PURPOSES : The objective of this study was to review roadway management strategies that can be utilized in the event of a radiological emergency, select feasible alternatives, and simulate a portion of the West Coast network to analyze the effectiveness of these strategies. METHODS : The methodology of the study involved reviewing the relevant literature, extracting the implications, establishing an analysis procedure, and selecting an effectiveness evaluation scale. Using a national transportation database, a network was constructed using Toba, a macroscopic model. RESULTS : A reverse-flow lane system was applied to the West Coast Expressway Glory IC–Hampyeong IC (total 25 km), and a plan to increase the number of lanes was applied to the Seokgyo Street–Shinpyeong Intersection on National Route 23 (total extension 28 km). Consequently, both road management strategies were found to be effective. CONCLUSIONS : This study examined roadway management strategies that can be utilized in the event of a radiological emergency, selected feasible alternatives, and simulated a portion of the West Coast network to verify the effectiveness of these strategies. In the case of reverse flow lanes, it is most effective when applied to expressways that can restrict the entrance and exit of vehicles. In the case of increasing the number of lanes, it is most effective when applied to general roads, and institutional arrangements should be made to enable two-way traffic to use the reserved shoulder lanes.

Thermal cutting processes that can be applied to dismantling nuclear power plants include oxygen cutting, plasma cutting, and laser cutting. According to the global trend, research projects are being carried out in various countries to upgrade laser cutting, and many studies are also being conducted in Korea with plans to apply laser cutting processes when dismantling nuclear power plants. However, with the current technology level of the laser cutting process, the maximum thickness that can be cut is limited to 250 mm. Therefore, in this study, a laser-oxygen hybrid cutting process was implemented by adding a laser heat source to the oxygen cutting process that can cut carbon steel with a thickness of 250 mm or more (RV, beam, column, beam, etc.) when dismantling the nuclear power plant. This has the advantage of improving the cutting speed and reducing the cutting width Kerf compared to conventional oxygen cutting. In this research, the laser-oxygen hybrid cutting process consisted of laser cutting to which Raycus’ 8 kW Fiber Laser power source was applied and oxygen cutting to which hydrogen was applied with Fuel Gas. The oxygen torch was placed perpendicular to the test piece, and the laser head was irradiated by tilting 35° to 70°. The effects of cutting directions on quality and performance were studied, and cutting paths were selected by comparing cutting results. Thereafter, it was confirmed that there is an optimal laser output power according to the cutting thickness by studying the effect on the cutting surface quality by changing only the laser output power under the same cutting conditions. The results of this study are expected to be helpful in the remote cutting process using laser-oxygen hybrid cutting when dismantling domestic nuclear power plants in the future.

Considering the non-linear behavior of structure and soil when evaluating a nuclear power plant's seismic safety under a beyond-design basis earthquake is essential. In order to obtain the nonlinear response of a nuclear power plant structure, a time-domain SSI analysis method that considers the nonlinearity of soil and structure and the nonlinear Soil-Structure Interaction (SSI) effect is necessary. The Boundary Reaction Method (BRM) is a time-domain SSI analysis method. The BRM can be applied effectively with a Perfectly Matched Layer (PML), which is an effective energy absorbing boundary condition. The BRM has a characteristic that the magnitude of the response in far-field soil increases as the boundary interface of the effective seismic load moves outward. In addition, the PML has poor absorption performance of low-frequency waves. For this reason, the accuracy of the low-frequency response may be degraded when analyzing the combination of the BRM and the PML. In this study, the accuracy of the analysis response was improved by adjusting the PML input parameters to improve this problem. The accuracy of the response was evaluated by using the analysis response using KIESSI-3D, a frequency domain SSI analysis program, as a reference solution. As a result of the analysis applying the optimal PML parameter, the average error rate of the acceleration response spectrum for 9 degrees of freedom of the structure was 3.40%, which was highly similar to the reference result. In addition, time-domain nonlinear SSI analysis was performed with the soil's nonlinearity to show this study's applicability. As a result of nonlinear SSI analysis, plastic deformation was concentrated in the soil around the foundation. The analysis results found that the analysis method combining BRM and PML can be effectively applied to the seismic response analysis of nuclear power plant structures.

Laser cutting has been attracting attention as a next-generation tool in application for nuclear decommissioning. It enables high-speed cutting of thick metal objects, and its narrow kerf width greatly reduces the amount of secondary waste compared to other cutting methods. In addition, it only requires the relatively small cutting head without any complicated equipment, and long-distance cutting apart from a laser generator is possible using beam delivery through optical fiber. And there is almost no reaction force because it is non-contact thermal cutting. For these reasons, the laser cutting is very advantageous for remote cutting. In laser cutting, the irradiated laser power is absorbed and consumed to melt the material of the cutting target. When the applied laser power is greater than the power consumed for melting, the residual power is transmitted to the back of the cut object. This residual power may unintentionally cut or damage undesired objects located behind the cutting target. In order to prevent this, it is necessary to adjust the laser power for each thickness of the target object to be cut, or to increase the distance between the cut target and the surrounding structures so that the transmitted power density can be sufficiently lowered. In this work, safety study on residual power that penetrates laser-cut objects was conducted. Experimental studies were performed to find safe conditions for irradiation power density that does not cause surface damage to the stainless steel by adjusting the laser power and stand-off distance from the target.

본 연구에서는 기존 상용 SCR 촉매보다 비표면적, 경량성 및 온도 응답성이 우수한 SCR 촉매의 개발을 목적으로 바나듐과 텅스텐의 함량과 바인더의 첨가량을 달리하여 Metal foam 형태의 지지체에 코팅하여 SCR 촉매를 제조한 후, 실험실 규모의 마이크로 상압반응기상에서 공간속도별로 NOx 저감 성능을 측정하였다. 촉매의 특성은 Porosimeter, SEM(scanning electron microscope), EDX(energy dispersive x-ray spectrometer) 및 ICP(inductively coupled plasma), 실체현미경(Stereomicroscope) 기기를 이용하여 분석하였다. 연구 결과 NOx 저감 성능은 공간속도가 증가할수록 감소하였고, 바나듐과 텅스텐의 함량이 3.5 wt.% 일 때 가장 우수한 것으로 확인하였다. 또한, 바인더 첨가량이 많을수록 NOx 저감 성능이 감소하는 것으로 나타났는데, 이는 촉매 표면상의 활성점수가 바인더에 의해 점유되어 감소된 것에 따른 것으로 판단된다. 또한 표면 코팅 상태 분석을 통하여 바인더의 첨가량이 적절히 조절 되어야 함을 알 수 있었다.

본 논문에서는 원전해체 시 적용 가능한 제염기술을 조사하여 분석하였다. 이를 기반으로 최적의 제염기술을 선정하기 위 해 의사결정 기법(EXPERT-CHOICE)을 사용하여 기술성을 평가하였다. 이 평가방법은 해당 분야의 전문가로 이루어진 전 문가 집단에 의해 수행되는 것이 일반적이다. 가중치를 고려한 결과는 각 기준에 대한 가중치에 평가점수를 곱한 총합을 구 하는 식으로 수행하였다. 평가 점수를 3단계로 하여 High, Medium, Low로 구분한 후 가중치를 부여하여 차별화 시킬 수 있 다. 하위분류 기준의 세분화와 각 기준 별 가중치의 추가 정량화를 통하여 기술성 분석의 수준을 제고할 수 있고, 좀 더 설 득력 있는 결과의 도출을 예상할 수 있다. 평가의 기본 가정은 각 기준 별 가중치를 전문가 조사에 의해 부여하며, 평가 기 준은 High에 좀 더 비중을 주는 식으로 차별화 하였다. 이를 반영하면 H, M, L는 대략“10:5:1”의 비율로 평가 점수를 부여 받는데, 이는 EXPERT-CHOICE 기법의 최적화 분석에 따른 것이다. 최고 및 최저값을 제외한 나머지 결과값의 평균을 평가 치로 고려하였다.

The tsunami hazard analysis is performed for testing the application of probabilistic tsunami hazard analysis to nuclear power plant sites in the Korean Peninsula. Tsunami hazard analysis is based on the seismic hazard analysis. Probabilistic method is adopted for considering the uncertainties caused by insufficient information of tsunamigenic fault sources. Logic tree approach is used. Uljin nuclear power plant (NPP) site is selected for this study. The tsunamigenic fault sources in the western part of Japan (East Sea) are used for this study because those are well known fault sources in the East Sea and had several records of tsunami hazards. We have performed numerical simulations of tsunami propagation for those fault sources in the previous study. Therefore we use the wave parameters obtained from the previous study. We follow the method of probabilistic tsunami hazard analysis (PTHA) suggested by the atomic energy society of Japan (AESJ). Annual exceedance probabilities for wave height level are calculated for the site by using the information about the recurrence interval, the magnitude range, the wave parameters, the truncation of lognormal distribution of wave height, and the deviation based on the difference between simulation and record. Effects of each parameters on tsunami hazard are tested by the sensitivity analysis, which shows that the recurrence interval and the deviation dominantly affects the annual exceedance probability and the wave heigh level, respectively.

The Voronoi diagram of spheres and power diagram have been known as powerful tools to analyze spatial characteristics of weighted points, and these structures have variety range of applications including molecular spatial structure analysis, location based optimization, architectural design, etc. Due to the fact that both diagrams are based on different distance metrics, one has better usability than another depending on application problems. In this paper, we compare these diagrams in various situations from the user’s viewpoint, and show the Voronoi diagram of spheres is more effective in the problems based on the Euclidean distance metric such as nearest neighbor search, path bottleneck locating, and internal void finding.

Monitoring autocorrelated processes is prevalent in recent manufacturing environments. As a proactive control for manufacturing processes is emphasized especially in the semiconductor industry, it is natural to monitor real-time status of equipment throug

Expanded graphites were used as anode materials of high power Li-ion secondary battery. The expanded graphite was prepared by mixing the graphite with HClO4 as a intercalation agents and KMnO4 as a oxidizing agents. The physical and electrochemical properties of prepared expanded graphites through the variation of process variables such as contents of intercalation agent and oxidizing agent, and heat treatment temperature were analyzed for determination of optimal conditions as the anode of high power Li-ion secondary battery. After examing the electrochemical properties of expanded graphites at the different preparing conditions, the optimal conditions of expanded graphite were selected as 8 wt.% of oxidizing agent, 400 g of intercalation agent for 20 g of natural graphite, and heat treatment at 1000℃. The sample showed the improved charge/discharge characteristics such as 432 mAh/g of initial reversible capacity, 88% of discharge rate capability at 10 C-rate, and 24 mAh/g of charge capacity at 10 C-rate. However, the expanded graphite had the problems of potential plateaus like natural graphite and lower initial efficiency than the natural graphite.

본 연구는 기상자료모델 (Atmospheric Data Model, ADM) 중 한국의 중규모 수치기상모의에 자주 사용되는 WRF (Weather Research and Forecasting) 모델을 재생에너지 연구에 활용할 수 있도록 시각적으로 표출하고 이를 웹 기반의 공간정보 자료와 매시업 (mesh-up) 하였다. WRF 모델 포맷인 NetCDF 자료로부터 풍속, 풍향, 시간 정보를 읽어 바람의 시각화 표출 및 풍속을 시각적으로 전달하기 위한 형태 및 색상 정의 등 바람기호 (wind barb)를 설계하였다. 이를 위해 바람기호로 시각화에 사용되는 자료량을 최소화하고 웹 표출 DB 변환을 최적화 하였다. 본 연구는 재생에너지 활용과 더불어 도시 및 국토 연구에 활용함으로써 관련 활동의 기상학적 이해를 높이고 신뢰도 높은 의사결정 수립에 기여할 것이다.