14.4.1 Asse II

At the same time that Germany was constructing its first NPPs, the govern­ment recognized that methods and technologies would need to be devel­oped for the final geological disposal of related heat-generating wastes. The permanent disposal of these wastes in salt domes was seen as providing a promising option for the development of a HLW repository. To further investigate the ability of a salt-rock formation to serve as a potential reposi­tory host rock, the German Federal Ministry of Education and Research (Bundesministerium fur Bildung und Forschung, BMBF) acquired the former Asse potash and rock salt mine in 1965 as a prototype facility for LLW and ILW disposal with strong emphasis on research and disposal technologies (BfS, 2011e). The facility was managed at the time by the GSF (Gesellschaft fur Strahlen — und Umweltforschung mbH), a major research centre in Germany, which later became the Helmholtz Zentrum Munchen (HZM). Management and operations of the Asse facility were conducted by the Helmholtz Zentrum Munchen (HZM) until the facility was trans­ferred to the BfS in 2009. From its initiation until 2009, Asse was regulated under German mining laws.

Research and experimental work on remotely handled ILW disposal started in the summer of 1972 and continued until waste disposal practices ended in 1978. From 1971 until 1978 the facility was also used to store a major part of the LLW and ILW produced in the Federal Republic of Germany. Altogether 125,787 drums and waste packages containing RAW were emplaced in the mine (BfS, 2011f). The layout of the Asse facility including chambers containing RAW is shown in Fig. 14.4.

The AtG was amended in 1976. The amendment implemented a licensing (i. e., plan approval) process for RAW storage and as a result waste storage practices were discontinued in 1978. At the time, as no additional RAW was being transferred to the site, German mining law continued to provide the legal basis for the operation of the facility as an underground research labo­ratory (URL). After phasing out of the disposal practices in 1978, the facil­ity continued to be used as an underground research laboratory with a major focus on the development of disposal technologies for heat­generating waste.

In 1995, after research and development came to an official end, backfill­ing of the former mining chambers in the southern flank of facility was initi­ated along with efforts to evaluate the long-term safety of the former mine. However, research was allowed to continue as long as related activities did not interfere with mine closure operations (Kappei, 2006).

Although the facility was initiated as a URL, because of the disposal practices that were conducted concurrent with research, the facility became

by default a repository. It has since been recognized that the operation and regulation of Asse under mining law did not provide an adequate regula­tory framework to manage and close the facility. On 4 September 2008, the BMBF, the BMU and the Lower Saxony Ministry for the Environment and Climate Protection (Niedersachsisches Ministerium fur Umwelt und Kli — maschutz, NMU) jointly agreed that the facility would be closed under the Atomic Energy Act. On 1 January 2009, transfer of the facility to the BMU under management of the BfS was completed.

Despite legal and political issues surrounding the Asse facility today, considerable experience and information was gained during the period of its operation. This experience and the tests that were conducted at Asse resulted in improved waste handling practices and technologies, as well as an improved understanding of salt as a host rock and engineered barrier system behaviour. Several national and international research studies were conducted at the URL. Examples include the following:

• a cooperative research programme with the US Department of Energy examined brine moisture migration, thermal mechanical response of salt, and material corrosion studies;

• drilling optimization studies were conducted as part of the Commission of European Communities COSA Project;

• the longest running drift-scale thermal simulation study was initiated by the Karlsruhe Institute of Technology (KIT) and later expanded and finalized under the European Union sponsored multi-national BAMBUS I and BAMBUS II projects, which included dismantling and retrieval exercises.

The BAMBUS projects were the last significant research conducted at the facility (Bechtold et al, 2004). Upon assuming operational responsibility for the Asse repository in January 2009, the BfS conducted a comparative study to assess the effectiveness of the various closure options. The options investigated included:

• retrieval: removal of waste from the mine for emplacement in another disposal facility

• relocation: construct and license a repository in deeper sections of the salt dome.

• complete backfilling: complete backfilling of all of the subsurface cavi­ties with concrete and installation of sealing systems in shafts and drifts at appropriate geological intersections.

After evaluation of the result of the comparative assessment, published in January 2010 (BFS, 2010), the BfS selected retrieval as the preferred option for final closure of the facility and is currently in the process of elaborating technical processes and requirements to achieve this goal.