• Nuclear Engineering and Technology
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• 제33권4호
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• pp.423-440
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• 2001

For sodium cooling liquid metal reactors during the last 25 years, it was most important to verify the safety of the steam generator, which absolutely requires a water leak detection system with fine sensitivity and response. This study describes the structure and leak classification of the HAMMER (Korea Advanced Liquid Metal Reactor) steam generator, compared with other classifications, and explains the effects of leak development. The requirements and experimental situations for the development of the KALIMER acoustic leak detection system (KADS) which detects micro leaks, not intermediate leaks, are introduced. We proposed four frequency bands, 1∼8kHz, 8∼20kHz, 20∼40kHz and 40∼200kHz, split effectively for analyzing the detected acoustic leak signals obtained from the sodium-water reaction model or water model in the mock-up system.

• Nuclear Engineering and Technology
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• 제33권2호
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• pp.145-155
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• 2001

This simulation first allows us to define a transition zone from a bubble to jet mode of the argon out-flow and hereinafter to define a similar area for water-steam leak in the KALIMER SG (Korea Advanced Liquid Metal Reactor Steam Generator) using a water mock-up system, taking into account the KALIMER leak classification and tube bundle design, as a simulation of a real water-steam into sodium leak. in accordance with leak conditions in the KALIMER SG, the transition from bubbling to jetting is studied by means of turbulence regime simulation for argon out-flow through a very small orifice, which has the equivalent diameter of about 0.253 mm. finally the noise generation mechanism is explained from the existing experimental data. We also confirmed the possibility of micro-leak detection from the information of the bubbling mode through simulations and the experiment in this study.

• 비파괴검사학회지
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• 제35권5호
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• pp.307-313
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• 2015

배관의 누설 검출은 주로 AE(acoustic emission) 센서와 같은 접촉식 센서가 이용되고 있다. 그러나 이러한 접촉식 센서는 고온이나 고방사능 지역에서 설치 및 운용의 어려움이 따른다. 이에 최근 원거리 감시 및 광역감시가 가능한 카메라를 이용한 누설 검출 방법에 대한 연구가 진행되어 왔다. 기존 카메라를 이용한 방법은 누설 검출을 위해 차영상 기법을 이용하고 있다. 그러나 이 방법은 누설뿐만 아니라 구조물의 진동이 누설로 검출되는 오류를 보이고 있다. 본 논문에서는 카메라를 이용한 누설 검출 방법에서 누설 검출 오류를 줄이기 위한 이동평균 차영상 및 히스토그램 분석법을 제안하였으며 실험을 통하여 성능을 평가하였다.

• 한국소음진동공학회논문집
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• 제20권9호
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• pp.828-833
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• 2010

Steam leakage is one of the major issues for the structural fracture of pipes of nuclear power plants. Therefore a method to inspect a large area of piping systems quickly and accurately is needed. In this paper, we proposed the method for the detecting steam leakage by using image signal processing. Our basic idea come from heat shimmer which shine with a soft light that looks as if it shakes slightly. To test the performance of this technique, experiments have been performed for simple heat source and steam generator. Results show that the proposed technique is quite powerful in the steam leak detection.

• 한국압력기기공학회 논문집
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• 제16권2호
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• pp.25-34
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• 2020

As leakage in nuclear power plants could cause a variety of problems, it is very critical to monitor leakage from the safety point of view. Accordingly, a new type of leak detection system is currently being developed and flow characteristics of the sampling and transportation system are investigated by using numerical analysis as a part of the development process in this study. The results showed that the steam mass fraction varied according to the effect of the gap between the insulation and piping component, transportation velocity, and material properties of porous media during the sampling and transportation process. The results of this study should be useful for understanding flow characteristics of the sampling and transportation system and its design and application.

• 비파괴검사학회지
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• 제36권5호
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• pp.384-390
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• 2016

플랜트 배관의 누설감시 시스템은 누설 유무 판단뿐만 아니라 누설의 위치를 신속히 파악하는 것 또한 매우 중요하다. 플랜트 배관의 누설 검출 방법에는 주로 AE(acoustic emission)센서, 마이크로폰어레이 그리고 카메라 영상을 이용한 방법들이 있다. 최근 광역감시 및 원거리감시의 이점이 있는 카메라 영상을 이용한 방법에 대한 연구가 진행되어 왔다. 하지만 기존 카메라 영상을 이용한 방법들은 누설 유무와 대략적인 누설의 위치를 판단하고 있으나 누설이 시작되는 정확한 위치 추정에 대한 연구는 아직 미흡한 상태이다. 따라서 본 논문에서는 카메라를 이용한 누설 검출 방법을 이용해 누설영역을 산출하고 누설 검출 결과를 분석하여 누설 위치를 추정하는 방법을 제안하였으며 실험을 통하여 성능을 평가하였다.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3122-3125
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• 2021

Electromagnetic vortex flowmeter is a new type of instrument for detecting leakage of steam generator, and the signal processing method based on the envelope to calculate energy ratio can effectively detect bubbles in sodium flow. The signal processing method is not affected by changes in the amplitude of the sensor output signal, which is caused by changes in magnetic field strength and other factors. However, the detection sensitivity of the electromagnetic vortex flowmeter is reduced. To this end, a signal processing method based on inverse Fourier transform to calculate energy ratio is proposed. According to the difference between the frequency band of the bubble noise signal and the flow signal, only the amplitude in the frequency band of the flow signal is retained in the frequency domain, and then the flow signal is obtained by the inverse Fourier transform method, thereby calculating the energy ratio. Using this method to process the experimental data, the results show that it can detect 0.1 g/s leak rate of water in the steam generator, and its performance is significantly better than that of the signal processing method based on the envelope to calculate energy ratio.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.75-76
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• 2005

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 추계학술발표회논문집(1)
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• pp.183-190
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• 1996

Leak-before-break(LBB) approach has been shown to be both cost and risk effective by reducing maintenance cost and occupational exposure when applied to high energy piping in nuclear power plants. For Korean Next Generation Reactor(KNGR) development, LBB is considered for the Main Steam Line(MSL) piping inside containment. Unlike the reactor coolant piping leakages which can be detected by particulate and gaseous radiation monitoring, main steam line leak detection systems must be based on principles that do not involve radioactivity. Ceramics are widely used as humidity sensor materials which can be further developed for nuclear applications. In this paper, we describe the progress in the development of ceramic humidity sensors for use with the main steam lines of KNGR.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1829-1835
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• 2000

The experimental results of sodium-water reaction noise measurement in frequency range $1{/sim}200kHz$ are presented. The experiments of noise generation under the condition of sodium test facility, water leak rate $0.01{\sim}1.2g/s$ and temperature of sodium $250{\sim}500^{\circ}C$, were carried out. From theoretical study it is noted that the noise resonant attenuation on hydrogen bubbles in liquid sodium plays the significant role for leak noise spectra formation. Interaction of leak noise and hydrogen bubbles in sodium being accompanied by thermal, emission and viscosity energy dissipation was studied. Acoustic noise spectra were investigated from point of view of water leak detection in sodium/water steam generator. The results of sodium-water reaction noise absorption on hydrogen bubbles in liquid sodium by temperature $250{\sim}500^{\circ}C$ are presented. The theoretical model of noise absorption using the coefficients of attenuation was developed. From calculation the coefficients of attenuation were estimated.