file under:
Europe, Facilities, Germany, Government
Safety in Numbers
The German government determined that by 2036, the country’s last nuclear power station will be turned off. The country’s Atomic Energy Act aims at phasing out nuclear energy, but ensuring human and environmental protection does not stop there. Germany is also breaking ground to safely dispose of low- and medium-level radioactive waste, which is produced from the dismantling of nuclear power plants, as well as from hospitals, research centers and industry.
An Underground Solution
An estimated 110,000 cubic meters of low- and medium-level radioactive waste is currently stored in aboveground interim storage facilities in Germany. In 2018, it will be transported 850 meters underground into the former Konrad iron ore mine, which is being developed into a radioactive waste repository. Located near the city of Salzgitter, the repository is the result of more than 20 years of research and planning to confirm the suitability of the mine for waste disposal, as well as ease public concern.
CDM Smith is working with the German Company for the Construction and Operation of Waste Disposal Facilities [Deutsche Gesellschaft zum Bau und Betrieb von Endlagern für Abfallstoffe mbH (DBE)] to provide planning and design services, as well as construction supervision, for the storage facility that will hold a total capacity of 303,000 cubic meters of waste—the amount expected to accumulate in Germany over the next 40 years. The mine’s existing galleries will be expanded from diameters of approximately 4.5 meters to larger cross-sections of up to 12 meters to accommodate the transport and storage of waste containers, and new routes will be excavated. In addition, the team will be joining mine cavities; widening shafts; and creating workshop facilities, turning points and fuel depots.
Leaving Nothing to Chance
Driven by a mission to protect human and environmental health, as well as strengthen public confidence, the project team is taking every measure to assure safety. “Expanding the tunnels’ diameter by more than 7 meters is a significant undertaking. Each layer of rock mass has its own geological properties. Gathering all the required measurements and calibrating them for the site is time consuming, but it is critical to prevent the risk of collapse during construction and ensure long-term stability,” says Sven Möller, CDM Smith numerical analysis specialist.
Additional complexities—such as planning for the storage area’s high-stress level and the massive size of the entire site extending up to 3 kilometers in length and almost 2 kilometers in width—also require sophisticated geotechnical expertise. According to Möller, the team must create multiple 3D numerical models separately and combine them, which is an extensive process. “We are not taking anything for granted to ensure the security of the repository.”
Further demonstrating its commitment to quality, the team will adapt the numerical models as necessary during construction, which is scheduled to begin in fall 2011. Typically, a structural analysis would be performed to predict ground loads on linings. Due to the precision required for this project, the models will be recalibrated if necessary as construction is happening—a unique approach to the observation method. The team is also taking into account possible changes of ground loads over the next 40 years to arrive at a safe structural design.
An Impassable Barrier
The repository’s safety involves more than structural reliability—it must be an extremely safe solution from all perspectives. Not only will the waste be stored in galleries 850 meters below ground, but the repository is entirely dry, isolated from local groundwater and surrounded by a 400-meter-thick clay barrier. Each gallery will be filled with a hardening substance made from materials extracted during excavation, and then sealed with a concrete wall to isolate the waste and prevent the release of radioactivity.
Valuable Experience
As the first repository authorized under the Atomic Energy Act, Konrad will pave the way for the development of similar storage facilities. Peter Jordan, CDM Smith senior vice president and regional chief technical officer says, “Our team is pleased to contribute expertise in rock mechanics and structural design for such a landmark effort. It’s exciting to think that this former mine will provide a much-needed solution for radioactive waste storage while setting an example for future repositories.”
