Finland has approved the construction of the world’s first permanent nuclear waste disposal facility, which will be able to store the waste for 100,000 years. Built into bedrock, the facility will consist of underground tunnels at depths of between 400 and 450 meters (1,300 – 1,480 feet), which have already been built while engineers were looking into the feasibility of the project. It is estimated that the facility will be able to hold 6,500 tonnes (7,165 tons) of high-level nuclear waste when completed.

Nuclear waste can be divided into three categories: low, intermediate and high-level waste. Low-level waste contains mostly short-lived radioactivity and comes from places like hospitals – usually consisting of paper, clothing, tools and such – and is typically buried. Intermediate-level waste is usually resins and chemical sludge, as well as material from reactor decommissioning, and is normally solidified in concrete or bitumen.

High-level waste is the nasty stuff. This is what remains from the “burning” of uranium, and due to the decay heat, usually needs cooling and shielding. There are currently around 240,000 tonnes (264,555 tons) of used high-level nuclear waste in storage, most of which is still at the site at which it was created. Around 90 percent of this waste is currently held at the bottom of storage ponds covered by between seven and 12 meters (23 – 40 feet) of water. The newly approved site in Finland will encapsulate the fuel in copper-lined containers, cache it in the tunnels, and then seal it in with bentonite clay, a volcanic ash that expands when mixed with water.

Finland currently has four nuclear reactors up and running, which supply 30 percent of the country’s energy, with the rest of the nation’s electricity demand being met by coal and gas from Russia and Poland. The country is also building a fifth nuclear power reactor that, when it was approved in 2002, was the first new nuclear unit to be given the go-ahead in Europe for more than a decade. It has not, however, been without controversy.

Expected to have been completed in 2009, the new reactor, called Olkiluoto 3, still hasn’t been built and has overrun considerably on cost. Expected to finally reach completion in 2018, it’s likely to come in at around £2.7 billion ($4.2 billion) over budget. Ironically, the plant was supposed to be a model construction showcasing how the Generation III reactor can be safe, affordable and delivered on time, which would allow similar reactors to be rolled out across the rest of Europe.

Main image: BBC World Service/Flickr CC BY-NC 2.0