There are lot of problems involved in the plans to bury nuclear waste. It can work, provided conditions in the plant and the bedrock stay the way Posiva has assumed for hundreds of thousands of years. But will they?
Phase one – transportation
First the nuclear waste caskets have to be transferred from Loviisa to Olkiluoto by ships, through the vulnerable Finnish archipelago. There has been frequent radioactive contamination on these castor caskets. In Germany and France, measures up to 1000 times above allowed levels have been metered on the surface of caskets.
Shipping of the nuclear waste also risks sinking of the ship. Castor caskets do not stand over 8 hours in the depth of 15 meters or 1 hour in the depth of 200 meters . The mean depth of the Baltic Sea is 54 meters, the deepest point being 450 meters. Nor can they stand temperatures over 1000 degrees produced by ordinary ship fires.
Phase two – capsulation
In Olkiluoto the high level nuclear waste is then taken from the casket in a nuclear waste capsulation plant and placed into specially fabricated steel-copper canisters that are closed by a robot. As the waste is highly radioactive and toxic and usually contains radioactive gases, capsulation plant has to be contained from the environment, in order to avoid radioactive releases to the environment.
Phase three – placing canisters
Canisters are placed into tunnels 500 meters deep into the bedrock of Olkiluoto. The tunnels are supposed to be placed so that they avoid the dense fracture zones in the bedrock of Olkiluoto, which transfer groundwater from the deep to the surface. Because the canisters produce a lot of heat, 100°C for hundreds of years, they are dispersed to a relatively large area, which increases the probability of hitting a fracture zone in the bedrock. The canisters are placed to holes in the tunnels surrounded by a soft clay-like substance called bentonite, designed to protect the canister from water and outside impacts.
Phase three – filling the tunnels and the repository
When all the waste has been transferred, the tunnels will be filled with rock and bentonite, and the repository filled with groundwater. For example cement cannot be used in the repository as it increases the corrosion of the canisters.
Phase four – monitoring
The present plan is to guard the site only 50 years after burying the waste and then close the repository without monitoring. There has also been almost no discussion of how to adequately warn future generations up to 100 000 years to the future about what lies buried inside the repository.
However, there have been demands that the repository should be designed to be reopened later, in case the future generations come up with a better solution of how to deal with nuclear waste. However, presently the costs of retrieving the nuclear waste have been left to future generations. It is also very difficult if not impossible to retrieve nuclear waste if it proves out that it has already leaked to the bedrock. Thus exactly in the situation when the future generations would have to be able to retrieve the waste, they will not be able to do it.
The waste can leak
Nuclear waste can leak to the environment even without human intrusion to the repository. Whole nuclear waste canisters can brake during earthquakes or rock slides caused by ice ages. During the hundreds of thousands of years nuclear waste stays dangerous, several ice-ages and warmer periods, like we presently experience, will take place in the area of Northern Europe. During the last ice-age just 12 000 years ago, a 2 km thick ice sheet was covering Olkiluoto, and then pressing the site under the bottom of the sea for thousands of years. The rise of the bedrock after ice ages can cause earthquakes up to 8 richters in scale. According to international law, it is forbidden to bury nuclear waste under the seabed. This is however exactly what will happen in Olkiluoto after the next ice-age.
Canisters can also brake without earthquakes. Even microscopic holes in canisters can lead to serious leaking of the canisters through corrosion. As not a single adequately dense canister has been produced yet, Posiva is assuming in their reports that around 4 of the at least 1500 canisters in the repository can be leaking already when leaving the factory.
Ground water, which will fill whole of the waste storage, will transfer radioactive substances through large fractures of rock to the surface or the sea. Bentonite is supposed to shield canisters from groundwater. However, the heat from the canister is known to increase the penetration of groundwater through bentonite, thus increasing the flow of radioactive materials. If ice ages cause new fractures to cross the tunnels of the repository this will further increase the flow of radioactivity to the environment. The high salinity of the groundwater in Olkiluoto will also increase the flow of radioactive materials. The impacts of the flow-waters from the retreating and melting glaciers or increased corrosion caused by bacteria in the repository are poorly known.
As a conclusion, the waste solution, which Posiva claims it has, is yet far from being proven. The only solution Finns have to the problems of nuclear waste is the old one: silencing the debate about risks. Risks of burying nuclear waste are largely dismissed in the Finnish media and public discussion. This will not, however, make burying of nuclear waste any safer.