• Journal of the Korean Society for Nondestructive Testing
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• v.15 no.2
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• pp.407-414
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• 1995

원자력발전소의 주요 기기들에 대한 가동중검사는 관련법규에 따라 철저히 수행되고 있다. 그러나 최근 선진국에서는 이에 만족하지 않고 원전 기기의 안전성을 더욱 확고히 하기 위해 기존의 가동중검사 요건을 계속 강화하고 있으며, 원전 관련 당사자들은 강화된 요건들을 충족시키기 위한 노력을 끊임없이 계속하고 있다. 이 글에서는 원전 기기 가동중검사 신규 요건들인 초음파탐상검사 시스템의 기량검증(Performance Demonstration) 요건, 비파괴검사자 및 초음파검사자 자격 인정 요건(ANSI/ASNT CP-189, Appendix VII of ASME Sec. XI), 증기발생기 전열관 와전류검사, 신호평가자 자격인정(Qualified Data Analyst : QDA), 미국규제기관(NRC)에서 발행하고 있는 NRC Bulletin, NRC information 등의 가동중검사 관련 사항들을 살펴보고 선진 외국에서는 이들 요건 및 정보에 대해 어떻게 대처하고 있는가를 알아본다. 또한 국내에서도 이들 신규 요건에 대한 대처 현황과 대처 방안을 모색한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.384-389
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• 2004

As the increase of the operation year of nuclear power plants, the probabilities of the degradation of the major facilities and materials in the nuclear power plants are increased. The integrity of those facilities shall be monitored and verified by the non-destructive examination methods with the regulation codes, so called inservice inspection(ISI). The ISI of Yonggwang unit 6 was performed in four different parts, 1) non-destructive examinations for the components, piping weldments and structures, 2) automated ultrasonic examinations for pressure vessels, 3) visual examinations for the interior structures of the reactor, 4) eddy current examinations for the steam generator tubes. As the results, there was no severe indication and all detected indications were evaluated as non-relavent. Especially for the examinations of the piping weldments, PD(Performance Demonstration) was applied as a W examination method defined in the 1995 edition of ASME Code Sec. XI. The implementation of the PD for the piping weld results in an improvement of the reliability of the UT examinations.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.1
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• pp.38-44
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• 2003

Performance demonstration with real flawed specimens has been strongly required for nondestructive evaluation of safety class components in nuclear power plant. Mechanical or thermal fatigue crack and intergranular stress corrosion cracking could be occured in the in-service nuclear power plant and mechanical fatigue crack was selected to study in this paper. Specimen was designed to produce mechanical fatigue flaw under tensile stress. The number of cycles and the level of stress were controlled to obtain the desired flaw roughness. After the accurate physical measurement of the flaw size and location, fracture surface was seal-welded in place to ensure the designed location and site. The remaining weld groove was then filled by using gas-tungsten are welding(GTAW) and flux-cored arc welding(FCAW). Results of radio graphic and ultrasonic testing showed that fatigue cracks were consistent with the designed size and location in the final specimens.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.1
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• pp.14-20
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• 2003

Piezoelectric ultrasonic transducers for high temperature contact measurement were developed. These high temperature ultrasonic transducers (HTUT) consisted of bismuth titanate piezoceramic element whose Curie temperature is higher than $600^{\circ}C$, a backing material of the mixture of tungsten powder and inorganic binder, an inner alumina tube, a wear Plate and a housing. The operational frequencies or the HTUT were 1.04 and 2.08 MHz, respectively. Various commercially available couplants for high temperature were evaluated and compared. As a couplant for high temperature ultrasonic testing between HTUT and test specimen, gold epoxy was selected. The peak amplitude of pulse-echo signals from steel test specimen decreased with increasing temperature. The operational temperature of the HTUT reached up to $500^{\circ}C$ at which the continuous contact measurement was possible.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.2
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• pp.130-136
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• 2009

Turbine, which is one of major components in nuclear power plants, requires reliable nondestructive inspections. But, accessibility of transducers is limited and interpretation of acquired signals is not easy at all due to the complication. So, in this study, we have fabricated mock-up specimens of real size and shape. we applied pulse-echo method and time-of-flight diffraction(TOFD) method for precise inspection of turbine key and wheel bore. And phased array ultrasonic testing method was adopted for wheel dovetail of turbines by using mock-up. Furthermore, an automatic scanner system was developed for in-service inspection of the developed methods.

• Journal of the Korean Society for Nondestructive Testing
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• v.15 no.1
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• pp.310-317
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• 1995

Crack detection technique by ultrasonics in structures and components made of austenitic stainless steel often loses its reliability due to the material characteristics during inservice inspection of nuclear power plants, especially in the area of detection and sizing in centrifugally cast stainless steel pipings. In order to understand and overcome this problem, computer program for tracing the ultrasonic rays within material has been developed to simulate the process of defect detection within weld. The program simulates through transmission and reflection technique in crack detection of austenitic stainless steel as well as ultrasonic beam propagation through multiple media including stainless steel cladding interface.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.5
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• pp.431-437
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• 2000

Standard Test Block(STB) for UT(Ultrasonic Testing) is a block approved by authoritative for material, shape and quality. STB is used for characteristic tests, sensitivity calibration and control of the time base range of UT inspection devices. The material, size and chemical components of STB should be strictly controled to meet the related standards such as ASTM and JIS because it has an effect upon sensitivity, resolution and reproductivity of UT. The STBs which are not approved are sometimes used because the qualified STBs are very expensive. So, the purpose of this study is to survey the characteristics, quality and usability of Non-Standardized Test Blocks. Non-Standardized Test Blocks did not meet the standard requirements in size or chemical components, and ultrasonic characteristics. Therefore if the Non-Standardized Test Blocks are used without being tested, it's likely to cause errors in detecting the location and measuring the size of the defects.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.317-323
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• 2010

The manual ultrasonic examination for the nuclear power plant piping welds has been demonstrated by using KPD(Korean Performance Demonstration) generic procedure. For automated ultrasonic examination, there is no generic procedure and it should be qualified by using applicable automated equipment. Until now, most of qualified procedures used pulse-echo technique and there is no qualified procedure using phased array technique. In this study, data acquisition and analysis software were developed and phased-array transducer and wedge were designed to implement phased array technique for nuclear power plant in-service inspection. The developed procedure are qualified for performance demonstration for the flaw detection, length sizing and depth sizing. The qualified procedure will be applied for the field examination in the nuclear power plant piping weld inspection.

• Journal of the Korean Society for Nondestructive Testing
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• v.11 no.1
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• pp.44-51
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• 1991

This paper describes the practical difficulties experienced with ultrasonic testing during site fabrication of the offshore structures, and indicates some of the problems when UT indications are evaluated according to written procedure which is prepared to the requirements of the applicable code (standard) and/or specification.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.4
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• pp.271-277
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• 1998

Nondestructive method can include both testing itself and analysis or evaluation of the testing results. Although vast amount of testing can be accomplished in a fairly short amount of time due to the advancement of electronic technology. it is really difficult matter to identify whether the indication found during testing corresponds to be a real defect. Thus, in ultrasonic testing, advanced digital signal processing techniques have been widely studied in order to identify the shape of the defect during testing, and one of the signal processing techniques, synthetic aperture focusing technique(SAFT) was tried for holes machined in carbon steel plate in this study. Result showed that signal to noise ratio has been improved considerably compared to the result from original RF signals.