Results of the first drilling and further approach

A measuring probe is placed into the drilling

The first of the planned drillings into chamber 7 that started on 1 June runs diagonally to the outer, upper edge of the chamber. Given that the chamber was completely backfilled with salt grit after the end of emplacement operations, there will possibly be a small cavity at this place only. For safety reasons, it needs to be ensured at the same time that no waste is hit directly.

The technically complex drilling was chosen to be the first one, because several objectives can be achieved.

Before the drilling was started, it was uncertain whether there is still a cavity at the upper edge. This will be a result of the current investigations. In the past, the chamber and its position were only depicted in a rudimentary manner and were not documented exactly. The last surveys took place more than 30 years back, not measuring the chamber roof. In this part of the mine there are also very strong deformations causing the salt rock and the chambers to “move” over the years.

Results of the first drilling

In the current procedure of the first drilling, the length of the bore hole was extended several times in order to be able to determine the exact drift of the chamber roof with additional radar measurements. The previously gained results can be summarised as follows:

• The first drilling has reached the upper surrounding of the chamber.
• It has not reached the outer, upper edge of the chamber itself. Accessible information about the chamber from the past is not correct. The so far assumed position of the chamber needs to be revised. The chamber position has further changed through dislocations in the mine, so that one needs to expect that the roof of chamber 7 is below the first drilling, although the drilling has reached the planned site.
• A partial area of the surrounding of the chamber lying underneath the drilling was investigated with the help of radar measurements. The position of the first part of the chamber roof has been determined.
• In order to be able to measure a second part of the chamber position, the drilling is extended to 35 metres and another radar measurement is carried out.
• So far, no cavity has been found during the drilling process.
• The debris produced by drilling was examined for radioactivity. So far, no contamination could be detected.
• The structure of the about 20-metre-thick sealing in front of chamber 7 has been determined for the area the first drilling runs through.

With the help of the information about the actual chamber position gained from the radar measurements, the second drilling can be planned much more exactly by Asse-GmbH.

Further approach

The second drilling was started on 30 April 2013. As the upper edge of the emplacement chamber was reached and the position of the chamber was determined, the second drilling will now be placed in a shallower angle of descent. A drill depth of about 23 metres is planned. Once this depth has been reached, it is planned to carry out a comprehensive measuring and prospecting program. Also in the case of this drilling, it is particularly important not to drill into waste drums.

Furthermore, when carrying out the drillings, the state of the chamber roof is to be examined for damages and permeability and it is to be determined whether radioactivity has been released from the waste drums. With the help of other drillings the pillar loads, tensions and deformations in the pillars beside the emplacement chamber are to be investigated.