In case of Korea, unlike overseas nuclear power plants, adjacent units are located in permanently stopped nuclear power plants. Radioactive substances from airborne and liquid effluents are released into the environment from the NPP, and the radioactivity of the released substances must be reported to the regulatory authorities. Radioactive effluents are released into the environment not only in operation but also after permanent shutdown. Due to domestic conditions in which multiple units exist on the same site, it is necessary to consider radioactive effluents generated after permanent shutdown of NPPs. In particular, liquid effluent may have an increased tritium concentration due to draining the spent fuel pool. This paper summarizes the annual liquid emissions of PWR power plants that have been permanently shut down. The data was obtained from the Nuclear Regulatory Commission’s (NRC) annual radioactive effluent release report, which provides information on the annual emissions power plants into the environment. The liquid emissions of each plant were organized into an annual table, providing an overview of the amount of liquid released by each plant. This study aims to raise awareness about the potential environmental impact of permanently shut down nuclear power plants and the need for proper management of their liquid emissions. The findings of this study can used by operator, policymakers, and other stakeholders to make informed decisions regarding the decommissioning and management of nuclear power plants.

Prior to dismantling a nuclear facility, full site characterization should be carried out to identify basic data for various stages of decommissioning, such as deregulation of sites and structures, selection of decontamination technology, decommissioning methods, and waste management and disposal. Radiological characterization is implemented through information collection, on-site measurement, sampling and analysis, and theoretical calculations and proven codes for radioactive material at the time of decommissioning of the nuclear facility. There are issues in that it takes a lot of time and money to collect and analyze samples for characterization of contaminated sites and radioactive structures. Therefore, in the entire process of decommissioning a nuclear facility, a technology that can quickly measure the radiological characteristics of various decommissioning objects and wastes on site is required. In this project, the utilization of gamma cameras that can be analyzed in the field for quick and accurate characteristic evaluation at the dismantling site was studied. A gamma camera, iPIX from Canberra (Now it became Mirion Technology), was tested in this study. It is a unique gamma imager, which have a CdTe sensor with TIMEPIX chip and a coded aperture collimator, quickly locates and identifies low to high level radioactive sources from a distance while estimating the dose rate at the measurement point in real time. It also can be combined with CZT sensor which called iPIX-NID (nuclide Identification) provides users with clear understanding of radionuclides presence with no need of any spectroscopic knowledge. iPIX with iPIX-NID convert the gamma camera into a hot-spot detector with radionuclide information. To verify the applicability of a gamma camera in Nuclear power plant, it was implemented to Kori unit-1 which was permanently shut down from 2017. Various Systems were observed at restricted area including reactor cooling system, boron recovery system, residual heat removal system, containment spray system, and etc. The locations of hot spots were clearly revealed by iPIX and these results can be used for selecting the locations of destructive samples and help to decide the conservative decision making. Condensate water systems in turbine building were also observed by a gamma camera and showed no nuclide. Based on this preliminary gamma camera applications, further investigation and tests will be carried out to Kori Unit-1.