r^ TECHNICAL REPORT 85-08 Feasibility study for siting of a deep repository within the Storuman municipality Swedish Nuclear Fuel and Waste Management Co January 1995 SVENSK KÄRNBRÄNSLEHANTERING AB SWEDISH NUCLEAR FUEL AND WASTE MANAGEMENT CO BOX 5864 S-102 40 STOCKHOLM TEL. 08-665 28 00 TELEX 13108 SKB TELEFAX 08-661 57 19 FEASIBILITY STUDY FOR SITING OF A DEEP REPOSITORY WITHIN THE STORUMAN MUNICIPALITY January 1995 Key words: Deep repository, site selection, feasibility study, Storuman FOREWORD 1 his report summarizes the results of the feasibility study in Storuman. It also contains SKB's collective evaluation of the results (Chapter 11). A status report was published in June 1994. The purpose of the status report was to give the municipality, its reference group and other interested groups in Storuman and in the region, a basis for discussion and opinions before the final report was written. Numerous viewpoints have been presented and have occasioned some supplemen- tary studies or adjustments and additions to the final report. The viewpoints of the reference group on the status report are compiled in an appendix to this final report. For SKB's part, this report represents the conclusion of the feasibility study. As is evident from the viewpoints of the reference group, there are important questions that have not been fully answered within the framework of the feasibility study. Answering some of these questions requires information that can only be provided by a site investigation. Other questions of a more general nature can be taken up if the final evaluation of the feasibility study results in a common interest to continue site investigations in Storuman. The municipality's planned independent review may also identify questions that should be further examined before a decision can be made on a possible continuation. Proposals for such additional studies must be discussed between SKB and Storuman Municipality. In conjunction with the inde- pendent review, SKB is prepared to provide additional data if required, as well as clarifications of SKB's attitude and viewpoints. The feasibility study in Storuman is the first of its kind. Similar feasibility studies are planned for 5-10 municipalities. For SKB's part, this first feasibility study has provided va'sjable experience for the siting work. SKB would like to thank all those who have, in different ways and from different points of departure, con- triu :evl Jo the locution of the feasibility study. Stockholm, hm--.-ry 1995 SWEDISH f. Ut f FAR FUEL AND WASTE MANAGEMENT CO Sten Bjurström President GENERAL BACKGROUND A deep repository differs from other industrial activities and other underground facilities in one essential respect: The facility is intended for the handling and disposal of materials with a high concentration of radioactive materials. This leads to special requirements on quality and safety, and consequently the foremost reason why the facility and its siting arouse discussion. To understand both the potential for safe handling and disposal and the potential risks associated with the waste, it is necessary to be aware of certain fundamental facts regarding the properties of the waste and the radiation emitted. The properties of the nuclear waste and the protective measures that are employed are described in concise and fundamental terms below. RADIOACTIVITY Radioactive materials (radionuclides) can be dangerous in two ways: • They emit radiation (mainly gamma radiation) that can harm humans. This is protected against by surrounding the radioactive waste with sufficiently thick radiation shields that absorb the radiation. Extensive experience of such protective measures has been gained from work at nuclear power plants and within medical applications. • They could conceivably get into the air or water and in this way reach man and enter the human body. This is protected against by making sure that the waste is in a solid form that makes it difficult or impossible for it to be vaporized in air or dissolved in water. In addition, the waste is surrounded by several barriers - e.g. canister, clay and rock - that prevent it from coming into any kind of contact with the human environment. HIGH-LEVEL RADIOACTIVE WASTE The spent nuclear fuel comes to the deep repository encapsulated in canisters of steel and copper, see Appendix I. The radioactive materials are contained (en- trapped) in the nuclear fuel, a ceramic material. The canister provides a hermetic- enclosure which prevents the radioactive substances in the fuel from coming into contact with the environment. The canister also attenuates the gamma radiation emitted by the fuel. An outer radiation shield is required during shipment and handling of the canisters. This is achieved by placing the canisters inside transport casks with steel walls up to two decimetres thick. When the canisters have been placed in the deep repository, all radiation is attenu- ated by the canister, the surrounding clay and the rock around the deposition holes so that the radiation level beyond one to two metres from each canister is not elevated above the natural background radiation level. There is therefore no way for radiation or radioactive materials to reach the environment and people on the ground surface directly. In other words, the deep repository is designed to prevent any radioactive release whatsoever (zero release). Thorough studies are made in the safety assessments of whether, and how, the different protective barriers can be damaged, and what consequences this would have. A fundamental principle - the multibarrier principle - is that safely shall not be dependent solely on one barrier, but that each of the barriers (the waste form, the canister, the clay, the rock) shall in itself be an effective obstacle against the escape of un> radioactive rudionu- elides. In a canister containing spent nuclear fuel, there is no generation of energy of the kind that is generated in a nuclear power plant. Nor is it physically possible for the fuel to be melted by heat or explode. Heat output in nuclear fuel at different times is illustrated in the table below. Heat in the spent fuel I decay heat) is generated by the disintegration (decav) of the radionuclides. Table 1. Heat output in nuclear fuel at different times. Time Heat output (kW/t fuel) During reactor operation 25.000 After reactor shutdown 1.500 During transport to interim storage (after I year) 10 During transport to deep repository (after about 40 years) 1 PURPOSE OF THE DEEP REPOSITORY In general, it can be concluded that the handling of encapsulated spent nuclear fuel at a deep repository is simpler than the handling of non-encapsulated fuel that takes place today at the nuclear power plants and the interim storage facility. CLAB. Total activity content and radiation are much lower and the waste is better pro- tected due to the fact that it is encapsulated. Nevertheless, the encapsulated fuel still contains large quantities of radionuclides. some of which are long-lived. This is the reason why it is necessary to arrange safe containment and isolation of the spent fuel from the living biosphere. Supervised storage, such as takes place in CLAB. is an effective method for interim (temporary) storage, but it is not a permanent solution, since if surveillance is suspended or relaxed, man and the environment still need to be protected. Swedish law therefore requires final dispo- sal, which is why Sweden, along with other countries, is working to bring about final disposal in deep geological formations (deep repositories). WASTE QUANTITIES Altogether, it is estimated that the Swedish nuclear power programme up to 2010 will have produced some S.000 tonnes of spent nuclear fuel. This waste will be encapsulated in approximately 4,500 copper/steel canisters which will be em- placed (deposited) in the deep repository. Besides spent fuel, approximately 20.000 m of other long-lived waste will be deposited in the deep repository. The deep repository will be constructed in two stages. Approximately 400 canisters of spent fuel will be deposited in the first stage. It is estimated that this initial operating period will start not earlier than 2008 and continue for roughly 5 years, after which the experience gained from this stage will be evaluated by SKB and the VI regulatory authorities. If the verdict is favourable, the rest of the repository will be built (stage 2). The largest quantities of waste from the nuclear power plants and other nuclear facilities consist of operational and decommissioning waste. The total volume is estimated at 190.000 m'. This waste is planned to be emplaced in the Final Repository for Radioactive Operational Waste (SFR) in Forsmark. ABBREVIATIONS The Swedish Nuclear Fuel and Waste Management Company. SKB. is responsible for the management and disposal of Sweden's radioactive waste. The primary category is waste from the nuclear power plants, but radioactive waste is also produced by hospitals, industry and research institutions. SKB was formed jointly by the power utilities that produce nuclear energy in Sweden. The Swedish Nuclear Power Inspectorate. SKI, and the Swedish Radiation Protec- tion Institute, SSI, are the public authorities who scrutinize the activities of SKB and oversee safety both in the operation of the nuclear power plants and in waste management. SKI also administers fees charged on the production of nuclear- generated electricity that are intended to finance the management and disposal of the nuclear waste. Besides these two authorities, there is a scientific council. KASAM (the National Council for Nuclear Waste). KASAM is associated with the Ministry of the Environment and has been given the task of submitting a report to the Government every third year with its independent assessment of the state of knowledge in the nuclear waste field. Numerous references are made in this report to CLAB, SFR and the Äspö HRL.