The conventional research trend on spent fuel was safety analysis based on mechanical perspective. Analysis of spent fuel cladding is based on the temperature of cladding and pressure inside cladding. To improve fuel cladding analysis, precise and accurate thermal safety evaluation is required. In this study a database which is about thermal conductivity and emissivity for the thermal modeling was established for a long-term safety analysis of spent fuel. As a result, we confirmed that the thermal conductivity of zirconium hydride was not accounted in conventional model such as FRAPCON and MATPRO. The conductivity of zirconium and its oxide was evaluated only as a function of temperature. However, the behavior of heat conductivity and emissivity is determined by the change of the material properties. The material properties depend on the microstructural characteristic. It can be seen that this conventional approach does not consider the microstructure change behavior according to vacuum drying process or burn-up induced degradation phenomena. To improve the thermal properties of spent nuclear fuel cladding, the measurement experiments of heat conduction and emissivity are required according to spent fuel experience and status such as the number of vacuum drying, cooling rate, burn up, hydrogen concentration and oxidation degree. In previous domestic reports and papers, we found that relative data between thermal properties and spent fuel experience and status does not exist. Recently, in order to understand the failure mechanism of hydrogen embrittlement, many studies have been conducted by accounting and spent fuel experience and status in a mechanical perspective. If microstructure information could be obtained from these studies, the modeling of thermal conductivity and emissivity will be possible indirectly. According to a recent abroad paper, it was confirmed that the thermal conductivity decreased by about 30% due to irradiation damage. The radiation damage effects on thermal conductivity also has not been studied in zirconium oxide and hydride. These un-revealed phenomena will be considered for the thermal safety model of spent fuel.

PURPOSES : Abroad, road pavement materials vary depending on the speed and traffic volume of vehicles, but owing to the negative perception of block pavements, sidewalks, parking lots, and parks are primarily used in Korea. In addition, since speed restriction policies such as safety speed 5030 have been implemented recently, it is necessary to use block pavements for roadways, which are considered to have the effect of reducing speed. Therefore, it is necessary not only to actively discuss the introduction of block pavements for roadways but to continue research on the effectiveness of the performance evaluation and to change the perception of roads in Korea. METHODS : In this study, five indicators (surface damage, surface temperature, driving speed of vehicle, noise, and suspended dust) were selected for a sustainable road environment. The performance evaluation index of block pavement for roadways was decided according to the domestic and international literature, and the data were collected based on the evaluation index in the section with block pavement for roadways in Korea. RESULTS : The damage rate was calculated 0.35% according to the breakage of block and Maintenance Control Index(MCI) was ranked A~B even though the pavement was used for more than 4~5 years. The surface temperature of block pavement has a temperature reduction effect of 7 ℃ compared with ordinary asphalt pavement and a speed reduction of approximately 4 km/h on average; therefore, the traffic calming effect of block pavements can be expected. The noise of block pavement and asphalt pavement exhibited a similar level, and the noise level experienced by pedestrians did not change significantly as a result of frequency analysis. The measurement of road suspended dust around the road confirmed the possibility of reducing the concentration of road dust in the air owing to the smooth surface drainage and the results indicated the possibility. CONCLUSIONS : The results of this study are expected to contribute to the recognition and functional improvement of domestic block pavements by continuous monitoring to ensure the reliability of blocks. In addition, it is necessary to ensure the reliability of the quality and functional evaluation of paving materials through continuous on-site monitoring.

지방관리 무역항은 비교적 중소형 무역항으로 지방도시의 경제력 강화 및 지역 산업 부가가치 제고를 위해 활발한 운영이 필요 하다. 또한, 선박대형화가 이루어지고 있는 국제적 흐름에서 지방관리 무역항의 효율성 증대를 위해 항만기본계획상 기존 선석규모 대비 대형선박의 접안이 필요하며, 부두 및 선박의 안전성 확보를 위해 대형선박 접안시 계류시설 확충 및 안전운용기준 마련이 필요하다. 본 연구에서는 지방관리 무역항 중 옥계항을 선정하여, 현행 2만 DWT급 부두에 5만 DWT급 선박이 계류시 시나리오에 따른 계류안전성 평 가를 수행하였다. 평가 결과, 대상 부두에 100톤급 계선주를 신설하였을 경우, 긴급이안기준은 기존 파주기 3.2초에서 풍속 27노트, 파주기 5.0초에서 풍속 22노트의 계류 한계 조건이 파주기 3.2초에서 풍속 41노트, 파주기 5.0초에서 풍속 36노트로 약 50 % 정도 증가하는 것으로 분석되었다. 본 연구 결과는 지방관리 무역항에 기존 선석규모 대비 대형선박 접안시 부두 계류시설의 안전성 강화와 안전운용기준 설정 을 위한 기초 자료로 활용될 수 있다.

PURPOSES : The purpose of this study is to evaluate the road design elements affecting the lateral driving safety under high-speed driving conditions with a speed limit of 140 km/h and to derive useful implications to design of safer roads. METHODS : A full-scale driving simulator was used to evaluate the various design scenarios. Different regression techniques and a random forest method were adopted to conduct comprehensive comparisons among the simulation scenarios. The relationships between the safety indicators, including the frequency of the lane departures and the standard deviation of the lateral acceleration, and the design elements were explored in terms of lateral driving safety. RESULTS : The length of the combined alignment was found to be a significant factor affecting the lateral driving safety based on the analysis of the frequency of lane departures. Regarding the standard deviation of the lateral acceleration, it was identified that the length of the horizontal curve, the length of the bridge, and the right-side superelevation must be considered significant factors associated with driving safety while designing the road under high-speed driving conditions. CONCLUSIONS : Based on the findings of this study, a set of recommendations for designing roads was proposed. For example, the proper length of the combined alignment and the horizontal curve should be determined to prevent crashes due to hazardous lateral driving events because the installation of sufficient superelevation in the bridge section would be limited under high-speed driving conditions. In addition, applying a larger horizontal curve radius with longitudinal grooving is a promising approach to tackle risky driving conditions.

The purpose of this study is to investigate the effect of organizational safety and health management activities on safety and health performance by using the results of safety activity level evaluation of public organizations. To this end, a research model was established by using three fields as independent variables among the four areas of the safety activity level evaluation index: safety and health system, safety and health activity plan, and safety and health activity level, and the safety and health activity performance field as a dependent variable. Correlation analysis and regression analysis between major variables were performed. As a result of the correlation analysis, the safety and health activity performance had a significant positive (+) correlation with all of the safety and health system, safety and health activity plan, and safety and health activity level. The safety and health system had a significant positive (+) correlation with the safety and health activity plan and safety and health activity level, and the safety and health activity plan had a significant positive (+) correlation with the safety and health activity level. And as a result of the regression analysis, it was found that the organization’s safety and health system, safety and health activity plan, and safety and health activity level all had a significant positive (+) effect on safety and health activity performance.

카페리 선박의 안전 운항을 위한 요소 중 화물 고박안전성 분야는 2015년 이후 화물고박기준이 적용되어 파랑에 의해 발생하는 선체운동과 고박력을 상호 비교하여 평가하고 있다. 항해 중 카페리 선박의 안전 운항을 담보하기 위해서는 운항해역의 기상정보를 바탕으로 선체운동을 해석하여 화물의 이동을 방지할 수 있는 고박력을 결정하는 것이 중요하다. 이 연구에서는 부산-제주를 항행하는 총톤수 3,700톤급 카페리 선박을 대상으로 기상청이 운용하는 해상파고부이 3기의 최근 5년간 기상정보를 분석하였으며, 실제 해상에서 선체운동을 계측하고 수치시뮬레이션을 수행하여 선체가속도를 비교하였다. 태풍기간을 제외한 2~3월의 유의파고를 입력조건으로 선체운동을 해석한 결과, 유의파고 2.5 m 조건에서 횡방향 가속도가 실선계측에서는 1.5 m/s2, 수치계산에서는 1.8 m/s2로 이론적 수치시뮬레이션의 결과가 크게 나타났다. 파고별 선체운동을 추정하는 가속도를 실선결과 기반으로 보정하는 근사식을 제안하여, 운송화물의 고박안전성 평가에 적용한 결과 풍랑경보 대비 일반 기상조건에서는 40 % 이하로 분석되었다. 운항해역의 기상정보를 바탕으로 실선계측에 따른 정량적인 가속도 결과를 활용하는 고박안전성 평가 기법이 널리 보급되어 국내 연안 카페리선박의 안전 운항 지침에 적용되기를 기대한다.

The railroad facilities are intended for long-term operation as the initial acquisition costs necessary for infrastructure construction are high. Therefore, regular maintenance of railroad facilities is essential, and furthermore, system reliability through systematic performance evaluation is required. In this study, the signal control system of railroad electrical equipment was selected as the subject of research and the performance evaluation target facility selection study was conducted using AHP. The results of the study can contribute to the reliability of the signal control system as well as to the reliability of the railroad system, which is a higher system.

The purpose of this study was to evaluate microbiological contamination of knives and cutting boards in child-care centers. Materials used in this study were swabbed of cutting boards and knives (blade, handle of knife, and joint of handle and blade) in 129 child-care centers. Mean values of total aerobic bacteria of swabs of knives and cutting boards were 1.7±0.7 log cfu/100 cm2 and 1.7±0.9 log cfu/100 cm2, respectively. Contamination levels of coliform bacteria from knives and cutting boards were 1.5±0.6 log cfu/100 cm2 and 1.7±0.8 log cfu/100 cm2, respectively. Comparing microbiological contamination levels of knives and cutting boards according to type and size of child-care centers, there was no significant difference. Bacillus cereus was detected in knife handles and cutting boards. Diarrhea-type toxin gene (entFM) was detected in B. cereus isolates. Antibiotic resistance tests showed that B. cereus was resistant to β-lactam antibiotics. To reduce microbiological contamination levels of knives and cutting boards in child-care centers and prevent food poisoning from bacteria contamination, continuous education by children's food-service management center is needed for sterilization and disinfection of knives and cutting boards.

As modern industries are highly being developed, it is required that mechanical parts have to be manufactured with a high precision. In order to have precise parts, error-free designs have to be done before manufacturing with accuracy. For this intention being fulfilled, a mechanical analysis is essential for design proof. Nowadays, FEM simulation is a popular tool for verifying a machine design. In this paper, an impeller, being utilized in a compressor or an oil mixer as an actuator, is studied for an evaluation. The purpose of this study is to present a safety of an impeller for a proof of its mechanical stability. A static analysis for stress, strain, and deformation within a regular usage is examined. This simulation test shows 357.26×106 Pa for maximum equivalent stress and 0.207mm for total deformation. A fatigue test is carried to provide durability and its result shows that minimum safety factor is 3.2889, which guarantees that it runs without a fatigue failure in 106 cycles. The natural frequencies for the impeller is ranged from 228.09Hz to 1,253.6Hz for the 1st to the 6th mode. Total deformations at these natural frequencies are shown from 6.84mm to 12.631mm. Furthermore, Campbell diagram reveals that a critical speed is not found throughout regular rotational speeds. From the test results for the analysis, this paper concludes that the suggested impeller is proved for its mechanical safety and good to utilize at industries.

해양플랜트는 발주처와 선급에서 요구하는 다양한 항목들을 설계할 시에 반영하여야 한다. 특히, 해양구조물에 탑재되는 Topside Module의 경우 육상플랜트와는 다르게 공간적 제약이 크고 구조물의 움직임과 같은 해상 환경조건 및 안전과 관련된 요구사항들이 많아 그 설계 과정이 매우 까다롭다. 본 연구에서는 Topside Module에 들어가는 주요장비 중 하나인 HPU(Hydraulic Power Unit) 구조물에 작용하는 하중을 DNVGL 규칙에 따라 계산하고, 각 하중조건에 따른 구조안전성 평가를 진행하였고 개발된 제품의 구조 신뢰성을 향상하고자 하였다. 구조해석은 범용프로그램인 MSC 소프트웨어를 사용하였고, 총 5가지 하중 조건으로 구조해석을 진행하여 다양한 움직임에 대한 안전성을 검토하였다. 그 결과 선미 방향 Pitching 상태(Load Case 5)에서 최대 응력이 발생하였고, 응력 수준은 허용응력의 약 85 % 수준이고, 최대변위는 허용치의 약 5 % 수준으로 구조안전성이 확인되었으며 부재 간 간섭은 발생하지 않았다.