Federal Office for Radiation Protection backfills area of Asse that is no longer used with concrete

Today, the Federal Office for Radiation Protection (BfS) starts backfilling an area of Asse where no radioactive waste is stored and which is no longer used. Solely cavities below the emplacement chambers and in a depth of 850 m are backfilled with a special type of concrete (so-called Sorel concrete). The objective is to fill up open cavities. The licences required for these works have been granted. These works do not compromise any of the decommissioning options currently being examined.

The former operator had planned to backfill the cavities in a depth of 850 m with loose salt and liquid – a so-called "protective fluid”. BfS will now backfill the remaining cavities with Sorel concrete. Sorel concrete is swellable and hardens quickly. The purpose of this measure is to reduce open cavities and to contribute to the stabilisation of the mine.

Other components added to the concrete are saline solutions flowing into the Asse mine from the adjoining rock. The solutions used are solutions which are not delivered to the Mariaglück mine on account of the negotiated environmental agreement of BfS.

To prepare the works, available pumping equipment was technically converted and the system control was expanded. In a first step, the operational capability of these devices is inspected before the Sorel concrete is produced and used in normal operation. Initially, a cavity with a total volume of approximately 4,000 cubic metres is backfilled.

Furthermore, BfS plans a larger programme for the stabilisation of the mine (“backfilling of roof clefts”), within the scope of which it is intended to backfill cavities in the chambers located in the southern flank. Corresponding applications were filed at the Landesamt für Bergbau, Energie und Geologie Niedersachsen (LBEG).

After the waste stored in emplacement chamber 7 has been secured against pieces of rock falling down, BfS has evaluated the situation in emplacement chamber 5 in a depth of 750 m which has not been sealed either. The examination has not yet been concluded. Currently, BfS examines whether it is necessary to cover the waste in chamber 5 or whether it needs to be sealed with a concrete plug.