A final resting place for nuclear waste: Finland to open world’s first high-level nuclear waste depository

As we think about the transition to low-carbon energy infrastructure, the role of nuclear energy is one that is increasingly questioned. It currently provides about 10% of the world’s electricity and is generally seen as one of the ‘cleanest’ forms of energy. However, it has a high cost and takes a long time to build, and there are often concerns about the safety of reactors. There’s also the unresolved issue of what to do with the waste produced – this material is radioactive, and thus remains dangerous to the environment and human health for hundreds of thousands of years. Thus, its management is a major issue.

As of 2016, there are around 260,000 tons of spent nuclear fuel in interim storage around the world, but it’s a situation that cannot be maintained indefinitely. Thus, a new permanent storage solution needed to be found, and it looks like Finland might have discovered an answer. Its Geological Disposal Facility (GDF), a geological repository for high-level radioactive nuclear waste for civilian operations, is shortly to be completed in a world first, 23 years after plans were first approved. The Onkalo site cost around €1bn to build, and it has already been hailed as a game changer by many, including the International Atomic Energy Agency (IAEA). What makes it different, and will it work?

Typically, the waste is difficult to manage because it produces a radiation level that could prove lethal to a nearby person

‘Onkalo’ is a Finnish word meaning ‘cave’ or ‘hollow’, the idea being that it implies something big and deep – it is impossible to know where an onkalo ends, or whether it ends at all. The Onkalo site lies about 450m deep inside the bedrock of Olkiluoto island in the southwest of Finland, and the motivation for building the storage site here is that it is also home to three nuclear reactors. The third was launched earlier this year, the first new reactor to provide power in Western Europe in 15 years, and these three reactors (alongside two others in Loviisa on the south coast) produces around a third of the country’s electricity.

What exactly is Onkalo? It’s a different solution to the spent fuel problem – typically, the waste is difficult to manage because it produces a radiation level that could prove lethal to a nearby person. Waste has been placed in storage ponds and concrete-and-steel containers known as dry casks. Onkalo offers another approach, placing the waste within a stable rock formation and then building two other barriers to surround it. The Onkalo bedrock’s conditions are very favourable, especially as it is very stable geologically and at low risk of earthquakes – it is a barrier against the radiation, but the rock must also be stable enough to allow the construction of deposition tunnels and holes deep below the ground.

Finland has set an example to the world of what can be achieved with successful cooperation and transparent communication with the public

–Lewis Blackburn, Lecturer in Nuclear Materials at the University of Sheffield

Discussing the impact of nuclear energy, Lewis Blackburn, a Lecturer in Nuclear Materials at the University of Sheffield, said: “We’ve all benefitted from nuclear energy for over 60 years. It’s our generation of scientists’ and engineers’ responsibility to undertake the challenge to dispose of the waste, instead of leaving it to future generations.” He noted that Onkalo has public support and was created through a democratic process: “It’s exceptional and a huge milestone. Finland has set an example to the world of what can be achieved with successful cooperation and transparent communication with the public.” The fact that the site is based so close to existing nuclear facilities reduced the risk of the local opposition that normally accompanies nuclear construction.

This is not to say that there is universally positive reception to this news. There has been a debate over the fact that Onkalo will take spent fuel rods without reprocessing them first. Some scientists say that reprocessing would reduce the overall volume of waste and make the remainder safer, while others say that it increases the risk of nuclear terrorism and that sufficient waste is produced to require a disposal facility anyway. There were also doubts raised about the corrosion resistance of one of the three barriers, made of copper – researchers at the Swedish Royal Institute of Technology (KTH) suggested it might corrode under the conditions of Onkalo, something that developers Posiva have disputed but which had already delayed plans for a similar repository in Sweden until January last year.

It has been suggested that the site will fill up in around 100-120 years, but that the waste should be safe for at least 100,000 years. The Finnish and the Swedish repositories might provide a hint as to dealing with nuclear waste in the future (and France is likely to open similar sites by the 2030s), but they aren’t the only strategies – Norway is considering deep borehole disposal, where waste would be lowered in canisters to a much deeper site in thin boreholes. But the level of proactivity shown by these countries is not echoed by many others, and there are fears that the political issue might be kicked down the round for future generations once the financial costs start to weigh on the decision-making process.