Experimental fuel assemblies containing mixed dense nitride uranium-plutonium fuel (MNUP-fuel) intended for Russia’s planned BN-1200M sodium-cooled fast reactor are to be tested in the BN-600 fast reactor at unit 3 of the Beloyarsk NPP, Rosatom’s Fuel Company TVEL has announced. The assemblies, which were manufactured and successfully accepted at the Siberian Chemical Combine in Seversk (SCC, part of TVEL), will be loaded into the BN-600 in 2023, in accordance with the reactor test programme.
The BN-1200M is a new generation sodium-cooled fast reactor, which is intended to become a standard design for a 1200 MWe fast reactor as part of a two-component nuclear power industry with high-power thermal and fast reactors and a closed nuclear fuel cycle. Production of the new fuel will use secondary products of the nuclear fuel cycle - depleted uranium, plutonium and regenerated uranium separated from irradiated fuel. The first BN-1200M power unit is planned to be built at unit 5 of the Beloyarsk NPP in the Sverdlovsk region, where predecessor fast nuclear reactors - BN-600 and BN-800 - are already operating.
Fast reactors can use plutonium as fuel making it possible to close the nuclear fuel cycle to be closed and the optimal fuel for such plants is a uranium-plutonium mixed oxide fuel (MOX). The BN-800 reactor at Beloyarsk unit 4 was switched to MOX this year. Another type of uranium-plutonium fuel for fast reactors is nitride MNUP fuel, which will be used in the first innovative lead-cooled reactor BREST-OD-300 being built at SCC in Seversk as part of the Breakthrough (Proryv) project).
“Both options are being considered for the BN-1200M core – both oxide and nitride fuel. In the case of MOX fuel, we have worked out the entire production technology and are accumulating experience in operating the BN-800 with a full core load of uranium-plutonium fuel. Dense MNUP currently appears to be a priority option,” said Alexander Ugryumov, Senior Vice President for Scientific and Technical Activities at TVEL. “In this regard, research is underway at the AA Bochvar Research Institute of Inorganic Materials (VNIINM), on the justification of nitride fuel with a gradual increase in its efficiency for the BREST-OD-300 and, in the future, for the BN-1200.” Experimental fuel assemblies with MNUP fuel manufactured by SCC have been tested in the BN-600 reactor since 2014 during which increasingly higher burnup of the nuclear fuel has been achieved.
“The substantiation of the maximum fuel burnup creates the prerequisites for the maximum economic efficiency of its use. As part of the Breakthrough project, a programme is being implemented to gradually increase the burnup of MNUP fuel to an average value of 12%. For this purpose, the BN-600 also provides irradiation of assemblies with removable containers, which makes it possible to test nitride fuel to the limit of its design parameters. In addition, during irradiation in the BN-600, the material science assembly with samples of materials for promising cores of fast reactors is being tested using various steels of the ferritic-martensitic class,” commented Mikhail Skupov, Deputy General Director of VNIINM and head of the joint group of the industry project “Development of fuel elements and fuel assemblies with MNUP-fuel".
Image: Experimental fuel assembly with MNUP fuel (courtesy of Rosatom)
