Gorleben salt dome

The Gorleben salt dome is a salt deposits near Gorleben, Lower Saxony. The deposit is available as a potential repository for high -level radioactive waste in the discussion. Since 1986 a mine was built to explore the suitability of the salt dome for final disposal.

Discussion of the repository

Site selection (1973-1979)

End of 1973, the search began for a suitable repository salt dome. The plan was ( and still is ) a repository for all types of radioactive waste in a salt dome. Were considered 24 salt domes. This also planned nuclear waste disposal center should also be built at the location of the repository. The federal government asked the company KEWA ( nuclear fuel reprocessing company) with this search.

On 1 July 1975, the KEWA struck three salt domes in Lower Saxony in front for a more detailed investigation:

• Lutterloh in South Heath,
• Lichtenhorst in the light peat and
• Delusion in Emsland.

The Gorleben site does not belong in this category best. The investigations of the sites began with holes. In November 1976, the government of Lower Saxony called on the federal government to suspend the investigations at the three sites until it has been designated by from one location.

In February 1977, the government of Lower Saxony finally named the Gorleben salt dome as a single location for the repository and the waste disposal center. The definition of Gorleben was preceded by the work of a project group, which examined 140 salt domes within a few months. Four of these salt domes remained: Lichtenhorst, delusion, Mariaglück ( Höfer in the district of Celle ) and Gorleben.

Of these, Gorleben was chosen. The selection criteria were, among others, existing land use, population density, radiation protection and disposal geology. Today, it should be noted that geoscientific arguments were at low priority. Unlike, for example, not understanding why the salt dome Höfer ( Mariaglück ), which is much too small has come for a repository, to the last selection round. The final decision for Gorleben has fallen after the then Prime Minister of Lower Saxony Albrecht mainly from structural reasons for the economic development of the former border zone area. Security-oriented geoscientific arguments did not play the main role in setting to Gorleben. How is the one involved in the site selection geologist Gert Lüttig recalls, and its proximity to Morsleben and located there in the construction DDR repository played a role.

About -day exploration (1979-1983)

The above-ground exploration of the Gorleben site began in April 1979 and lasted until 1983. Several additional above-ground work was carried out according to the German reunification from 1992 on former GDR territory. Already towards exploring to protests organized by local opponents of nuclear power, the 1979 and 1980 occurred at the Tiefbohrstellen 1002 and 1003. On May 3, 1980 occupied about 5,000 opponents of nuclear power in the Cernosin Tiefbohrstelle 1004, the Republic proclaimed Free Wendland and build a hut village, which admitted the police on June 4, 1980.

The tests consisted primarily of 44 salt mirror drilling, geophysical investigations, including seismic reflection measurements, hydrogeological investigations ( approximately 500 exploration and level holes ), four deep wells up to 2,000 m in the marginal zones of the salt dome, two Schachtvorbohrungen to about 1000 m depth to confirmation of the selected slot starting points, a seismic station network for monitoring seismic activity and a variety of other studies, for example, long-term pumping tests, hydrological studies on the receiving waters and geological mapping.

The exploration results and their evaluation were summarized in two reports by the Physikalisch -Technische Bundesanstalt ( 1983) and the Federal Office for Radiation Protection ( 1990). Despite the negative findings exploring the Gorleben site was still called " eignungshöffig ". This was achieved by a change in the safety philosophy: the importance of the overburden as a barrier against the spread of radionuclides was withdrawn and considered in turn, the salt dome alone as a major barrier. Based on this change in the safety philosophy began with the underground exploration. After researching the Frankfurter Rundschau - published in 2009 - was this reduction in security requirements back to a direct influence of the then new CDU / FDP government of Helmut Kohl.

Underground Exploration (1986-2000)

In 1986 the Sinking of shaft 1, and the breakdown took place in October 1996 between the shafts 1 and 2 on the 840 m level. The main objective of the underground exploration is the detection of rock salt, which are needed for the disposal. Here, the location and extent of Hauptanhydrits and Kaliflözes Staßfurt are significant because they represent limitations for final disposal appropriate areas of the salt dome. In particular, the main anhydrite is considered because of its widespread gap formation as a potential solution bringer, through which the repository can drown.

The exploration area 1 is largely open and examined. It was led by comprehensive geoscientific and geotechnical investigations and mining technical measurements and tests.

Moratorium (2000-2010)

In the agreement between the Federal Government and the power companies on 14 June 2000, a moratorium on the planned Gorleben was agreed in addition to the phase-out of nuclear power use. After exploring in Gorleben for ten years was ( October 2000-September 2010 ) interrupted to clarify conceptual and safety-related issues. The mere maintenance costs amounted annually at this stage at 22 million euros.

The final synthesis report of the Federal Office for Radiation Protection was published in 2005. In December 2006, the then Federal Environment Minister Sigmar Gabriel pointed out that he would resume the exploration of Gorleben, if his concept for comparison of locations will be accepted.

After assertion of the Frankfurter Rundschau on May 2009 there is an internal paper of the Federal Office for Radiation Protection, according to the " already begun to expand into a repository in parallel to explore " was. This message came across a wide coverage in the public and especially among the opponents of a repository Gorleben. However, the Federal Office for Radiation Protection denied the existence of the alleged paper and pointed out that a statement regarding the suitability of the salt dome could be taken to a disposal site at the earliest in 15 years.

On 1 October 2010, the exploration moratorium by Federal Environment Minister Norbert Röttgen was lifted.

Results of the tests

The results of the above-ground investigations have been summarized in two reports by the Physikalisch -Technische Bundesanstalt ( 1983) and the Federal Office for Radiation Protection ( 1990). It states (PTB 1983): " A first assessment of the overburden in terms of its barrier function for potential contaminated groundwater shows that occurring over the central portions of the Gorleben salt dome clayey sediments have no such thickness and continuous distribution that they would be able to prevent contamination permanently from the biosphere. "

This review is still true today and will be complemented by other negative site characteristics, such as anticipatory selective Subrosion, the Gorleben channel with a filling of massive groundwater conducting quaternary sediments of the Elster time, short maturities of the underlying water from the salt dome top to the biosphere. The expectations of the barrier overburden were not met. According to these findings, the importance of the overburden was withdrawn as a barrier against the spread of radionuclides by the Cabinet Kohl and explains only the salt dome alone the decisive barrier.

The results of the subsurface investigation can be summarized by the Federal Institute for Geosciences and Natural Resources (BGR 1998) as follows:

• In the boundary between the core zone and the southern salt dome flank the layers involved are highly deformed and reduced in thickness. Area- missing Hauptanhydrit and accompanying layers. The main anhydrite is broken down into individual floes. Larger insulated solutions and gas reserves are possible in the Hauptanhydritschollen.
• Between the core zone and the northern flank of the salt dome limit is pleated, and the layers involved are still largely in their original sedimentary association. The main anhydrite is fractured, but not broken down into individual floes.
• Core zone of the salt dome with main salt: Here there is a wide saddle with no solution and gas deposits.
• In the bay -related areas located in the border area Zechstein 2/ 3 Zechstein before an intense folding of the layers with high thickness reduction. In the border area of ​​the Kaliflözes Staßfurt the Zechstein 3 partial disturbances are that are healed by secondary rock salt. Limited solution and gas deposits can occur in the interference environment, but have no connection to the salt levels.

With these results for the exploration area 1 is true for the northern and southern boundary of the main salt that for the scenario " continuous Hauptanhydrit the salt levels up to the exploration area and thus a potential solution Bringer" so far there are no clues. A suitability of Gorleben can not be derived. Particularly when considering the results of surface exploration, the location of many is assessed as unsuitable. Then the negative characteristics of the overburden should not be outweighed by the good properties of the salt dome itself.

Controversies

The moratorium was used to clarify conceptual and safety-related issues. These do not affect the suitability or otherwise of Gorleben, but general issues associated with the disposal, such as isolation and detection period, gas development, safety objectives and safety indicators, multi-barrier concept, host rocks. After the final synthesis report of the Federal Office for Radiation Protection no clear advantages or disadvantages of a host rock over another has been made. Therefore, each site is to check for themselves, where appropriate to classify him as a relatively best location. This also applies to Gorleben.

A comparative site evaluation was requested by the former Federal Environment Minister Gabriel. In the coalition agreement of 2009, it was agreed to further explore Gorleben to end its possible suitability.

On the other side are the representatives who call for a new location search with a location comparison with the involvement of Gorleben. This is seen as an urgent need to defuse the debate about Gorleben and to open up new options for action. In addition, a comparative site evaluation for methodological reasons is necessary and in many countries already standard, for example, in Switzerland and in Sweden. Only in Germany was at Gorleben, when selected, security-oriented criteria could have possibly played a subordinate role, be detained.

In part, the demand was made to exclude Gorleben in the search for a repository, as the already invested development costs make any neutral opinion impossible.