The height of all the buildings and structures is +10 metres above sea level. Even a 10-metre rise in sea level would not constitute a major safety risk, as Posiva only handles cooled fuel and only in small amounts for short periods at a time. Once the fuel is placed in the transport cask or in the final disposal canister, it is safe from natural disasters.

Posiva Oy was founded to carry out the final disposal of spent fuel on behalf of its owner companies, TVO and Fortum Power and Heat Oy. All the expertise in final disposal of nuclear fuel gathered in the founder companies over the decades was transferred to Posiva, when it was founded. No public funding has been or will be used for the operation of Posiva. Read more on Posiva's web site.

An earthquake would probably not affect final disposal at all. The final disposal facility is built inside an intact bedrock block and the stresses caused by the movement of the earth's crust will be relieved along existing block boundaries, while the actual block remains intact. Olkiluoto bedrock is stable and about 1800 million years old.

Isotope U-235 of uranium changes in the reactor into fission products. They are the reason for the strong radiation of spent fuel. Substances that are heavier than uranium are also formed in the fuel, such as plutonium. Otherwise the fuel assembly remains unchanged in size and in practice weighs as much as when loaded in the reactor. Fresh assemblies are shiny, but the oxide layer forming on the surface of the assemblies during the four-year fuel cycle makes them dark.

Spent fuel from Olkiluoto will be emplaced for final disposal in the final disposal facility to be constructed in Olkiluoto by Posiva Oy for its owners TVO and Fortum. Final disposal is based on the use of multiple release barriers, which guarantee that nuclear waste cannot come into contact with organic nature or anywhere near people. These barriers include the state of the fuel, the final disposal canister, the bentonite buffer, the backfilling of the repository tunnels and the surrounding bedrock. Read more on Posiva's web site.

Even a rich natural uranium deposit is dangerous in terms of radiation. Spent fuel begins to resemble a rich uranium deposit after a few hundreds of thousands of years. The penetrating gamma radiation disappears from spent fuel in a few hundred years. The multiple barrier system used has been designed to guarantee that the spent fuel does not constitute a safety risk to future generations. The final disposal repository will be closed in a way that makes it possible for the normal life of society to go on above the repository. Read more on Posiva's web site.

Waste generated in the operation of the plant is primarily categorised as low and medium-level waste. Nuclear fuel is categorised as high-level waste.

The fuel can be recycled by separating components suited for reuse from the fuel. The amount of high-level waste can be reduced through reprocessing, but its radioactivity cannot be influenced with the methods available at present. Fuel is not being reprocessed in Finland.

By virtue of the Nuclear Energy Act, spent fuel may not be exported and there are no reprocessing facilities in Finland. The price level of reprocessing at present also makes it an uneconomical alternative for Finnish nuclear power plants. The amount of spent fuel generated in Finland is so small that reprocessing is not economically viable.