Seventeen tons of molten copper. In a foundry in Pori, Finland, something important has just happened for the future of radioactive waste: the first casting of metal destined to create containers that will have to last for 100 years. It is not a laboratory experiment, but the first concrete step towards the “definitive” (inverted commas) solution to one of humanity’s most complex problems.
The world is still arguing about where to put its nuclear waste, but the Finns have already started producing the “copper coffins” that will protect it for millennia.
Copper that challenges eternity
Jouko Lammi, container production coordinator at Posiva the company that deals with it, does not hide its satisfaction: "The casting was a great success". Behind this apparently simple sentence lies a goal that the nuclear industry has been pursuing for decades. Copper was not chosen at random: it is one of the most stable metals on Earth, capable of resisting corrosion for geological times.
The casting will produce the first of six containers planned for this experimental phase. Each canister will have 5-centimeter-thick walls and will house 12 spent nuclear fuel elements inside a cast iron core. The initial weight of 17 tons will be reduced to about 12 after processing: excess copper is removed during the shaping and quality control process.
THERadiological and Nuclear Safety Authority of Finland (STUK) personally supervised the process. And I would like to say: this copper will have to prove itself worthy of a mission that will span an incredible time.
Radioactive waste, the repository that thinks in millennia
The containers are intended for Onkalo, the world's first permanent geological repository for radioactive waste. Located 450 meters underground on Olkiluoto Island, this labyrinth of tunnels is Finland's answer to the problem of nuclear waste.
The concept is simple: three successive barriers to isolate the radioactive material. The gneiss bedrock provides the outer protection, bentonite (a clay that swells when in contact with water) acts as an intermediate buffer, and copper containers form the last line of defense.
Construction of Onkalo has been underway since 2004, but the operational phase is only now beginning. The first containers of radioactive waste will arrive at the repository by 2025, starting a filling process that will last about a century.
Radioactive waste, the long march towards 2120
When Onkalo is completely filled, around the 2120, will house approximately 6.500 tons of spent nuclear fuel. At that point, the entire structure will be sealed and abandoned. No signs, no monuments: the goal is complete oblivion.
The research published in several international scientific journals confirms the soundness of the Finnish approach. Studies show that even in the event of water infiltration, radiation release would remain within safe limits.
This is not to underestimate the challenge. One hundred millennia is a time span difficult to conceive: by the time these containers complete their mission, our civilization will likely be unrecognizable.
The legacy for posterity
Finland is addressing pragmatically an issue that other countries continue to postpone. Italy, for example, has yet to identify the site for its national repository, and 235 tons of Italian waste are waiting to return from France and the United Kingdom.
The Finnish project shows that a definitive solution is possible, but it requires a very long-term vision and a social consensus that is difficult to obtain. The local population accepted Onkalo also thanks to the transparency of the process and trust in scientific institutions.
One curious detail remains: how to let the inhabitants of the Earth know in 100 years what is hidden under their feet? The designers considered several options, from monoliths with multilingual inscriptions to more creative signaling systems. In the end, however, they chose the path of silence: better to focus on the effectiveness of the barriers than on messages that could be incomprehensible.
A hundred thousand years is a long time, but sooner or later they will end too. And by then, let's hope our descendants have developed better technologies to manage the legacy we are preparing for them. In the meantime, Finnish copper will do its job, one atom at a time.
