Safety assessment for normal operation of combustible radioactive waste incineration facility

Abstract

As of September 2023, a total of 128,270 drums of Low- and Intermediate-Level radioactive Waste (LILW) in Korea are stored in nuclear and non-nuclear facilities, and about 4,000 drums of radioactive waste are generated annually. According to the "2020 Management Implementation Plan for Low- and Intermediate-Level Radioactive Waste" announced by the Korea Radioactive Waste Agency (KORAD), it is predicted that around 710,000 drums of LILW will be generated by 2095. However, as additional generation are expected depending on operating conditions, such as the construction of new nuclear power plants, the continuous operation and decommissioning of existing plants, the development of technologies such as Small Modular Reactors (SMR), and expansion of radioactive isotope utilization research, the cost burden on operators for the disposal of LILW is expected to increase, and there are concerns about the saturation of disposal facilities with a total storage capacity of 800,000 drums. Therefore, there is a need to introduce a technology with better volume reduction efficiency compared to the currently applied technology in Korea. This is crucial to achieve cost reduction in waste disposal and secure storage space for disposal facilities. In the composition of LILW, approximately 45% of the total is identified as combustible waste. Among the thermal volume reduction treatment of combustible waste, incineration technology exhibits the highest volume reduction efficiency with a ratio of 100. Leading nuclear countries such as France, Japan, and the United States actively utilize incineration technology for radioactive waste. However, there are no radioactive waste incineration facility in Korea, and similar facilities such as vitrification and pyrolysis are either not currently in operation or are operated on a small scale, so utilization of related technologies is limited. The most representative causes for this defensive utilization status are the problem of resident acceptance and the uncertainty of radioactive secondary waste disposal. Assuming that radioactive waste incineration facilities are introduced in Korea, concerns about the environmental impact by radioactive gaseous effluents from facilities and their exposure will be the main cause of the problem of residents' acceptance and radioactive nuclides in the waste due to high volume reduction rate are concentrated in the secondary waste in the form of ash, so the problems of the possibility of this secondary waste disposal must be considered. In this study, the environmental impact and resident exposure doses of gaseous radioactive effluents generated during the operation of the reduction treatment facility by incineration of combustible radioactive waste were evaluated and compared with the notification standards announced by Nuclear Safety and Security Commission (NSSC). The air concentration of radioactive nuclides emitted from facility was about 0.03% compared to the standard and the annual effective dose value was about 1.53% compared to the standard, indicating that the impact of radioactive waste incineration treatment technology on the environment was very insignificant. In addition, the characteristics of secondary waste in the form of ash generated after the incineration treatment were analyzed and the suitability for disposal of the waste was compared with the waste acceptance criteria (WAC) notified by KORAD. According to the criteria, secondary waste generated from incineration facility is dispersible, so it must be disposed of after immobilization. To assess disposal suitability, the compressive strength and leaching tests of the produced ash-solidified body were conducted to confirm their compliance with the solidification test requirements outlined in the acceptance criteria. Additionally, the concentration limit of incinerable waste is calculated