The Mining and Chemical Combine in Zheleznogorsk began serial production of MOX fuel for the BN-800 fast-neutron reactor. The first batch of 18 MOX fuel assemblies was sent to BN-800 on 16 August 2019. It is now stored at the reactor site.
The construction of the production line was completed in 2014 and it was formally launched in September 2015. The BN-800 reactor began operations in 2015 with a mixture of HEU fuel and MOX fuel assemblies manufactured elsewhere.
It is important to note that the Zheleznogorsk MOX fabrication plant used reactor-grade plutonium, referred to as a "high-background material" in Russia. According to the original plan, the plant was to process weapon-grade plutonium that Russia committed to eliminate under the US-Russian Plutonium Management and Disposition Agreement (PMDA). However, Russia suspended the implementation of the agreement in 2016. Even though it confirmed at the time that the 34 tonnes of the weapon-grade plutonium covered by that agreement will not be used for any military purpose, Russia apparently postponed the disposition of that material, turning to its civilian plutonium stock. Russia reported having 59 tonnes of civilian plutonium as of the end of 2017. The plutonium for the first MOX fuel assemblies also came from the civilian stock, although it was said to be a weapon-grade material produced in fast-neutron reactor blankets in the past.