• Journal of Welding and Joining
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• 제29권1호
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• pp.5-8
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• 2011

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.326-327
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• 2005

• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1740-1747
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• 2017

To investigate allowable peak cladding temperature and hoop stress for maintenance of cladding integrity during interim-dry storage and subsequent transport, zirconium alloy cladding tubes were hydrogen-charged to generate 250 ppm and 500 ppm hydrogen contents, simulating spent nuclear fuel degradation. The hydrogen-charged specimens were heated to four peak temperatures of $250^{\circ}C$, $300^{\circ}C$, $350^{\circ}C$, and $400^{\circ}C$, and then cooled to room temperature at cooling rates of $0.3^{\circ}C/min$ under three tensile hoop stresses of 80 MPa, 100 MPa, and 120 MPa. The cool-down specimens showed that high peak heat-up temperature led to lower hydrogen content and that larger tensile hoop stress generated larger radial hydride fraction and consequently lower plastic elongation. Based on these out-of-pile cladding tube test results only, it may be said that peak cladding temperature should be limited to a level < $250^{\circ}C$, regardless of the cladding hoop stress, to ensure cladding integrity during interim-dry storage and subsequent transport.

• 한국재료학회지
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• 제25권8호
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• pp.376-385
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• 2015

The effects of Nb and Cr addition on the microstructure, corrosion and oxide characteristics of Zr based alloys were investigated. The corrosion tests were performed in a pressurized water reactor simulated-loop system at $360^{\circ}C$. The microstructures were examined using OM and TEM, and the oxide properties were characterized by low-angle X-ray diffraction and TEM. The corrosion test results up to 360 days revealed that the corrosion rates were considerably affected by Cr content but not Nb content. The corrosion resistance of the Zr-xNb-0.1Sn-yCr quaternary alloys was improved by an increasing Nb/Cr ratio. The crystal structure of the precipitates was affected by a variation of the Nb/Cr ratio. The Zr-Nb beta-enriched precipitates were mainly formed in the high Nb/Cr ratio alloy while $Zr(NbCr)_2$ precipitates were frequently observed in the low Nb/Cr ratio alloy. The studies of oxide characteristics revealed that the corrosion resistance was related to the crystal structure of the precipitate.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.776-783
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• 2019

Laser welding is usually a more effective method than electron-beam one since a vacuum chamber is not required. It is important for joining Zr-1%Nb (E110) alloy in a manufacturing process of nuclear fuel rods. In the present work, effect of energy parameters of pulsed laser welding on properties of butt joints of sheets with a thickness of 0.5 mm is investigated. The most efficient combination has been found (8-11 J pulse energy, 10-14 ms pulse duration, 780-810 W peak pulse power, 3 Hz pulse frequency, 1.12 mm/s welding speed). The results show that ultimate strength under static loading can not be used as a quality criterion for zirconium alloys welds. Increased shielding gas flow rate does not allow to protect weld metal totally and contributes to defect formation without using special nozzles. Several types of imperfections of the welds have been found, but the major problem is branching microcracks on the surface of the welds. It is difficult to identify the cause of their appearance without additional research on improving the welding zone protection (gas composition and flow rate as well as nozzle configuration) and studying the hydrogen content in the welds.

• 한국재료학회지
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• 제12권5호
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• pp.369-374
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• 2002

To investigate the corrosion behavior of Zr-1.0Nb-xSn (x=1.0, 1.5, 2.0 and 2.5wt. %)alloy system, the corrosion tests of Zr-1.0Nb-xSn alloys were carried out in steam at $400^{\circ}C$ for 125 days and in 70ppm LiOH solution at $360^{\circ}C$ for 180 days. The matrix microstructures of the test specimens were analyzed using TEM and the oxide structures on the test specimens were analyzed using XRD. It was found from the analyses that the more Sn content the alloy had, the faster it was corroded and with the increase of Sn content in the alloy the fraction of $t-ZrO_2$ to $m-ZrO_2$ was decreased. It was also found that the alloys having more Sn showed more dislocation density than those having less.

• Nuclear Engineering and Technology
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• 제50권2호
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• pp.223-228
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• 2018

AREVA NP (Courbevoie, Paris, France) is actively developing several enhanced accident-tolerant fuels cladding concepts ranging from near-term evolutionary (Cr-coated zirconium alloy cladding) to long-term revolutionary (SiC/SiC composite cladding) solutions, relying on its worldwide teams and partnerships, with programs and irradiations planned both in Europe and the United States. The most advanced and mature solution is a dense, adherent chromium coating on zirconium alloy cladding, which was initially developed along with the CEA and EDF in the French joint nuclear R&D program. The evaluation of the out-of-pile behavior of the Cr-coated cladding showed excellent results, suggesting enhanced reliability, enhanced operational flexibility, and improved economics in normal operating conditions. For example, because chromium is harder than zirconium, the Cr coating provides the cladding with a significantly improved wear resistance. Furthermore, Cr-coated samples exhibit extremely low corrosion kinetics in autoclave and prevents accelerated corrosion in harsh environments such as in water with 70 ppm Li leading to improved operational flexibility. Finally, AREVA NP has fabricated a physical vapor deposition prototype machine to coat full-length cladding tubes. This machine will be used for the manufacturing of full-length lead test rods in commercial reactors by 2019.

• 대한치과보철학회지
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• 제45권2호
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• pp.240-249
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• 2007

Statement of problem: A phenomenon of screw-loosening in implant abutment is frequently occurred in a single and multiple implant restoration. Purpose: This study was performed to evaluate an effect of abutment material on screw-loosening before and after a cyclic loading. In a single-tooth implant, different materials of abutment, Type III Gold alloy and Zirconium composite$(ZrO_2/Al_2O_3)$ were used. Material and method: The Gold alloy(Type III) and Zirconium composite$(ZrO_2/Al_2O_3)$ were used to make a superstructure of implant, the one of types of UCLA, Each group was constituted of 5 sample with a 30-degree offset angulated loading platform. The external hexagonal fixture was rigidly hel d in a special holding zig to ensure solid fixation without rotation during the tightening and a cyclic loading. A Titanium-alloy screw was used to connect and controlled to be tighten in 20Ncm torque by a digital torque gauge. A 20 times of consecutive closing/opening cycle were performed to evaluate the immediate torque loss. In 5 sample of each material group, an initial opening torque was recorded during 3 closing/opening cycle, then 2Hz, 200N, 1,000,000 cyclic loadings were performed, then a opening torque was evaluated. Result & Conclusion: 1. In this limited study, titanium alloy screw tightened in 20Ncm, a cold-welding phenomen on was not observed during the 20 times of closing/opening cycle(p=0.11, p=0.18). 2. In titanium alloy abutment screw, repeated opening and closing of the screw caused to progressive decrease of opening torque(p=0.014). 3. The difference in preload of screw between gold alloy abutment and ceramic$(ZrO_2/Al_2O_3)$ abutment was not significant(p=0.78). 4. The difference in torque loss of screw between gold alloy abutment and ceramic$(ZrO_2/Al_2O_3)$ abutment was not significant after 2Hz,200N, 1,000,000 cyclic loading(p=0.92). 5. In titanium alloy abutment screw tightened by 20Ncm, the screw loosening was not significant on each group after 2Hz, 200Ncm, 1,000,000 cyclic loading(p=0.59).

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.352-359
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• 2020

The effects of hydrogen precipitation on the mechanical properties of Zircaloy-4 and Zirlo alloys were examined with uniaxial tensile tests at room temperature and at 400 ℃ and accompanying microstructural changes in the Zircaloy-4 and Zirlo alloy specimens were discussed. The elastic moduli of Zircaloy-4 and Zirlo alloys decreased with increasing hydrogen concentrations. Yield strengths of both materials tended to decrease gradually. The reductions of yield stress seems to be caused by the dissipation of yield point phenomena shown in stress-strain curves. Ultimate tensile strengths (UTS) of Zircaloy-4 and Zirlo slightly increased at low hydrogen contents, and then decreased when the concentrations exceeded 500 and 700 wppm, respectively. Uniform elongations were stable until 600 wppm and drops to 0% around 1400 wppm at room temperature.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.121-122
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• 2012

합금도금강판의 일시 방청과 기능성 부여 후처리는 크로메이트, 인산염처리 등과 같은 방법을 시행하는 것이 일반적이다. 최근에는 아연합금도금 강판의 사용 및 보관 환경이 가혹해짐에 따라 보다 우수한 일시 방청성과 내식성이 요구되고 있다. 본 연구는 솔젤법을 이용하여 zirconium n-propoxide와 3-glycidoxypropyltrimethoxysilane(GPTS)으로부터 중합된 코팅막과 이에 zirconia nanoparticle입자를 첨가한 코팅막의 공극율(prosity)과 방식효율(protective efficiency)을 분극데이터를 이용하여 비교 평가하였으며, 염수분무시험을 통해 내식성 평가를 진행하였다.