Work has begun at unit 4 at Russia's Beloyarsk NPP to prepare the BN-800 sodium-cooled fast reactor for commercial operation this autumn, according to Russian state nuclear corporation Rosatom. The 789MWe reactor has begun its first planned outage since being connected to the grid in December 2015, Rosatom said. Since then, operators have been gradually increasing the reactor's power levels as part of the operational testing phase. Rosatom said the main aim of the current planned outage, to be completed between 5 and 10 August, is to prepare the unit for commercial operation. Beloyarsk-4 is Russia's first reactor of the BN-800 design, which uses mixed uranium-plutonium (mox) fuel. However a smaller BN-600 has been in commercial operation at unit 3 of the Beloyarsk station since 1980 and is the world's only commercially operating fast reactor. Russia is considering further expansion of the Beloyarsk station with the construction of unit 5, with a larger 1,200MWe fast reactor, but this will depend on the operational experience gained from unit 4.