• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 춘계학술발표회요약집
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• pp.73-73
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• 1999

• 대한기계학회논문집A
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• 제26권3호
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• pp.505-513
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• 2002

During heatup and cooldown of pressurized water reactor, thermal stress was generated in the reactor pressure vessel (RPV) because of the temperature gradient. To prevent potential failure of RPV, pressure was required to be maintained below the P-T limit curves. In this paper, several methods for constructing the P-T limit curves including the ASME Sec. XI, App. G method were explained and the results were compared. Then, the effects of the various parameters such as flaw size, flaw orientation, cooldown rate, existence of chad, and reference fracture toughness, were evaluated. It was found that the current ASME Sec. XI App. G method resulted in the most conservative P-T limit curve. As the more accurate fracture mechanics analysis results were used, some of the conservatism can be removed. Among the parameters analysed, reference flaw orientation and reference fracture toughness curve had the greatest effect on the resulting P-T limit curves.

• 대한기계학회논문집
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• 제14권6호
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• pp.1669-1678
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• 1990

본 연구에서는 다중선회연소기의 원리에 기초하여 연료와 산화제의 접촉면적 및 혼합속도를 증가시킴으로써 연소부하의 증대 및 연소효율의 향상효과를 얻을 수 있 는 새로운 연소방식을 개발하기 위한 시도로서 속도차가 있는 동축의 두 공기분류 사 이의 전단층에 기체연료를 분출시켜서 형성되는 난류확산 화염에 관하여 유동장의 성 상이 화염안정한계 및 화염구조에 미치는 영향을 조사하여 실용연소기의 유도장제어 및 고부하연소기설계를 위한 기초자료를 얻는데 목적이 있다.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.2052-2056
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• 2015

This Paper analyzes the characteristics of the WRSM in high-speed operation range. To verify the control characteritics of various WRSM models, the relative position of the central point of current limit circle and voltage limit ellipse is defined as M value and 3 models according to M_max value are designed through inductance change. Through the designed models, the current control method of 3-variables control for maximum power especially in high-speed operation range is presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.28-30
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• 2000

This paper introduces a power flow model of SSSC for voltage stability study. The SSSC model is obtained from the injection model of voltage source inverter by adding the condition that SSSC injection voltage is in quadrature with current of SSSC-installed branch. This model is incorporated into modified CPF algorithm to study effects of SSSC on the security-constrained interface flow limit. Determination of interface flow limit is simply briefed. In case study a 771-bus real system is used to show that SSSC can improve interface flow limit in terms of voltage stability.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.251-253
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• 2005

This paper presents a study on a current control of a PM synchronous motor which is fed by two-level voltage source inverter in the high modulation index area. In order to increase dynamic response and extend speed limit caused by voltage limit, overmodulation method is generally used. The current control in overmodulation have voltage limit. So larger voltage command than voltage limit should be diminished. In this paper, the problem conventional normalization method is analyzed and New normalization method in overmodulation region is proposed.

• Structural Engineering and Mechanics
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• 제14권2호
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• pp.191-208
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• 2002

A comparative assessment study for a generation of the pressure-temperature (P-T) limit curve of a reactor vessel is performed in accordance with ASME code. Using cooling or heating rate and vessel material properties, stress distribution is obtained to calculate stress intensity factors, which are compared with the material fracture toughness to determine the relations between operating pressure and temperature during reactor cool-down and heat-up. P-T limit curves are analyzed with respect to defect orientation, clad thickness, toughness curve, cooling or heating rate and neutron fluence. The resulting P-T curves are compared each other.

• 대한기계학회논문집A
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• 제39권5호
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• pp.453-460
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• 2015

후쿠시마 원전 사고 이후로 원자력 발전 플랜트의 배관 시스템에 가해지는 비틀림 하중의 영향에 대한 연구가 여러 연구자들에 의해서 수행되었다. 발전 플랜트의 원주방향 균열을 포함한 배관은 정상운전 조건이나 갑자기 발생한 사고에 의해서 굽힘과 비틀림과 같은 하중을 받을 수 있다. ASME 코드에서는 균열 배관의 구조건전성 확보를 위해서 한계하중 기법을 사용해서 완전소성 파단에 대한 결함평가를 제공한다. 최근 개정된 코드에 따르면, 복합하중은 막응력과 굽힘 응력만을 포함하고 있다. 실제로 운전 환경에서 비틀림 하중이 가해질 수 있음에도 불구하고, 비틀림 하중을 평가하는 방법론에 대해서는 언급하지 않았다. 본 논문에서는 한계하중 분석을 기반으로 원주방향 균열 존재하는 배관에 단순 굽힘과 단순 비틀림, 인장을 포함한 굽힘 비틀림 복합하중이 가해질 경우에 대한 유한요소해석 결과를 포함하고 있다. 전단면 완전항복 기준을 만족하는 한계하중 이론해를 제안하고 유한요소해석을 통해서 이를 검증하였다.

• 대한기계학회논문집A
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• 제27권11호
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• pp.1979-1985
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• 2003

Fretting is a kind of surface degradation mechanism observed in mechanical components and structures. The fretting damage decreases in 50-70% of the plain fatigue strength. This may be observed in the fossil power plant and the nuclear power plant used in special environments and various loading conditions. The thermal degradation of material is observed when the heat resisting steel is exposed for long period time at the high temperature. In the present study, the degraded 1Cr-0.5Mo steel used for long period time at high temperature (about 515$^{\circ}C$) and artificially reheat-treated materials are prepared. These materials are used for evaluating an effect of thermal aging on the fretting fatigue behavior. Through the experiment, it is found that the fretting fatigue endurance limit of the reheat-treated 1Cr-0.5Mo steel decreased about 46% from the non-fretting fatigue endurance limit, while the fretting fatigue endurance limit of the degraded 1Cr-0.5Mo steel decreased about 53% from the non-fretting fatigue endurance limit. The maximum value of fatigue endurance limit difference is observed as 57%(244 MPa) between the fretting fatigue of degraded material and non-fretting fatigue of reheat-treated material. These results can be a basic data to a structural integrity evaluation of heat resisting steel considered to thermal degradation effect.

• 대한기계학회논문집A
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• 제34권9호
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• pp.1293-1298
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• 2010

본 연구에서는 인공감육엘보에 대해 내압 및 굽힘의 복합하중을 작용시킨 실 배관 실증실험으로부터 생성한 회전각 대비 모멘트 곡선으로부터 감육결함 엘보에서 소성변형이 시작되는 1 배탄성구배법에 기초한 OES 탄성하중과 2 배탄성구배법에 기초한 TES 소성하중의 거동 및 상관관계를 살펴보았다. ASME 에서도 제시하고 있는 TES 소성하중은 균열손상에 따른 배관계통 구조 건전성 상실을 배제하면서도 지속사용을 허용할 수 있는 대체 관리 기준으로서 적합한 것으로 판단된다.