A Probabilistic Methodology to Determine Failure Probabilities and Acceptance Criteria for the KBS-3 Inserts Under Ice-Age Load Conditions
| Autor: | Claes-Göran Andersson, Fred Nilsson, Lars-Erik Björkegren, Philip Minnebo, Bo Erixon, Mats Andersson, Karl-Fredrik Nilsson, P. Dillström |
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| Rok vydání: | 2008 |
| Předmět: |
Nuclear and High Energy Physics
Insert (composites) business.industry 020209 energy 02 engineering and technology Structural engineering engineering.material Design load Condensed Matter Physics Compression (physics) 020303 mechanical engineering & transports 0203 mechanical engineering Nuclear Energy and Engineering Acceptance testing 0202 electrical engineering electronic engineering information engineering Fracture (geology) engineering Cast iron Ductility Material properties business Geology |
| Zdroj: | Nuclear Technology. 163:3-14 |
| ISSN: | 1943-7471 0029-5450 |
| DOI: | 10.13182/nt08-a3964 |
| Popis: | The Swedish KBS-3 copper-cast iron canister for geological disposal of spent nuclear fuel is in an advanced stage. This paper deals with the cast iron insert that provides the mechanical strength of the canister and outlines an approach to assess the failure probabilities for manufactured canisters at large isostatic pressure (44 MPa) that could occur during future glaciations and first steps to derive acceptance criteria to ensure that failure probabilities are extremely small. The work includes a statistical test program using three inserts to determine the tensile, compression, and fracture properties. Specimens used for material characterization were also investigated by microstructural analysis to determine the microstructure and to classify and size defects. It was found that the material scatter and low ductility were caused by many defect types, but slag defects in the form of oxidation films were the most important ones. These data were then used to compute defect distributions for the probabilistic failure analysis of the KBS-3 canisters. A large number of finite element-analyses of canisters were performed at the maximum design load (44 MPa) covering distributions of material parameters and geometrical features of the canisters. The computed probabilities for fracture and plastic collapse were very low even for material data with low ductility. Two large-scale isostatic compression tests of KBS-3 mock-ups to verify safety margins are also described. The failure occurred at loads above 130 MPa in both cases, indicating a safety margin of at least a factor 3 against the maximum design load. As a result of the project, new acceptance criteria are being proposed for insert geometry and material properties, and the manufacturing process for inserts has been modified to ensure that these criteria are always fulfilled. |
| Databáze: | OpenAIRE |
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