Each fuel assembly contains 24 fuel elements with four various combinations of cladding and fuel matrix materials. Fuel pellets were made of traditional uranium dioxide, as well as uranium-molybdenum alloy with increased density and thermal conductivity. Zirconium alloy with a chromium coating and chromium-nickel alloy were either used as the rod cladding material.
After each irradiation cycles, several fuel rods of each fuel assembly were extracted for further post-irradiation studies, and the new non-irradiated samples were installed instead. All the irradiated fuel rods have been remaining hermetic.
Furthermore, the Bochvar Institue (a research facility of TVEL Fuel Company of ROSATOM) has started the project of developing the fabrication technology for uranium disilicide pellets (U3Si2) as another option for the ATF fuel matrix. An experimental U3Si2 ingot has been manufactured for the further producing of powder and pellets.
“The new parallel research on accident tolerant fuel is caused by the advantages of uranium disilicide. First, it is high density and uranium content, which may enable introduction of longer fuel cycles without increasing the enrichment level. Second, it is high thermal conductivity and low heat capacity, which means less accumulated heat in the reactor core and lower temperature of the rod claddings. And third, the lower operating temperature may improve the performance characteristics of the fuel in general”, Alexander Ugryumov, Vice President for Research, Development and Quality at TVEL, commented.
For reference:
TVEL Fuel Company of ROSATOM (Fuel Division of ROSATOM) includes facilities for nuclear fuel fabrication, uranium conversion and enrichment, gas centrifuges manufacturing, as well as research and development enterprises. Being the sole supplier of the Russian nuclear power plants, TVEL provides fuel for 75 power reactors in 15 countries in total, research reactors in nine countries, as well as reactors of the Russian nuclear vessels fleet. Every sixth commercial reactor in the world runs on TVEL fuel. The Fuel Division of ROSATOM is the world’s largest producer of enriched uranium.
