• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.843-848
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• 2000

The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle and it's containment vessel. If a flaw is found during the periodic inspection from the pressure tubes, the integrity evaluation must be carried out, and the safety requirements must be satisfied for continued service. In order to complete the integrity evaluation, complicated and iterative calculation procedures are required. Besides, a lot of data and knowledge for the evaluation are required for the entire integrity evaluation process. For this reason, an integrity evaluation system, which provides efficient way of evaluation with the help of attached databases, was developed. The developed system was built on the basis of ASME Sec. XI and FFSG(Fitness For Service Guidelines for zirconium alloy pressure tubes in operating CANDU reactors) issued by the AECL, and covers the delayed hydride cracking(DHC). Various analysis methods are provided for the integrity evaluation of pressure tube. In order to verify the developed system, several case studies have been performed and the results were compared with those from AECL. A good agreement was observed between those two results.

• 비파괴검사학회지
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• 제15권1호
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• pp.310-317
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• 1995

원자력 발전소의 주요 계통 재료로 사용되는 오스테나이트계 스텐레스강에 대한 초음파탐상은 초음파 에너지가 전파될 경우 재질 자체가 갖는 여러 문제점으로 인하여 결함 위치나 크기 측정에 많은 문제점을 야기한다. 본 연구에서는 이러한 문제점을 이해하기 위하여 여러가지 경우를 가정하여 선 추적(ray tracing) 기법을 사용한 컴퓨터 모의(simulation)를 실시하였다. 우선 종파를 사용하여 모재에 초음파가 입사하여 진행할 시 어느정도의 휘어짐이 발생하는지를 계산하였으며 재질 특성상 용접부와 모재가 큰 차이를 보이지 않는 경우와 원자로 노즐 부위와 같이 서로 다른 금속으로 용접된 경우에 결함이 존재한 경우를 가정하여 계산하였다.

• 비파괴검사학회지
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• 제34권1호
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• pp.1-9
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• 2014

A two-dimensional numerical model based on the finite element method was built to simulate the wave propagation phenomena that occur during the ultrasonic time of flight diffraction (TOFD) process. First, longitudinal-wave TOFD was simulated, and the numerical results agreed well with the theoretical results. Shear-wave TOFD was also investigated because shear waves have higher intensity and resolution. The shear wave propagation was studied using three models with different boundary conditions, and the tip-diffracted shear-to-longitudinal wave was extracted from the A-scan signal difference between the cracked and non-cracked specimens. This signal showed very good agreement between the geometrical and numerical arrival times. The results of this study not only provide better understanding of the diffraction phenomena in TOFD, but also prove the potential of shear-wave TOFD for practical application.

• 방사성폐기물학회지
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• 제18권3호
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• pp.407-414
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• 2020

Thermal decomposition of the uranyl phosphate mineral phase meta-ankoleite (KUO₂PO₄·3H₂O) has been considered in relation to high temperature thermal sintering for the immobilisation of a uranyl phosphate containing waste. Meta-ankoleite thermal decomposition was studied across the temperature range 25 - 1200℃ under an inert N₂ atmosphere at 1 atm. It is shown that the meta-ankoleite mineral phase undergoes a double de-hydration event at 56.90 and 125.85℃. Subsequently, synthetically produced pure meta-ankoleite remains stable until at least 1150℃ exhibiting no apparent phase changes. In contrast, when present in a mixed waste the meta-ankoleite phase is not identifiable after thermal treatment indicating incorporation within the bulk waste either as an amorphous phase and/or as uranium oxide. Visual inspection of the waste post thermal treatment showed evidence of self-sintering owing to the presence of glass former materials, namely, silica (SiO₂) and antimony(V) oxide (Sb₂O₅). Therefore, incorporation of the uranium phase into the waste as part of waste sentencing and immobilisation via high temperature sintering for the purpose of long-term disposal is deemed feasible.

• 전기학회논문지P
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• 제55권4호
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• pp.196-201
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• 2006

A electrical fault that may generate an electrical disaster is defined as any abnormal condition caused by reduction in the insulation strength. To find out the abnormal condition, periodical inspections have being performed every 3 years. Recently, the number of empty houses during normal working hours is rising by dramatic increase in the number of nuclear families and double income families. To define the potential risk of the electric installation, measurement of zero phase current has been being considered. But the measured value could not be adapted to an absolute reference to the installation because the measured zero phase current value also contained capacitive leakage current. Therefore, in this paper, the correlation between the condition of the electrical installation and the zero phase current was analyzed. The result focuses on to detect them in a cost efficient way.

• Corrosion Science and Technology
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• 제11권3호
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• pp.89-95
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• 2012

U.S. Electric Power Research Institute (EPRI) has developed CHECWORKS program and applied it to power plant piping lines since some lines were ruptured by flow-accelerated corrosion (FAC) in 1978. Nowadays the CHECWORKS program has been used to manage pipe wall thinning phenomena caused by FAC. However, various erosion mechanisms can occur in carbon-steel piping. Most common forms of erosion are cavitation, flashing, liquid droplet impingement erosion (LDIE), and Solid Particle Erosion (SPE). Those erosion mechanisms cause pipe wall thinning, leaking, rupturing, and even result in unplanned shutdowns of utilities. Especially, in two phase condition, LDIE damages a wide scope of plant pipelines. Furthermore, LDIE is the major culprit to cause such as power runback by pipe leaking. This paper describes the methodologies that manage wall thinning and also predict LDIE wall thinning area. For this study, current properties of two-phase condition are investigated and LDIE areas are selected. The areas are checked by B-Scan method to detect the effect of wall thinning phenomena.

• 천문학회보
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• 제36권1호
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• pp.63.2-63.2
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• 2011

We present a photometric study of star clusters in three nearby barred spiral galaxies NGC 1300, NGC 1672 and NGC 6217. We use the Hubble Heritage CCD images taken with Advanced Camera for Surveys (ACS) of Hubble Space Telescope (HST) in several filters. We have selected hundreds of star clusters with V $\leq$ 24 mag in each galaxy, based on the morphological parameters and visual inspection. Most of the blue star clusters with B-V $\leq$ 0.5 are strongly concentrated in spiral arms. A significant fraction of these star clusters are distributed in ansae (the joint between spiral arms and bar structure). Some of the blue star clusters are also found in the nuclear starburst region, especially in NGC 1672. A small number of star clusters are found in the bar region. In contrast, the red star clusters with B-V < 0.5 are relatively uniformly located over the entire field of galaxy, and show some central concentration around the bulge. We discuss the physical properties of these star clusters with the expected results from simulations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 D
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• pp.2603-2605
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• 2003

증기발생기(SG : Steam Generator)는 다수의 세관으로 구성되어 원자로에서 발생한 열을 이용하여 발전기 터빈을 구동시키는 원동력인 증기를 생성해 주는 기능을 하는 원자력발전소의 핵심 설비이다. 증기 발생기 세관의 건전성을 확보하기 위해 매주기 계획예방 정비, 즉 가동중검사마다 정기적인 와전류검사를 수행하고, 검사결과에 따라 전열관 보수 등과 같은 제반 조치를 취하고 있다. 현재 검사데이터 DB 구축은 일부 발전소에 개발되어 운영중에 있고, 세관 DB와는 별도로 통계정보만을 관리하는 증기발생기 성능관리시스템이 운영되고 있으며, 또한 각 발전소마다 수질을 계측하여 수화학 성분을 감시하는 수질관리시스템이 운용되고 있다. 이러한 이원화된 DB 및 시스템을 통합하고 연계하여 전 원전의 증기발생기를 종합적으로 관리 할 수 있는 시스템의 필요성이 대두되었다. 따라서 본 논문에서는 현장에 보관되어 있는 모든 세관 검사데이터를 취득하여 대용량 데이터베이스를 설계 및 구축하고 이기종의 분산된 수질관리시스템 DB를 연계하여, 증기발생기의 설계/제작부터 검사결과 Mapping, 추이 분석을 통한 수명평가에 이르는 전 과정을 통합 관리한 수 있는 시스템을 개발하고 그 구현방안을 제시한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.930-933
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• 2005

Non-destructive inspection techniques using laser have been breading their application areas as well as growing their measurement skills together with the rapid development of circumferential technology like fiber optics. computer and image processing The ESPI technique is already on the stage of on-line testing with commercial products in developed country nations. Especially, this technique is expected to be applied to the nuclear industry, automobile and aerospace because it is proper for the vibration measurement and it can be applied to objects of a high temperature. This paper describes the use of the ESPI system for measuring vibration patterns on the reflecting objects. Using this system, high-quality Jo fringes for identifying mode shapes are displayed. A bias vibration is introduced into the reference beam to shift the Jo fringes so that fringe shift algorithms can be used to determine vibration amplitude. Using this method. amplitude fields for vibrating objects were obtained directly from the time-average interferometer recorded by the ESPI system.

• 대한기계학회논문집A
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• 제20권4호
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• pp.1233-1240
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• 1996

Conventional measurement methods using ultrasonic wave or x-ray, eddy current for non-destructive testing(NDT) in nuclear power plants and other industrial plants have been utilized as the method of contact with objects to be inspected. For this reason these methods require relatively much time and inspection area is limited by the location of probe or film. But holograpic interferometry which is a non-contact optical measurement method using a coherent light source has an advantage that quantative measurement can be performed at a time. In this paper a new method using realtime holographic interfreometry and image processing for detecting internal flaws of pressure vessels is presented.