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Characteristics of Radioactive Discharges and Anticipated Offsite Doses for Korean Nuclear Power Plants Under Permanent or Long-term Shutdown
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The International Atomic Energy Agency (IAEA) refers to the possibility of changes in the discharge characteristics of radioactive effluents that are different from those during operation when a nuclear power plants (NPPs) are decommissioned. In addition, the IAEA recommends differentiated radioactive effluent management for each phase during decommissioning that reflects changes in discharge characteristics, and changes to authorization and program that are different from those in operation. Bonavigo et., al. estimated the discharge and dose of liquid and gaseous radioactive effluents based on the decommissioning plan of the Trino NPP in Italy during decommissioning, but there is a fundamental limitation in that actual data were not used. Kang and Cheong analyzed the discharge characteristics of radioactive effluents at each activities of decommissioning after permanent shutdown using actual data on radioactive effluents from the United States and Europe, and performed theoretical modeling of discharge characteristics during permanent shutdown. However, there are limitations in that only the emitted radioactivity was considered, the dose assessment was not taken into account, and the improvement methods for the differentiated monitoring program for each phase of decommissioning mentioned in the IAEA were not proposed. Most studies of radioactive effluents discharge from NPPs focus on normal operation, and studies of shutdown or decommissioned NPPs is very limited. Existing studies have not been extended to research on decommissioned NPPs, and there are limitations in that they do not consider the characteristics of decommissioned NPPs mentioned in the IAEA. Therefore, this study aims to improve the effluent monitoring program based on the analysis of the discharge characteristics NPPs that are permanently or long-term shutdown and the change in offsite dose to public. For this purpose, research was conducted on Kori Unit 1 and Wolsong Unit 1 in Korea, which were virtually permanently shutdown, and other long-term shutdown NPPs due to prolonged planned outage maintenance or replacement/repair of equipment in nuclear facility. The discharge characteristics of each radionuclide group, and further, the effect of radioactive effluent released to the environment on the offsite dose are analyzed in details.
