Engineering for Operation of a Future Belgian Deep Geological Repository for ILW and HLW - 12379
- DBE TECHNOLOGY GmbH, Peine (Germany)
- ONDRAF/NIRAS, Brussels (Belgium)
- Tractebel Engineering SA, Brussels (Belgium)
In Belgium, an advanced conceptual design is being elaborated for deep geologic disposal of high level waste (HLW) and for low and intermediate level waste (LILW) not amenable for surface disposal. The concept is based on a shielded steel and concrete container for disposal of HLW, i.e., the Super-container. LILW will be disposed of in separately designed concrete caissons. The reference host rock is the Boom Clay, a poorly indurated clay formation in northeastern Belgium. Investigations into the potential host rock are conducted at the HADES underground research laboratory in Mol, Belgium. In 2009 the Belgian Agency for Management of Radioactive Waste and Enriched Fissile Materials (ONDRAF/NIRAS) initiated a four year research project aimed at confirming the fundamental feasibility of building and operating a repository. The goal of the program is to demonstrate at a detailed conceptual level that the proposed geologic disposal system can be safely constructed, operated, and progressively closed. Part of the broader research efforts being conducted includes evaluations optimization of the waste transportation shaft, subsurface transportation system, ventilation system, and evaluation of backfilling and sealing concepts for the repository design. The potential for implementation of a waste retrieval strategy encompassing the first 100 years after emplacement is also considered. In the framework of a four year research program aimed at confirming the fundamental feasibility of building and operating a repository in poorly indurated clay design studies have been underway to optimize the waste transportation shaft, subsurface transportation system, and ventilation system. Additionally backfilling and sealing concepts proposed for the potential repository have been reviewed in conjunction with impacts related to the potential future inclusion of a retrievability requirement in governing regulations. The main engineering challenges in the Belgian repository concept are size limitations on the underground facilities imposed by the mechanical behavior of the candidate host rock type (i.e., poorly indurated clay) and the resulting ground support requirements. Underground excavations in the Boom Clay require a significant level of ground support to ensure the openings remain stable. A concrete lining system has been developed to address this engineering requirement. As a result strict size limits are imposed on both the diameter of the tunnels and the dimensions of the shaft stations resulting in unique design challenges requiring maximal optimization of the available space. Ongoing studies indicate that a significant (20%) reduction in shaft diameter can be achieved by diagonally orienting the hoist guide rails with respect to the cage, optimizing the counter weight dimensions, and reconfiguring the auxiliary hoisting system as a single rope system. Reliable subsurface transportation of waste packages can be achieved through a hybrid rail/wheel system powered by a battery operated electric locomotive. Key components of the system, including the battery-powered locomotive and a turntable used for transitioning waste shipments from the access gallery into disposal galleries without the need for constructing turnouts, have been successfully demonstrated at the Gorleben exploratory facility and the Konrad repository in Germany, respectively. By optimizing the available space in the disposal galleries and limiting the introduction of hazardous gases by using electric powered systems combined with the relatively small number of workers envisioned in the Belgian repository concept adequate ventilation can be achieved to ensure safe operational conditions. The proposed sealing and backfill systems in the Belgian repository concept should provide adequate safeguards as currently planned. Should a future retrievability requirement be imposed on the design it appears likely that a partial backfilling strategy could be employed. The key component in ensuring retrievability in the design would be the selection of a backfill that combines the safety functions required in the current design concept with a material strength amenable to removal by hydro-jet excavation techniques. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9-332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 22293627
- Report Number(s):
- INIS-US-14-WM-12379; TRN: US14V1283115151
- Resource Relation:
- Conference: WM2012: Waste Management 2012 conference on improving the future in waste management, Phoenix, AZ (United States), 26 Feb - 1 Mar 2012; Other Information: Country of input: France; 5 refs.
- Country of Publication:
- United States
- Language:
- English
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