Enhanced caesium activity in a control drilling
No additional risk for staff and environment
In a control bore hole that had been set up by the former Asse operator Helmholtz Zentrum München (HMGU) the Federal Office for Radiation Protection (BfS) detected an enhanced activity of caesium-137. The BfS carried out the measurement near the so-called brine swamp in front of emplacement chamber 12 in a depth of 750 meter. In the bore hole there is approximately one litre of radioactive brine which escaped from the waste chamber. Approximately 240,000 becquerel per litre were measured. The BfS has been granted a licence to handle these radioactive brines. The basic situation in the Asse mine and the running decommissioning procedure for the Asse mine are not affected by the enhanced measured levels. Neither the staff nor the population in the vicinity are at risk.
There is nothing new about contaminated brine in front of chamber 12. Already in 2008 the former operator of the facility measured an activity concentration of approximately 90,000 becquerel per litre in the same bore hole. Thus the activity concentration at this measuring point has increased, however, the brine is not among those saline solutions that enter the mine from the outside but have been emplaced in the mine together with waste material. Liquid escaping from the chamber has been concentrating in front of chamber 12 in the so-called brine swamp for years. It has been ensured that all protection measures are being taken and observed that are required for the safety of the staff. A release of the substances into the environment can be ruled out. The exact origin of this local contamination within the Asse II mine is currently still under investigation. In all probability it originates from waste chamber 12 or, respectively, the neighbouring chamber 11.
In addition to caesium-137 also the radionuclide cobalt-60 was measured in the brine. However, only a low level of cobalt-60 has been measured, amounting to 10.5 becquerel per litre.