SR 97: Post-Closure Safety for a KBS 3 Deep Repository for Spent Nuclear Fuel - Overview -
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SR 97: Post-Closure Safety for a KBS 3 Deep Repository for Spent Nuclear Fuel - Overview Allan Hedin, Ulrik Kautsky, Lena Morén, Jan-Olof Selroos, Patrik Sellin, Anders Ström and Tönis Papp Swedish Nuclear Fuel and Waste Management Company, P.O. Box 5864, SE-102 40 Stockholm, Sweden ABSTRACT In preparation for coming site investigations for siting of a deep repository for spent nuclear fuel, the Swedish Nuclear Fuel and Waste Management Company, SKB has carried out the longterm safety assessment SR 97, requested by the Swedish Government. The repository is of the KBS-3 type, where the fuel is placed in isolating copper canisters with a high-strength cast iron insert. The canisters are surrounded by bentonite clay in individual deposition holes at a depth of 500 m in granitic bedrock. Geological data are taken from three sites in Sweden to shed light on different conditions in Swedish granitic bedrock. The future evolution of the repository system is analyzed in the form of five scenarios. The first is a base scenario where the repository is postulated to be built entirely according to specifications and where present-day conditions in the surroundings, including climate, persist. The four other scenarios show the evolution if the repository contains a few initially defective canisters, in the event of climate change, in the event of earthquakes, and in the event of future inadvertent human intrusion. The principal conclusion of the assessment is that the prospects of building a safe deep repository for spent nuclear fuel in Swedish granitic bedrock are very good. The results of the assessment also serve as a basis for formulating requirements and preferences regarding the bedrock in site investigations, for designing a program for site investigations, for formulating functional requirements on the repository’s barriers, and for prioritization of research. PURPOSE AND PREMISES In preparation for coming site investigations for siting of a deep repository for spent nuclear fuel, the Swedish Government and nuclear regulatory authorities have requested an assessment of the repository’s long-term safety with the following purpose: “…to demonstrate that the KBS3 method has good prospects of being able to meet the safety and radiation protection requirements which have been specified in recent years.” SR 97 is the requested safety assessment. The purpose is to demonstrate by means of a systematically conducted analysis whether the risk of harmful effects in individuals in the vicinity of the repository complies with the acceptance criterion formulated by the Swedish regulatory authorities, i.e. that the risk may not exceed 10-6 per year. Geological data are taken from three sites in Sweden to shed light on different conditions in Swedish granitic bedrock. Data have been taken from SKB’s investigations at Gideå in Ångermanland, from Finnsjön in northern Uppland County and from the Hard Rock Laboratory
on Äspö outside Oskarshamn in Småland. The sites have been selected as calculation examples to reflect different conditions
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