This article was first published in the May 2016 issue of WIRED magazine. Be the first to read WIRED's articles in print before they're posted online, and get your hands on loads of additional content by subscribing online.
Stuck with thousands of tonnes of old radioactive material? Bury it underground, says the Finnish government. It has just approved a €3 billion (£2.3bn) project to do just that - after more than 30 years of planning. "That budget includes the operating time of about 100 years," says Erkki Palonen, senior vice president at Posiva, the firm building the repository.
The island of Olkiluoto is the preferred site thanks to a mixture of hard rock underfoot and willingness from the local community. Tunnels will be drilled into bedrock at a depth of between 400 and 450 metres, and spent nuclear fuel will be placed into 5cm-thick copper canisters at a special above-ground encapsulation facility. The canisters will be purged with argon gas to displace any internal moisture and then sealed by electron beam welding.
Ultrasound and X-ray scans, among other inspections, will be performed to ensure the canisters are secure. Then they will be transported to the disposal holes along underground tunnels and packed in with "buffer blocks" of bentonite clay. Finally, the holes are plugged with concrete. Once the repository is full, sometime after the year 2120, all tunnels will be closed and the buildings above ground dismantled.
Storing spent nuclear fuel underground is not popular with everyone, given that no-one knows whether such a facility will remain leak-free for millennia. And the Swedish Radiation Safety Authority recently published a report suggesting the copper canisters may not be quite as immune to corrosion as hoped. "Copper was selected because of its non-corrosive characteristics, so it was kind of a surprise," says Palonen. Further studies, he says, are ongoing. Still, Posiva insists that conditions for such corrosion won't be possible at the repository.
This article was originally published by WIRED UK
