"We are 300 meters underground in a dug laboratory" to study the burial of radioactive waste in clay, explains geologist Christophe Nussbaum, head of the international laboratory of Mont Terri, near St-Ursanne in the canton of Swore.

Three sites in the north-east of Switzerland, close to Germany, are in the race to receive this waste.

Plant operators are expected to announce their preference in September.

The government will decide in 2029, but opponents could launch a referendum.

The center of Mont Terri is actually made up of 1.2 km of galleries dug into the rock.

Niches, whose walls about 5m high are stabilized with shotcrete, house various storage simulations, thanks to small quantities of radioactive elements monitored by thousands of sensors.

More than 170 experiments were carried out to simulate the different phases - placement of the waste, sealing of the galleries, monitoring - and to reproduce all the physical and chemical effects imaginable.

8,000 generations of human beings

According to experts, it takes about 200,000 years - or about 8,000 generations of human beings - for the radioactivity of the most toxic waste to return to its natural level.

But the researchers, indicates Mr. Nussbaum, analyze a storage whose duration is estimated at approximately “a million years, since it is the duration for which one must ensure a safe confinement”.

So far the "results are positive".

For Greenpeace, Switzerland is moving too fast.

"There are a myriad of technical questions that are unresolved: that is, the guarantee that the system will not lead to releases of radioactivity, whether in 100, 1,000 or 100,000 years", indicates to AFP Florian Kasser, responsible within the NGO for nuclear issues.

"We put the cart before the horse because without having resolved heaps of questions we are looking for sites", he continues, believing that Switzerland should also first decide how the site would be reported so that not be forgotten and that the generations of the centuries to come are aware of the danger.

Horizon 2060

In Switzerland, radioactive waste has been produced for more than 50 years in power plants, and is managed by the National Cooperative Society for the Storage of Radioactive Waste (Nagra), founded in 1972 by the operators of nuclear power plants and the Confederation.

For now, they are in an "intermediate depot" in Würenlingen, about 15km from Germany.

Very few countries are at advanced stages in deep geological disposal.

Only Finland has built a site (in granite), and Sweden gave the green light at the end of January to the burial of waste, also in granite.

Next comes France, whose Cigeo project, led by the National Agency for Radioactive Waste Management (Andra), plans to store radioactive waste underground in Bure (Meuse), in clay rock.

“We are awaiting the declaration of public utility, and at the same time we will submit a request for a building permit”, explains Andra spokeswoman Emilie Grandidier during the visit to Mont Terri.

Following the nuclear accident at the Fukushima power station, Switzerland decided to phase out nuclear power, but gradually: the four reactors used can be used as long as the power stations are safe.

About 83,000 m3 of radioactive waste, including a minority of high activity, will have to be buried.

This volume corresponds to the scenario of a 60-year operating life of the Beznau, Gösgen and Leibstadt nuclear power plants, as well as 47 years of that of Mühleberg closed at the end of 2019.

Landfill work should begin by 2060.

"It's the project of the century: for 50 years we have carried out scientific research, and we now have 50 years for the authorization and the realization of the project", indicates Felix Glauser, spokesperson for Nagra.

The monitoring period will span several decades before the site is sealed in the next century.

© 2022 AFP