Fuel rods


​Uranium fuel accounts for about 20% of the fuels acquired for Fortum’s own energy production. Uranium is a heavy and weakly radioactive element. Its symbol is U and its atomic number 92. In nature, uranium consists of three isotopes: 238U (99.28%), 235U (0.71%) and 234U (0.005%). Only nuclei of the isotope 235U have an inherent ability for fission when they are bombarded with neutrons. The energy released in this reaction is utilised in nuclear power plants.

Uranium fuel production is a multi-step process. Natural uranium is excavated from the bedrock and is concentrated like other ores. The uranium concentrate is converted into a gaseous form and enriched in special enrichment plants to increase the 235U proportion. The enriched uranium is converted into solid uranium oxide, which is then compressed into fuel pellets. The fuel pellets are loaded into fuel rods that are then grouped together into fuel assemblies for use in reactors.

The mining of uranium can be compared to any mining operation. But because of the radioactivity of uranium, special attention is paid to the processing and storage of the waste rock and tailings to minimise environmental impacts. The isotope enrichment of uranium is  carried out with centrifuges. This method uses only a small fraction (less 1%) of the electritcity required by the earlier gaseous diffusion method.

Fuel for the Loviisa power plant is acquired from the Russian TVEL as a turnkey delivery – from the acquisition of the raw uranium to the production of the fuel assemblies. We regularly assess the quality, environmental, and health and safety management systems of our nuclear fuel suppliers and the production of the fuel assemblies. Our experts also make regular visits to the uranium mine to assess the fuel supplier’s operations in Russia.

The spent fuel removed from a nuclear reactor is highly radioactive waste, which is initially stored in a controlled environment at the power plant. Loviisa power plant’s spent nuclear fuel will eventually be disposed of in Posiva’s final repository under construction in Olkiluoto.