BN-800 reactor

The BN-800 reactor (Russian: реактор БН–800) is a sodium-cooled fast breeder reactor, built at the Beloyarsk Nuclear Power Station, in Zarechny, Sverdlovsk Oblast, Russia. The reactor is designed to generate 880 MW of electrical power. The plant was considered part of the weapons-grade Plutonium Management and Disposition Agreement signed between the United States and Russia. The reactor is part of the final step for a plutonium-burner core (a core designed to burn and, in the process, destroy, and recover energy from, plutonium) The plant reached its full power production in August 2016. According to Russian business journal Kommersant, the BN-800 project cost 140.6 billion rubles (roughly 2.17 billion dollars).

Design
The plant is a pool-type LMFBR, in which the reactor, coolant pumps, intermediate heat exchangers and associated piping are all located in a common liquid sodium pool. This is similar to the general design of EBR-II, which went into service in 1963, but is otherwise significantly different. For example, EBR-II used metallic fuel, which is the major factor in its inherent safety, while BN-800 uses oxide fuel. The design of this plant was started in 1983 and was completely revised in 1987 after the Chernobyl disaster and to a somewhat lesser degree in 1993, according to the new safety guidelines. After the second revision, output power was increased by 10% to 880 MW due to the increased efficiency of the power generator steam turbines.

The reactor core is, in size and mechanical properties, very similar to the BN-600 reactor core, but the fuel composition is not. While BN-600 uses medium-enriched uranium dioxide, this plant burns mixed uranium-plutonium fuel, helping to reduce the weapons-grade plutonium stockpile and provide information about the functioning of the closed uranium-plutonium fuel cycle, which does not require plutonium separation or other chemical processing.

The unit employs a three-circuit coolant arrangement; sodium coolant circulates in both the primary and secondary circuits. Water and steam flow in the third circuit. This heat is transferred from the reactor core via several independent circulation loops. Each is composed of a primary sodium pump, two intermediate heat exchangers, a secondary sodium pump with an expansion tank located upstream, and an emergency pressure discharge tank. These feed a steam generator, which in turn supplies a condensing turbine that turns the generator.

Many infrastructure facilities were designed to accommodate both the BN-800 and a proposed BN-1200 reactor.

History
Construction started in 1983 as Unit 4 at the Beloyarsk nuclear power plant. It was put on hold after Chernobyl. It resumed in 2006 and BN-800 achieved minimum controlled power in 2014, but issues led to further fuel development work. On 31 July 2015, the unit achieved minimum controlled power again - 0.13% of rated power. Commercial operation was expected to start before the end of 2016, with a power rating of 789 MWe. The reactor was connected to the grid in February 2016 and achieved full power for the first time in August 2016. Commercial power production started on November 1, 2016.

The United States and Russia reached an agreement in 2001 to render a total of 34 tons of weapons grade plutonium into reactor grade plutonium to reach the "spent fuel standard," which is mixed with other more radioactive products within spent fuel.

US president Barack Obama canceled construction of the US MOX fuel fabrication facility in 2016, citing cost overruns. He proposed that the US share of plutonium be diluted with non-radioactive material and disposed of in the underground WIPP facility. However, the dilution could be reversed, and the material reconverted into weapons-grade plutonium.

On October 3, 2016, Russian president Vladimir Putin ordered the agreement to be suspended because the US did not meet its obligations.

In January 2020 the reactor started commercial operation with the first batch of MOX reprocessed uranium-plutonium fuel.

In 2023 the reactor completed one year of operation using a nearly full load of uranium (96%)/plutonium/americium/neptunium MOX fuel.

Plutonium disposal
The BN-800 could be used to close the fuel cycle. The core load of 15 tons of material consists mostly of U-238 and about 20.5% plutonium. This could be taken from reprocessed spent nuclear fuel assemblies.