Spent nuclear fuel will be disposed of in Finland
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 to this is the spent nuclear fuel from the research reactor FiR 1, which can legally be returned to the United States. 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 65 tonnes of uranium. By the end of 2015, a total of 13,500 bundles, which correspond approximately 2,040 tonnes of uranium, had accumulated in Finland as a result of nuclear energy use. 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 final disposal.
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 four meters long and contains between 120 and 180 kilograms of uranium, and there are a few hundred bundles in each reactor. The fuel is handled as bundles, and each bundle is replaced every three to five years. At that point, the proportion of the fissile uranium isotope U-235 has decreased to the level found in natural uranium.
Spent nuclear fuel is still mainly uranium (96%), even though the uranium also produces different fission products (e.g. iodine, caesium and technetium) in the reactor, as well as some other substances, such as plutonium.
Fuel bundles are cooled down before final disposal
Certain heavy nuclei, such as U-235 and Pu-239, are utilised in nuclear power plants for controlled fission chain reaction for production of electricity. The chain reaction occurs in the reactor core. The spent fuel is removed from the reactor and replaced by new fuel at regular intervals. The fission reactions in spent fuel will be prevented by taking care of the proper handling and storage circumstances in the temporary storages of the fuel bundles.
The fuel removed from the reactor, the spent nuclear fuel, includes significant amounts of radioactive substances. The radioactive substances decay and thus emit electromagnetic radiation and heat. Fuel bundles used in Finland are transferred from the reactor 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 at the moment of removal from the reactor. In principle, the fuel could also be cooled down using gas or air. After the cooling stage, fuel bundles are transferred in transport casks to temporary storage at the plant site, to wait for final disposal in the bedrock. Typical cooling time in intermediate storage is 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 final 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 eventually.
There is not a reprocessing facility for spent nuclear fuel in Finland and construction of such a facility is not techno-economically effective. Nor can the spent fuel be exported for reprocessing, as transferring nuclear waste abroad is forbidden by the Finnish Nuclear Energy Act.
Further information: linda.kumpula(at)tem.fi