• Journal of Radiation Protection and Research
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• 제32권4호
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• pp.190-193
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• 2007

The objective of this study is to recommend the radiation protection design parameters from the shielding point of view for concrete wall between the decay tank room and the primary pump room in TRIGA Mark-II Research Reactor Facility. The shield design for this concrete wall has been performed with the help of Point-kernel Shielding Code Micro-Shield 5.05 and this design was also validated based on the measured dose rate values with Radiation Survey Meter (G-M Counter) considering the ICRP-60 (1990) recommendations for occupational dose rate limit ($10{\mu}Sv/hr$). The recommended shield design parameters are: (i) thickness of 114.3 cm Ilmenite-Magnetite Concrete (IMC) or 129.54 cm Ordinary Reinforced Concrete (ORC) for concrete wall A (ii) thickness of 66.04 cm Ilmenite-Magnetite Concrete (IMC) or 78.74 cm Ordinary Reinforced Concrete (ORC) for concrete wall B and (iii) door thickness of 3.175 cm Mild Steel (MS) on the entrance of decay tank room. In shielding efficiency analysis, the use of I-M concrete in the design of this concrete wall shows that it reduced the dose rate by a factor of at least 3.52 times approximately compared to ordinary reinforced concrete.

• 설비공학논문집
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• 제29권5호
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• pp.220-230
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• 2017

In this study we apply and compare a variety of numerical methods for calculating residence time distribution in decay tanks, a major design component in the for reducing N-16 radioactivity. Our research group has used a streamlined method using user-defined particle numbers. However, this streamlined method has several problems, including low exiting particle ratios, particle diminishing, and unphysical time distribution, among others. We utilize three numerical methods to establish residence time and time distribution (streamlined, discrete phase method [DPM], and user defined scalar [UDS]) and subsequently compare the averaged results of each. The three tests demonstrate the flow features within the decay tanks, which are then numerically simulated to enable comparison. We conclude that although each simulation predicts similar time averages, the UDS methodology provides a smoother time distribution and tracer contour plots at specific times.

• 핵의학기술
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• 제12권1호
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• pp.19-26
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• 2008

목적: 방사성옥소 치료병실로부터 발생한 오 폐수는 반드시 전용 정화조에서 일정시간 자연 감쇄(decay)시켜 수중 방사능 농도치가 $8.1{\times}10^{-13}$ Ci/ml 이하가 될 때에만 비로소 방류를 하여야 한다. 현재까지 서울아산병원에서는 60 ton 용량의 전용정화조 3개를 구비하여 운영하고 있었지만 2005년 10월부터 방사성옥소 치료병실을 2병상에서 4병상으로 증설 운영함에 따라 급격히 늘어난 방사성 오.폐수량으로 인하여 본원의 정화조 용량으로는 충분한 감쇄(약 125일 이상)여력이 부족하게 되었다. 따라서 본 연구에서는 치료병실 정화조의 오 폐수 유입유량에 기여하는 원인 및 요인들을 밝혀내어 합리적인 개선 조치를 함으로써 정화조 용량 부족 문제를 해결하여 1차적으로는 엄청난 병원의 경제적 손실을 유발시키는 새로운 정화조의 증설을 피하고 방사성 물질의 인위적 배출로 인한 사회적 문제 유발에 따른 대형의료기관의 신뢰도 추락의 예방에 큰 목적이 있다. 대상 및 방법: 2006년 1월부터 10월까지 고용량 옥소 치료 환자 중 150~200 mCi 이상을 투여 받고 2박3일간 입원치료를 하는 환자 402명을 대상으로, 환자 1인당 평균 물 사용량 (변기사용량, 샤워량, 세면량, 기타 등등)을 측정하였으며, 본원의 정화조 60 ton 3개의 만수 후 배출까지의 감쇄 기간을 측정하였다. 또한 본원의 치료 업무 절차를 단계별로 분석하여 정화조 유입유량의 증가 요인을 찾아보았다. 결과: 다음과 원인에 대한 개선을 통하여 본원의 방사성 오 폐수 보관일수를 정화조 1개당 84일에서 2005년 12월말 현재 약 130일로 증가시킬 수 있었다. (1) 기존 변기의 과다한물 소모량 개선 $\rightarrow$ 절수형 변기로 교체 (2) 불필요한 샤워 및 세탁 방지 $\rightarrow$ 샤워 노즐 사용 자제 및 세면대 이용 교육 (3) 치료기간 중 잦은 배뇨를 유발하는 이뇨제 복용 중지 (4) 수분 섭취량과 퇴원시 체내 잔류선량과의 상관관계 분석 (5) 입실 후 치료 전까지의 대기시간에는 외부 화장실 사용 교육 (6) 정화조 만수위 용량 한계치를 최대 85%에서 90%로 증대 운용 결론: 근래에 들어 급격하게 증가된 갑상선질환 관련 환자로 인하여 전국적으로 거의 모든 의료기관에서 방사성옥소치료의 대기일 수가 크게 증가되고 있다. 이러한 시점에 발생된 방사성 오 폐수 관련 문제는 비단 어느 한 의료기관의 문제가 아닌 관련 우리 모두가 해결해야 하는 큰 과제임에 틀림 없을 것이다. 따라서 본 개선 활동은 그 시작을 알리는 신호탄이 될 것이라 생각되며 방사성 치료병실을 운영하고 있는 타 의료기관에서도 이와 관련된 유사상황이 발생된다면 합리적인 정화조운영의 모델방안으로 제시 될 수 있을 것으로 기대된다.

• 한국환경보건학회지
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• 제29권1호
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• pp.8-15
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• 2003

In this study, chlorine dose at water storage tank was predicted to meet the recommended guideline for free chlorine residual in drinking water distribution system, using EPANET which is a computer program that performs extended Period simulation of hydraulic and water quality behavior within pressurized pipe networks. The results may be summarized as follows. The decay of chlorine residual by season varied considerably in the following order; in summer ($25^{\circ}C$) > spring and fall (15$^{\circ}C$) > winter (5$^{\circ}C$). For re-chlorination at water storage tank by season, season-varying chlorine dose was required at its maximum of 1.00 mg/l in summer and minimum of 0.40 mg/l in winter as free chlorine residual. The decay of chlorine residual through out the networks increased with water age spent by a parcel of water in the network except for some points with low water demand. In conclusion, the season-varying chlorine dose as well as the monitoring of water quality parameters at the some points which showed high decay of chlorine residual may be necessary to deliver the safe drinking water.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.542-547
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• 2001

A non-intrusive Planar Laser-Induced Fluorescence(PLIF) technique was applied to study the turbulent mixing process in a Rushton turbine reactor. Instantaneous and ensemble averaged concentration fields are obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by a thin Nd:Yag laser sheet illuminating the whole center plane of the stirred tank. The gray level images captured by a 14-bit cooled CCD camera can be transformed to the local concentration values using a calibration matrix. The dye injection point was selected at the tank wall with three quarter height (3/4H) from the tank bottom to observe the mixing characteristics in upper bulk flow region. There exist distinct two time scales: the rapid decay of mean concentration in each region after the dye infusion reflects the large scale mixing while the followed slow decay reveals the small scale mixing. The temporal change of concentration probability functions conjectures the two sequential processes in the batch type mixing. An inactive column of water existed above the impeller disk, in which the fluid rotates with the shaft but is isolated from the mean bulk flow.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1145-1152
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• 2002

A non-intrusive Planar Laser-Induced Fluorescence(PLIF) technique was applied to study the turbulent mixing process in a Rushton turbine reactor. Instantaneous and ensemble averaged concentration fields was obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by a thin Nd:Yag laser sheet illuminating the whole center plane of the stirred tank. The gray level images captured by a 14-bit cooled CCD camera could be transformed to the local concentration values using a calibration matrix. The dye injection point was selected at the tank wall with three quarter. height (3/4H) from the tank bottom to observe the mixing characteristics in upper bulk flow region. There exist distinct two time scales: the rapid decay of mean concentration after the dye infusion reflects the large scale turbulent mixing while the fellowed slow decay reveals the small scale molecular mixing. The temporal change of concentration variance field conjectures the two sequential processes for the batch type mixing. An inactive column of water is existed above the impeller disk, in which the fluid rotates with the shaft but is isolated from the mean bulk flow.

• Nuclear Engineering and Technology
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• 제51권1호
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• pp.60-72
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• 2019

The air-cooled passive decay heat removal system (APDHR) was proposed to provide the ultimate heat sink for non-LOCA accidents. The APDHR is a modified one of Passive Auxiliary Feed-water system (PAFS) installed in APR+. The PAFS has a heat exchanger in the Passive Condensate Cooling Tank (PCCT) and can remove decay heat for 8 h. After that, the heat transfer rate through the PAFS drastically decreases because the heat transfer condition changes from water to air. The APDHR with a vertical heat exchanger in PCCT will be able to remove the decay heat by air if it has sufficient natural convection in PCCT. We conducted the thermal-hydraulic simulation by the MARS code to investigate the behavior of the APR + selected as a reference plant for the simulation. The simulation contains two phases based on water depletion: the early phase and the late phase. In the early phase, the volume of water in PCCT was determined to avoid the water depletion in three days after shutdown. In the late phase, when the number of the HXs is greater than 4089 per PCCT, the MARS simulation confirmed the long-term cooling by air is possible under extended Station Blackout (SBO).

• 상하수도학회지
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• 제12권2호
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• pp.90-98
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• 1998

The optimal rechlorination in water distribution systems was investigated by incorporating optimization techniques into a numerical water quality model. For a hypothetical system that consists of 10 junctions including a storage tank and 12 links, the bulk ($k_b$) and pipe-wall ($k_w$) decay-rate constants of chlorine residual are assumed to be 2.0 1/day and 1.5 m/day, respectively. It was also assumed that the lower and upper limits of chlorine residual in the network are 0.2 mg/L and 0.6 mg/L. When the chlorine source is only the storage tank (without rechlorination), the high levels of chlorine residual appear near the storage tank to maintain the chlorine residuals above the lower limit over the junctions. On the other hand, the chlorine residuals in the network are distribute within the desirable range (0.2 - 0.6 mg/L) after the optimal rechlorination through five injection sites including the storage tank. In case of a real water distribution system that comprises 28 junctions including a clear well and 27 links, the bulk and pipe-wall decay-rate constants are 0.3 1/day and 0.2 m/day, respectively. Before rechlorination, the required chlorine residual at the clearwell is 5.1 mg/L to keep the chlorine residuals above the minimum level (0.6 mg/L) over the junctions. By the optimal rechlorination at five injection sites, the chlorine residuals are distributed within a desirable range of 0.6 mg/L through 2.0 mg/L, which can avoid the excess of chlorine residuals near the clear well. Consequently, total chlirine doses are decreased by 81% in the hypothetical distribution network and 69 % in the real distribution network for satisfying the minimum chlorine residuals.

• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1321-1329
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• 2016

To get an insight into the operating characteristics of the passive residual heat removal system of molten salt reactors, a two-phase natural circulation test facility was constructed. The system consists of a boiling loop absorbing the heat from the drain tank, a condensing loop consuming the heat, and a steam drum. A steady-state experiment was carried out, in which the thimble temperature ranged from $450^{\circ}C$ to $700^{\circ}C$ and the system pressure was controlled at levels below 150 kPa. When reaching a steady state, the system was operated under saturated conditions. Some important parameters, including heat power, system resistance, and water level in the steam drum and water tank were investigated. The experimental results showed that the natural circulation system is feasible in removing the decay heat, even though some fluctuations may occur in the operation. The uneven temperature distribution in the water tank may be inevitable because convection occurs on the outside of the condensing tube besides boiling with decreasing the decay power. The instabilities in the natural circulation loop are sensitive to heat flux and system resistance rather than the water level in the steam drum and water tank. RELAP5 code shows reasonable results compared with experimental data.

• 대한조선학회논문집
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• 제58권5호
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• pp.271-280
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• 2021

The code developed using a pressure-based method for unified conservation laws of incompressible/compressible fluids is expanded to handle moving or deforming body boundaries using the hybrid Cartesian/immersed boundary method. An instantaneous pressure field is calculated from a pressure Poisson equation for the whole fluid domain, including the compressible gas region. The polytropic gas is assumed for the compressible fluid so that the energy equation is decoupled. Immersed boundary nodes are identified based on edges crossing body boundaries. The velocity vector is reconstructed at the immersed boundary node using an interpolation along the assigned local normal line. The developed code is validated by comparing the time histories of pressure and wave elevation for sloshing in a rectangular and a membrane-type tank. The validated code is applied to simulate air cushion effects in a rectangular tank under sway motion. Time variations of pressure fields are analyzed in detail as the air pocket pulsates. It is shown that the contraction and expansion of the air pocket dominate the pressure loads on the wall of the tank. The present results are in good agreement with other experimental and computational results for the amplitude and the decay of the pressure oscillations measured at the pressure gauges.