Cost estimations for deep disposal of spent nuclear fuels

According to the Act on the Financing of Future Expenses for Spent Nuclear Fuel etc. (Financing Act), the Swedish Nuclear Fuel and Waste Management Co. (SKB) must submit, every year, to the Swedish Nuclear Power Inspectorate (SKI), a cost estimate for the management of spent nuclear fuel and for the decommissioning and dismantling of the nuclear power plants. After SKI has examined and evaluated the cost estimates, SKI must submit a proposal to the Government concerning the fee which should be paid by the nuclear power companies per kWh of generated electricity. According to the Financing Act, the reactor owners must pledge collateral in the event that the accumulated fees should be found to be insufficient as a result of early closure of reactors or as a result of underestimating the future expenses of managing the spent nuclear fuel and of decommissioning and dismantling the reactors. The future total expenses resulting from the Financing Act are estimated at about SEK 48 billion at the January 1998 price level. Of this amount, the cost of the final disposal of spent nuclear fuel in SKB's programme is expected to amount to about SEK 12 billion. SKB's estimate comprises the cost of siting, construction and operation of a deep repository for spent nuclear fuel, based on the KBS-3 concept, and a rock cavern for other long-lived waste which SKB plans to locate next to the spent fuel repository. The cost estimate also includes the dismantling and closure of the facility once all of the fuel and the long-lived waste are deposited. The calculations are based on all of the fuel, which will be generated through the operation of the 12 Swedish reactors during a period of 25 years and for every additional year of operation. At the beginning of 1998, SKI commissioned BERGAB to evaluate the cost estimate for the deep disposal of the spent nuclear fuel. The task was divided into two stages, namely a study which was submitted in June 1998 concerning the technical feasibility of a deep repository. The subsequent main study comprised a cost estimate based on the findings of the feasibility study. In conducting the study, BERGAB hired PEAB Berg AB as a subcontractor to perform the calculations. An important part of the study was to closely study the cost of variations in the deep repository concept relating to an alternative repository layout, disposal method, site, time-schedule etc. This report is a summary of the feasibility study and the main study which confirmed BERGAB/PEAB's evaluation of SKB's cost estimate. On the basis of SKB's reference scenario in SKB PLAN 98 and the calculation based on this scenario, BERGAB/PEAB has reached the conclusion that it is possible to site, construct and operate a deep repository for the spent nuclear fuel within the framework of the total cost that SKB has estimated. The results of BERGAB/PEAB's evaluation shows that their estimate is about 4 % or SEK 500 million lower than SKB's estimate. However, the evaluation of the individual underlying items in the estimate shows considerable differences in SKB's and BERGAB/PEAB's calculations, which should be explained and investigated in detail by SKB. Some of the findings of BERGAB/PEAB's study are summarized: descriptions and background data concerning the content of the different items in the cost estimate were found to be very difficult to penetrate due to the lack of clarity concerning the costs which SKB assigned to the different items. One condition which should be fulfilled in order for SKI to form an opinion of the accuracy of the cost estimate submitted by SKB every year is that the calculations can be presented to SKI in a comprehensible and accessible manner. In its reference case, BERGAB/PEAB concludes that a larger site investigation area is required, compared with that postulated by SKB. BERGAB/PEAB's assumptions are based on the reports that SKB itself refers to in its background reports for site investigations. Similarly, both the transport tunnels and deposition tunnels are extended in BERGAB/PEAB's reference case. There is also a considerable risk that the detailed characterizations will have to cover a considerably larger area in order to secure the area required for spent fuel deposition. The investigation and the construction costs alone of increasing the area involved could amount to several hundred million kronor. One variation which has been investigated is tunnel excavation using a tunnel boring machine (TBM) which, with today's technology could mean an increased cost of about SEK 900 million. The reason that SKI has opted to investigate this technique is that tunnel excavation using the TBM is less damaging to the surrounding rock in comparison with conventional excavation methods. Another conclusion which can be drawn from the variations is that the total cost is sensitive to changes in the canister distance. On condition that the number of canisters which are deposited remains unchanged, an increase in the canister distance by 1 to 7 meters means that about 3,000 meters of extra deposition tunnel will be required. This will result in a cost increase and will have an effect on both the time schedule and the operating organization