This technical note is part of a set of reviews for Swedish Radiation Safety Authority (SSM) by external experts to assist with the Initial Review Phase. The overall goal of the Initial Review Phase is for SSM to achieve a broad coverage of the information provided in SR-Site and its supporting references and in particular to identify where complementary information or clarifications need to be delivered by Swedish Nuclear Fuel and Waste Management Company (SKB). Southwest Research Institute® (SwRI®)–Center for Nuclear Waste Regulatory Analyses (CNWRA®) staff have reviewed the numerical modelling that SKB performed to quantify potential slip on existing fractures due to an earthquake.
SKB has determined that canister damage due to an earthquake needs to be considered in the safety assessment of the KBS–3 disposal design because shear deformation of the near‑field rock due to seismically induced slip on existing fractures could generate forces sufficient to challenge the mechanical integrity of the waste canister. For the SR‑Site safety assessment, SKB considers that a fracture slip of 0.05 m across a deposition hole corresponds to canister damage. SKB used numerical modelling to define the potential magnitude of induced fracture slip as a function of the distance from an earthquake-generating fault and the size of existing fractures.
Based on the model, SKB defined a critical fracture size for each location as a function of distance from known faults. SKB proposed to avoid deposition hole locations that were intersected by fractures greater than the critical size or to assess the probability of canister damage for deposition holes that may inadvertently intersect such fractures.