• Nuclear Engineering and Technology
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• 제33권2호
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• pp.241-253
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• 2001

Under severe accidents, the pressure and temperature response has an important role for the integrity of a nuclear power plant containment. The history of the pressure and temperature is characterized by the amount and state of steam/air mixture in a containment. Recently, the heat transfer rate to the structure surface is supposed to be increased by the wavy interface formed on condensate film. However, in the calculation by using CONTAIN code, the condensation heat transfer on a containment wall is calculated by assuming the smooth interface and has a tendency to be underestimated for safety. In order to obtain the best- estimate heat transfer calculation, we investigated the condensation heat transfer model in CONTAIN 1.2 code and adopted the new forced convection correlation which is considering wavy interface. By using the film tracking model in CONTAIN 1.2 code, the condensate film is treated to consider the effect of wavy interface. And also, it was carried out to investigate the effect of the different cell modelings - 5-cell and 10-cell modeling - for KNGR(Korean Next Generation Reactor) containment phenomena during a severe accident. The effect of wavy interface on condensate film appears to cause the decrease of peak temperature and pressure response . In order to obtain more adequate results, the proper cell modeling was required to consider the proper flow of steam/air mixture.

• 한국구조물진단유지관리공학회 논문집
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• 제5권2호
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• pp.147-154
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• 2001

The prestressed concrete containment is one of the most important structures in nuclear power plants, which is required to prevent release of radioactive or hazardous effluents to the environment even in the case of a severe accident. Numerical analyses are carried out by using the ABAQUS finite element program to assess the ultimate pressure capacity of the Y prestressed concrete containment with light water reactor at design criteria condition and aging condition considering varied properties of time-dependant materials respectively. From the results, it is verified that the structural capacity of the Y prestressed concrete containment building under the present, aging condition is still robust. In addition, the parameter studies for the reduction of the ultimate pressure capacity of containment building according to the degradation levels of the main structural materials are carried out. The results show that when the degradations of each materials are considered as individual and combined forms, the influence is large in the order of tendon, rebar and concrete degradation, and tendon-rebar, tendon-concrete and rebar-concrete degradation respectively.

• 대한기계학회논문집A
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• 제28권2호
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• pp.158-164
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• 2004

Steam generator tubes experience widespread degradations such as stress corrosion cracking, wear, tube rupture, denting, fatigue and so on. The resulting damages can cause tube bursting or leak of the primary water which contains radioactivity Therefore the allowable size of the damage is required to be determined on the maintenance purpose. The burst pressure of a tube with a T-type combination crack consisting of longitudinal and circumferential cracks is obtained experimentally and analytically. Fracture parameters such as stress intensity factor and crack opening angle are investigated. Also the burst pressure for a T-type combination crack is compared with that of a single longitudinal crack to develop a length-based criteria.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.125-130
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• 2004

Experimental study on combustion characteristics of double swirl coaxial injectors has been conducted for the assessment of critical injector design parameters. A reusable, unielement thrust chamber has been fabricated with a water-cooled copper nozzle. Two principle design parameters, a swirl angle and a recess length, have been investigated through hot firing tests for the understanding of their effects on high pressure combustion. Clearly, both parameters considerably affect the combustion efficiency, dynamics and hydraulic characteristics of an injector. Internal mixing of propellants in a recess region increases combustion efficiency along with the increase of a pressure drop required for flowing the same amount of mass flow rates. It is concluded that pressure buildup due to flame can be released by the increase of LOx flow axial momentum or the reduction of a recess length. Dynamic pressure measurements of the thrust chamber show varied dynamic behaviors depending on injector configurations.

• 대한안전경영과학회지
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• 제19권1호
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• pp.9-13
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• 2017

In this study, the height of the flame required to estimate the heat flow path and flame spread in pool fire has been applied by the empirical formula, but it is calculated without applying the pressure and temperature parameters of the fire room. Until now, the height of the flame applied to pool fire was $l_F=0.235Q^{2/5}-1.02D$ in the Heskestad empirical formula, but accurate temperature calculation was not possible due to the temperature and pressure which are not influenced by the flame height. Therefore, applying the temperature and pressure around it can calculate the exact flame height, which can be applied to fire investigation and fire dynamics. The structure of the flame is divided into a continuous flame, an intermittent flame, and a buoyancy flame, but it is assumed that the flame height is calculated from the visual aspect to the intermittent flame region, and the temperature of the buoyancy flame is very low. The effect of heat of vaporization on the height of flame was investigated. The results showed that flame height was different according to the pressure and temperature around the fire room.

• 한국군사과학기술학회지
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• 제14권6호
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• pp.1159-1165
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• 2011

Telemetry techniques of rats have been used for assessing safety pharmacology of drugs and chemicals. Biological signals including blood pressure and heart rate measured under anesthesia were significantly different from those obtained under normal conditions. The stress of restraint in awake animals can also affect the accuracy of physiological evaluation. This paper details the surgery required to allow key cardiovascular parameters to be determined. The telemetric measurement of cardiovascular parameters such as blood pressure, heart rate, electrocardiograph(ECG) established. We carried out the continuous monitoring of cardiovascular parameters using the telemetry system in F344 rats. During the measurement, no significant changes were observed in the heart rate and blood pressure. ECG signals and body temperature were also constant during the measurement of biological signals. With the results of this study, we conclude that this telemetry system can be applied usefully for the assesment of biological parameters in the rats.

• Nuclear Engineering and Technology
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• 제27권2호
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• pp.165-175
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• 1995

가압경수로의 과압보호계통은 가장 심각한 비정상 과도운전시 원자로냉각재계통의 압력을 설계압력의 110% 이내로 유지시킬 수 있는 충분한 용량으로 설계되어져야 한다. 본 연구에서는 ABB-CE 설계의 2825 MWt 가압경수로에 기존의 스프링 탑재형 가압기 안전밸브 대신 SEBIM-POSRV를 채택할 경우 과압보호 기능 수행의 가능성을 연구하였다. 과압보호 기능을 수행하기 위한 SEBIM POSRV의 크기 및 작동 설정치를 영광 3, 4호기의 과압보호 해석에 사용했던 LTC 전산코드를 이용한 분석을 통해서 결정했다. 분석 결과 monobloc SEBIM POSRV를 이용한 과압보호계통은 원자로냉각재계통의 압력을 설계 압력의 110% 이내로 유지시킴으로써 ABB-CE 형태의 2825 MWt급 가압경수로에서 과압보호 기능을 수행할 수 있음이 입증되었다.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.869-876
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• 2018

The force of a direct current (DC) electromagnetic pump used to transport liquid lithium was analyzed to optimize its geometrical and electrical parameters by numerical simulation. In a heavy-ion accelerator, which is being developed in Korea, a liquid lithium film is utilized for its high charge-stripping efficiency for heavy ions of uranium. A DC electromagnetic pump with a flow rate of $6cm^3/s$ and a developed pressure of 1.5 MPa at a temperature of $200^{\circ}C$ was required to circulate the liquid lithium to form liquid lithium films. The current and magnetic flux densities in the flow gap, where a $Sm_2Co_{17}$ permanent magnet was used to generate a magnetic field, were analyzed for the electromagnetic force distribution generated in the pump. The pressure developed by the Lorentz force on the electromagnetic force was calculated by considering the electromotive force and hydraulic pressure drop in the narrow flow channel. The opposite force at the end part due to the magnetic flux density in the opposite direction depended on the pump geometrical parameters such as the pump duct length and width that defines the rectangular channels in the nonhomogeneous distributions of the current and magnetic fields.

• KSTLE International Journal
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• 제8권2호
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• pp.29-34
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• 2007

Recently, requirements relating to performance, environment and noise in the oil hydraulic system of the heavy construction equipment have been reinforced continuously. In order to solve these technical trends, studies on the system compactness, operation under high pressure and great rotating speed, electronic control, substitute oil, and noise reduction have been progressed briskly. Among these recent studies, the system operation under high pressure is quite difficult to carry into effect due to mechanical limitations; that is, for realizing the system operation in the hydraulic pump under high pressure, the improvements or innovations on the design techniques, the manufacturing techniques, and the lubrication performance of the working oil are required. Accordingly, in this study, the stress distribution and optimum design factors under the maximum pressure were discussed by using stress analysis on the cylinder block of the hydraulic axial piston pump, which is one of the most important relative sliding regions.

• 한국정밀공학회지
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• 제15권7호
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• pp.139-148
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• 1998

Internal and external heat sources will cause to deform to machine elements in the contact joint of structure, which results in the change of contact pressure distribution different from initial assembly. Heat induced variations of contact pressure will change the static and dynamic properties such as contact stiffness, damping as well as contact heat conduction in the structure In order to design and control the intelligent machine tool operating in variant conditions more sophisticatedly, the good prediction for the changes of prescribed properties are strongly required especially in the contact elements adjacent to the rotational or linear bearing. This paper presents some computational and experimental results in regard to static and dynamic characteristics of the press-fitted bush and shaft assembly which is a model of the bearing innerrace and shaft assembly. In the condition of heat generation on the outer surface of the bush, the effects of changes in the negative clearance and the heat flux on pressure distribution and dynamic properties are investigated. Results of this study show that the edge effect of the bush and the initial clearance have effects on the transient dynamic characteristics significantly.