In preparation for the creation of a final repository for nuclear waste in Switzerland, Nagra has studied sediments deposited in the depths of ancient glacial lakes, 600,000 years old. Good news: these layers have never been eroded by ice.
A final repository for nuclear waste must be safe, even if in the very distant future glaciers in the Alps were to advance again to the Swiss Plateau, the Eawag Water Research Institute said in a report on Tuesday. press release.
A research team also including scientists from ETH Zurich and the universities of Basel and Bern analyzed sediments extracted by the National Cooperative Society for the Storage of Radioactive Waste (Nagra) near Bülach in the Zurich region.
The core, 278 meters long, traces almost the entire geological history of the Quaternary, i.e. the last 2.6 million years. The scientists were particularly interested in the sediments deposited in an elongated lake which must have extended to Bülach, a kind of paleo-Greifensee.
This trough was first dug by Alpine glaciers, before being filled with sedimentary deposits. Two questions then arose: how old is this trough? And was it emptied during subsequent glacial advances?
Indeed, even if current climate signals indicate warming, a new cold period could occur in the future. A deep storage site for radioactive waste must remain safe for a million years, even in the face of further glacial advances.
No further erosion
To determine the age of the sediments, the scientists used a sophisticated method that relies on the concentrations of helium-4 in tiny amounts of water contained in the sediment’s pores.
According to these results published in the journal Geology, the sedimentary layers of the paleo-Greifensee date back around 600,000 years. They are therefore significantly older than the advances of the last ice age.
Described as the Strassberg trough by specialists, this basin has ceased to be eroded. The clay level at Opalinus, located more than 500 meters deep and deposited around 174 million years ago, has remained intact.
In other words: according to current knowledge, even an exceptional advance of the Rhine and Linth glacier, coming from Graubünden and the canton of Glarus, would not be enough to dislodge the nuclear waste possibly deposited in the clay at Opalinus.
On November 19, Nagra must submit its request for authorization to the Confederation for the construction of the depot planned on the northern slope of the Lägern massif. The choice of a site in Stadel (ZH) dates from September 2022. The start of construction work is planned for 2045.
This article was automatically published. Source: ats
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