• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.9
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• pp.2894-2900
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• 1996

The stream generator tubes represent an integral part of a major barrier against the fission product release to the environment. So, the rupture of these tubes could permit flow of reactor coolant into the secondary system and injure the safety of reactor coolant system. Therefore, if the crack was detected during In-Service Inspection of tubes the cracked tube should be evaluated by the pulgging criteria and plugged or not. In this study, the fracture mechanics evaluation is carried out on the thru-wall axial crack due to Primary Water Stress Corrosion Cracking in the roll transition aone of steam generator tube to help the assurence the integrity of tubes and estabilish the plugging criteria. Due to the Inconel which is used as tube material is more ductile than others, the plastic instability repture theory was used to calculate the critical and allowable crack length. Based on Leak Before Break concept the leak rate for the critical crack length and the allowable leak rate are compared and the safety of tubes was given.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.368.2-368.2
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• 2014

$SnO_2$을 이용한 반도체는 기체 센서, 트랜지스터, 태양전지와 같은 여러 분야에 적용 가능하기 때문에 많은 각광을 받고 있다. $SnO_2$을 이용한 반도체 소자는 높은 화학적 안정성과 독특한 물리 화학적 특성을 지니고 있을 뿐만 아니라 부피에 대한 높은 표면적 비율을 가지고 있다. 우수한 $SnO_2$나노구조를 얻기 위해서 전자관 박막증착, 졸겔법, 물리적 증기증착, 열증착과 같은 다양한 방법들이 사용되었다. 다양한 합성 방법들 중에서 전기화학 증착법은 높은 성장율, 대면적 공정, 낮은 가격과 같은 장점을 가지고 있어 많은 연구가 진행되었지만, $SnO_2$ 구조의 성장조건에 따른 체계적인 연구는 진행되지 않았다. 본 연구는 indium-tin-oxide (ITO)로 코팅된 유리 기판 위에 전기화학 증착법을 사용하여 다양한 성장 조건에 따라 성장된 $SnO_2$나노구조들의 물리적 특성들을 관찰하였다. ITO 유리 기판 위에 성장된 $SnO_2$나노구조는 음극의 전구체와 전류의 상호작용에 의해 생성되는 산소 분자의 환원에 의해 형성된다. $SnO_2$나노구조의 모양은 전기화학 증착의 성장 환경에 따라 달라진다. $SnO_2$나노구조를 관찰하기 위해 시간에 따른 전압-전류, X-ray광전자분광법, 주사형전자현미경, X-ray회절분석법을 사용하여 측정하였다. ITO 유리 기판 위에 성장한 $SnO_2$ 소자에 서로 다른 인가 전압을 가해 주었을 때에 따른 전류밀도를 측정하였다. 일정한 인가전압에서 $SnO_2$나노구조의 X-ray광전자분광법 측정 을 통해 화학적 결합과 X-ray회절분석법 통한 $SnO_2$ 성장 방향을 관찰하였다. 주사형전자현미경 측정을 통하여 $SnO_2$의 표면을 관찰하였다

• Journal of the Korean Wood Science and Technology
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• v.25 no.1
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• pp.15-22
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• 1997

The effectiveness of presteaming for improving CCA treatability on refractory Japanese larch heartwood was investigated in this study. Presteaming was effective on improving treatability, and the extent of improvement was dependent on moisture contents of wood specimen and steaming conditions. Green wood showed higher average value in both preservative retention and penetration than dry wood, and steaming under pressure conditions also had higher treatability than steaming at atmospheric conditions. The degree of improvement for treatability was increased with the extension of steaming period. Treatability of dry wood pres teamed under pressure conditions more than 6 hours and green wood for 3 hours was similar to that enhanced by conventional incising. Presteaming green wood under pressure conditions more than 6 hours was more effective than conventional incising in improvement of CCA treatability, and resultant treatability satisfied a minimum value required for CCA-treated wood for being used at the regions of hazard class H3 and H4. In addition, an improvement of treatability by presteaming was due to an increase in permeability resulted from the degradation of hemicelluloses within aspirated pit membrane and cell wall, not the removal of extractives from pit membrane. The reduction in strength, measured as longitudinal compressive strength, due to pres teaming was related with the degradation of hemicelluloses, and was increased as steaming conditions were severe. The degree of strength reduction associated with presteaming treatment to obtain required treatability could be quantified from the relatively good relation between the increase in treatability and the decrease in strength.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.330-337
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• 2010

In this paper, 3-dimensional electromagnetic numerical analysis is performed about the eddy current(EC) array probe characteristic which is the next generation probe for accurate diagnosis of steam generator(SG) in nuclear power plants(NPPs). ASME(American Society of Mechanical Engineers) Standard and X-probe combo calibration standard tube are selected for acquisition of eddy current testing(ECT) signals and this result of compared with the real test signals for reasonability of result. Based on the analysis result of calibration standard tube, ECT signals that are about the defects of pitting, stress corrosion cracking(SCC), multiple SCC and wear is obtained. Material of specimen was Inconel 600 which is usually used for SG tubes in NPPs. The operation frequency of 300 kHz were used. The signal characteristics could be observed according to the various defects. The results in this paper can be helpful when the ECT signals from EC array probe are evaluated and analyzed.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.3
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• pp.61-66
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• 2011

The integrity of the SG(Steam Generator) tubes has been challenged by numerous factors such as flaws, operation, atmosphere, inherently degraded materials, loose parts and even human errors. Of the factors, loose parts(or foreign materials) on the secondary side of the tubes can bring about volumetric defects and even leakage from the primary to the secondary side in a short period of time. More serious concerns about the loose parts are their unknown influx path and rapid growth rate of the defects affected by the loose parts. Therefore it is imperative to detect and characterize the foreign materials and the defects. As a part of the measures for loose part detection, TTS(Top of Tubesheet) MRPC(Motorized Rotating Pancake Coils) ECT has been carried out especially to the restricted high probability area of the loose part. However, in the presence of loose parts in the other areas, wide range loose part detection techniques are required. In this study, loose part standard tube was presented as a way to accurately detect and characterize loose part signals. And the SG tube ECT bobbin coil and MRPC ISI(In-service Inspection) data of domestic OPR-1000 and Westinghouse Model F(W_F) were reviewed and consequently, comprehensive loose part detection technique is derived especially by applying bobbin coil signals

• Restorative Dentistry and Endodontics
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• v.10 no.1
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• pp.85-92
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• 1984

The aim of this study was to examine the influence of the speed of grinding and coolants on mercury vaporization during amalgam removal. Forty amalgam filled stone dies were stored at $37^{\circ}C$ and 100% relative humidity for 7 days prior to the beginning of the mercury vapor experiment and were divided into 4 different groups; In Group I; Used by high speed without coolant & evacuator during amalgam removal. In Group II; Used by high speed with coolant & evacuator during amalgam removal. In Group III; Used by low speed without coolant & evacuator during amalgam removal. In Group IV; Used by low speed with coolant & evacuator during amalgam removal. The amalgam specimens were removed in a 30-second time period and mercury vapor was collected with membrane filter at 27mm from the site of removal and 45 degree above there. Samples in Group II, IV were removed with coolant spray at a flow rate of 30 ml/min with high-velocity evacuator. Mercury vapor collected membrane filter was analysed by Atomic Absorption Spectrophotometer using cold vapor method. The results were as follows; 1. The mercury vapor levels were obtained all of the Groups. 2. The mercury vapor levels of the Group II, IV (with coolant & evacuator) were less than that of the Group I, III (without coolant & evacuator). 3. The highest mercury vapor level recorded during amalgam removal procedure was Group I (used by high speed without coolant & evacuator) and its record was $0.78{\pm}0.09\;mg/m^3$, which exceed the T.L.V. by 15 times. 4. The mercury vapor level of the Group IV (used by low speed with coolant & evacuator) was more than that of the Group II (used by high speed with coolant & evacuator), but its difference was not significant, statistically. (p > 0.05)

• Corrosion Science and Technology
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• v.13 no.3
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• pp.112-119
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• 2014

In this work, it is aimed to develop the fabrication method of axial stress corrosion cracking (SCC) defects having various sizes, on the outer diameter surface of the steam generator (SG) tubings. To control the length of the artificial SCC defect, the specific area of the SG tubing samples was exposed to an acidic solution after a sensitization heat treatment. During the exposure to an acidic solution, a direct current potential drop (DCPD) method was adopted to monitor the crack depth. The size of the SCC defect was first evaluated by an eddy current test (ECT), and then confirmed by a destructive examination. From the comparison, it was found that the actual crack length was well controlled to be similar to the length of the surface exposed to an acidic solution (5, 10, 20 or 30 mm in this work) with small standard deviation. From in-situ monitoring of the crack depth using the DCPD method, it was possible to distinguish a non-through wall crack from a through wall crack, even though the depth of the non-through wall crack was not able to be precisely controlled. The fabrication method established in this work was useful to simulate the SCC defect having similar size and ECT signals as compared to the field cracks in the SG tubings of the operating Korean PWRs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.277-284
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• 2007

The steam generator in a nuclear power plant is a large heat exchanger that uses heat from a reactor to generate steam to drive the turbine generator. Rupture of a steam generator tube can result in release of fission products to environment outside. Therefore, an accurate integrity assessment of the steam generator tubes with cracks is of great importance for maintaining the safety of a nuclear power plant. The steam generator tubes are supported at regular intervals by support plates and rotations of the tubes are restrained. Although it has been reported that the limit load for a circumferential crack is significantly affected by boundary condition of the tube, existing limit load solutions do not consider the restraining effect of support plate correctly. In addition, there are no limit load solutions for circumferential cracks in U-bend region with the effect of the support plate. This paper provides detailed limit load solutions for circumferential cracks in top of tube sheet and the U-bend regions of the steam generator tube with the actual boundary conditions to simulate the restraining effect of the support plate. Such solutions are developed based on three dimensional finite element analyses. The resulting limit load solutions are given in a polynomial form, and thus can be simply used in practical integrity assessment of the steam generator tubes.

• Journal of The Korean Society of Clinical Toxicology
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• v.2 no.1
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• pp.20-22
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• 2004

Acute mercury inhalation poisoning is a rare cause of acute peripheral neuropathy. A 44-year-old female inhaled the fume from heating mercury to treat her palmar dermatitis. For 4 days, this procedure was done for 2-3 minutes after each meal. She subsequently complained flu like symptoms, such as headache, toothache, myalgia and arthralgia. She was admitted for 9 days and then symptoms disappeared. About 3 weeks after exposure, both knee pain developed and then she could not walk. To treat mercury intoxication, she was referred to our hospital. At that time, initial laboratory data were within normal limits, but blood and urinary mercury level were 5.6 11$\mu$g/dl, 132.8 $\mu$g/L. After treatment with D-penicillamine for 7 days, blood and urinary mercury level were 3.9 1$\mu$g/dl, 177.3 $\mu$g/L. During the following 1 month, both leg symptoms remained. Nerve conduction studies were performed, both leg sensory nerve amplitude decreased. These findings were suggestive of peripheral polyneuropathy.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.6
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• pp.464-476
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• 1998

Determination of location, shape and size of a flaw from its eddy current testing signal is one of the fundamental issues in eddy current nondestructive evaluation of steam generator tubes. Here, we propose an approach to this problem; an inversion of eddy current flaw signal using neural networks trained by finite element model-based synthetic signatures. Total 216 eddy current signals from four different types of axisymmetric flaws in tubes are generated by finite element models of which the accuracy is experimentally validated. From each simulated signature, total 24 eddy current features are extracted and among them 13 features are finally selected for flaw characterization. Based on these features, probabilistic neural networks discriminate flaws into four different types according to the location and the shape, and successively back propagation neural networks determine the size parameters of the discriminated flaw.