A unique industrial complex for the production of MOX fuel has been established at the Mining & Chemical Combine (MCC) I in Zheleznogorsk (Krasnoyarsk) with the support of Rosatom’s leading institutes and enterprises to ensure the manufacture and supply of fuel assemblies for the BN-800 fast reactor at unit 4 of the Beloyarsk NPP. It plays a key role in the establishment of a balanced nuclear fuel cycle based on the use of regenerated and recycled materials.

MCC manufactured the first three fuel assemblies with uranium-plutonium mixed oxide (MOX) fuel in December 2023. These also contained other transuranic elements including americium-241 and neptunium-237. The assemblies completed acceptance tests and were loaded into the BN-800 earlier this year. The fuel will undergo pilot operation (lead-test assemblies programme) during three micro-campaigns of approximately one and a half years.

Minor actinides are formed in irradiated nuclear fuel as the result of reactions during operation in a reactor core. Like plutonium, these elements arise from transmutation of uranium. Neptunium, americium and curium isotopes are particularly important to radiochemists because of their significance in used fuel reprocessing and radioactive waste management. They are highly radioactive and toxic, generate a great deal of heat and have long half-lives, making them the most hazardous components of nuclear waste.

The Russian solution is fast neutron reactors, which can be fuelled not only by enriched natural uranium, but also secondary products of the nuclear fuel cycle, such as depleted uranium and plutonium. In addition, the research has shown that minor actinides from used fuel under the flux of fast neutrons will fission into fragments representing a fairly wide range of radioactive and stable isotopes, which are potentially much less hazardous.

The fuel fabrication plant (ZFT – Zavod Fabrikatsii Topliva) at MCC not only provides the steady output of MOX assemblies for the scheduled refuelling of the BN-800, but also carries out continuous work to improve efficiency and develop new technological solutions.

ZFT began 2024 by putting in place glove boxes for the production of samples and press powder to minimise personnel contact with nuclear materials and enhance safety. In order to improve economics, a number of pilot batches of fuel elements and pellets have been produced. By eliminating the drying of screen tablets and reducing the number of operations, labour productivity has increased. The released equipment was then used in the technology of oxidising scrap with different isotopic compositions – MOX fuel pellets that are rejected because they do not meet the technical requirements.

Implementation of this technological innovation was a real achievement and an excellent result of the work of ZFT specialists. In the spring, the steady production of MOX assemblies for the 15th reload of Beloyarsk 4 was underway and 64 assemblies were sent to the plant in June. These included 23 containing americium-241 intended for the 13th reload, which was successful. Another 41 assemblies have already been sent for the 14th reload.

In the second half of the year, ZFT will have to solve an ambitious task, compensating for an accumulated backlog in meeting targets by increasing equipment productivity. In addition to measures already described, the productivity of furnaces at ZFT has increased significantly. The mass of one sintering is now 32 kg, more than one and a half times more than the previous 20 kg.

The dispatch of the next consignment of MOX fuel is already planned: for the 14th, as well as for the first part of the 15th refuelling, comprising fuel assemblies. And the next fulfilment of contractual obligations has already been formalised for the sale of 170 assemblies in November for the 15th reload at Beloyarsk 4.