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Uranium concentrate is sent for chemical processing stage for blending and clean-up from impurities. This operation results in generation of uranium tetrafluoride subject to conversion into uranium hexafluoride using fluoride gas. It can be gaseous under certain temperatures. Uranium hexafluoride is enriched by U-235 isotope at Rosatom’s enterprises.
Uranium dioxide powder is fabricated from enriched uranium hexafluoride at the Corporation’s enterprises. JSC TVEL enterprises apply both hydrochemical and gaseous technologies to convert uranium hexafluoride into uranium dioxide. In particular, MSZ runs both methods to produce uranium dioxide but NCCP applies hydrochemical technology.
Further, the powder is used to fabricate fuel pellets. This technology includes the following operations: preparation of press-powder with additions of softening agents and porophores; pellet pressing by cemented-carbide tool; high temperature sintering in the hydrogen medium; centerless grinding (wet and dry); finished pellet quality control.
There are 40 types of pellets (depending on size and enrichment), which are sorted by batches and verified for compliance with technical requirements. The pellet quality is at the level of the best global samples.
Similar technologies are used to fabricate uranium-erbium pellets for RBMK fuel assemblies as well as for production of uranium-gadolinium pellets for VVER-1000 and VVER-440 fuel assemblies with burnable poison.
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