• Nuclear Engineering and Technology
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• 제39권4호
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• pp.327-336
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• 2007

The influence of density differences on the mixing of the primary loop inventory and the Emergency Core Cooling (ECC) water in the downcomer of a Pressurised Water Reactor (PWR) was analyzed at the ROssendorf COolant Mixing (ROCOM) test facility. ROCOM is a 1:5 scaled model of a German PWR, and has been designed for coolant mixing studies. It is equipped with advanced instrumentation, which delivers high-resolution information for temperature or boron concentration fields. This paper presents a ROCOM experiment in which water with higher density was injected into a cold leg of the reactor model. Wire-mesh sensors measuring the tracer concentration were installed in the cold leg and upper and lower part of the downcomer. The experiment was run with 5% of the design flow rate in one loop and 10% density difference between the ECC and loop water especially for the validation of the Computational Fluid Dynamics (CFD) software ANSYS CFX. A mesh with two million control volumes was used for the calculations. The effects of turbulence on the mean flow were modelled with a Reynolds stress turbulence model. The results of the experiment and of the numerical calculations show that mixing is dominated by buoyancy effects: At higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this circumferential propagation. Therefore, density effects play an important role during natural convection with ECC injection in PWRs. ANSYS CFX was able to predict the observed flow patterns and mixing phenomena quite well.

• 한국화재소방학회논문지
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• 제33권6호
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• pp.35-42
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• 2019

본 논문은 피난기구의 사용시간 실험분석을 통한 안전체험교육 개선에 관한 방향을 알아보기 위해 진행되었다. 연구를 위해 피 실험자들을 체격과 체중이 비슷한 그룹으로 나누어 구성하였고, 4가지 피난기구를 직접 체험하게 함으로서 체험시간을 측정하여 분석하였다. 피난기구 설치에서부터 탈출까지의 전체시간 분석에서 완강기-경사식구조대-수직구조대-공기안전매트 순으로 탈출시간이 소요되었다. 피난기구의 탈출시간만 분석했을 경우에는 공기안전매트-경사식구조대-완강기-수직구조대 순으로 탈출시간이 분석되었다. 완강기의 1차 2차 실험에서 나타난 것처럼 1차 시간은 경험 후에 2차 시도에서 시간이 줄어들었다. 이처럼 체험을 통한 교육은 행동의 자신감 증가와 시간의 관리가 가능한 것으로 나타났다. 본 연구의 결론으로 안전교육의 목표는 인명과 재산피해의 최소화이고, 이를 위한 노력으로 많은 사람들에게 교육을 통해 최소화 하는 방법과 자신의 안전을 지키는 교육을 진행한다. 그러므로 더 많은 사람들에게 이러한 효과를 가져 오기 위해서는 체험교육을 통해 학습효과를 높이고, 자기안전을 지키게 하는 노력이 필요하다.

• 한국연소학회지
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• 제19권4호
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• pp.35-41
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• 2014

The experiment was conducted to measure temperature and pressure around operating portable butane gas ranges with oversized cookwares. In this experiment, portable butane gas range with different safety equipment and two kinds of oversized cookware, each of which is made of aluminum alloy and rock, was used. As a result, temperature of the bottom of the butane and the pressure of butane barrel tend to aligned with each other. Through this result, it is reasonable that a safety criteria can be decided based on the temperature of the bottom of butane. Especially, portable butane gas ranges are safely conducted under the condition of the temperature is under 50 degree and pressure is under 500 kPa, respectively, at the bottom of the butane barrel.

• 한방재활의학과학회지
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• 제19권1호
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• pp.169-186
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• 2009

Obejectives : The electroacupuncture(EA) on regional fat is often used by oriental medicine doctors in Korea. However, there have been few studies about safety and biocompatibility of its application. Therefore we investigated the safety and change of mechanical character of electroacupuncture after its application on localized fat deposit. Methods : Online surveys were completed from Aug 21 2008 to Aug 28 2008, by email, the online survey data were obtained from nearly 10,002 Korean medical doctors who listed their email address on the website of association of korean oriental medicine. This study includes an experiment on the physical strength and biological property of long needles. We represent each method which were collected in advance survey, then sealed the needles off and did laboratory experiment, which includes surface observation, analysis, vickers hardness test, and also biocompatibility and toxicity test. Results : There was no considerable difference about the physical property after applying electric current, the cell survival rate did not change in comparison with controlled group either. Conclusions : Although it seems there are no considerable acupuncture-related problem, we still need additional studies about clinical effectiveness difference related operation condition. Besides, it will need research on the actual condition, standardization, and criteria about the comsumed needle in Korea.

• 한국안전학회지
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• 제32권1호
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• pp.121-127
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• 2017

Recently, many patients in a hospital are threatened life by fire disaster. Because many patients like vulnerable people have more evacuation problem than ordinary person. So a patient who can escape by oneself with walking assistance device like crutches or wheelchair and another patient who can't escape by oneself are should be supported safety technologies and service. Earlier research of 'hospital evacuation' led by actual experiments or computer evacuation simulation. Actual experiment is effective to gain credibility of result but it is difficult for patients to experiment repeatedly and it requires consideration for spatial problem and economic problems. Although computer evacuation simulation have been used to solve these problems, almost have concluded only results based on velocity without evacuation device. In this study, evacuation results with support device application or not are analysed used by computer evacuation simulation based on MAS(Multi Agent System). As a result, it is drawn through proof of efficiency of evacuation device in the vertical space like stairs that can improve the evacuation plan for vulnerable people in the hospital.

• 한국안전학회지
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• 제21권5호
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• pp.1-5
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• 2006

This study provides a basic data necessary to design a facility of smoke management after calculating the critical velocity of the gradient scale model tunnel and reviewing its adequacy to establish an optimum disaster prevention system for a road tunnel at fire. The experiment is carried out by using Froude scaling to a scale model which is about 1/29 as big as the real tunnel, and its critical velocity calculation is calculated to the 0-2% gradient of the tunnel. The result shows that the higher the gradient is, the stronger the critical velocity, but that it doesn't affect the critical velocity so much when the gradient is less 2%. In addition, this result is studied in comparison with the results done by other researchers to review the adequacy of the critical velocity.

• 한국안전학회지
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• 제27권6호
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• pp.59-63
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• 2012

The use of dry chemical powder has been increased as it can be stored for a long period and sustain in stable condition compared to gas or liquid phase extinguishing agents. A new type of dry chemical powder using Zeolite was produced in the research. Chemical powder was adsorbed into Zeolite 13X, a porous material appearing negative catalytic effect, to create extinguishing powder obtaining core shell structure and measured physical properties and run a small scale fire extinguishment. SEM, XRD, TA analysis was also executed, and extinguishing characteristics were measured by fire extinguishing experiment on oil pool fire. The experiment showed that the average particle size of Zeolite 13X was equivalent, indicating about $3{\pm}1{\mu}m$ and thermal analysis result illustrated that Zeolite 13X showed exothermic reaction peaks at $900^{\circ}C$ due to solid-state transformation. Extinguishing characteristics on oil fire of $NaHCO_3$/Zeolite 13X and $NH_4H_2PO_4$/Zeolite were improved, influenced by adsorbed extinguishing powders on Zeolite 13X and Zeolite 13X that contains high phase transition temperature.

• 한국안전학회지
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• 제29권4호
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• pp.78-84
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• 2014

Viscosity agents were added to water to improve extinguishing performance of low pressure water mist suppression system on wood cribs fire, and a small scale wood cribs fire experiment was conducted to measure the extinguishing performance. CMC and agar were used for viscosity agent and as the amount of viscosity agent enlarges, it showed the increase of the viscosity of aqueous solution and the decrease of the fluidity. On wood cribs fire experiment, the extinguishing efficiency was improved with supplemental viscosity agent as it enhanced the adhesive time of aqueous solution on the wood, and therefore expanded the contact time of fire surface. The surface tension of aqueous solution was decreased with the addition of agar which to be assumed as an increase factor of extinguishing efficiency. By the extinguishing experimental result, the most effective extinguishing agent was CMC 0.6 wt.%, with the flame suppression time and the extinguishing time were reduced by 70s and 93s respectively at this concentration.

• 해양환경안전학회지
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• 제24권3호
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• pp.346-351
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• 2018

The proportion of collision in the total marine accidents is high. The main causes of collisions are navigation rule violation, safety speed violation, neglected watch-keeping and improper collision avoidance action. There are two main ways of avoiding collision situations during maritime navigation: the method of altering course and reducing ship's speed. The purpose of this study is to analyze the result of the collision avoidance action of the reserve officer in case of encountering a multiple number of ships using the ship handling simulator. Full-mission ship handling simulator was used to experiment the situation scenarios that encountered multiple ships. After the experiment, the questionnaire about the experiment was investigated. A total of 50 subjects were participated in the experiment. Experimental results showed that the number of the experimenters who used the engine was 11 and the number of the experimenters who did not use the engine was 39. In the case of using the engine, there were 0 collision accident, 1 grounding accident, and 10 no accidents. However, when the engine was not used, there were 28 collision accidents, 2 grounding accidents, and 9 no accidents. The causes of these results can be found in the survey results. 74 % of the non used engine participants said they were hesitate to use the engine. As can be seen from these results, the reserve officer are hesitant to use the engine and need a way to get correct of it. Maritime course subject can emphasize the importance of using ship's engines and case study also can be it. So, It is considered that various case study scenario will need to developed by various tools in the future.

• 한국가스학회지
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• 제17권5호
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• pp.81-86
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• 2013

분진폭발은 플라스틱류, 제약, 목재, 곡물 저장고, 고체연료 및 화학약품의 제조와 같은 다양한 산업에서 발생되고 있다. 본 연구에서는 폐목재를 재활용하여 Particle board를 생산하는 공정의 사이로 분진, 함머밀 분진 및 뉴송 분진을 선택하여 분진폭발 특성을 평가하였다. 실험은 20 L 구형 폭발용기를 이용하여 목재 부유분진의 최대폭발압력, 분진폭발지수, 폭발한하계, 및 최소 점화에너지를 측정하고, 평가하였다. 이들 연구결과는 Particle board를 생산하는 제조공정의 화재 폭발사고 예방을 위한 공정안전 정보로 활용할 수 있을 것이다.