Pressemitteilung Nr. 10/25 - Asse

BGE achieves first success in search for salt water in the Asse II mine

07/29/2025: A significant water flow was found during exploratory work on the changed water flow paths in the Asse II mine.

When drilling exploratory boreholes below the old containment liner at the 658-metre level, the BGE has encountered a significant flow of salt water. As the containment liner had shifted due to rock pressure, the influx of salt water could no longer be collected on the liner. Current findings from radar measurements show that the liner has subsided towards the southern wall, meaning that the salt water is probably not flowing towards the main collection point but rather towards the southern wall and further down.

Exploratory boreholes below the liner had already yielded small amounts of water at the beginning of the exploration. However, it is only now, after the State Office for Mining, Energy and Geology (LBEG) and the Federal Office for the Safety of Nuclear Waste Management (BASE) approved further investigation into the wall, that a regular stream of water has been found in a borehole after a distance of 36 metres. The BGE inspected the borehole using a camera. Images from inside the borehole show salt water streaming in.

In the space of about a week, the BGE was able to pump around 55 cubic metres of salt water out of the borehole. This corresponds to a collection rate of almost 8 cubic metres per day. “We’re relieved to have encountered such a significant amount of salt water at this point. We’re cautiously optimistic – but we’ll only be able to breathe a sigh of relief when there’s a decrease in the influx in the yielding arch support section at the 725 m level. This will still take some time because the salt backfill above that section is saturated and will continue to release water for a while,” says Iris Graffunder, Chair of the BGE Management Board.

The video shows the saltwater flow in the borehole at the 658-metre level.

Flow path found

The first samples of the salt water show that it has the same chemical composition as the water previously collected above the liner. “We now have to wait and see whether the salt water influx in the yielding arch support section decreases to be sure that the influx at the top is also the cause of the volumes of salt water further down in the pit. And we want to check whether there are further water flows underneath the old containment liner along the southern wall. Once all the facts are clear, we’re planning a new technical approach in order to collect the salt water well above the radioactive waste again,” says Jens Köhler, Asse project manager.

At present, the water pumped out of the borehole is channelled through a hose into the storage basin of the former main collection point. Once it has undergone radiological analysis by the Radiation Protection department, the salt water can be pumped above ground and handed over to the chemical industry.

Background

Since October 2024, the BGE has no longer collected salt water at the former main collection point at the 658-metre level. Instead, large quantities of salt water are collected in deeper areas of the mine. These areas are located directly above the emplacement chambers at the 750-metre level.

The yielding arch support section should actually be concreted over as part of the precautionary measures from the emergency planning in order to minimise the spread of radioactivity in the event of an uncontrollable influx of solution. This is not possible at the moment because almost all of the salt water is collected there. If the salt water can be captured stably at higher levels again, the precautionary measures can be implemented at the 725 m level.

About the BGE

The BGE is responsible for proposing the site for a repository for high-level radioactive waste that offers the best possible safety for one million years. It is also constructing the Konrad repository for low- and intermediate-level radioactive waste in Salzgitter. The BGE is decommissioning the Morsleben repository, planning the decommissioning of the Asse II mine following retrieval of the low- and intermediate-level radioactive waste, and closing the Gorleben mine.the emplacement chambers at the 750-metre level.