The current design of a deep geological repository for high-and intermediatelevel radioactive waste in France consists of a complex system of different underground structures (ANDRA, Dossier 2005 Argile, les recherches de l'Andra sur le stockage géolog-ique des déchets radioactifs à haute activité et à vie longue, collection les Rapports. Châte-nay-Malabry, France, 2005). For a comprehensive understanding of the long-term hydraulic evolution of the entire repository, numerical non-isothermal two-phase flow and transport simulation, taking into consideration the generation, accumulation, and release of hydrogen gas and decay heat, are compulsory. However, a detailed numerical model of the entire repository system would require a tremendous computational effort and pose a laborious task with respect to the operation of the model. To handle these difficulties, we have developed an efficient method for the numerical modeling of a complete repository system and its geologic environment. The method consists of the following steps: (i) subdivision of the repository plane into a large number of "sectors" based on the position of hydraulic seals and on other geometrical considerations, (ii) exploitation of existing symmetries (inside or between sectors), (iii) adoption of the "multiplying concept", and (iv) connection of the individual sectors at the drift interfaces to form the entire repository model. Each sector is modeled as a three-dimensional (3D) block, and the entire model is computed with TOUGH2-MP. The Electronic supplementary material The online version of this article (123 78 A. Poller et al.method allows for a massive reduction in overall finite-volume elements and, at the same time, provides an adequate representation of the small-sized structures in the repository. The main characteristics of the method and its application to an entire deep geological repository system in a clay host rock are presented.
Given that model‐based systems engineering (MBSE) captures the structure and behavior of an engineered system in an overarching system model, MBSE appears to be a promising approach to managing large infrastructure projects (LIPs). However, it is not apparent how to most appropriately organize the associated system model—and hence the infrastructure project itself. Furthermore, MBSE may today not be readily accepted by the civil engineering industry. In this research, a hypothetical project for the geological disposal of radioactive waste is taken as an example of an LIP and initial system models of the entire disposal project are created. Furthermore, a network representation of the project is generated and examined with network theory. Based on the results, different project organizations are synthesized and evaluated. Eventually, the initial system models are updated to accommodate the most suitable organization according to the network analysis results. In addition, the perception of, and attitude toward MBSE is assessed by means of a cross‐sectional survey in a civil engineering company. The generation of system models of LIPs is found to be straightforward. Network theory is able to unveil the complex structure of LIPs in order to identify the most suitable way to organize them and the associated system models. The survey results suggest that MBSE may find broad acceptance in the civil engineering industry.
In Switzerland, the Nuclear Energy Law requires the disposal of all radioactive waste in deep geological repositories. The procedure for selecting the repository sites is defined in the Sectoral Plan for Deep Geological Repositories and consists of three stages. In Stage 1, the National Cooperative for the Disposal of Radioactive Waste (Nagra) proposed geological siting regions based on criteria relating to safety and engineering feasibility. As part of Stage 2, Nagra has to select at least one site within each siting region, to carry out a provisional safety analysis for each site and a safety-based comparison of the sites. In order to achieve these objectives, the state of knowledge of the geological conditions in the siting regions has to be sufficient to perform the provisional safety analyses. In October 2010, Nagra submitted a report which documents Nagra’s technical-scientific assessment of this precondition, based on a comprehensive list of processes and parameters relevant for safety and engineering feasibility. A part of this assessment consists of test calculations for the provisional safety analyses. This paper summarizes how the numerous test calculations have been identified, how the concepts of radionuclide release from the repository are implemented into numerical codes and how input data and results are organized in order to ensure transparency and traceability.
Siting a deep geological repository for radioactive waste essentially involves two interrelated steps: deciding on an appropriate geological environment for the underground facilities and selecting a suitable location for the associated surface facility. An acceptable solution is more easily achieved if some flexibility exists for siting the surface facility, irrespective of the exact position of the underground facilities. Such flexibility is available if a ramp is used as the main access route from the surface facility to the underground facilities. Another option is to use a combination of shafts and (sub)horizontal tunnels as the main access route. Both variants include shafts for ventilation, etc.
In this paper, the two variants (i) main access via ramp and (ii) main access via shaft are compared in terms of long-term safety. To this end, the entire network of underground tunnels of a deep geological repository is implemented in an analytical resistor network flow model. Radionuclide release through the tunnel system and the host rock is then calculated with a numerical network transport model, using as input the results from the flow model. The results clearly indicate that, even in case of hypothetically deficient horizontal and subhorizontal sealing elements, the choice between ramp and shaft as the main access route is irrelevant to long-term safety.
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