• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1821-1829
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• 2023

The temperature distribution of the reactor pool under natural circulation induced by the RVACS operation was experimentally studied. According to the Bo' based similarity law, which could reproduce the temperature distribution of the working fluid under natural circulation, SINCRO-2D facility was designed based on the PGSFR. It was reduced to 1 : 25 in length scale, having water as a simulant of the sodium, which is the original working fluid. In general, temperature was stratified, however, effect of the natural circulation flow could be observed by the entrainment of the stratified temperature. Relative cooling contribution of the upper plenum (narrow gap) and lower plenum was approximately 0.2 and 0.8, respectively. In the range of decay heat from 0.2% to 1.0%, only the magnitude of the temperature was changed, while the normalized temperature maintained. Boundary temperature distribution change made a global temperature offset of the pool, without a significant local change. Therefore, the decay heat and cooling boundary condition had no significant effect on temperature distribution characteristics of the pool within the given range of the decay heat and boundary temperature distribution.

• Nuclear Engineering and Technology
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• 제41권1호
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• pp.53-62
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• 2009

A set of experiments has been conducted on the performance sensitivity of the passive residual heat removal system (PRHRS) for an advanced integral type reactor, SMART, by using a high temperature and high pressure thermal-hydraulic test facility, the VISTA facility. In this paper the effects of the opening delay of the PRHRS bypass valves and the closing delay of the secondary system isolation valves, and the initial water level and the initial pressure of the compensating tank (CT) are investigated. During the reference test a stable flow occurs in a natural circulation loop that is composed of a steam generator secondary side, a secondary system, and a PRHRS; this is ascertained by a repetition test. When the PRHRS bypass valves are operated 10 seconds later than the secondary system isolation valves, the primary system is not properly cooled. When the secondary system isolation valves are operated 10 or 30 seconds later than the PRHRS bypass valves, the primary system is effectively cooled but the inventory of the PRHRS CT is drained earlier. As the initial water level of the CT is lowered to 16% of the full water level, the water is quickly drained and then nitrogen gas is introduced into the PRHRS, resulting in the deterioration of the PRHRS performance. When the initial pressure of the PRHRS is at 0.1MPa, the natural circulation is not performed properly. When the initial pressures of the PRHRS are 2.5 or 3.5 MPa, they show better performance than did the reference test.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2053-2058
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• 2004

The pressurized light water cooled, medium power (330 MWt) SMART (System-integrated Modular Advanced ReacTor) has been under development at KAERI for a dual purpose : seawater desalination and electricity generation. The SMART design verification phase was followed to conduct various separate effects tests and comprehensive integral effect tests. The high temperature / high pressure thermal-hydraulic test facility, VISTA(Experimental Verification by Integral Simulation of Transient and Accidents) has been constructed to simulate the SMART-P (the one fifth scaled pilot plant) by KAERI. Experimental tests have been performed to investigate the thermal-hydraulic dynamic characteristics of the primary and the secondary systems. Heat transfer characteristics and natural circulation performance of the PRHRS (Passive Residual Heat Removal System) of SMART-P were also investigated using the VISTA facility. The coolant flows steadily in the natural circulation loop which is composed of the steam generator (SG) primary side, the secondary system, and the PRHRS. The heat transfers through the PRHRS heat exchanger and ECT are sufficient enough to enable the natural circulation of the coolant.

• Nuclear Engineering and Technology
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• 제41권6호
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• pp.765-774
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• 2009

For over 30 years, investigations of the thermohydraulic behavior of pressurized-water reactors under accident conditions have been carried out in the PKL test facility at AREVA NP in Erlangen, Germany. The PKL facility models the entire primary side and significant parts of the secondary side of a of pressurized water reactor at a height scale of 1:1. Volumes, power ratings and mass flows are scaled with a ratio of 1:145. The experimental facility consists of four primary loops with circulation pumps and steam generators (SGs) arranged symmetrically around the reactor pressure vessel (RPV). The investigations carried out encompass a very broad spectrum from accident scenario simulations with large, medium, and small breaks, over the investigation of shutdown procedures after a wide variety of accidents, to the systematic investigation of complex thermohydraulic phenomena. The PKL tests began in the mid 1970s with the support of the German Research Ministry. Since the mid 1980s, the project has also been significantly supported by the German PWR operators. Since 2001, 25 partner organizations from 15 countries have taken part in the PKL investigations with the support and mediation of the OECD/ NEA (Nuclear Energy Agency). After an overview of PKL history and a short description of the facility, this paper focuses on the investigations carried out since the beginning of the international cooperation, and shows, by means of some examples, what insights can be derived from the tests.

• 한국건축시공학회지
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• 제5권4호
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• pp.165-171
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• 2005

Nowadays, a source of all water, which has been spent by a lot of people, is the rainwater The rainwater is directly relating human being' life. According to how to use rainwater. human being' life is abundant or poor. Due to the lack of underground filtration quantity, the water circulation of the city is discontinued and the underground ecosystem is destroyed. This study suggest that the unused underground space of building and temporary structure can be used into rainwater storage tank in the facility to use rainwater. Moreover, in this study, while the building is constructed, It is showed that the water used in construction can be replaced in the rainwater.

• 한국환경과학회지
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• 제24권10호
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• pp.1239-1251
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• 2015

Impervious areas have been expanded by urbanization and the natural structure of water circulation has been destroyed. The limits of centralized management for controlling storm water runoff in urban areas have been suggested. Low impact development (LID) technologies have been promoted as a crucial alternative, establishing a connection with city development plans to build green infrastructures in environmentally friendly cities. Thus, the improvement of water circulation and the control of nonpoint source were simulated through XP-SWMM (storm water and wastewater management model for experts) in this study. The application of multiple LID combination practices with permeable pavements, bioretention cells, and gutter filters were observed as reducing the highest runoff volume by up to 70%. The results from four different LID installation scenarios indicated that permeable paving is the most effective method for reducing storm water runoff. The rate of storm water runoff volume reduced as the rainfall duration extended. Based on the simulation results, each LID facility was designed and constructed in the target area. The LID practices in an urban area enable future studies of the analysis of the criteria, suitable capacity, and cost-efficiency, and proper management methods of various LID techniques.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 추계학술발표회논문집(1)
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• pp.772-777
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• 1997

Previous MELCOR and SCDAP/RELAP5 nodalizations for simulating the counter-current, natural circulation behavior of vapor flow within the RCS hot legs and SG U-tubes when core damage progress can not be applied to the steady state and water-filled conditions during the initial period of accident progression because of the artificially high loss coefficients in the hot legs and SG U-tubes which were chosen from results of COMMIX calculation and the Westinghouse natural circulation experiments in a 1/7-scale facility for simulating steam natural circulation behavior in the vessel and in the hot leg and SG during the TMLB' scenrio. The objective of this study is to develop a natural circulation modeling which can be used both for the liquid flow condition at steady state and for the vapor flow condition at the later period of in-vessel core damage. For this, the drag forces resulting from the momentum exchange effects between the two vapor streams in the hot leg was modeled as a pressure drop by pump model. This hot leg natural circulation modeling of MELCOR was able to reproduce similar mass flow rates with those predicted by previous models.

• Ecology and Resilient Infrastructure
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• 제2권4호
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• pp.305-310
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• 2015

서울시는 2014년 기존의 서울시 물순환 조례에 저영향개발 (low impact development, LID)을 포함하는 조례개정을 통해 빗물관리의 토대를 마련하였다. 새롭게 개정된 조례에서는 2050년까지 연 강수량의 약 630 mm를 저류 및 침투시킬 것을 계획하고 있으며, 침투, 저류 및 식생을 활용하는 빗물관리시스템을 도입하여 관리하고자 한다. 저영향개발기법은 개발사업에서 생태, 물순환, 환경 등의 목표를 달성하고자 할 때 적용할 수 있는 중요한 기법이다. 본 연구에서는 서울시에 적용한 침투형 빗물받이, 생태저류형 배수로 및 투수성 포장 등의 다양한 물순환 시설 (LID)의 효과를 평가하기 위하여 수행되었다. 모니터링 결과 다른 시설에 비하여 투수성 포장에서 강우유출 저감효과가 가장 높게 나타났으나, 공극막힘현상을 줄이기 위한 방안이 설계에 반영되어야 하는 것으로 나타났다. 비점오염물질 유출저감의 경우 자동차 운행정도에 의한 오염물질 축적이 큰 영향을 끼친 침투형 빗물받이, 물리 및 생물학적 기작의 영향을 받은 생태저류형 배수로에서 높게 분석되었다. 다양한 목적으로의 저영향개발 기법 적용은 물순환 효과뿐만 아니라 환경오염저감, 생태복원, 심미적 효과 등의 다양한 효과를 보이는 것으로 나타났다.

• 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.

• 한국조경학회지
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• 제49권2호
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• pp.113-127
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• 2021

공원녹지와 물길을 연결하는 조경계획기법이 보편화되었지만, 대규모 계류형 수경시설의 운영과 관리상의 문제가 빈번하게 발생하고 있다. 이에 본 연구는 전주·완주 혁신도시를 대상으로 빗물을 이용한 계류형 수경시설의 지속가능한 관리와 운영을 모색할 수 있는 설치방안을 검토하였다. 이 연구의 목적을 수행하기 위해 수원지와 수로 부분으로 나누어 각각의 시나리오를 설정하였다. 첫째, 수원지에 관한 시나리오는 수로와 수원지에 필요한 유지용수량과 저장공간을 산정하기 위해 물수지를 분석하였다. 분석 결과, 수로 부분 자체는 676.8톤/월의 급수가 필요하지만, 수원지의 생태적 또는 경관적 측면을 고려하여 3,018톤~5,512톤의 저장 공간과 0.75m~1.37m의 수심 유지가 요구되었다. 둘째, 수로에 관한 시나리오는 계류형 수경시설의 유지관리에 효과적인 설비의 계통을 선정하는 것이다. 이를 위해 용수를 고지대로 압송하여 흘려보내는 단일순환계통과 각각의 수공간에 별도 공급하여 독립 운전하는 다중순환계통을 비교 분석하였다. 그 결과, 소규모 동력장치에 의해 독자적으로 운전하는 다중순환계통이 용수공급에 필요한 운전시간을 최소화 할 수 있어 더 효과적인 것으로 나타났다.