Investigations and monitoring of environmental radiation are important for preventing expected accidents or for early detection of unexpected accidents, in nuclear facilities and the surrounding. In the event of an environmental radiation accident, it should be possible to identify and analyze the radiation-contaminated area. Therefore, a rapid radiation monitoring system is required for immediate response and necessary measures. In this study, the distribution of radiation mapping is performed on a contaminated area using 2-dimensional or 3-dimensional contour mapping techniques. The entire surrounding area can be understood at a glance by displaying the radiation contour line on the map of the measured area.

Identifying plausible scenarios is necessary to evaluate the performance of the repository reliably over a very long period. All features, events, and processes (FEPs) expected in the repository should be comprehensively well-defined and structured into scenarios based on the relation analysis. A platform for the FEP DB management and relation analysis is needed to facilitate the efficient composition of the scenarios. For this purpose, the CYPRUS program was developed, but abandoned due to suspended FEPs and scenario research. Thus, it became necessary to build a new easy-tomaintain platform that inherits the legacy of CYPRUS and reflects the latest research. The data structure and user interface configuration were derived to develop a new platform. The new platform provides extensive data such as the assessment context, the FEP DB, the interaction between FEP contents, the relevance to other project FEPs, the influence on performance, the scenarios for the TSPA, the AMF, and the PA Data. The platform displays the long-term evolution FEPs developed by KAERI, the international and major project FEPs in table format. The correlation between FEP items is composed of a detailed interaction matrix and visualized as the chord diagram or arc diagram. The relevance and linkages between the project FEP items are mapped and presented in the form of network diagrams and network tables. The platform designed in this study will be used to manage the FEP DB, analyze and visualize the relationship between the FEP and scenarios, and finally construct the performance assessment scenarios. It is expected that the platform itself will be used as a part of the knowledge management system and facilitate efficient collaboration and knowledge exchange among experts.

For Dry Storage of Spent Nuclear Fuel (SNF), all moisture must be removed from the dry storage canister through subjected to a drying process to ensure the long-term integrity. In NUREG-1536, the evacuation of most water contained within the canister is recommended a pressure of 0.4 kPa (3 torr) to be held in the canister for at least 30 minutes while isolated from active vacuum pumping as a measure of sufficient dryness in the canister. In the existing drying process, the determination of drying end point was determined using a dew point sensor indirectly. Various methods are being studied to quantify the moisture content remaining inside the canister. We presented a moisture quantification method using the drying process variables, like as temperature, pressure, and relative humidity operation data. During the drying process, it exists in the form of a mixed gas of water vapor and air inside the canister. At this time, if the density of water vapor in the mixed gas discharged out of the canister by the vacuum pump is known, the mass of water removed by vacuum drying can be calculated. The canister is equipped with a pressure gauge, thermometer and dew point sensor. The density of water vapor is calculated using the pressure, temperature and relative humidity of the gas obtained from these sensors. First, calculate the saturated water vapor pressure, and then calculate the humidity ratio. The humidity ratio refers to the ratio of water vapor mass to the dry air mass. After calculating the density of dry gas, multiply the density by the humidity ratio to calculate the density of water vapor (kg/m3). Multiply the water vapor density by the volume flow (m3/s) to obtain the mass value of water (kg). The calculated mass value is the mass value obtained per second since it is calculated through the flow data obtained every second, and the amount of water removed can be obtained by summing all the mass values. By comparing this value with the initial moisture content, the amount of moisture remaining inside the canister can be estimated. The validity of the calculations will be verified through an experimental test in the near future. We plan to conduct various research and development to quantify residual water, which is important to ensure the safety of the drying process for dry storage.

As drone technology and industry develop around the world, the use of drones are increasing in number and expanding to different fields. On the other hand, illegal flight and terrorist incidents using drones are also increasing day by day. In Korea, it is reflected in the “Design Basis Threat (DBT)”, which is the standard for designing and evaluating the physical protection system of nuclear power plants in accordance with the “Act on Physical Protection and Radiological Emergency”, that nuclear power plants continue to establish physical protection against drone threats. A total of 141 drone attacks or incidents have occurred around the world since 2015. Cases related to the Russian-Ukraine war, in which so many cases occurred, were excluded. There were 112 cases (79%) of terrorism or suspected terrorism using a single drone. There were 4 cases of terrorism using more than 5 drones, and a total of 20 drones were used to attack an oil facility in Yemen (2019). By region, a total of 111 incidents occurred in Middle East & North Africa. By country, there were 49 cases in Iraq, 35 cases in Saudi Arabia, and 8 cases in Syria. Among major countries, three cases occured in Korea, five in the United States, two in England, Canada, and Italy, and one in Japan and France. Since 2021, there have been 15 drone attacks. Multiple drones were used in attacks targeting military or large-scale Important National Facilities such as the Saudi oil refinery, Indian Kashmir air base, and reconnaissance of Iranian Natanz nuclear and surrounding military facilities. Also in 89% of the cases, the drones were loaded with explosives in order to cause large-scale damage. Accordingly, nuclear power plants, which are important national facilities, need to establish a system that can detect and respond to multiple drones. Furthermore, additional protective measures are needed for areas that are expected to be severely damaged which can be established by evaluating the impact of explosives on major points in the plant. In additionthere is a high possibility of terrorism by organizations aiming for national turmoil rather than individual terrorists. So it is important to identify signs of terrorism in advance and prepare through cooperation with related agencies.