MOX fuel with minor actinides produced for BN-800 reactor

15 December 2023

The first three fuel assemblies with uranium-plutonium mixed oxide fuel containing transuranic elements americium-241 and neptunium-237 have been produced by Rosatom's Mining and Chemical Combine.

(Image: TVEL)

The fuel has been accepted and is due to be loaded into the BN-800 fast neutron reactor at Beloyarsk nuclear power plant in 2024, with pilot operation "during three micro-campaigns (approximately one-and-a-half years)".

Minor actinides are transuranic elements other than plutonium which are formed in irradiated nuclear fuel. They are highly radioactive and have long half-lives.

Rosatom said that the proposed Russian solution to what are the most hazardous components of nuclear waste is via fast neutron reactors which can be fuelled not only by enriched natural uranium, but also by secondary products of the nuclear fuel cycle, such as depleted uranium and plutonium. "In addition, the research shows that minor actinides from spent nuclear fuel under the flux of fast neutrons will fission into fragments representing a fairly wide range of radioactive and stable isotopes, but in general their potential hazard will be much lower than that of the original minor actinides," the company said.

Alexander Ugryumov, senior vice president for research and development at Rosatom's fuel division, TVEL, said: "Rosatom is step-by-step taking the unique advantages that powerful fast neutron reactors provide to our industry. The introduction of MOX fuel enables the expansion of the resource base for nuclear power multifold involving depleted uranium and plutonium, and also to reprocess irradiated fuel instead of storing it. Afterburning of minor actinides is the next step in closing nuclear fuel cycle, which should not only reduce the amount of nuclear waste for final isolation, but also significantly reduce its radioactivity. In the long term, it could avoid the complicated and expensive deep burial of waste."

These lead-test assemblies were manufactured at Mining and Chemical Combine in Zheleznogorsk in the Krasnoyarsk region, based on fuel fabrication technology developed at TVEL's Bochvar Institute in Moscow.

TVEL says that the pilot operation in the BN-800 reactor "is the key stage of the comprehensive research programme" for minor actinides afterburning which began in 2021 and is due to run until 2035, saying: "The programme includes projects of minor actinides separation into different fractions, their intermediate storage, involvement in fast reactor fuel, operation of such fuel, post-irradiation studies, etc. Another important issue is optimisation of reactor facilities for burning the maximum volume of minor actinides."

Beloyarsk 4 is a BN-800 reactor -  a sodium-cooled fast reactor which produces about 820 MWe - which was brought to minimum controlled power for the first time in June 2014, and connected to the grid on 10 December 2015. The 789 MWe reactor entered commercial operation on 31 October 2016. It was fully loaded with MOX fuel in September 2022 and recently became the first such facility to complete a year operating on MOX fuel. MOX fuel is manufactured from plutonium recovered from used reactor fuel, mixed with depleted uranium which is a by-product from uranium enrichment.

Researched and written by World Nuclear News