A Study on the Alternative Reducing Measures and Decommissioning Costs of Large Radwaste Materials in Kori Unit 1 Based on the Radioactivity Data of Steam Generator Replacement in Korea

The contents of the AIF/NESP–036 report in relation to the assessment of the decommissioning costs of nuclear power plants and the ISDC report of NEA on the cost evaluation methodology were reviewed with the decommissioning cost for Kori unit 1 based on the related domestic laws, regulations. Additionally through the performance of domestic steam generator replacements and the thesis on disposal of large radioactive wastes, the review and analysis were made on the adequacy of disposal plans and alternative measures for the decommissioning of the Kori unit 1 with the corresponding costs. As a result, the decommissioning cost of nuclear power plants differed by country depending on the scope of the assessment methods and the components of decommissioning costs. The the components of the decommissioning costs was usually 1) the cost of dismantling facilities of nuclear power plants, 2) the disposal cost of radioactive wastes, and 3) the cost of storage before final disposal of spent fuel. It was difficult to compare decommissioning costs by country since these three costs were mixed. So, the feasibility of decommissioning cost and dismantling volume of the Kori unit 1 was assessed. As a result, it has been confirmed that the decommissioning cost of the Kori unit 1 has been calculated as the basic assumption for the method of disposing by cutting all of the large radioactive wastes such as the steam generators, and putting them in a 200L drum. It was found that the expenses required for reducing treatments and clearance activities were not included in the decommissioning costs, in spite that 90% of the wastes were needed for reducing treatments and clearance activities and only 10% of them were disposed to the disposal facility as radioactive wastes. Based on the results of the survey on the disposal method of large equipment and the decommissioning costs of the Kori unit 1, the economic feasibility of the steam generator was analyzed for the purpose of storing and recycling instead of cutting, melting, packing, and disposing of the it in accordance with the current radioactive waste disposal criteria. In other words, if the system for recycling radioactive metal wastes is applied so that they can be recycled as various storage and disposal containers, such as spent fuel dry storage containers, not only the cost of withdrawal of steam generators is same as decommissioning cost of steam generators, but also the need for additional construction of disposal facility is reduced. Although the review of the operation of metal melting facilities for low and very low levels of radioactive waste for recycling was not addressed in this paper, radionuclides contaminated with steam generators are only cesium and cobalt isotopes. Since it exists mainly in the tubes and water chamber in steam generator, it was estimated that by separating, cutting and melting it, up to 98% of metal wastes could be recycled. The economic effects of reducing the amount of radioactive wastes to be disposed of at a national level were analyzed by recycling metal radioactive wastes that already have some contamination into spent fuel dry storage containers or radioactive waste disposal containers. As the decommissioning of Kori unit 1 is gradually taking shape, it is urgent to demonstrate the methods for the recycle of metal radioactive wastes and establish a new recycling system. It is deemed that the disposal costs of radioactive wastes should be discriminated and that additional research should be conducted to operate a disposal facility safely suitable for the form of waste by diversifying the disposal containers