Influent solution in front of emplacement chamber 8 increases
No indication of generally increased inflow of water into the Asse mine
According to most recent measurements, the volume of the radioactively contaminated saline solution being collected in front of emplacement chamber 8 on the 750-m level of the Asse mine has doubled from eight to sixteen litres per day compared to the volume measured half a year ago. This must be considered in relation to the current, daily inflow of uncontaminated saline solution amounting to approximately 12,000 litres. The radiological analyses carried out on a regular basis show that the activity concentration of caesium-137 has increased from 4.3 to about 10.5 kilobecquerel per litre since December 2010.
Classification of this value: Permitted is the handling of a radioactivity concentration which is about 120 times higher. Those solutions that need to be pumped out of the collecting point are intermediately stored underground in containers. Already in December 2010, the BfS had observed and reported an increase in the influent solution. The increase of the inflow in front of chamber 8 detected does not indicate a possible overall increase in the inflow of saline solutions into the Asse, however.
The detected increase is no indication for a requirement of changes to the protection concept or the plans for the first step of the fact-finding. For precautionary reasons, the BfS had already based its calculations on significantly higher loads in order to be able to respond to unfavourable developments. The same applies to precautionary and emergency measures for the protection of staff and population which were presented by the BfS in March 2010.
Regarding the retrieval of the radioactive waste the BfS is currently carrying out a finding of facts to be able to state the necessary safety requirements for the procedure. The findings in front of chamber 8 are taken into account.
The contaminated solutions from the overburden go through an emplacement chamber where radioactive waste is stored. On their way they take up radionuclides. In chamber 8, 11,278 waste packages containing low-level radioactive waste have been stored. The increased inflow of solution through emplacement chamber 8 is probably associated with the backfilling of the adjacent chamber 9 (where no waste is stored) by the former operator HMGU which had been responsible until 2008. In front of chamber 9 different volumes and chemical compositions of the influent saline solutions were already observed in autumn of 2009.
As to whether the volume of contaminated solution will continue to increase, cannot be prognosticated. Already some time ago, the BfS had started to examine measures that are to prevent groundwater from flowing into the emplacement chambers. The measures comprise drillings with the help of which one wants to try to collect the groundwater at the next level. Meanwhile the works have been approved by the competent Landesamt für Bergbau, Energie und Geologie and will be implemented as soon as possible. They are a component of the so-called emergency planning of the BfS.
Update 27 July 2012:
The volume of influent solution in front of chamber 8 is currently about 14.6 litres per day. On a daily basis, the volume of influent solution varies only slightly. The activity concentration of caesium-137 is 14.0 kilobecquerel per litre or, respectively, 11.1 kilobecquerel per kilogram (kBq/kg), as of June 2012. Permitted is the handling of a radioactivity concentration which is about 90 times higher (1,000 kilobecquerel per kilogram – the 100-fold of the exemption limit of the StrlSchV, Annex III, Table 1, Column 3)..
The works at the drillings that are to help collect the groundwater at the level above the 750-m level have been approved by the Landesamt für Bergbau, Energie und Geologie and are being implemented currently.
Update 27 March 2014
Currently the volume of influent solution in front of emplacement chamber 8 is 12.6 litres per day. It has decreased again after it had increased for a short period of time in January to 14.3 litres per day. Altogether a trend can be observed since July 2012 that the inflow rates at the place of inflow decrease, although the rates in particular for January but also for February 2014 do not follow this trend. The activity concentration of caesium-137 is currently ca. 11.5 kBq/kg (kilobecquerel per kilogram). For the Asse II mine, handling is permitted with a radioactivity concentration of up to 1000 kBq/kg, the 100-fold of the exemption limit set out in the Radiation Protection Ordinance (StrlSchV, Annex III, Table 1, Column 3). For tritium, an activity concentration of ca. 2,000 kBq/kg was measured. The 100-fold of the exemption limit is here 100 million kBq/kg.