Unit 4 at Russia's Beloyarsk nuclear power plant, which has the world's largest sodium-cooled fast neutron reactor - the BN-800 - will begin commercial operation before the end of 2016, according to plant chief engineer Yuri Nosov of nuclear utility Rosenergoatom.
Rosatom announced on 11 November that the unit had been brought to the minimum controlled power level for the third time. It was first brought to minimum controlled power in June 2014 and was expected to be online by the end of the year. However, in December Rosenergoatom said fuel for the unit would first have to be developed further. It achieved minimum power for a second time last August.
The first power programme will end with the turbine generator connection to the grid and a 72-hour integrated trial, Nosov said. This will be followed by a step-by-step power build-up.
On 9 November, Russian regulator Rostechnadzor approved Rosenergoatom's amendments to the unit's operating licence, allowing it to start up. Beloyarsk staff had prepared 5540 sets of documents to support the application for those amendments. Startup will involve an increase in the unit's power level from the 1% of nominal capacity to 35%, the level at which power generation can begin. It will then be increased to 50%, at which point it will be ready for pilot operation.
There will be tests and inspections of equipment at every stage to confirm reliability and safety for further operation. "For example, the planned revision under the 'power start-up' phase alone takes 30-40 days. Once the reactor power level of 30-35% of nominal capacity has been achieved, the first turbine generator unit can be started, because that is the level required to produce enough steam to run the turbines and ensure its normal operation," Rosenergoatom said. Power will then be gradually increased to the nominal capacity of 800MWe.
The BN-800 is a unique reactor. Its predecessor - the BN-600 at Beloyarsk unit 3 - began operation 35 years ago, and the new unit includes a large number of design and technological improvements. Fundamental features of the BN-800 reactor include an active reactor protection system with a passive system that works automatically in the event of loss of sodium-cooling liquid pressure, according to Rosenergoatom. During normal operation, the reactor's control rods float in the cooling liquid on top of the reactor core. If cooling liquid pressure drops, the rods fall into vertical control rod channels in the reactor core and stop the chain reaction by absorbing neutrons. It also has a passive supplementary air cooling system, used to remove of residual decay heat.
Construction of the BN-800 and plans for a larger BN-1600, began in 1984, with startup of the BN-800 then planned for 1992. But after the 1986 Chernobyl accident in Ukraine, construction of all new nuclear plants in Russia was frozen. Later, in the 1990s, construction was delayed because of the economic situation in the wake of the Soviet collapse. During this period, the project was improved to take account of state-of-the-art technology and revised regulations concerning reliability, safety and ecological requirements. Construction began in earnest in 2006.
Russia is now considering further expansion of Beloyarsk plant with the construction of unit 5 which would have an even larger 1200MWe reactor. Rosenergoatom says construction of this unit would be easier and faster because many infrastructure facilities, which are already in place on the BN-800 site, are designed for two power units. There is also a team of builders, with experience accumulated in the course building the BN-800.
The BN-1200, if successfully built, would be the reference plant for serial construction of fast reactors.