Unit 1 of Russia’s Smolensk NPP has begun using an improved type of nuclear fuel with reduced enrichment of uranium-235 and a lower content of erbium oxide. Smolensk hosts three RBMK-1000 light water graphite moderated reactors that have been highly upgraded and equipped with advanced safety systems. They began operation in 1983, 1985 and 1990. A fourth RBMK reactor was under construction but was cancelled in 1993 following the Chornobyl disaster.
Following a 15-year life extension beyond their original 30-year design limit, the three units are currently slated to be retired sequentially after 45 years of generation in 2027, 2030 and 2034/5 and will be replaced with VVER-TOI units. The new fuel may make it possible to extend their operating lives to 50 years.
Calculations have shown that the new type of RBMK fuel will make it possible to compensate for changes in the neutron-physical parameters of the core that arose after graphite repair, providing optimal conditions for extended operation. The use of optimised fuel assemblies is aimed at increasing the level of safety and improving the technical and economic performance of the power unit.
“The uranium-erbium fuel that we have been using since the mid-2000s contains uranium enriched to 2.8% with the mass content of erbium oxide, which serves as a burnable neutron absorber, at 0.6%,” said Smolensk NPP Deputy Chief Engineer Anatoly Karpinsky. “The need to change the fuel composition arose in connection with the implementation of work at the power unit to manage the resource characteristics of graphite masonry in order to increase safety and extend the service life of the power unit. The decision to optimise the fuel composition with uranium enrichment at 2.7% and erbium content at 0.35%, was made based on the results of independent computational studies by NIKIET [Nauchno-Issledovatelskii i Konstruktorskii Institut EnergoTekhniki – the NA Dollezhal Scientific Research & Design Institute of Power Engineering], the Kurchatov Institute and VNIIAES [Vserossiiskii Nauchno Issledovatelskii Institut po Expluatatsii Atomnikh Elektrostantsii – All-Russian Research Institute for the Operation of Nuclear Power Plants].”
Preparations for loading the new fuel assemblies included: an analysis of various operating modes of the reactor installation; a justification for nuclear and radiation safety when handling a new type of fuel; certification of new software tools; bench tests with the participation of specialists from the nuclear safety and reliability department and the thermal automation and measurement workshop; and changes to the operating licence for unit 1.
“Modernisation of existing power units, including the transition to a new type of fuel, and extension of service life, is our contribution to the implementation of the strategic task set for Rosatom by Russia’s President – to increase the share of nuclear generation in the overall energy balance of Russia to 25% by 2045,” said Plant Director Ivan Sidorov. “We are consistently increasing the reliability and efficiency of equipment in order to continue to ensure a stable energy supply to the regions and create the basis for the long-term development of the industry.”
Analysis of the operation of the first batch of 200 fuel assemblies will make it possible to justify full-scale loading at all Smolensk units and ensure the possibility of extending their operation to 50 years.
