• Fire Science and Engineering
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• v.19 no.3 s.59
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• pp.13-19
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• 2005

An experimental study is presented for extinguishing characteristics of liquid fuel fire by water mist containing sodium acetate trihydrate. To evaluate the extinguishing performance of water mist containing an additive, the evaporation characteristics of a water droplet on a heated surface was examined. The evaporation process was recorded by a charge-coupled-device camera. Also, small-scale extinguishing tests were conducted for n-heptane pool fire in ventilated space to measure flame temperature variation. The average evaporation rate of a water droplet containing an additive was lower than that of a pure water droplet at a given surface temperature due to the precipitation of salt in the liquid-film and change of surface tension. In case of using an additive, the flame temperature was lower than that of pure water at a given discharge pressure and it was because the momentum of a water droplet containing an additive was increased reducing flame size. And also dissociated metal atoms, sodium, were reacted as a scavenger of the major radical species OH^-,\;H^+$ which were generated for combustion process. Moreover, at a high pressure of 4MPa, the fire was extinguished through blowing effect as well as primary extinguishing mechanisms.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.262-262
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• 2015

풍수해보험은 국민안전처가 관장하고 민영보험사가 운영하는 정책보험으로 국민이 예기치 못한 풍수해 피해에 대처할 수 있도록 보험료의 일부를 국가 및 지방자치단체에서 보조해 주는 제도이다. 그러나 풍수해보험은 불합리한 보험요율체계 등의 문제점으로 인해 저조한 가입률을 보이고 있다. 현재 풍수해보험요율 산정시 과거의 피해이력만을 근거로 보험요율을 산정하고 있다. 또한 풍수해 보험은 태풍, 홍수, 호우, 강풍, 풍랑, 해일, 대설, 지진을 대상재해로 분류하고 있으나 동일 시군구 내에서는 재해요인별 원인별 가중치가 동일하게 적용되어 단일 보험요율을 적용하고 있다. 현재의 불합리한 보험요율체계의 문제점을 보완하고 향후 피해발생 위험을 고려하여 피해 특성에 따라 지역적으로 차등화된 보험요율을 적용하는 방안이 필요하다. 이에 따라 본 연구에서는 풍수해보험요율 산정을 위해 풍수해보험 대상재해 중 내수침수에 대한 분석 방안을 제시하고 적용성을 검토하고자 하였다. 우선 다양한 내수침수분석방법 중 전국단위의 내수침수분석을 위해 경제성, 간편성, 정확성을 고려하여 Level-Pool 방법을 선정하였다. 그리고 기존 Level-Pool 방법의 문제점을 보완하기 위해 내수침수분석 결과의 정확성을 향상시킬 수 있도록 도시계획 용도지역을 고려한 수정 Level-Pool 방법을 제시하고, 풍수해저감종합계획과 비교 검토를 실시하여 적용성을 검토하였다. 또한, 제시한 수정 Level-Pool 방법을 울산, 대구, 경북, 강원지역에 적용하여 내수침수위험지역을 도출하였다. 본 연구에서 제시한 수정 Level-Pool 방법을 통해 전국단위 내수침수 해석시 지역별로 차등화되고, 정확도가 높은 내수침수지역을 도출하여 풍수해보험요율 산정을 위한 기초자료로 활용할 수 있을 것으로 판단된다.

• Investigative Magnetic Resonance Imaging
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• v.3 no.2
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• pp.159-166
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• 1999

Purpose : To evaluate the effect of rotational correlation time (${\tau}_R$) and the possible related changes of other parameters, ${\tau}_M,{\;}{\tau}_S,{\;}and{\;}(\tau}_V$ of gadolinium (Gd) chelate on T1 relaxation enhancement in two pool model. Materials and Methods : The NMRD (Nuclear Magnetic Relaxation Dispersion) profiles were simulated from 0.02 MHz to 800 MHz proton Larmor frequency for different values of rotational correlation times based on Solomon-Bloembergen equation for inner-sphere relaxation enhancement. To include both unbound pool (pool A) and bound pool (pool B), the relaxivity was divided by contribution from unbound pool and bound pool. The rotational correlation time for pool A was fixed at the value of 0.1 ns, which is a typical value for low molecular weight complexes such as Gd-DTPA in solution and ${\tau}_R$ for pool B was changed from 0.1 ns to 20 ns to allow the slower rotation by binding to macromolecule. The fractional factor of was also adjusted from 0 to 1.0 to simulate different binding ratios to macromolecule. Since the binding of Gd-chelate to macromolecule cab alter the electronic environment of Gd ion and also the degree of bulk water access to hydration site of Gd-chelate, the effects of these parameters were also included. Results : The result shows that low field profiles, ranged from 0.02 to 40 MHz, and dominated by contribution from bound pool, which is bound to macromolecule regardless of binding ratios. In addition, as more Gd-chelate bound to macromolecule, sharp increase of relaxivity at higher field occurs. The NMRD profiles for different values of ${\tau}_S$ show the enormous increase of low field profile whereas relaxivity at high field is not affected by ${\tau}_S$. On the other hand, the change in ${\tau}$V does not affect low field profile but strongly in fluences on both inflection fie이 and the maximum relaxivity value. The results shows a fluences on both inflection field and the maximum relaxivity value. The results shows a parabolic dependence of relaxivity on ${\tau}_M$. Conclusion : Binding of Gd-chelate to a macromolecule causes slower rotational tumbling of Gd-chelate and would result in relaxation enhancement, especially in clinical imaging field. However, binding to macromolecule can change water enchange rate (${\tau}_M$) and electronic relaxation ($T_le$) vis structural deformation of electron environment and the access of bulk water to hydration site of metal-chelate. The clinical utilities of Gd-chelate bound to macromolecule are the less dose requirement, the tissue specificity, and the better perfusion and intravascular agents.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.757-762
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• 2002

Many reports have been shown that the buoyancy, electromagnetic force, surface tension, and gas shear stress are the driving forces of weld pool circulation in arc welding. Among them, the surface tension of molten metal plays an important role in the flow in weld pool, which are clarified by the specially designed experiments with small particles as well as the numerical simulations. The surface tension is also related to the penetration in arc welding. Therefore, a quantitative evaluation of surface tension is demanded for the development of materials and arc process control. However, there are few available data published on the surface tension of molten metals, since it depends on the temperature and the composition of materials. In this study, a new method was proposed for the evaluation of surface tension and its temperature dependence, in which it is evaluated by the equilibrium condition of acting forces under a given surface geometry, especially back surface. When this method was applied to the water pool and to the back surface of molten pool in the stationary gas tungsten arc welding of thin plate, following results were obtained. In the evaluation of surface tension of water, it was shown that the back surface geometry was very sensitive to the evaluation of surface tension and the evaluated value coincided with the surface tension of water. In the measurement of molten pool in the stationary gas tungsten arc welding, it was also shown that the comparison between the surface tension and temperature distribution across the back surface gave the temperature dependent surface tension. Applying this method to the mild steel and stainless steel plates, the surface tension with negative gradient for temperature is obtained. The evaluated values are well matched with ones in the published papers.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.813-820
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• 2001

The Safety depressurization System(SDS) of KNGR prevents RCS from overpressurization by discharging high pressure and temperature coolant through the I-sparger into the IRWST during an accident. If IRWST water temperature rise locally, around the sparger, beyond $200_{\circ}$2000 F by the discharged coolant, unstable steam condensation can cause large pressure load on the IRWST wall. To investigate whether this condition can be avoided for the design basis event IOPOSRV(Inadvertent Opening of one Pilot Operated Safety Relief Valve), the flow and temperature distribution of water in the IRWST is calculated by using CFX 4.3 computational fluid dynamic code. According to the results, since pool water temperature does not exceeds temperature limit within 50 seconds after the opening of one POSRV, it can be assured that the integrity of IRWST wall is maintained.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.430-436
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• 1997

피동형 원자로에서 냉각수 펌프의 작동불능시나 계통 내의 강제 순환이 충분치 못할 경우, 냉각수와 분리된 비상 저온 고농축의 붕산수를 노심에 피동으로 주입시키고 자연 대류에 의한 잔열 제거가 이루어져야 한다. PIUS형 원자로나 SPWR형 원자로에서는 Honeycomb구조의 Density Lock을 사용하여 Shutdown 및 잔열 제거 기능을 수행하며 정상운전시에는Primary Coolant(고온, 저농축 붕산수)와 Pool Water(저온, 고농축 붕산수)를 분리하고 있다. Density Lock을 사용할 경우, 기동 운전이나 출력 변경과 같은 비정상 운전시 Density Lock을 통하여 노심으로 Pool Water가 유입될 수가 있다. 따라서 불필요한 Pool Water의 유입을 방지하고 피동형 원자로의 설계 개념을 만족시키며, 피동적으로 강제 순환으로부터 자연 순환으로의 경로를 열어 줄 수 있는 Hydraulic Valve에 대한 이론적 해석을 수행하여 실제 밸브를 제작하여 실험을 통해 이론과 비교하고 Valve의 특성곡선을 개발한다.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.02a
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• pp.42-50
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• 2004

The pool $(3m{\times}6m{\times}10m{\times}$ in Irradiated Materials Examination Facility is generally used to transport irradiated materials between a moving cask and hot-cell. During the operation in the pool such as loading/unloading the cask, holding specimen and bucket elevation, water maybe contaminated by radioactive or contaminated impurities from irradiated materials. Then, it must be purified and filtered continuously to keep lower radioactivity than that of regulation prescribed by RCA Korea Activity in a part of radioactive contamination control. This paper described radioactive contamination distribution of water as transported materials, which is related to effective operation of purification and filtration system.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.179-185
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• 1996

피동형 원자로에서 냉각수 펌프의 작동불능시나 계통 내의 강제 순환이 충분치 못할 경우, 냉각수와 분리된 비상저온 고농축의 붕산수를 노심에 피동으로 주입시키고 자연 대류에 의한 잔열 제거가 이루어져야 한다. PIUS형 원자로나 SPWR형 원자로에서는 Honeycomb구조의 Density Lock을 사용하여 Shutdown 및 잔열 제거 기능을 수행하며 정상운전시에는 Primary Coolant(고온, 저농축 붕산수)와 Pool Water(저온, 고농축 붕산수)를 분리하고 있다. Density Lock을 사용할 경우, 기동 운전이나 출력 변경과 같은 비정상 운전시 Density Lock을 통하여 노심으로 Pool Water가 유입될 수가 있다. 따라서 불필요한 Pool Water의 유입을 방지하고 피동형 원자로의 설계 개념을 만족시키며, 피동적으로 강제 순환으로부터 자연 순환으로의 경로를 열어 줄 수 있는 Hydrauric Valve에 대한 이론적 해석을 수행하여 실제 밸브를 제작하였다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.337-342
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• 1996

The pool-boiling critical heat flux (CHF) of water on small flat plates has been experimentally investigated focusing on the effects of the inclination angle and size of the heated surface under near atmospheric pressure. The second-phase experiment was accomplished to find out the general CHF behavior for over-all inclination angles from -90$^{\circ}$ to 90$^{\circ}$using two plate-type test sections (30$\times$150 mm and 40$\times$150 mm) submerged in a slightly subcooled water pool. Test results generally confirm the first-phase findings and show little effect of inclination angle for inclined upward-facing cases. CHF position moves to lower position with the increase of the heater characteristic size and inclination angle(from -30$^{\circ}$to 60$^{\circ}$).

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.657-662
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• 1999

This study was conducted for the purpose of assessing the pollutant removal possibilities of sedimentation pool formed by deep dredging of a reservir inlet. Water quality data were collected in the Masan reservoir, whose inlet has been dredged deep like sedimentation pool. The average concentration of chemical oxygen demand(COD), total nitrogen(T-N) adnd total phosphorous(T-P) in the deep dredged area were 8.3∼28.4mg/$\ell$ (COD), 2.0∼6.0mg/$\ell$(T-N), 0.17∼1.34mg/$\ell$(T-P), which were 3.3% (COD) , 30.6%(T-N) and 46.4%(T-P) higher than those of middle part of the reservoir. From these results, it was considered the deep dredged area in the inlet of reservoir might play a key role to improve reservoir water quality.