BfS improves stability of Asse
Remaining cavities in salt chambers of the southern flank are filled with special type of concrete.
Today, Asse GmbH started filling residual cavities in some salt chambers with a special type of concrete. The works are carried out in the so-called southern flank of the mine which contains a large number of cavities. According to information provided by the Federal Office for Radiation Protection (BfS) in Salzgitter as the operator of the facility, the deformation of the mine and the risk of an increased inflow of solution are to be reduced through this measure. Only chambers are backfilled where no radioactive waste has been stored.
Since the mid nineties, the empty chambers from former rock salt mining were filled with ground salt. Since this so-called salt grit has slumped over the years, however, cavities have formed between the chamber ceiling (or roof) and the salt. These cavities (roof clefts) are now filled with Sorel concrete. For this special type of mining concrete, magnesium oxide and rock salt are used instead of sand or gravel.
Altogether, one intends to fill the roof clefts of about 80 chambers with Sorel concrete. The chambers to be backfilled are located on the 532-m level. They were drilled into from the 511-m level where there is also a building material facility mixing the Sorel concrete. In two weeks, the roof cleft in the first chamber should be backfilled. By and by, all cavities are filled with Sorel concrete. This is a very laborious process and numerous preliminary and accompanying works need to be carried out. The process of backfilling will last at least until 2011.