국제시장 개방 등에 대비한 전력설비정비 경쟁력 제고방향

장기옥 대한전기협회 1992 대한전기협회지 Vol.- No.185

우리나라 원전산업과 해외시장

장기옥 한국원자력산업회의 1994 원자력산업 Vol.14 No.1

중성자에 조사된 Mn-Mo-Ni 저합금강의 열처리 회복거동

장기옥,지세환,심철무,박승식,김종오,Jang, Gi-Ok,Ji, Se-Hwan,Sim, Cheol-Mu,Park, Seung-Sik,Kim, Jong-O 한국재료학회 1999 한국재료학회지 Vol.9 No.3

The recovery activation energy, the order of reaction and the recovery rate constant were detemined by isochronal and isothermal annealing treatment to investigate the recovery behaviors of neutron irradiated Mn-Mo-Ni low alloy steels$(fluence: 2.3\times10^{19}ncm^{-2}, 553K, E\geq1.0 MeV)$. Vickers microhardness tests were conducted to trace the recovery behavior after heat treatments. The results were analyzed in terms of recovery stages, behavior of responsible defects and recovery kinetics. It was shown that recovery occurred through two annealing stages(stage I : 703-753K, stage n : 813-873K) with re$\infty$very activation energies of 2.5 eV and 2.93 eV for each stage I and n, respectively. From the comparison of unirradiated and irradiated isochronal anneal curves, a radiation anneal hardening(RAH) peak was identified at around 813K. Most of recovery have occurred during about 120 min irrespective of isothermal annealing temperatures of 743K and 833K. Recovery rate constants were determined to be $3.4\times10^{-4}min^{-1} and 7.1\times10^{-4}min^{-1}$ for stage I and II, respectively. The order of reaction was about 2 for both recovery stages. Comparing the obtained data with those of previously reported results on neutron irradiated Mn- Mo- Ni steels, the thermal recovery be­havior of the present material seems to occur by the dissociation of point defect clusters formed during irradiation, and by the recombination process of self-interstitials and vacancies from dissociated vacancy clusters.

중성자에 조사된 Mn-Mo-Ni 저합금강의 기계적 및 자기적 성질 변화

장기옥,지세환,박승식,김병철,김종오,Jang, Gi-Ok,Ji, Se-Hwan,Park, Seung-Sik,Kim, Byeong-Cheol,Kim, Jong-O 한국재료학회 1998 한국재료학회지 Vol.8 No.11

Irradiation-induced changes in mechanical properties and magnetic parameters were measured and compared to explore possible correlations for Mn-Mo-Ni low alloy steel surveillance specimens which were irradiated to a neutron fluence of $2.3\times10^{19}n/cm^2$(E>1.0MeV) in a typical pressurized water reactor environment at about $288^{\circ}C$. For mechanical property parameters, microvickers hardness, tensile and Charpy impact test were performed and Barkhausen noise amplitude, coercivity, remanence, maximum induction were measured for magnetic parameters. respectively. Results of mechanical property measurements showed an increase in yield and tensile strength, microvickers hardness. 41J indexed $RT_{NDT}$ and a decrease in upper shelf energy irrespective of base and weld metals. However, in the case of tensile properties, the changes in weld metal were negligible compared to the base metal. In the case of magnetic measurements, it is found that magnetic remanence, BN amplitude. BN energy have dropped significantly but coercivity(H,) has increased rapidly after irradiation. In this study. the measurements conducted on surveillance specimens of Mn-Mo-Ni low alloy steel showed that there were strong correlations between mechanical properties and magnetic properties.

土木技術 發展을 위한 提言

張基玉(장기옥) 대한토목학회 1994 대한토목학회지 Vol.42 No.3

중성자 조사 및 열처리에 따른 SA508 Cl.3강의 자기특성 변화

장기옥(K. O. Chang),김택수(T. S. Kim),심철무(C. M. Sim),지세환(S. H. Chi),김종오(C. O. Kim) 한국자기학회 1998 한국자기학회지 Vol.8 No.5

In relation to the application of magnetic method to the evaluation of irradiation damage (embrittlement) changes in the magnetic parameters(hysteresis loop and Barkhausen noise) and Vickers microhardness due to neutron irradiation and heat treatment were measured and compared. In the case of irradiation (2.3×10^(19) n/㎠, E≥1 Mev, 288 ℃) hysteresis loop measurements show that susceptibility decreases as coercivity increases. Saturation magnetization do not show any change. Barkhausen noise amplitude and Barkhausen noise energy have decreased while Vickers microhardness has increased. For isothermally heat treated condition of irradiated specimen at 470 ℃ and 540 ℃, Barkhausen noise energy has increased while Vickers microhardness has decreased. Results of BNE and Vickers microhardness are reversed to the results on irradiated condition. All these consistent changes in magnetic parameter and Vickers microhardness measurement, which are thought to be resulted from the interaction between irradiationinduced defects and dislocation, and magnetic domain, respectively, show a possibility that magnetic measurement may be used to the evaluation of material degradation and recovery due to neutron irradiation and heat treatment, respectively, if a relevent large database in prepared.

중성자 조사에 따른 원자로 재료의 조사 손상 비파괴평가 기술

최순필,장기옥,이삼래,김병철 韓國非破壞檢査學會 1997 한국비파괴검사학회지 Vol.17 No.1

원자로 압력용기 재료의 중성자 조사 취화 문제는 원자력발전소의 안전성 및 수명 관리에 가장 중대한 영향을 미친다. 재료의 조사 취화를 평가하기 위하여 수행하고 있는 충격 및 인장시험같은 파괴적 시험 결과는 석출몰 크기나 분포, 전위 밀도 등, 재료 자체의 조직학적 특성에 좌우되므로 한정된 시편을 이용한 평가에는 많은 불확실성이 존재하게 된다. 따라서 이와 같은 문제점을 해결하기 위하여 비파괴기술을 이요한 조사를 분석하기 위하여 응용되고 있는 비파괴기술로는 전기, 자기, 전자기, 초음파 및 경도측정법 등이 있으나 비파괴시험 결과와 미세조직의변화, 기계적 성질 및 취화 정도 등과의 상관 관계를 정립해야만 기존 파괴적 시험의 대체가 가능하게 된다. 따라서 현재까지 수행되고 있는 어러 비파괴기술을 이용한 조사 취화 평가 연구 결과를 비교 분석하여 보다 실현 가능성 있는 비파괴기술을 검토하였다.

집속 신호 합성 기법에 의한 초음파 탐상 신호 개선

이삼래,장기옥,김병철,김기길 韓國非破壞檢査學會 1998 한국비파괴검사학회지 Vol.18 No.4

비파괴검사는 검사 자체와 검사 결과를 해석 또는 평가하는 것으로 크게 둘로 나눌 수 있다. 검사 자체는 전자 기술 수준의 발전에 따라 많은 양을 단시간 내에 정밀하게 수행할 수 있으나 검사 결과 발견된 지시(indication)가 결함인지 혹은 이와 유사한 거짓 결함인지를 확인하기는 대단히 어려운 일이다. 초음파 탐상의 경우 검사 결과 결함의 형상을 정확하게 인식하기 위해 컴퓨터를 활용한 다양한 첨단 신호 해석 기술이 개발되어 일부 활용되어오고 있는데 본 논문에서는 신호처리 기법의 하나인 집속 신호합성 기법(synthetic aperture focusing technique, SAFT)을 활용하여 탄소강에서의 결함 신호 해석을 시도하였으며 탄소강 평판내에 가공된 hole을 대상으로 수집된 초음파 신호를 이 기법을 적용하여 처리한 결과 결함으로부터의 신호대 잡음비에 있어서 많은 개선이 이루어진 것으로 판단된다. 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.

초음파특성 분석에 의한 원자로 재료의 중성자 조사량 예측

이삼래,장기옥,김병철 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.3

운전중인 원자로 재료의 건전성 평가를 위한 기계적 시험의 하나인 샤르피 충격 시험편에 대하여 초음파 신호분석이 이루어졌다. 시험편으로는 모재와 용접재를 사용하였는데 이들 재료는 고온, 고압의 냉각수 및 지속적인 고속 중성자가 방출되고 있는 가동중인 발전소에서 감시시험을 통한 원자로재료의 건전성평가를 목적으로 정지기간동안 인출된 것이다. 분석결과 속도 및 감쇠와 같은 초음파 특성들이 재질이 비교적 균일한 모재에 있어서는 중성자 조사량과 밀접한 관련이 있는 것으로 보였으며 이를 활용하여 비파괴적인 방법으로 재료에 대한 중성자 조사량이 어느 정도인지를 예측할 수 있는 가능성을 보여주었다. Ultrasonic signals from Charpy impact test specimen have been analyzed in order to evaluate the integrity of reactor pressure vessel. Base and weld metal that were extracted from reactor vessel during plant outages according to the schedule of the surveillance test required by the related regulations have been used and the ultrasonic test parameters including velocity, attenuation, etc. showed a close correlations with the amount of neutron irradiation for base metal, relatively homogeneous materials. This result showed certain possibility where a nondestructive method could be used to predict the fluence of the irradiation due to neutron in nuclear reactor vessel materials.

渦電流 標潗浸透 깊이·表皮效果와 缺陷信號 位相角의 關係解析

鄭泰彦,張基玉,朴大英 韓國非破壞檢査學會 1985 한국비파괴검사학회지 Vol.5 No.1

An experiment to invertigate the rate of change of phase angle of eddy current output signal caused by outer surface defect of nonferromagnetic tube by variation of standard depth of penetration and variation of percent of tube wall penetration was carried out. The results of the experiment show that the phase angle of defect signal is increased with decreasing the standard depth of penetration or the depth of defect. The results also show that the phase angle is decreased with increasing the skin effect of eddy current, and that the resolution is decreased with decreasing the depth of defect.