Rosatom plans accident-tolerant fuel loading

Each of the three TVS-2M model fuel assemblies contains 12 ATF rods with two variants of cladding material - zirconium alloy with chromium coating or chrome-nickel alloy. TVEL says both options make claddings more heat-resistant.

Alexander Ugryumov, vice president for research and development at TVEL, said the company had met all the milestones of its ATF programme for 2019.

"Next year, we are committed to making another important step and will start parallel testing of samples not only in a research reactor, but also in a commercial high capacity reactor. Having all the necessary validations for the reactor core, we will test the rod claddings at a functioning power unit without changing the traditional fuel pellets composition, which is uranium dioxide. At the same time, in the research reactor, we will continue to irradiate fuel rods with various combinations of cladding and fuel pellets materials, as well as simulate different operational conditions, including load changing modes. The results of these tests will help to choose the best technological solution," he said.

TVEL this year completed the first phase of ATF testing in the MIR research reactor at the State Research Institute of Atomic Reactors. In separate water loops, two experimental fuel assemblies with fuel elements of VVER and PWR type fuel rods were irradiated, it said. Each of these consisted of 24 fuel rods with four different combinations of cladding materials and fuel composition. Fuel pellets were made of traditional uranium dioxide, as well as uranium-molybdenum alloy with increased density and thermal conductivity. Afterwards, several fuel rods from each fuel assembly were removed for further post-irradiation studies, and new non-irradiated samples were installed instead.

ATF is nuclear fuel resistant to severe beyond-design basis accidents at nuclear power plant with loss of coolant in a reactor, TVEL noted. Even in the event of heat removal failure in the reactor core, ATF is designed to keep its integrity for sufficient time without a zirconium-steam reaction inducing hydrogen release. ATF is of critical importance, it said, for "further elevating the integral safety and reliability of nuclear power". The company's research, design and testing of ATF is provided and coordinated by the Bochvar High-Technology Scientific Research Institute of Inorganic Materials in Moscow.