원전 구조물의 실시간 모니터링 기술이 요구되고 있지만, 현재 운영 중인 지진 감시계통으로는 동특성 추출 등 시스템 식별이 제한 된다. 전역적인 거동 데이터 및 동특성 추출을 위해서는 다수의 센서를 최적 배치하여야 한다. 최적 센서배치 연구는 많이 진행되어 왔 지만 주로 토목, 기계 구조물이 대상이었으며 원전 구조물 대상으로 수행된 연구는 없었다. 원전 구조물은 미미한 신호대잡음비에도 강건한 신호를 획득하여야 하며, 모드 기여도가 저차 모드에 집중되어 있어 모드별 잡음 영향을 고려해야 하는 등 구조물 특성을 고려 해야 한다. 이에 본 연구에서는 잡음에 대한 강건도와 모드별 영향을 평가할 수 있는 최적 센서배치 방법론을 제시하였다. 활용한 지표 로서 auto MAC(Modal Assurance Criterion), cross MAC, 노드별 모드형상 분포를 분석하였으며, 잡음에 대한 강건도 평가의 적합성을 수치해석으로 검증하였다.

Offshore wind power development has been promoted in countries around the world to cope with global warming. Despite its many advantages, offshore wind power affects the marine environment during construction and operation. As a result, the reduction of fishing areas, changes in the habitat of marine animals, damage to fishing gear, and impeding the safety of fishing activities are occurring. If the offshore wind power generation project is carried out, a fishing damage investigation is nescssary. There are only four fishing damage investigations related to offshore wind power, which are being conducted similarly to the existing fishing damage investigation related to offshore construction. Therefore, this study reviewed and analyzed the report on fisheries damage investigation related to offshore wind power conducted in Korea and suggested problems and improvement measures accordingly.

This study is to propose ways to improve the system for rational procedures for offshore wind power generation projects. The results of this study are summarized as follows. In order to quickly distribute and develop offshore wind power projects, the permitting period should be shortened through special laws, the government actively intervenes to support the formation and operation of privat-public councils to ensure residents' acceptance. In this way, it can be competitive in the future energy market. Above all, a special law (proposal) related to offshore wind power currently pending in the National Assembly should be passed as soon as possible. Finally, the government and local governments that manage public waters should provide active administrative support based on system improvement measures in consideration of these permits, and the project’s main body should minimize damage to the marine environment and ecosystem. Through these subject-specific roles, offshore wind power generation will be able to reduce carbon emissions and help establish a sustainable energy production system.

외부하중을 받는 구조물로부터 계측된 신호의 파워 스펙트럴 밀도함수는 모달 파라미터(고유진동수, 감쇠비)에 대한 상당량 의 정보를 함축하고 있다. 시스템 식별기술은 이러한 신호나 해당 스펙트럼으로부터 모달 파라미터를 추출하는 기법이라고 볼 수 있 다. 파라미터를 추출하는 또 다른 기법으로는 샘플링(신호)을 이용하여한 확률분포의 모수(평균, 분산)를 추정하는 기법이다. 본 연구 에서는 파워 스펙트럼 밀도함수를 확률분포로 치환함으로써 기존 확률통계분야에서 모수를 추출하는 기법(최대우도법)에 의해 모달 파라미터를 추정하는 기법을 제안한다. 모드형상을 추정하는 기법을 개발하고 모드형상에 의해 분해된 모드응답으로부터 고유진동수, 고유감쇠비를 순차적으로 산정하는 기법을 제시한다. 더 나아가, 외부하중이 스펙트럼 해석모델로 치환 가능한 경우에는 이 하중모델 은 통합하여 모델 파라미터까지 산정하는 기법으로 확대한다. 본 연구에서 제시된 기법을 검증하기 위한 수치해석과 실구조물의 응답 에 대한 적용이 이루어졌으며, 검증결과 제안된 모드식별체계가 안정적이며, 신뢰도가 높은 모달파라미터 추정이 가능함을 알 수 있었다.

지난 20년간에 걸쳐 유머 경영은 효과적인 경영전략 기법으로 간주되고 있으며, 유머 경영의 실천적 방안 중 하나인 상사 유머는 부하직원의 태도, 행동에 바람직한 효과를 발휘한다는 결과가 제시되고 있다. 하지만 상사 유머를 설명하는 이론들, 상사 유머의 효과 연구 등에서 상사 유머의 혼재된 결과가 나타나 고 있다. 이러한 논쟁을 해소하기 위하여 상사 유머에 부하직원이 반응하는 데 있어 제한적 조건 (boundary condition)을 고려할 필요가 있다. 본 연구는 수평적인 조직문화가 확산되고 있다는 측면과 더 불어 상사 유머를 하향식 의사소통 방식으로, 부하직원의 발언 행동을 상향식 의사소통 방식으로 보고 상사의 관점을 수용하기 위해서는 개인이 인식하고 있는 권력거리가 중요한 제한적 조건이라고 판단하였다. 이에 권력거리를 낮게 인식할수록 상사의 유머 관점을 쉽게 수용하게 되면서 부하직원은 발언 행동을 증가시킬 수 있지만 권력거리를 높게 인식할수록 상사의 유머 관점을 수용하기 어려워지면서 부하직원은 발언 행동을 감소시킬 수 있다고 보았다. 국내 기업에 종사하는 220명 중간 관리자급을 대상으로 한 연구 결과를 보면 다음과 같다. 상사 유머와 발언 행동 간의 관계에서 권력거리는 조절 효과가 있는 것으로 나타났다. 구체적으로 권력거리를 낮게 인식할수록 상사 유머는 발언 행동에 정적인 영향을 주는 것으로 나타났지만, 권력거리를 높게 인식할수록 상사 유머는 발언 행동에 부적인 영향을 주는 것으로 나타났다. 이상의 결과를 바탕으로 본 연구는 관점수용이론을 토대로 상사 유머의 효과에 대한 제한적 조건 연구 분야를 확장하는 데 기여하고 실무적으로 리더에 의하여 발현되는 하향식 의사소통인 상사 유머와 부하 직원에 의하여 발현되는 상향식 의사소통인 발언 행동 간의 관계에서 권력거리의 인식이 중요한 성향적 조절 효과가 있다는 결과를 제시함으로써 조직 내 의사소통에 유용한 시사점을 제시하고자 하였다.

Conventional flipped learning instructional models are operated in a blended learning environment online and offline. In contrast, this study moved onto fully online systems and explored how a sense of presence worked for students’ learning outcomes at university English writing courses. The two research questions for this study are: 1) What is the relationship between a sense of presence (teaching, cognitive, social presence) and learning outcomes (group cohesion, class satisfaction)? and 2) What are the variables among a sense of presence that affect group cohesion and class satisfaction? For the purposes of this study, 46 university students from English composition courses answered student questionnaires in the spring of 2021. Correlation and multiple-regression analyses were conducted to look into the relationships among the variables. Additionally, focus-group interviews were conducted and teaching journals were analyzed. The major findings were revealed as follows: Firstly, a sense of presence was significantly related to group cohesion and satisfaction. Secondly, social presence and cognitive presence only had a predictive power of group cohesion. Thirdly, cognitive presence and teaching presence were significant predictors of class satisfaction. Pedagogical implications are discussed for those interested in applying flipped learning in a fully online setting.

Given the limited terrestrial reserves of uranium (approximately 4.6 million tons), exploring alternative resources is necessary to secure a sustainable, long-term supply of nuclear energy. Uranium extraction from seawater (UES) is a potential solution since the amount of uranium dissolved in seawater (approximately 4.5 billion tons) is about 1,000 times that of terrestrial reserves. However, due to the ultra-low concentration of uranium in seawater (approximately 3.3 ppb), making UES economically viable is a challenging task. In this paper, we explore the potential of using thermal discharge from domestic nuclear power plants for uranium extraction. The motivation for this comes from previous research showing that the adsorption capacity of amidoxime-based adsorbents is proportional to the temperature of the seawater in which they are deployed. Specifically, a study conducted in Japan found that a 10°C increase in seawater temperature resulted in a 1.5-fold increase in adsorption capacity.

Zinc injection into the coolant system of nuclear power plants is an effective method for reducing corrosion and improving performance. The effectiveness of this method is influenced by various factors such as zinc concentration and injection rate. This paper provides an overview of the factors affecting the effectiveness of zinc injection in nuclear power plants, with a focus on zinc concentration and injection rate, and discusses various research results on the effects of these factors on corrosion reduction and coolant system performance. Zinc concentration is an important factor affecting the effectiveness of zinc injection. The research results show that gradual increases in zinc concentration are more effective for coolant system stability. However, the concentration should not exceed the recommended levels as high zinc concentrations can have negative effects on the system. Injection rate is also an important factor affecting the effectiveness of this method. The research results show that gradual increases in injection rate are more effective for coolant system stability. However, excessive injection rates can have negative effects on the system such as overload of the zinc injection facility and chemical shocks within the coolant system, and therefore, should be optimized. In conclusion, zinc concentration and injection rate are important factors affecting the effectiveness of zinc injection in nuclear power plants. The optimal concentration and injection rate should be determined based on specific reactor conditions and system requirements, and efforts should be made to maximize corrosion reduction and performance improvement.

The 2007 Recommendation of the International Commission on Radiological Protection recommended the application of dose constraints to optimize radiation protection to resolve the inequity of exposure among radiation workers. The average annual occupational doses in Korean nuclear power plants (NPPs) are 0.3-0.8 mSv. These doses are much lower than the annual effective dose limit of 50 mSv for radiation workers stipulated by the Nuclear Safety Act. In addition, most NPP workers received less than 0.1 mSv per year. These doses are lower than the average annual occupational doses of 0.3- 0.8 mSv. Korean regulatory body conducted the study to legislate the dose constraints in the Korean regulatory system and determine dose constraints (draft) for radiation workers. The legislation of dose constraints would not greatly affect the radiation protection programs in Korean NPPs because most workers received very low doses. However, some workers received relatively higher doses than others. This study analyzed the occupational exposure conditions, such as exposure type and situation, in Korean NPPs. This study investigated the internal and external radiation doses and the radiation doses depending on the NPP operating conditions, including normal operation, planned maintenance, and intermediate maintenance, for the last ten years (2012-2021). As a result, most NPP workers received external exposure rather than internal exposure. Furthermore, most radiation exposures occurred during the planned maintenance period. The results of this study can be used for optimizing occupational doses in Korean NPPs.

In this research, the dose rate was measured using a backpack-type scan survey device at 4 sites in sites around Nuclear Power Plants (Kori, Wolsong, Hanbit, Hanul), and the radioactivity ratio for each nuclide was evaluated using an high-purity germanium (HPGe) detector. Kori, Wolsong and Hanul power plants were measured within 2 km of the power plant, and Hanbit power plants were measured about 6.7 km from the power plant. As a result of measuring the dose rate with a backpacktype scan survey device, the average dose rate was the lowest in the measurement site 1 at 0.090 μSv/h, and the highest in the measurement site 4 at 0.145 μSv/h. All measurement points showed the domestic environmental dose rate level. The data obtained by the scan survey was visualized using the classed post and gridding functions of the surfer program. As a result of measurement with the HPGe detector, 137Cs was not detected, and only natural nuclides were detected. Among the detected natural nuclides, the radioactivity ratio was the highest for 40K with an average of 94.56%, and the lowest for 214Pb with an average of 0.26%. The results of this research can be used as basic data for radiation environment surveys around nuclear power plants. Further studies are needed to evaluate the radiation impacts by region and environment through periodic measurements.

According to attached Table 1 of the Enforcement Ordinance of the Nuclear Safety Act, the effective dose limit of transport workers shall not exceed 6 mSv per year. In addition, the enforcement ordinance defines a transport worker as a person who transports radioactive substances outside the radiation management area and does not correspond to a radiation worker. In the nuclear power plants (NPPs), substances in radiation management areas are frequently transported inside or outside the plant. During loading of substances in the radiation management area onto the vehicle, the transport workers (including driver) are located outside the radiation management area. And also the exposure dose of transport workers is managed by using Automatic Dose Reader (ADR). However, the exposure dose of transport workers managed by NPP licensee is limited to the exposure caused by the transport actions required by the plant. This means that radiation exposure caused by the transport of radioactive materials carried out separately by individual transport workers other than the plant requirements cannot be managed. Therefore, even if the NPP licensee manages the transport worker’s dose below 6 mSv, it is difficult to guarantee that the total annual exposure dose, including the transport worker’s individual transport behavior, is less than 6 mSv. Therefore, it would be appropriate to manage the dose of the transport worker by the transport worker’s agency rather than by the NPP licensee.

One aspect of securing safety from the operation of Nuclear Power Plants (NPPs) is to evaluate the impact on residents at the facility’s exclusive area boundary to confirm that the radiological risk is below the allowable level. Normally, the risks from gaseous and liquid effluents are evaluated during the operation of facilities. Meanwhile, in order to be approved for the decommissioning plan, the environmental risks caused by activities during dismantling is also evaluated. Therefore, this study aims to investigate the exposure pathways considered in evaluating the risks to nearby residents from the operation and decommissioning of nuclear facilities and to examine the differences. The emission rate by radionuclide is calculated by evaluating the amount of leak from nuclear fuel during the operation of the facility through design data of the NPP. Each of the liquid and gaseous effluents is calculated, and the exposure dose received by nearby residents is calculated by considering the exposure pathways with these emission rates. In order to initiate the decommissioning of nuclear facilities, approval of the Final Decommissioning Plan (FDP) must be obtained. The FDP chapter shall describe the results of the environmental impact assessment of the decommissioning. It will not differ significantly in the exposure pathways during operation. However, the decommissioning of nuclear facilities is ultimately to remove Systems, Structures, and Components (SSCs) and to remove the regulation of the Nuclear Safety Act by ensuring that sites and remaining buildings meet the criteria for the license termination. In terms of release and reuse of nuclear facilities, the exposure dose to be considered in evaluating the dose can be considered for two main types: the site and the remaining building. The factors affecting the exposure pathways considered in assessing the environmental impacts considered in the operation and decommissioning of nuclear facilities are due to gaseous and liquid effluents. However, the difference should reflect the impact of NPP operations and decommissioning activities when evaluating the amount of radionuclides released by these effluents. Decommissioning should consider the impact after decommissioning, which is the effect of the receptor by radionuclides remaining on the site and in the remaining buildings. At this time, the effects of the source from the soil and the source from the surface of the building should be considered for the external and internal exposure pathways.

The decommissioning of the Nuclear Power Plant (NPP) is a long-term project of more than 15 years and will be carried out as a project, which will require project management skills accordingly. The risk of decommissioning project is a combination of many factors such as the decommissioning plan, the matters licensed by the regulatory agency, the design and implementation of dismantling, the dismantling plan and organization, and stakeholders. There will be some difficulties in risk management because key assumptions about many factors and the contents of major risks should be well considered. Risk management typically performs a series of processes ranging from identification and analysis to evaluation. In order to analyze and evaluate risks here, identification of potential risks is the first step, and in order to reasonably select potential risks, various factors mentioned should be considered. Therefore, the purpose of this study is to identify possible risks that should be considered for the decommissioning project in various aspects. The risk of the decommissioning project can be defined using the hazard keyword, and the risk family presented in the IAEA safety series can also be referred. It would be better to approach the radiological or non-radiological risks that may occur in the dismantling work with the hazard keyword, and if the characteristics of the decommissioning project are reflected, it would be a good idea to approach it on a risk family basis. There are 10 top risks in the risk family, 25 risks at the level 2 and 61 risks at the level 3 are presented. It may be complex to consider these hazards and risks recommended as risk families at the same time, so using the results of safety evaluation as input data for risk identification can be a reasonable approach. Therefore, this study intended to derive the possible risks of the decommissioning project based on the risk family structure. At this point, the reflection of the safety assessment results was intended to be materialized by considering the hazards checklist. As a result, this study defined and example of 38 possible risks for the decommissioning project, considering the 10 top risk family and lower level risk categories. This result is not finalized, and it will be necessary to further strengthened through expert workshops or HAZOP in the future.

As a result of various generation, transmutation, and decay schemes, a wide variety of radionuclides exist in the reactor prior to accident occurrence. Considering all of the radionuclides as the accident source term in an offsite consequence analysis will inevitably take up excessive computer resources and time. Calculation time can be reduced with minimal impact on the accuracy of the results by considering only the nuclides that have a significant effect on the calculation among the potential radioactive sources that may be released into the environment. In earlier studies related to offsite consequence analysis, it is shown that the principal criteria for the radionuclide screening applied are as follows; radionuclide inventory in the reactor, radioactive half-life, radionuclide release fraction to the environment, relative dose contribution of nuclides within a specific group, and radiobiological importance. As a result, it is confirmed that 54, 60, and 69 nuclides are applied to the risk assessment performed in WASH-1400, NUREG-1150, and SOARCA (State-of-the-Art Reactor Consequence Analyses) project in the United States, respectively. In addition, in this study, the technical consultations with domestic and foreign experts were carried out to confirm details on criteria and process for screening out radionuclides in offsite consequence analysis. In this paper, based on the literature survey and technical consulting, we derived the screening process of selecting a list of radionuclides to be considered in the offsite consequence analysis. The first step is to eliminate radionuclides with little core inventory (less than specific threshold) or very short half-lives. However, important decay products of radionuclides that have short half-lives should not be excluded by this process. The next step is to further eliminate radionuclides by considering contribution to offsite impact, which is defined as a product of radioactivity released to the environment (i.e. ‘inventory in the reactor’ times ‘release fraction to offsite’) and comprehensive dose (or risk) coefficient taking into account all exposure pathways to be included. The final step is to delete isotopes that contribute less than certain threshold to any important dose metric through additional computer runs for each important source term. Even though it is presumed that this process is applicable to existing light water reactors and the set of accidents that would be considered in PSA, some of the assumptions or specific recommendations may need to be reconsidered for other reactor types or set of accident categories.

To evaluate the characteristics of radioactive waste from permanently shut down nuclear power plants for decommissioning, there is a method of directly analyzing samples and, on the other hand, a computerized evaluation method based on operation history. Even if the radioactivity of the structures or radioactive wastes in the nuclear power plant is analyzed by the computerized evaluation method, a method of directly analyzing the sample must be accompanied in order to more accurately know the characteristics of the nuclear power plant’s radioactive waste material. In order to obtain such samples, we need a way to collect materials from radioactive waste. However, in the case of a permanently shut down nuclear power plant with a long operating history, human access is limited due to radiation of the material. In this study, we propose a method of remotely collecting samples that guarantees radiation protection and worker safety at the site where radioactive waste is located.

Radioactive Oxide is formed on the surface of the coolant pipe of the nuclear power plant. In order to remove the oxide film that is formed on the surfaces of the coolant pipe, chemical and physical decontamination technologies are used. The disadvantage of traditional technologies is that they produce secondary radioactive wastes. Therefore, in this study, the short-pulsed laser eco-friendly technology was used in order to reduce the production of secondary radioactive wastes. It was also used to minimize the damage that was caused to the base material and to remove the contaminated oxide film. The study was carried out using a Stainless steel 304 specimen that was coated with nickel-ferrite particles. Additionally, a transport robot was 3D modeled and manufactured in order to efficiently remove the oxide film from the coolant pipe of the nuclear power plant. The transport robot has a fixed laser head to move inside the horizontal and vertical pipes. The rotating laser head removes the contaminated oxide film on the inner surface of the coolant pipe. In the future, as a condition of the 1064nm short-pulsed laser ablation technique determined by basic analysis, we plan to analyze whether the transport robot is applicable to the radiation contamination site of the nuclear power plant.

With the rapid growth of nuclear power in China, a large number of dry wastes, which mainly include the high efficiency particulate air filters (glass fiber), cotton, polyethylene, and absorbent paper with low-level radioactivity and high volume, will be produced during the operation and maintenance of the nuclear power plants. Thermal plasma treatment is a world acceptable technology to incinerate and immobilize radioactive wastes, owing to the high volume reduction factor and the excellent chemical durability of the vitrified waste form. China has developed thermal plasma technology for the treatment of dry wastes from nuclear power plants for more than 15 years and the pilot plant has been constructed. This work will concentrate on the formulation of waste glass fiber to adapt to the vitrification process. A three-component (glass fiber-CaO-Na2O) constrained-region mixture experiment was designed and their viscosity data was mainly studied. The quadratic Scheffé model was used to plot the component effect on melting temperature. The retentions of simulated nuclides, such as Co, Sr, and Cs in the glasses were analyzed. In addition, the glass fiber as a glass matrix to immobilize residual ashes from the thermal plasma gasification of cotton, polyethylene, and absorbent paper was investigated as well.

Kori-1 and Wolseong-1 nuclear power plants were permanently shut down in June 2017 and December 2019, and are currently in the preparation stage for decommissioning. In this regard, it is necessary to secure nuclear power plant decommissioning capacity in preparation for the domestic decommissioning marketplace. To address this, the Korea Research Institute of Decommissioning (KRID) was established to build a framework for the development of integrated nuclear decommissioning technology to support the nuclear decommissioning industry. The institute is currently under construction in the Busan-Ulsan border area, and a branch is planned to be established in the Gyeongju area. Recently, R&D projects have been launched to develop equipment for the demonstration and support verification of decommissioning technology. As part of the R&D project titled “Development and demonstration of the system for radioactivity measurement at the decommissioning site of a nuclear power plant”, we introduce the plan to develop a radioactivity measurement system at the decommissioning site and establish a demonstration system. The tasks include (1) measurement of soil radioactive contamination and classification system, (2) visualization system for massive dismantling of nuclear facilities, (3) automatic remote measurement equipment for surface contamination, and (4) bulk clearance verification equipment. The final goal is to develop a real-time measurement and classification system for contaminated soil at the decommissioning site, and to establish a demonstration system for nuclear power plant decommissioning. The KRID aims to contribute and support the technological independence and commercialization for domestic decommissioning sites remediation of nuclear power plant decommissioning site by establishing a field applicability evaluation system for the environmental remediation technology and equipment demonstration.

The nuclear power plant decommissioning project inevitably considers time, cost, safety, document, etc. as major management areas according to the PMBOK technique. Among them, document management, like all projects, will be an area that must be systematically managed for the purpose of information delivery and record maintenance. In Korea, where there is no experience in the decommissioning project yet, data management is systematically managed and maintained during construction and operation. However, if the decommissioning project is to be launched soon, it is necessary to prepare in consideration of the system in operation, what difference will occur from it in terms of data management, and how it should be managed. As a document that can occur in the decommissioning project, this study was considered from the perspective of the licensee. Therefore, the types of documents that can be considered at Level 1 can be divided into (1) corresponding documents, (2) project documents, (3) internal documents, and (4) reference materials. Four document types are recommended based on Level 1 for the classification of documents to be managed in the decommissioning of nuclear facilities. In this study, documents to be managed in the decommissioning project of nuclear facilities were reviewed and the type was to be derived. Although it was preliminary, it was largely classified into major categories 1, middle categories 2, and 3 levels, and documents that could occur in each field were proposed. As a result, it could be largely classified into corresponding documents, project documents, internal documents, and reference materials, and subsequent classifications could be derived. Documents that may occur in the decommissioning project must be managed by distinguishing between types to reduce the time for duplication or search, and the capacity of the storage can be efficiently managed. Therefore, it is hoped that the document types considered in this study will be used as reference materials for the decommissioning project and develop into a more systematic structure.