본 연구에서는 자기공명영상검사실 방사선사의 환자안전 문화 인식을 분석하고자 하였다. 수도권 자기공명영상검사 실에서 근무하는 방사선사 109명을 대상으로 일반적인 특성, 실태조사, 환자안전 문화 인식에 대해 설문 조사하였 다. 의료종사자들을 대상으로 개발된 한국형 환자안전문화 측정 도구에서 최상위 리더십을 경영진으로, 부서장이라 는 단어를 파트장으로 수정하였고 전문가 5인에게 내용 타당도를 검증받았다. 결과적으로 자기공명영상검사실에서 근무하는 방사선사의 환자안전 문화 인식 점수는 평균 3.97로 높았지만, 안전사고경험 비율이 65.1%로 높게 나타났 다. 따라서 정기적으로 이루어지고 있는 자기공명영상검사 안전교육의 효율성 제고를 위한 연구가 필요하며 본 연구 가 기초자료를 제공할 것이라 사료된다.

본 연구에서는 자기공명영상 검사 시 와인색 반영구 문신용 염료가 신호 강도에 미치는 영향을 분석하고, 전자파흡수 에 의한 발열 감소 방안을 연구하고자 하였다. 한천과 와인색 반영구 문신용 염료를 이용하여 염료가 퍼진 형태의 팬텀(패드형 팬텀)과 한곳에 뭉친 형태의 팬텀(주사형 팬텀)을 제작하였다. 두 팬텀은 전신용 자기공명영상장치에서 고속스핀에코(turbo spin echo, TSE)와 경사에코(gradient echo, GRE) 계열의 펄스열을 이용하여 2D와 3D로 검사하였다. 검사 후 영상 분석은 팬텀의 몸체, 염료, 공기 방울, 배경을 대상으로 총 720회의 신호강도를 측정하였 다. 전자파흡수에 의한 발열 감소 방안을 확인하기 위해 삽입형 온도계를 팬텀에 삽입 후 검사 전후 팬텀의 온도 변화를 확인하였다. 이때, 대기 온도의 상승 변화를 고려하기 위해 검사 전 대기 온도를 측정하였고, 발열 감소를 위한 방법으로 장치에 내장된 팬, 젖은 거즈, 얼음을 이용하였다. 신호 강도는 2D 영상보다 3D 영상이 좋았고, TSE 계열이 GRE 계열보다 좋았다. 특히 와인색 반영구 문신용 염료가 있는 부위의 신호강도는 공기 때문에 발생한 자화 율 인공물보다 신호강도가 낮게 측정되었다. 온도 측정 검사는 패드형 팬텀과 주사형 팬텀 모두 검사에 의한 온도상 승 효과가 있었으며 온도의 저감을 위한 방법으로 얼음 패드, 팬, 젖은 거즈 순서였다. 본 연구를 통해 와인색 반영구 문신용 염료는 자기공명영상 검사에서 영상과 환자의 안전에 문제를 일으킬 수 있음을 확인하였고, 발열 감소 방안으 로 얼음 패드가 효과적이었다는 것을 확인할 수 있었다.

The KINAC resident inspectors are responsible for conducting on-site regulatory and intergovernmental support tasks related to safeguards, physical protection, and cybersecurity in each NSSC regional office. In nuclear material accounting and control, resident inspectors primarily perform tasks such as national inspections and technical support for IAEA inspections. However, with the increasing cases of non-compliance with the advance notification procedure by operators, there is a growing need for improvement in the role of resident inspectors in on-site regulation. In response to this situation, the safeguards division in KINAC has analyzed and improved the on-site check procedures of resident inspectors at LWR facilities. The existing procedure outlines the process where resident inspectors receive the advance notification documents submitted by operators and utilize them as a reference for conducting weekly checks during the overhaul period when IAEA surveillance cameras are installed. Additionally, according to the attached forms specified in the procedure, resident inspectors are required to submit the check results report to the director of the safeguards division in KINAC every week and to the NSSC every month. The inspection items include checking the execution and changes of advance notification, verifying unnotified matters, discussing other issues, assessing the integrity of things such as the operational status of IAEA surveillance equipment, and so on. On April 13-14, 2023, the Safeguards division organized a two-day resident inspector’s work-sharing workshop to discuss improvements in the on-site check procedures of resident inspectors at LWR facilities. During the workshop, a comparison and analysis were conducted between the existing procedures and actual on-site activities. Unnecessary tasks such as advance notification document reception and monthly reporting were eliminated, and the focus was shifted towards emphasizing essential tasks. The opinions of resident inspectors were taken into account to derive directions for improvement. The existing procedure was applicable only during Overhaul periods for resident inspectors. It has been improved by removing this limitation, allowing its use during routine times. Furthermore, the procedure has been enhanced by clarifying its purpose, scope, users, and definitions of terms and specifying responsibilities and authorities. Unnecessary terminology has been eliminated. Remarkably, the definition of advance notification has been detailed, and the reporting of check results has been simplified through weekly task reporting. The Safeguards division in KINAC has strived to enhance the efficiency and simplification of on-site regulatory activities for resident inspectors at LWR facilities by improving their on-site check procedures. These improvement activities are expected to aid resident inspectors in effectively performing a wide range of tasks, including safeguards, physical protection, cybersecurity, and government support. In the future, it will be possible to continue refining the on-site check procedures by sharing the results of using the procedure in meetings and gathering various opinions from resident inspectors.

Among the public notices of the NSSC, five notices related to safeguards, including “Education of Nuclear Control, International Regulatory Materials, Preparation of Regulation of NMAC (Nuclear Material Accounting and Control), the National Inspection of NMAC, and Reporting of International Regulatory Materials” The regulations on the National Inspection of NMAC have remained the same since some revisions were made on December 26, 2017, raising the need to revise the public notice due to changes in the domestic and international safeguards regulatory environment. Accordingly, this paper analyzes the public notice of the National Inspection of NMAC and proposes the revision direction. The regulation regarding the National Inspection of NMAC comprises sections such as Purpose and Definition, Types - Scope - Frequency of the National Inspection, Notification of the National Inspection’s plan, and Management of Violation. Appendices include the contents of the violation table, explanations regarding types of violations, and various forms related to the National Inspection, which are attached separately. IAEA mentioned that ROK was selected as a pilot country for the Improved SLA (State-Level Approach) project starting in November 2020. IAEA explained that a quantitative and standardized methodology was adopted and developed for this purpose. As a result, the Unannounced Inspection at LWR facilities will transition to the Random Interim Inspection. Additionally, the Physical Inventory Verification in CANDU facilities will increase to once a year per reactor. This status will change the frequency and intensity of inspection at domestic nuclear facilities. Furthermore, domestically, there is an ongoing trend of continuous growth and diversification of nuclear facilities. In light of the changing domestic and international safeguards environment, it is necessary to set a direction for revising the regulation regarding the National Inspection of NMAC that was partially amended in 2017 to align with the current status. Firstly, due to the increased burden on operators resulting from the increased number of IAEA inspections following the application of Improved SLA, there is a need to streamline the National Inspection of NMAC frequency to enhance overall regulatory efficiency. Furthermore, the definition section should also be revised to include matters related to the regulation to reflect the current reality accurately. Considering the operation and name changes of new domestic nuclear facilities, there may be a need to add or modify computer input codes. While pursuing the revision of regulations regarding the National Inspection of NMAC, an analysis of the need for revision of other regulations related to safeguards should also be conducted, and directions should be set. Through this process, improving the regulatory framework that forms the basis of safeguards can help prevent confusion among operators and promote regulatory efficiency. We can better cope with these changes by proactively adapting to the rapidly changing domestic and international nuclear environment.

Uranium extraction from seawater has been a topic of considerable interest over the past decades. However, Commercial facilities for uranium extraction from seawater have not yet been constructed due to its lack of economic feasibility. With the increasing demand for sustainable energy sources, there is a growing interest in eco-friendly uranium extraction methods. Despite this, the safeguards associated with these extraction techniques remain relatively under-researched, necessitating comprehensive studies that address both the economic feasibility and safeguards approach. The Korea Hydro & Nuclear Power Central Research Institute is poised to elucidate the economic value of uranium extraction from seawater and embark on research to extract Yellow Cake from seawater on a laboratory scale. Given these advancements, it becomes imperative to consider the approach to safeguards. In this study, a comprehensive review was conducted to understand the relevant regulations that encompass both international obligations in partnership with the IAEA and domestic guidelines, specifically the Nuclear Safety Act. Emphasis was placed on a detailed examination of the IAEA’s comprehensive safeguards agreement and its additional protocol, focusing on deriving the necessary regulatory timings, subjects, and methodologies for effective reporting and verification. We reviewed the safeguards guidelines and the IAEA policy to confirm the international non-proliferation obligations. The study also reviewed the impact of the State-Level Approach promoted by the IAEA and its implications on state-specific factors and evaluations of state technological advancement. Additionally, the regulatory aspects of extracted uranium as an internationally regulated material under the Nuclear Safety Act were critically assessed. In conclusion, this study explains the international and domestic regulatory considerations for uranium extraction from seawater. Ultimately, this study will provide valuable understanding for policymakers, researchers, and practitioners involved in uranium extraction from seawater. Additionally, we expect that this study will contribute to establishing the safeguards approach and regulatory framework for the commercialization of uranium extraction from seawater in the ROK.

According to the ROK-IAEA Comprehensive Safeguards Agreement (CSA), the ROK submits inventory change reports (ICRs), physical inventory lists (PILs), and material balance reports (MBRs). Suppose inventory changes occur in each material balance area (MBA). In that case, the facility operators prepare ICRs monthly, conduct physical inventory taking (PIT) every 12 to 18 months, and submit PILs and MBRs to KINAC. KINAC reviews ICR presented by the facility operators, submits it to the IAEA, and reports it to the Nuclear Safety and Security Commission (NSSC). Various methods have been prepared and implemented to minimize errors in reviewing the accounting reports submitted by the facility operators. Accordingly, this paper analyzes the mistakes in the accounting reports that occurred over the past two years and proposed methods to improve them. The basis for carrying out the accounting reports is stipulated mainly in the CSA and the Nuclear Safety Act. First, Article 63 of the CSA describes the rationale for submitting the accounting reports, and the details are described in detail in the subsidiary arrangement. Article 98 of the Nuclear Safety Act stipulates information related to accounting reports, and details are described in the regulations on reporting internationally regulated materials, etc., of the NSSC Notice No. 2017-84. Among the accounting reports submitted in 2021, a total of 36 errors were confirmed. There were ten errors related to inventory changes, followed by six errors in the material balance period (MBP) in the header information. There were four cases of spacing, weight mismatch, and overdue errors, and the rest were related to grammar errors. There were a total of 30 errors in the accounting reports identified in 2022. MBP errors of header information, which occurred the second most in 2021, was the highest with nine, followed by six inventory change errors and five weight mismatch and overdue errors, respectively. Compared to 2021, the total number of errors has decreased by about six, which is interpreted as the result of outreach activities through accounting reporting workshops and nuclear control education conducted by KINAC. Accounting reporting is the most critical part of the Nuclear Material Accounting and Control (NMAC) system. Efforts to check errors in accounting reports and improve report quality through outreach activities could be confirmed by the statistics of the two years analyzed earlier. In the future, if the reporting program used by the facility operators is improved to minimize errors and manage the accounting reporting system through continuous maintenance work, the quality of the accounting reports will be upgraded to the next level.

KINAC began dispatching the resident inspector in 2012 to strengthen on-site Wolsong nuclear power plants (NPPs) regulations. The dispatched resident inspector is a member of the regional office of the Nuclear Safety and Security Commission (NSSC) and is in charge of technical support, on-site regulation of safeguards, and physical protection for the Wolsong regional office of NSSC. As the number of nuclear facilities in the ROK increased, the resident inspectors began to be dispatched to other regional offices. The resident inspectors were assigned to Hanul in November 2015, Kori in March 2017, Hanbit in March 2015, Saeul in March 2022, and Wolsong in March 2023. Accordingly, this paper intends to reflect on the increasing role of resident inspectors and predict on-site regulatory work in the field of nuclear control. The role of the resident inspectors is described in detail in the internal regulations of KINAC. Among the tasks in the common field is technical support at regional offices for the most critical areas of nuclear control implementation, and on-site verification of the matters requested by the director of each implementation division shall be carried out. Tasks in the field of safeguards include an on-site check of facility regulation review, implementation of national inspections, technical support for IAEA inspections, and information management. Among them, technical support work for Unannounced inspections should be the top priority. These days, in particular, the importance of reviewing the results of checking advanced information and containment and surveillance equipment by facility operators is emerging. Among the tasks performed by the resident inspectors, more than 80% of the functions related to physical protection account for. The resident inspectors check the status of the physical protection system by weekly/monthly/quarter, implement physical protection regulation review and inspection, conduct exercise evaluation, and perform technical support for special assessments. Recently, regulatory activities related to radioactive terrorism and the emergence of illegal drones have been strengthened. In the field of cybersecurity, where its role has recently been increasing, the resident inspectors are performing basic field regulation tasks. Similar to the area of physical protection, the resident inspectors check the cybersecurity system for weekly, monthly, and quarterly readiness, and on-site inspections of cybersecurity review and inspection technical support, exercise evaluation, and other requests are mainly performed. The role of the resident inspectors is expected to expand further in the future due to the increase in terrorist risks at home and abroad and changes in the regulatory environment. However, there is a limit to performing an increasing number of tasks, with the human resources of the resident inspectors limited to one to two for each site. If the resident inspectors are dispatched for each field of safety measures, physical protection, and cybersecurity, they can perform their duties more efficiently, but problems may arise in the operation of our personnel. Therefore, the proper and precise allocation of work while maintaining the current system is an essential part. The roles and prospects of the resident inspectors analyzed in this paper can be used to deploy the headquarters and field regulation personnel and set the direction of work in the future.

According to the “Law on protection and response measures for nuclear facilities and radiation”, Nuclear Power Plant (NPP) licensees should conduct periodic exercises based on hypothetical cyberattack scenarios, and there is a need to select significant and probable ones in a systematic manner. Since cyber-attacks are carried out intentionally, it is difficult to statistically specify the sequences, and it is not easy to systematically establish exercise scenarios because existing engineering safety facilities can be forcibly disabled. To deal with the above situation, this paper suggests a procedure using the Probabilistic Safety Assessment (PSA) model to develop a cybersecurity exercise scenario. The process for creating cyber security exercise scenarios consists of (i) selecting cyber-attack-causing initiating events, (ii) identifying digital systems, (iii) assigning cyber-attack vectors to a digital system, (iv) determining and adding type for operator’s response, (v) modifying a baseline PSA model, and (vi) extracting top-ranked minimal cut sets, and (vii) selecting a representative scenario. This procedure is described in detail through a case study, an expected cyber-attack scenario General Transient-Anticipated Transient Without Scram (GTRN-ATWS). It refers to an accident scenario for ATWS induced by GTRN. Since ATWS is targeted for cyber training in some NPPs, and GTRN is one of the most common accidents occurring in NPPs, GTRN-ATWS was chosen as an example. As for the cyber-attack vector, portable media and mobile devices were selected as examples based on expert judgment. In this paper, only brief examples of GTRN-ATWS events have been presented, but future studies will be conducted on an analysis of all initiating events in which cyber-attacks can occur.

The purpose of this study is to investigate the determinants that affect individual’s decision on whether or not to visit a winery in their state, and estimate the economic value that winery provide in terms of tourism. Survey data obtained from the residents in North Carolina, New York, and Virginia are used. First, a probit model is adopted to examine the factors that affect an individual’s decision whether or not to visit a winery in their state. Second, the economic value that wineries provide their visitors is derived from the winery trip demand that is estimated by a truncated negative binomial model. The consumer surplus estimates of visiting wineries are $28.9 per visit when the opportunity cost of time is not included, and $149.6 per visit when one-third of the wage rate is assumed as the opportunity cost of time.

Spent nuclear fuels are temporarily stored in nuclear power plant site. When a problem such as cracking of spent nuclear fuel assembly or cladding occurs or uranium that has not been separated during the reprocessing remains, it is necessary to treat it. The borosilicate glasses have been considered to vitrify whole spent nuclear fuel assembly. However, a large amount of Pb addition was necessary to oxidize metals in assembly to make them suitable for oxide glass vitrifcation. Furthermore, these borosilicate glasses need to be melted at high temperatures (> 1,400°C) when UO2 content is more than 20wt%. Iron phosphate glasses can be melted at a relatively low temperature (< 1,300°C) even with a similar UO2 addition. A composition of iron phosphate glass for immobilization of uranium oxide has been developed. The glasses have glass transition temperatures of ~555°C that are high enough to maintain its phase stability in geological repositories. The waste loading of UO2 in the glass is ~33.73wt%. Normalized elemental releases from the product consistency test were well below the US regulation of 2 g/m2. Nuclear criticality safety and heat generation in deep geological repositories were calculated using MCNP and computational fluid dynamics simulation, respectively. The glass had effective neutron multiplication factor (keff) of 0.755, which is smaller than the nuclear- criticality safety regulation of 0.95. Surface temperature of the disposal canister is expected to lower than the limit temperature (< 100°C). Most of the U in the glass is in the 4+state, which is more chemically durable than the 6+state. As a result of long-term dissolution experiment, chemically-durable uranium pyrophosphate (UP2O7) crystals were formed.

Safety assessment is important for the radioactive waste repositories, and several methods are used to develop scenarios for the management of radioactive waste. The intent of the use of these scenarios is to show how the radio nuclides release can affect the safety of disposal system. It plays an essential role of providing scientific and technical information for performance assessment of safety functions. As important as scenario is, numerous studies for their own scenario development have been conducted in many countries. Scenario development methodology is basically divided into four categories: (1) judgmental, (2) fault/event-tree analysis, (3) simulation, and (4) systematic. Under numerous research, these methods have been developed in ways to strengthen the advantages and make up for the weakness. However, it was hard to find any judgmental or fault/event-tree analysis approach in recent safety assessments since they are not well-systemized and difficult to cover all scenarios. Simulation and systematic approaches are used broadly for their convenience of analyzing needed scenarios. Furthermore, several new methodologies, Process Influence Diagram (PID)/Rock Engineering System (RES)/Hybrid, were developed to reinforce the systematic approach in recent studies. Currently, a government project related to the disposal of spent nuclear fuel is in progress in Korea, and the scenario development for safety case is one of the important tasks. Therefore, it is necessary to identify the characteristics and strengths and weaknesses of the latest scenario development and analysis methods to create a unique methodology for Korea. In this paper, the existing methodologies and cases will be introduced, and the considerations for future scenario development will be summarized by considering those used in the nuclear field other than repository issues. Systematic approach, which is the mostly commonly used method, will be introduced in detail with its use in other countries at the subsequent companion paper entitled ‘Case Study for a Disposal Facility for the Spent Nuclear Fuel’.

In Korea, research on the development of safety case, including the safety assessment of disposal facility for the spent nuclear fuel, is being conducted for long-term management planning. The safety assessment procedure on disposal facility for the spent nuclear fuel heavily involves creating scenarios in which radioactive materials from the repository reach the human biosphere by combining Features, Events and Processes (FEP) that describe processes or events occurring around the disposal area. Meanwhile, the general guidelines provided by the IAEA or top-tier regulatory requirements addressed by each country do not mention detailed methods of ‘how to develop scenarios by combining individual FEPs’. For this reason, the overall frameworks of developing scenarios are almost similar, but their details are quite different depending on situation. Therefore, in order to follow up and clearly analyze the methods of how to develop scenarios, it is necessary to understand and compare case studies performed by each institution. In the previous companion paper entitled ‘Research Status and Trends’, the characteristics and advantages/disadvantages of representative scenario development methods were described. In this paper, which is a next series of the companion papers, we investigate and review with a focus on details of scenario development methods officially documented. In particular, we summarize some cases for the most commonly utilized methods, which are categorized as the ‘systematic method’, and this method is addressed by Process Influence Diagram (PID) and Rock Engineering System (RES). The lessons-learned and insight of these approaches can be used to develop the scenarios for enhanced Korean disposal facility for the spent nuclear fuel in the future.

Since the 1992 ‘Joint Declaration of South and North Korea on the Denuclearization of the Korean Peninsula’ was agreed, various negotiations and policies have been conducted. There were policies such as CVID, Strategic Patience, Top-Down Approach, Calibrated Practical Approach, Audacious Initiative and the Geneva Agreement, and 9.19 Joint statement by the six-party talks were signed to denuclearize Korean Peninsula. However, starting with the first nuclear test in 2006, North Korea conducted six nuclear tests to develop atomic bombs, boosted fission bombs, ICBMs, and SLBMs to enhance its weapon capabilities. In addition, nuclear security crisis on the Korean Peninsula has been rising day by day as signs of restarting the North Korea’s Yongbyon 5MWe Graphite-moderated reactor were observed and the possibility of a seventh nuclear test have been increased. Since North Korea’s nuclear issue has a lot of influence on international security, especially on the Northeast Asian countries, a realistic denuclearization policy that reflects North Korea’s current domestic situation along with the international situation is needed. It’s been six months since Russia invaded Ukraine on February 24, 2022. The war between Russia, which has nuclear weapons, and Ukraine, which gave up its possession of nuclear weapons due to the Cooperative Threat Reduction (CTR) program known as the Nunn-Lugar program, is expected to have a significant impact on North Korea, which is considering denuclearization due to UN sanctions on North Korea. Therefore, in this study, based on the war patterns of Russia-Ukraine war, perspective on how it could affect North Korea’s denuclearization is analyzed. Also, significance and limitations of the previous nuclear negotiations, the North Korea’s political regime, the ‘five-year strategy for North Korea’s economic development’ and the ‘five-year plan for North Korea’s economic development’ were analyzed to suggest practical DPRK’s denuclearization policy.

This study is intended to determine the antimicrobial resistance properties and class 1 integrons of 30 Citrobacter freundii strains isolated from pet turtles in order to determine their threat to human health. Citrobacter freundii isolates were isolated and identified by employing biochemical tests and 16SrRNA gene sequencing. Disc diffusion test and PCR amplification were employed to detect antimicrobial resistance patterns and genes, respectively. Ampicillin, amoxicillin, cephalothin and nalidixic acid resistance were observed among all isolates. Rifampicin and cefoxitin resistance was the second most prevalent and observed in 97% of the isolates, respectively. All isolates scored multiple antimicrobial resistance (MAR) indices ≥ 0.2. Aminoglycoside resistant genes were the most prevalent. aac(3')-IIa was detected in 80% of the isolates followed by aphAI-IAB and strA-strB genes in 33% and 50% of the isolates, respectively. β-lactamase encoding blaTEM, blaCTX and blaSHV genes were detected in 53%, 43% and 17% of the isolates, respectively. tetA and tetB genes were the only tetracycline resistance genes detected in 17% and 10% of the isolates, respectively. Class 1 integron integrase encoding intI1 gene (47%) and dfrA17-aadA5 gene cassette array (7%) were also detected. Pet turtle-borne multidrug-resistant C. freundii is a reservoir of antimicrobial resistance determinants in the domestic environment which poses a risk of infection.

Magnesium potassium phosphate cements (MKPCs) are prepared by the acid-base reaction of dead burned magnesia (MgO) and monopotassium phosphate (KH2PO4). Low-pH cementitious materials such as MKPCs are currently of interest for the geological disposal of nuclear waste. MKPCs have advantages such as high early strength, high bonding strength, small drying shrinkage, low permeability, and high sulfate resistance. According to the results of previous studies, it is known that cesium, strontium, and cobalt are immobilized in the form of MgCsxK1−xPO4·6H2O, MgxSr1−xKPO4·6H2O, and Co3(PO4)2, respectively, in MKPCs. However, these results were predicted based on thermodynamic data, not directly observed precipitates to clearly show the evidence. Therefore, in this study, we directly analyzed the immobilized forms of Cs, Sr, and Co, respectively. CsNO3, Sr(NO3)2, and Co(NO3)2·6H2O powders (0.3 mol each) were mixed individually in each of the MKPC suspensions. The suspensions in which KH2PO4 was dissolved were pH 4.3 and the dissolution of MgO decreased the H+ concentration, raising the pH close to 11. The hydration products according to pH evolution in the MKPC suspensions were analyzed, and the change in the concentration of ions in the aqueous solution was also measured. An aqueous solution was obtained using a syringe filter (0.45 μm) to analyze the ion concentrations in the solution of the suspension. The collected solutions were diluted with nitric acid and analyzed using inductively coupled plasma mass spectrometry. To characterize the solid phases, the suspensions were obtained with a pipette at specific times and filtered under a vacuum in a Buchner funnel. Because the amounts of hydration products including Cs, Sr, and Co were small, it was not observed by XRD and TGA analysis, but their components could be analyzed by SEM-EDS. The final precipitate forms of Cs, Sr, and Co in the MKPC matrix are MgCsPO4·6H2O, SrHPO4, and Co3(PO4)2·8H2O, respectively.

Since July 2021, the Korea Radioactive Waste Agency has been conducting a safety case development study for the Korean deep geological repository program. The safety case includes generating scenarios in which radioactive materials from spent nuclear fuel repository reach the human biosphere by combining selective FEPs (Features, Events, and Processes). This safety case should be able to transparently explain the process in which conclusions have been drawn not only to stakeholders but also to the public by presenting safety arguments. The scenario development stage consisting of FEP screening, scenario generation, and uncertainty analysis procedures should have a database management system. Database management system was performed in countries such as Sweden, which obtained approval for the construction of spent nuclear fuel repositories, and the United States, where various preliminary research was carried out. Korea Atomic Energy Research Institute also has experience in designing and operating its own database, which has conducted preliminary research on disposal of the spent nuclear fuel. Currently, the safety assessment of the Korean spent nuclear fuel repository is in the early stages of research, but it is necessary to set up a basic framework for database design while the collection of FEP data from domestic and international preliminary studies is under development, and it is advantageous for efficient database construction and operation. Therefore, this paper presents the current status of database design considering completeness and transparency from the FEP screening stage to the scenario development stage in the safety assessment process of the Korean spent nuclear fuel repository. In this process, the functional requirements that the database should provide, the database schema capable of implementing them, and simple examples are presented together. The objectives of this database design are flexible FEPs management, high integrity and consistency, and expandability for linking with the safety case database. The FEP data to be inputted into the database includes a list of major opened FEPs, including International FEPs from Nuclear Energy Agency, which were referred for PFEPs (Project-specific FEPs), and PFEPs applied to POSIVA's Olkiluoto repository. As an additional function, queries from the database are used to visually express the process of deriving scenarios through Rock Engineering System, a widely known scenario generation methodology.

In South Korea, the master plan for high-level radioactive waste management, announced in 2016, suggested the construction and operation of intermediate storage facilities on a permanent disposal site and specified the adoption of dry storage in consideration of the ease of operation and expansion. As of 2021, the government is again reviewing its overarching policy on the back-end fuel cycles, including intermediate storage and permanent disposal. In the case of dry storage facilities, safety evaluation is being conducted using a combination of deterministic and probabilistic approaches, similar to that of nuclear power plants. The two methods are complementary, of which Probabilistic Safety Assessment (PSA) has the advantage of being able to identify key scenarios affecting safety, but its use in storage facilities has not been highlighted so far. However, depending on the spent fuel management phases such as loading, transportation, and storage, it may be not enough to capture effective and efficient safety evaluation only deterministically, and probabilistic methods may contribute to the evaluation of long-term operation or external events such as an earthquake. There have already been cases where PSA has been performed on a part of the nuclear fuel cycle through previous studies. This paper created the safety assessment model based on open sources such as the released EPRI reports, by targeting arbitrary intermediate storage facilities. The model considered the scenarios for loading, transportation, and storage, with human error respectively. It will be able to be modified and improved to fit domestic and specific intermediate storage facilities in the future.

The decommissioning of a nuclear power plant generates large amounts of radioactive waste, which is of several types. Radioactive concrete powder is classified as low-level waste, which can be disposed of in a landfill. However, its safe disposal in a landfill requires that it be immobilized by solidification using cement. Herein, a safety assessment on the disposal of solidified radioactive concrete powder waste in a conceptual landfill site is performed using RESRAD. Furthermore, sensitivity analyses of certain selected input parameters are conducted to investigate their impact on exposure doses. The exposure doses are estimated, and the relative impact of each pathway on them during the disposal of this waste is assessed. The results of this study can be used to obtain information for designing a landfill site for the safe disposal of low-level radioactive waste generated from the decommissioning of a nuclear power plant.