Design management and stress analysis of a circular rock tunnel for storage of spent nuclear fuel

In this report a Critical Path Method (CPM) diagram and a logic net are proposed for the design cycle of the rock tunnel system of a high level nuclear waste repository. Considerations for changes in the aspect ratios and geometry of the tunnel system, placement and spacing of the canisters, heat diffusion and heat transfer analysis, stresses analysis and boring techniques are included in the CPM diagram and in logic net. This research project also deals with stress analysis, using the finite element method, of a circular rock tunnel, part of a system of tunnels used for the long term storage of high level nuclear waste. In the analysis, the tunnel is subjected to the pre-existing in-situ temperature and overburden loads, at construction. High thermal stresses develop later due to the long term influx of heat from the stored canisters. Results indicate that thermal stresses reach a critical level for the rock in the vicinity of the canisters which may lead to local collapse of the rock and possible damage to the canisters. Results of the analysis also imply the need for a continuous cooling scheme of the tunnel system to prevent overheating of the rock