Spent nuclear fuel will be disposed of in Finland
Based on the Finnish Nuclear Energy Act, spent nuclear fuel from Finland must be disposed of in Finland. Accordingly, fuel from abroad may not be transferred to Finland for disposal. The import and export of spent nuclear fuel was prohibited in 1994 when the Nuclear Energy Act was amended. The amendment in question entered into force in 1996. The only exception is spent nuclear fuel from a research reactor. Spent nuclear fuel from the only research reactor in Finland, FiR 1, was returned to the United States between 2020 and 2021. Until 1996, the spent nuclear fuel from the Loviisa nuclear power plant was returned to Russia.
In a year, the amount of spent nuclear fuel accumulating in Finland corresponds to approximately 100 tonnes of uranium. By the end of 2022, a total of 16,100 bundles, which correspond approximately 2,400 tonnes of uranium, had accumulated in Finland as a result of use of nuclear energy.
In a reactor, uranium fuel is used as bundles of fuel rods. The uranium is in the form of ceramic pellets inside the rods. Each bundle is about three to five meters long and contains between 120 and 540 kilograms of uranium, and there are a few hundred bundles in each reactor. Each bundle is replaced after a few years of use. U-235, the fissile isotope of uranium, is initially present in the fuel in a proportion of about 3-5%, and over the lifetime of the fuel, its proportion decreases to about the same level as natural uranium.
Spent nuclear fuel is still mainly uranium (95%), even though the uranium also produces different fission products in the reactor, as well as some other substances, such as plutonium.
Fuel bundles are cooled down before disposal
Fission reactions in spent fuel outside the reactor core are prevented by ensuring the proper conditions for handling and storing the fuel bundles. The spent nuclear fuel includes significant amounts of radioactive substances. The radioactive substances decay and emit radiation and heat. Therefore, spent nuclear fuel must be cooled even after it has been removed from the reactor core and must be handled in a way that ensures effective radiation protection.
Fuel bundles used in Finland are transferred from the reactor core to water-filled pools in the reactor building to cool down for a few years. After a year in a pool, the radioactivity of fuel bundles has decreased to a hundredth of the level compared to the moment of removal from the reactor core. After the cooling phase, the fuel bundles are transferred in transport casks to interim storage on site, awaiting disposal in the bedrock. The interim storage period is typically some tens of years.
In some countries spent fuel is reprocessed. During reprocessing, the usable uranium and plutonium are separated from the spent nuclear fuel for further use in new fuel elements. Reprocessing does not eliminate the need for disposal, even though it reduces the volume of the waste. The process always leaves some high level waste that has to be permanently disposed of.
Finland does not have a reprocessing facility for spent nuclear fuel and construction of such a facility is not technically and economically viable. Moreover, according to the Finnish Nuclear Energy Act, spent nuclear fuel cannot be exported for reprocessing.
Further information: linda.kumpula(at)gov.fi