Russia’s AA Bochvar Research Institute of Inorganic Materials (VNIINM - part of Rosatom’s fuel company TVEL) has developed a new method of manufacturing spacer grids for assemblies with dense nitride uranium-plutonium fuel (MNUP-fuel).
Specialists from the research department of structural materials and products at VNIINM have received a Russian patent for an invention concerning a method of manufacturing spacer grids for the BREST-OD-300 fast reactor fuel assembly, TVEL said. The invention will reduce the number of technological operations in the manufacture of the product.
The spacer grid is an element of the fuel cartridge frame, with the help of which the fuel elements are assembled into a single structure. The BREST-OD-300 reactor, which is being built as part of the Proryv (Breakthrough) project will use liquid lead as a primary coolant, and MNUP-fuel.
Because of the increased requirements for the operational characteristics of nuclear fuel in the BREST-OD-300 core, VNIINM proposes to manufacture the spacer grid from ferritic-martensitic steel with a high chromium content. This provides radiation and corrosion resistance, heat resistance, reduced erosion when interacting with the coolant.
VNIINM scientists have also changed the technology for manufacturing spacer grids in order to additionally ensure a higher quality of welded seams. It is proposed to use a bimetallic pipe consisting of ferritic and ferritic-martensitic steel as the material for the spacer grid cell. This will lead to the formation of a significant proportion of the ferrite phase in the weld.
“The principle of creating welded joints developed by us is universal and can be applied in any structures made of ferritic-martensitic steels. It allows you to exclude the postweld tempering operation, which will help to reduce the process time and the cost of products,” said Irina Naumenko, a leading researcher at VNIINM’s research department of structural materials and products.
Photo: Dense nitride uranium-plutonium or MNUP-fuel (Credit: TVEL)