NUCLEAR

Finland buries its waste

Does the disposal of radioactive materials in geological formations really enable them to be stored safely for several hundred thousand years? Two countries have taken the plunge: the United States, with its Yucca Mountain Repository, and Finland, which is generally considered to be the world’s geological-storage pioneer.

Les travaux de creusement en cours du dépôt souterrain finlandais d’Onkalo atteindront en 2008 une profondeur de 300 m, soit les trois quarts du niveau prévu pour le stockage des déchets radioactifs. Les dernières études sur la fiabilité géologique du confinement seront alors entreprises <em>in situ </em>avant toute mise en opération. © Posiva
The work currently under way to excavate Finland’s Onkalo underground storage facility will have reached a depth of 300 metres in 2008, that is to say, three-quarters of the planned depth for the disposal of radioactive waste. The final studies on the safety of geological containment will then be conducted in situ before the facility is allowed to enter into operation. © Posiva

Radioactive waste is extremely bulky. Although, according to French Atomic Energy Commission figures, it represents less than one kilogram per inhabitant per year in France (the country with the highest nuclear-electricity share in the world), the planet as a whole produces a massive 12 000 tons of high-level radioactive waste every year, mainly in the form of spent nuclear fuel from the reactor core. Finland’s definitive solution is to bury spent fuel 500 metres below ground level, in the deep geological formation of crystalline rocks in the Baltic Shield, which is reputedly free of seismic activity. The site is in western Finland, close to the Olkiluoto nuclear power station. Work started in 2004 with the construction of a rock characterisation laboratory to verify the underground rock’s properties and behaviour.

“The nuclear fuel rods will be placed inside six-metre-tall copper containers measuring one metre in diameter, coated in a 35-centimetre layer of bentonite, a natural type of clay. After the storage facility comes into service in 2020, it will be filled gradually over a period of 100– 120 years”, explains Tero Varjoranta, Director of the Nuclear Waste and Material Regulation Department of the Finnish Radiation and Nuclear Safety Authority (STUK). The facility will be the final resting place for spent fuel from Finland’s two existing power stations, Olkiluoto and Loviisa, as well as from the future European pressurised water reactor planned for 2011.

In 2001, virtually the entire Finnish parliament endorsed the decision in principle to construct the site, bringing to an end a debate that had begun in 1983. “The 1994 Nuclear Energy Act stipulates that all nuclear waste produced in Finland shall be stored in the country. The company Posiva, project manager of the works, was created in 1995 jointly by TVO and Fortum, the firms that manage Finland’s two Finnish nuclear power stations. It is therefore the industries producing the waste that finance long-term waste management, according to the polluter-pays principle.”(1) The basic principle for the permanent disposal of irradiated nuclear fuel is to isolate it for an unbelievably long time: “When spent fuel leaves the power station, it is four million times more radioactive than natural uranium.

It only returns to the background level of radioactivity after 250 000 years.” Safety will be maintained entirely passively, without human intervention. “The copper, bentonite and uranium used for storage are naturally occurring materials; we know how they have behaved for millions of years. It would be problematic for us to integrate artificial titanium structures, as it is still too soon to assess their safety.” Advocates of this technology see it as a sort of return to nature. Since it is not possible to predict the evolution of human society so far ahead, the odds are that the very existence of the site will be forgotten. In any case, the knowledge of its whereabouts will be preserved for the first 350 years, during which time the radioactivity level will be monitored from the Earth’s surface. Does this comply with the ethic of sustainability, which requires that the planet should be left clean for future generations?

In any case, the Finnish initiative has created a precedent and is ahead of other more futuristic solutions such as transmuting long-lived waste into short-lived elements. This new alchemy will perhaps come to supplement another type of transformation: converting today’s waste into the fuel of tomorrow for the fourth-generation reactors that are expected to spring up in the 21st century.

Axel Meunier

  1. All quotes are from Tero Varjoranta


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