Contaminated brine was already pumped off in 1988
So far it has been known that radioactively contaminated brines were primally relocated in 2005.
Date 2009.02.10
Much earlier than previously known, radioactively contaminated brines were pumped off the so-called “brine swamp” in front of emplacement chamber 12 of the Asse II mine. They were taken to higher-located parts of the mine which were previously considered to be not contaminated with these brines. That is the result of enquiries made by the Federal Office for Radiation Protection (BfS).
As early as in 1988, these brines were pumped off the “brine swamp” in front of chamber 12 on the 750-m level and transported in sheet steel containers with a forklift to chamber 11 on the 700-m level. There the brines were dumped from the containers on the pieces of rock stacked there (the so-called debris) of the partially backfilled chamber.
This has become evident from a miner's report of December 2008 which was submitted to BfS in January and has been evaluated. The amounts in question are not known, neither is it known where the contaminated brines were taken.
Previously one had assumed that radioactively contaminated brine was pumped off the "brine swamp" in front of emplacement chamber 12 on the 750-m level for the first time in 2005. According to examinations carried out by the Lower Saxony Environment Ministry (NMU), the radionuclides contained in these brines very probably originate from the low-level radioactive waste stored in chamber 12. According to information of BfS, the brines that were already pumped off in 1988 were contaminated with radioactive caesium, cobalt-60, strontium-90, and tritium.
Furthermore, solutions of unknown origin from the 750-m level were used between 1984 and 1986. The solutions were said to be used for backfilling a chamber on the 658-m level for dust-collection purposes. Whether these solutions were contaminated is not known so far. BfS currently examines the issue and the question on which licensing basis the measures were carried out.
Background:
The BfS inquiries are associated with the question whether the saline solutions on the 750-m level were contaminated during the transport of waste to the emplacement chambers or whether the drums in the emplacement chambers do currently have contact to saline solutions. Furthermore it needs to be clarified whether the saline solutions on the 750-m level are old so-called “stowing solutions” (as in chamber 12) or whether saline solutions from the southern flank have already found their way into the emplacement chambers. For mining and radiation protection reasons, it is not possible to directly examine the chambers. Therefore, it is necessary to carry out elaborate inquiries in the operational documents and geo-chemical examinations.
Helmholtz Zentrum München (HMGU), who was the operator of Asse until the end of 2008, had started to relocate contaminated saline solutions into other parts of the mine already in 2005, without having been granted the necessary licence for use and manipulation according to Radiation Protection Ordinance. These solutions were clearly above the release levels. The contaminated saline solution was taken through a bore hole from the swamp in front of chamber 12 on the 750-m level to an area in a depth of approximately 975 m. This procedure was stopped on 18 June 2008.