• 대한기계학회논문집A
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• 제38권8호
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• pp.831-836
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• 2014

본 연구에서는 한국원자력연구원 내에 설치될 예정인 소듐시험 시설인 SELFA(Sodium Thermal-hydraulic Experiment Loop for Finned-tube Sodium-to-Air heat exchanger) 내에서 정상상태 가동온도가 $510^{\circ}C$의 고온 압력용기인 팽창탱크에 대해 고온 건전성 평가를 수행하였다. 팽창탱크에 대해 3 차원 유한요소해석에 기초하여 고온설계 기술기준인 ASME Section III Subsection NH 와 프랑스의 RCC-MRx 코드를 따라 크리프-피로 손상평가를 수행하였다. 평가결과 팽창탱크는 크리프-피로 설계 과도 하중 하에서 구조적 건전성을 유지하는 것으로 나타났다. 316L 스테인리스강 재질의 동 압력용기에 대해 정량적 코드 비교 분석을 수행하였다.

• Journal of Welding and Joining
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• 제30권6호
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• pp.10-14
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• 2012

Recently the low alloy steel plate made with manganese-molybdenum is used widely in steam drum and separator of the new coal-fired power plant boiler. This material is suitable for the vapor storage of high pressure and high temperature. The high temperature creep strength of Mn-Mo alloy is higher than the carbon plate(SA516) that used in the subcritical pressure boiler. It reduces the thickness of the pressure vessel and makes the lightweight possible. Recently in the power plant boiler operation and production process, the damage has happened frequently in the heat affected zone and base material according to the hydrogen crack and delayed crack. This paper describes the research result about the damage case experienced in the boiler steam drum production process and present the optimum manufacture method for the similar damage prevention of recurrence.

• Nuclear Engineering and Technology
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• 제32권4호
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• pp.410-423
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• 2000

A two-dimensional numerical model is developed and applied to the LAVA-EXV tests performed at the Korea Atomic Energy Research Institute (KAERI) to investigate the external cooling effect on the thermal margin to failure of a reactor pressure vessel (RPV) during a severe accident. The computational program was written to predict the temperature profile of a two-dimensional spherical vessel segment accounting for the conjugate heat transfer mechanisms of conduction through the debris and the vessel, natural convection within the molten debris pool, and the possible ablation of the vessel wall in contact with the high temperature melt. Results of the sensitivity analysis and comparison with the LAVA-EXV test data indicated that the developed computational tool carries a high potential for simulating the thermal behavior of the RPV during a core melt relocation accident. It is concluded that the main factors affecting the RPV failure are the natural convection within the debris pool and the ablation of the metal vessel, The simplistic natural convection model adopted in the computational program partly made up for the absence of the mechanistic momentum consideration in this study. Uncertainties in the prediction will be reduced when the natural convection and ablation phenomena are more rigorously dealt with in the code, and if more accurate initial and time-dependent conditions are supplied from the test in terms of material composition and its associated thermophysical properties.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1915-1918
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• 2003

Atherosclerosis, which is a degenerate disease, is believed to occur in the vascular system due to deposition of cholesterol and low density lipoprotein(LDL) or thrombosis on the blood vessel. Atherosclerosis narrows arterial lumen, which is known as stenosis phenomenon of blood vessel. Pathogenesis of atherosclerosis is thought to occur mainly by aging. Restenosis phenomenon is observed in the same site of insertion of a stent and balloon angioplasty after treatment of interventional theraphy. Several hypothetical theories related to the generation of atherosclerosis have been reported: high shear stress theory, low shear stress theory, high shear stress gradient theory, flow separation and turbulence theory and high pressure theory. However, no one theory clearly explains the causes of atherosclerosis. In the present study the generation of atherosclerosis in the left coronary artery is investigated. The hypotheses are verified by using the computer simulation.

• 한국압력기기공학회 논문집
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• 제12권1호
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• pp.115-125
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• 2016

The prototype SFR has currently been under design by KAERI. The size of its major components is much larger than that of APR1400 and high temperature materials are applied for it. The increased size of components and those specific materials effect on material procurement, manufacturing process and fabrication facilities. The manufacturing methods are studied for Reactor Vessel/Guard Vessel, Control Rod Drive Mechanism, Heat Exchanger, Primary Pump, Reactor Vessel Internals, Steam Generator and In-Vessel Transfer Machine. The proper manufacturing methods are suggested for each component including side forging technology for ultra large forgings of Reactor Vessel to minimize the weld seams on which In-service Inspection should be conducted.

• 한국군사과학기술학회지
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• 제4권1호
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• pp.246-254
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• 2001

The breech system can be considered as a pressure vessel with an internal plug under high explosive pressure. The system consists of a breech block(internal plug) whose front surface subjects to pressure, and a breech ring(pressure vessel). There is the geometric discontinuity around roots of connection parts and then stress concentration is introduced due to pressure, where contact effect may be ignored because contact plane between two equipments is parallel ideally, Generally high stress concentration phenomena shorten the life cycle of the mechanical system. It is well known that shock load is much more harmful on safety of the system than static load. In this present paper, several geometric design variables which may affect stress condition on the system are chosen and the parametric study on the design variables is carried using commercial FEM codes. Finally, the obtained results in the single lug breech system are applied to design the 3 lugs breech system. The 3 lugs breech system can reduce the maximum stress level.

• 한국압력기기공학회 논문집
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• 제16권1호
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• pp.84-91
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• 2020

The APR1400 reactor stud holes can be stuck due to high temperatures, high pressure, prolonged engagement, and load changes according to pressure changes in the reactor. Threaded surfaces of a stud hole should be cleaned for the sealing of pressure in reactor vessel by removing any foreign materials which may exist in the stud holes. Human workers can access to the stud hole for the cleaning of stud holes manually, but the radiation exposure of human workers is increased. Robot is an effective way to work in hazardous area. So we introduced robot for the cleaning of stud holes. Localization of mobile robots is generally based on odometry, but with increased mileage, position errors can be accumulated. In order to eliminate cumulative error and to ensure stability of its driving, laser sensors and new control algorithm were utilized. The distance between the robot and the wall was measured by laser sensors, and the control algorithm was implemented so as to travel the desired trajectory by using the measured values from sensors. The performance of driving and hole sensing were verified through field application, and mobile robot was confirmed to be applicable to the APR 1400 NPP.

• 한국해양공학회지
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• 제14권1호
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• pp.44-51
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• 2000

Safety and integrity are required for reactor pressure vessels because they are operated in high temperature. There are single specimen method multiple specimen method and load ratio analysis method which used as evaluation of safety and integrity for reactor pressure vessels. In this study the fracture resistance curve(J-R curve) elastic-plastic fracture toughness($J_{IC}$) and material tearing modulus ($T_{mat}$) of SA 508 class 3 alloy steel used as reactor pressure vessel steel are measured and evaluated at room temperature 20$0^{\circ}C$ and 30$0^{\circ}C$ according to unloading compliance method and load ration analysis method. And then the comparison with experimental $J_{IC}$ and theoretical$J_{IC}$ by local fracture strain is managed.

• Journal of Mechanical Science and Technology
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• 제17권9호
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• pp.1371-1379
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• 2003

The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated. The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore, this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 22 MPa to 112 MPa using a high pressure injection system (ECD-U2). Also, we conducted simulation study by modified KIVA-II code. The results of simulation study are compared with experimental results. The images of liquid and vapor phase for free spray were simultaneously taken by exciplex fluorescence method. As experimental results, the vapor concentration of injected fuel is leaner due to the increase of atomization in the case of the high injection pressure than in that of the low injection pressure. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.

• 대한조선학회논문집
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• 제53권2호
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• pp.144-153
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• 2016

This paper aims to demonstrate the design, structure analysis, and hydrostatic pressure test of the cylinder used in 2000m water depth. The cylinder was designed in accordance with ASME pressure vessel design rule. The 1.5 times safety factor required by the general rule was applied to the design of the cylinder, because ASME rule is so excessive that it is not proper to apply to the hydrostatic pressure test. The finite element analysis was conducted for the cylinder. The cylinder was produced according to the design. The hydrostatic pressure test was conducted at the hyperbaric chamber in KRISO. The results of finite element analysis(FEM) and those of the hydrostatic pressure test were almost the same, which showed that the design was exact and reliable.