosenergoatom has stated that no decision to continue will be made before 2019. Fast reactors of the BN series use a core running on enriched fuels like highly (80%) or, at least, medium (20%) enriched uranium or plutonium. This design produces many neutrons that are able to escape the core area due to its basic geometry and details of operating cycle. These neutrons are then used to create additional reactions in a "blanket" of material, normally natural or even depleted uranium or thorium, where respectively new plutonium- or uranium 233 atoms are formed. These atoms have different chemical behavior and can be extracted from the blanket material through basic reprocessing. The resulting plutonium metal can then be mixed with other fuels and used in conventional reactor designs. For the breeding reaction to be positive, producing more fuel than it uses, the neutrons released from the core should retain as much energy as they can. Additionally, as the core is very compact, the heating loads are very high. These requirements both lead to the use of liquid sodium as a coolant, as this is both an excellent conductor of heat, as well as being largely transparent to neutrons. Sodium is also highly flammable, and careful design is needed to build a primary cooling loop that can be safely operated, although sodium fires in air are not very energetic in nature. Alternate designs use lead. Although the plutonium produced by breeders is useful for weapons, there are more traditional designs, notably the graphite-moderated reactor, that generate plutonium more easily.