Based on the random-vibration-theory methodology, dynamic responses of nuclear facilities subjected to obliquely incidental and incoherent earthquake ground motions are calculated. The spectral power density functions of the 6-degree-of-freedom motions of a rigid foundation due to the incoherent ground motions are obtained with the local wave scattering and wave passage effects taken into consideration. The spectral power density function for the pseudo-acceleration of equipment installed on a structural floor is derived. The spectral acceleration of the equipment or the in-structure response spectrum is then estimated using the peak factors of random vibration. The approach is applied to nuclear power plant structures installed on half-spaces, and the reduction of high-frequency earthquake responses due to obliquely incident incoherent earthquake ground motions is examined. The influences of local wave scattering and wave passage effects are investigated for three half-spaces with different shear-wave velocities. When the shear-wave velocity is sufficiently large like hard rock, the local wave scattering significantly affects the reduction of the earthquake responses. In the cases of rock or soft rock, the earthquake responses of structures are further affected by the incident angles of seismic waves or the wave passage effects.

In general, after the decommissioning of nuclear facilities, buildings on the site can be demolished or reused. The NSSC (Nuclear Safety and Security Commission) Notice No. 2021-11 suggests that when reusing the building on the decommissioning site, a safety assessment should be performed to confirm the effect of residual radioactivity. However, in Korea, there are currently no decommissioning experiences of nuclear power plants, and the experiences of building reuse safety assessment are also insufficient. Therefore, in this study, we analyzed the foreign cases of building reuse safety assessment after decommissioning of nuclear facilities. In this study, we investigated the Yankee Rowe nuclear power plant, Rancho Seco nuclear power plant, and Hematite fuel cycle facility. For each case, the source term, exposure scenario, exposure pathway, input parameter, and building DCGLs were analyzed. In the case of source term, each facility selected 9~26 radionuclides according to the characteristics of facilities. In the case of exposure scenario, building occupancy scenario which individuals occupy in reusing buildings was selected for all cases. Additionally, Rancho Seco also selected building renovation scenario for maintenance of building. All facilities selected 5 exposure pathways, 1) external exposure directly from a source, 2) external exposure by air submersion, 3) external exposure by deposited on the floor and wall, 4) internal exposure by inhalation, and 5) internal exposure by inadvertent ingestion. For the assessment, we used RESRAD-BUILD code for deriving building DCGLs. Input parameters are classified into building parameter, receptor parameter, and source parameter. Building parameter includes compartment height and area, receptor parameter includes indoor occupancy fraction, ingestion rate, and inhalation rate, and source parameter includes source thickness and density. The input parameters were differently selected according to the characteristics of each nuclear facility. Finally, they derived building DCGLs based on the selected source term, exposure scenario, exposure pathway, and input parameters. As a result, it was found that the maximum DCGL was 1.40×108 dpm/100 cm2, 1.30×107 dpm/100 cm2, and 1.41×109 dpm/100 cm2 for Yankee Rowe nuclear power plant, Rancho Seco nuclear power plant, and Hematite fuel cycle facility, respectively. In this study, we investigated the case of building reuse safety assessment after decommissioning of the Yankee Rowe nuclear power Plant, Rancho Seco nuclear power plant, and Hematite fuel cycle facility. Source terms, exposure scenarios, exposure pathways, input parameters, and building DCGLs were analyzed, and they were found to be different depending on the characteristics of the building. This study is expected to be used in the future building reuse safety assessment after decommissioning of domestic nuclear power plants. This work was

A large spectrum of possible stakeholders and important factors for safety improvement during decommissioning of nuclear facilities should be identified. Decommissioning includes additional aspects which are of interest to a wider range of stakeholders. The way in which local communities, the public in general, and a wide range of other parties are engaged in dialogue about decommissioning of nuclear facilities is likely to become an increasingly important issue as the scale of the activity grows. Timely stakeholder involvement may enhance safety and can encourage public confidence. Stakeholder engagement may result in attention to issues that otherwise might escape scrutiny. Public confidence is improved if issues that are raised by the public are taken seriously and are carefully and openly evaluated. Experience in many countries has shown that transparency can be an extremely effective tool to enhance safety performance. It sets out the development and implementation of an effective two-way process between the organization and stakeholders. Meaningful engagement is characterized through a flow of communication, opinions and proposals in both directions and the use of collaborative approaches to influence and explain decisions. The process is one in which an organization learns and improves its ability to perform meaningful stakeholder engagement while developing relationships of mutual respect, in place of one-off consultations. The evolving nature of this process is particularly relevant to pipeline projects, which will have differing stakeholder engagement requirements at each phase of the project lifecycle. Activity undertaken at all stages of the process should be documented to ensure engagement success can be reviewed and improved and to ensure historical decisions or engagements are captured in case stakeholders change during the progression of time and previous consultation records are required.

In order to enter a nuclear power plant, access approval is required in advance, and biometric information such as fingerprints of visitors must be registered when issuing a key card, and only those certified through biometric equipment can enter the nuclear facilities (Protected area II). Fingerprint recognizers and facial recognizers are installed and operated in domestic nuclear facilities for access control. Domestic nuclear facilities establish and implement a protection system in accordance with physical protection requirements under the “Act on Physical Protection and Radiological Emergency” and “Physical Protection Regulations” of each nuclear facility. Detailed implementation standards are specified in Regulation Standard (RS) documents established and distributed by KINAC. Biometrics are mentioned in a KINAC RS-104 (Access Control) document. In this study, it was analyzed what points should be considered in order to prepare for performance tests and establish plans for biometric devices. In order for the results of performance evaluation of biometric devices to obtain high reliability and to be applied to nuclear facilities in the future, standardized performance evaluation targets, procedures, standards, and environments must be created. In order to collect samples such as fingerprints for performance evaluation, the size roll of the sample shall be determined, and the appropriateness of the sample size shall be evaluated in consideration of reliability and error range. In addition, the analysis results for the characteristics (gender, age, etc.) of the sample should be presented. When collecting samples, conflicts with other laws such as personal information protection should be considered, and the reliability of the performance test result data should be analyzed and presented. Quality evaluation should also be performed on forged biometric information data such as silicon fingerprints. In addition, when establishing a performance evaluation plan, a systematic evaluation procedure should be established by referring to domestic and foreign certification and evaluation systems such as the Korea Internet & security Agency (KISA). In order to improve the completeness of the access control system using the biometrics of nuclear facilities, it is necessary to test the performance of biometric devices and to install and operate only devices that have the ability to defend against counterfeit technology. In this study, it was analyzed what points should be considered in order to prepare for performance tests and establish plans for biometric devices.

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.

The guidelines for cyber security regulations at domestic and foreign nuclear facilities, such as KINAC/RS-015, NRC’s RG5.71 and NEI 13-10, require the establishment of security measures to maintain the integrity of critical digital assets (CDAs) and protect them as threats to the supply process. According to the requirements, cyber security requirements shall be reflected in purchase requirements from the time of introduction of CDAs, and it shall also be verified whether cyber security security measures were properly applied before introduction. Domestic licensees apply measures to control the supply chain in the nuclear safety sector to cyber security policies. The safety sector supply chain control policy has areas that functionally overlap with the requirements of cyber security regulations, so regulatory guidelines in the safety sector can be applied. However, since most of the emergency preparedness and physical protection functions introduce digital commercial products, there is a limit to applying the control of the supply chain in the safety field as it is. It is necessary to apply supply chain control operator policies, procedures, and purchase requirements for each SSEP function, or to establish cyber security integrated supply chain control requirements. In this paper, based on the licensee’s current supply chain control policy, the cyber security regulation plan for supply chain control according to the SSEP (Safety-Security-Emergency Preparedness) function of CDAs is considered.

Kori unit 1, Korea’s first light-water nuclear power plant, was permanently shut down in June 2017. The operator, Korea Hydro & Nuclear Power Co. (KHNP), submitted a final dismantling plan for Kori unit 1 to the Nuclear Safety and Security Commission (NSSC) in May 2021. Pursuant to this procedure, the NSSC is preparing regulations for the decommissioning stage of large nuclear facilities for the first time in the Republic of Korea. The Korea Institute of Nuclear Non-proliferation and Control (KINAC) is also considering applying regulations on safeguards. Moreover, the International Atomic Energy Agency (IAEA) developed the “International Safeguards Guidelines for Nuclear Facilities under Decommissioning” in 2021. The guidelines describe the detailed application of safeguards measures to be considered when decommissioning nuclear facilities, dismantling essential equipment, and providing relevant information to the IAEA, as well as the scope of IAEA inspections. In addition, Dr. R. Bari of the Brookhaven National Laboratory (BNL) proposed the Facility Safeguardability Assessment (FSA), a methodology that reflects facility characteristics from the design stage to ensure that designers, national regulators, and the IAEA communicate smoothly regarding safeguards measures. The FSA process derives expected problems with safeguards measures considering new nuclear facilities by analyzing the gap of safeguards measures applied to existing similar nuclear facilities. This study uses the existing FSA methodology to predict problems related to safeguards measures when decommissioning nuclear facilities and to analyze deviations from safeguards measure requirements according to IAEA guidelines. To this end, the reference facility is set as an operating pressurized light water reactor; the issues with the safeguards measures are summarized using the FSA Process; and a draft safeguards concept for nuclear facilities under decommissioning is designed. Furthermore, validity is confirmed through a simple analysis of the diversion path, and implications and lessons are derived. Through this, it is possible to anticipate new safeguards measures to be applied when decommissioning nuclear facilities in the Republic of Korea and review problems and considerations in advance.

The transport of radionuclides at oceanic scales can be assessed using a Lagrangian model. In this review an application of such a model to the Atlantic, Indian and Pacific oceans is described. The transport model, which is fed with water currents provided by global ocean circulation models, includes advection by three–dimensional currents, turbulent mixing, radioactive decay and adsorption/release of radionuclides between water and bed sediments. Adsorption/release processes are described by means of a dynamic model based upon kinetic transfer coefficients. A stochastic method is used to solve turbulent mixing, decay and water/sediment interactions. The main results of these oceanic radionuclide transport studies are summarized in this paper. Particularly, the potential leakage of 137Cs from dumped nuclear wastes in the north Atlantic region was studied. Furthermore, hypothetical accidents, similar in magnitude to the Fukushima accident, were simulated for nuclear power plants located around the Indian Ocean coastlines. Finally, the transport of radionuclides resulting from the release of stored water, which was used to cool reactors after the Fukushima accident, was analyzed in the Pacific Ocean.

Today, the domestic and international nuclear power industry is experiencing an acceleration in the scale of the nuclear facility decommissioning market. This phenomenon is also due to policy changes in some countries, but the main reason is the rapid increase in the proportion of old nuclear power plants in the world, mainly in countries that introduced nuclear power plants in the early stages. Decontamination is essential in the process of decommissioning nuclear facilities. Among various decontamination targets, radionuclides are adsorbed between pores in the soil, making physical decontamination quite difficult. Therefore, various chemical decontamination technologies are used for contaminated soil decontamination, and the current decontamination technologies have a problem of generating a large amount of secondary wastes. In this study, soil decontamination technology using supercritical carbon dioxide is proposed and aimed to make it into a process. This technology applies cleaning technology using supercritical fluids to decontamination of radioactive waste, it has important technical characteristics that do not fundamentally generate secondary wastes during radioactive waste treatment. Supercritical carbon dioxide is harmless and is a very useful fluid with advantages such as high dissolution, high diffusion coefficient, and low surface tension. However, since carbon dioxide, a non-polar material, shows limitations in removing polar and ionic metal wastes, a chelating ligand was introduced as an additive. In this study, a ligand material that can be dissolved in supercritical carbon dioxide and has high binding ability with polar metal ions was selected. In addition, in order to increase the decontamination efficiency, an experiment was conducted by adding an auxiliary ligand material and ultrasonic waves as additives. In this study, the possibility of liquefaction of chelating ligands and auxiliary ligands was tested for process continuity and efficiency, and the decontamination efficiency was compared by applying it to the actual soil classified according to the particle size. The decontamination efficiency was derived by measuring the concentration of target nuclides in the soil before and after decontamination through ICP-MS. As a result of the experiment, it was confirmed that the liquefaction of the additive had a positive effect on the decontamination efficiency, and a difference in the decontamination efficiency was confirmed according to the actual particle size of the soil. Through this study, it is expected that economic value can be created in addition to the social value of the technology by ensuring the continuity of the decontamination process using supercritical carbon dioxide.

Nuclear operators must sort out their digital assets as Critical Digital Asset (CDA) and manage their vulnerabilities. Since vulnerabilities are continually found and can be abused anytime, and the number of digital assets in nuclear facilities is increasing, it is important to collect publically-known vulnerabilities in automated mechanism to reevaluate their risks. KINAC is now in progress of establishing an automated mechanism of collecting publically-known vulnerabilities for nuclear facilities. This paper will discuss about criteria of selecting database when establishing an automated mechanism of collecting publically-known vulnerabilities for nuclear facilities. When selecting sets of vulnerability database, the characteristic of sets of digital assets need to be managed, importance of each digital asset, and where and who will use the set of digital assets should be mainly considered. Most of safety-related CDAs are made and used in the United States, and safety-related CDAs are similar to Information and Communication Technology (ICT) facilities. Therefore, the main vulnerability database used in the United States should be included when collecting the database of vulnerabilities. Especially, US government actively provides vulnerabilities of digital assets, enacting vulnerability disclosure policy to make each organization report their own potential vulnerabilities. The main vulnerability database of the US is National Vulnerability Database (NVD) of NIST. It contains over 150,000 vulnerabilities on ICT and Industrial Control System (ICS). Nuclear Energy Institute (NEI) published “Cyber Security Vulnerability and Risk Management”, Addendum 5 to NEI 08-09, and informed that US-CERT, ICS-CERT, and NVD can be used as publically-known vulnerability database, and US National Regulatory Commission (NRC) endorsed the publication. In South Korea, KrCERT and National Cyber Threat Intelligence (NCTI) share publically-known vulnerabilities, however, the number of vulnerabilities are less than those of NVD, and most of the data are duplication of those of NVD. Moreover, certain portion of information are only opened to authorized organizations, so it is unable to access those databases. Therefore, considering the fact that most information of vulnerabilities of CDAs are included in NVD and ICS-CERT, vulnerability database should also contain information from NVD and ICS-CERT. Otherwise, the database must contain equivalent information compared to NVD and ICS-CERT. Furthermore, the methodology for collecting vulnerabilities of digital assets from other countries is also required to be studied in the future research.

In accordance with the Enforcement Decree of the Act on Physical Protection and Radiological Emergency, operators of Nuclear Power Plants (NPP)s must conduct full cyber security exercise once a year and partial exercise at least once every half year. Nuclear operators need to conduct exercise on systems with high attack attractiveness in order to respond to the unauthorized removal of nuclear or other radioactive material and sabotage of nuclear facilities. Nuclear facilities identify digital assets that perform SSEP (Safety, Security, and Emergency Preparedness) functions as CDA (Critical Digital Assets), and nuclear operators select exercise target systems from the CDA list and perform the exercise. However, digital assets that have an indirect impact (providing access, support, and protection) from cyber attacks are also identified as CDAs, and these CDAs are relatively less attractive to attack. Therefore, guidelines are needed to select the exercise target system in the case of unauthorized removal of nuclear or other radioactive material and sabotage response exercise. In the case of unauthorized removal of nuclear or other radioactive material, these situations cannot occur with cyber attacks and external factors such as terrorists must be taken into consideration. Therefore, it is necessary to identify the list of CDAs that terrorists can use for cyber attacks among CDAs located in the path of stealing and transporting nuclear material and conduct intensive exercise on these CDAs. A typical example is a security system that can delay detection when terrorists attack facilities. In the case of sabotage exercise, a safety-related system that causes an initiating event by a cyber attack or failure to mitigate an accident in a DBA (Design Basis Accident) situation should be selected as an exercise target. It is difficult for sabotage to occur through a single cyber attack because a nuclear facility has several safety concepts such as redundancy, diversity. Therefore, it can be considered to select an exercise target system under the premise of not only a cyber attack but also a physical attack. In the case of NPPs, it is assumed that LOOP (Loss of Offsite Power) has occurred, and CDA relationships to accident mitigation can be selected as an exercise target. Through exercise on the CDA, which is more associated with unauthorized removal of nuclear or other radioactive material and sabotage of nuclear facilities, it is expected to review the continuity plan and check systematic response capabilities in emergencies caused by cyber attacks.