Zircaloy-4의 플라즈마 아크용접에서 용접변수가 비이드형상에 미치는 영향

고진현,김수성,이영호 대한용접접합학회 1997 대한용접·접합학회지 Vol.15 No.6

A study was undertaken to determine the influence of welding variables such as shielding and plasma gases, torch standoff, travel speed and heat input, etc. on the quality of plasma arc welds in Zircaloy-4 sheet, 2mm thick. Effect of shielding gases and their flow rates on the mechanical properties of Zircaloy-4 welds by plasma arc welding were determined in terms of tensile, bardness and bend tests. The microstructure and fracture surface of Zircaloy-4 welds were investigated by optical and scanning electron microscopies. In addition, the causes of porosity and undercut in plasma arc welds of Zircaloy-4 were also investigated. Zircaloy-4 weld bead width and depth by helium shielding gas showed a wider and deeper than those by argon. It was found that Zircaloy-4 welds with shielding gas of helium did dxhibit a little smoother and uniform weld beads than those with shielding gas of argon. It was also found that the optimum gas flow rates for Zircaloy-4 welding were 0.45l/min for plasma gas with Ar and 4.5 - 6 l/min for shielding gas with He. In addition, there was no big difference in the microstructure and fracture surface of the weld metals made by either Ar shielding gas or He shielding gas.

Studies on the Electrochemical Dissolution for the Treatment of 10 g-Scale Zircaloy-4 Cladding Hull Wastes in LiCl-KCl Molten Salts

You Lee Lee,Chang Hwa Lee,Min Ku Jeon,Kweon Ho Kang 한국방사성폐기물학회 2012 방사성폐기물학회지 Vol.10 No.4

전해정련을 이용한 폐 피복관 처리의 타당성을 살펴보기 위하여, 500℃의 LiCl-KCl 용융염 내에서 표면이 산화된 10 g 규모의 Zircaloy-4 피복관 및 순수한 Zircaloy-4 피복관의 전기화학적 거동을 살펴보았다. 산화된 Zircaloy-4 피복관이 담긴 basket을 작업전극으로하여 전압-전류 관계를 측정한 결과, 산화되지 않은 Zircaloy-4 피복관과 비교해 Zr의 산화 peak는 Ag/AgCl 기준전극 대비, 약 -0.7 V ~ -0.8 V로 유사한 반면, 산화 전류의 크기는 확연하게 감소하는 것으로 나타난다. 이러한 결과는 -0.78V의 일정전위를 가한 전기화학적 용해 실험에서 살펴본 전류-시간 곡선에서도 유사하게 나타나며, 피복관 조각들의 평균 두께 및 무게 변화로부터 확인할 수 있다. Zircaloy-4 피복관이 산화되었을 경우, 표면의 산화막이 피복관의 전도성에 영향을 주어 basket 내 위치에 따라 전기화학적 용해의 균일성 및 속도를 떨어뜨리는 것으로 나타나지만, 표면의 미세한 결함과 Zr 산화물의 상 특성으로 인해 전기화학적 용해가 진행되는 것으로 판단된다.

Investigation of NH4OH on Zircaloy-4 Surfaces Using Electron Emission Spectroscopy

Hye Yoon Jung,Yong-Cheol Kang* 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.10

The interaction of ammonium hydroxide (NH4OH) with zircaloy-4 (Zry-4) was investigated using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) methods. In order to study the surface chemistry of NH4OH/Zry-4 system, the binding energies of N1s, O1s and Zr3d electrons were monitored. The N1s peak intensity was remarkably increased by following cycles of Ar+ sputtering of NH4OH dosed Zry-4 surface at room temperature. Because the nitrogen stayed under the subsurface region was diffused out onto the Zry-4 surface after oxygen concentration was decreased. These could be occurred after the surface oxygen was diffused into the bulk or desorbed out from the surface until Ar+ fluence was 6.0 ´ 1016 Ar+/cm2 then the surface was relatively atomic deficient state. The O1s peak intensity was decreased by stepwise Ar+ sputtering. After many cycles of Ar+ sputtering, the peak intensities of Zr3d peaks did not change much but the shape of the peak clearly did change. This implies that the oxidation state of zirconium was changed during stepwise Ar+ sputtering of NH4OH/Zry-4. The Zr3d peak intensity of zirconium nitride (ZrNx) increased as the intensity of N1s (from zirconium nitride) increased but the Zr3d peak intensity of zirconium oxide (ZrOx) decreased due to the depopulation of the oxygen species on the surface region. We also observed that the peak intensity of Zr4+ was nearly same after Ar+ sputtering processes but the peak intensity of metallic zirconium increased compared to that of before the sputtering process was performed.

Modified Zircaloy-4에서의 산화막 형성에 따른 수소투과 특성

林病赫,洪鉉善,李經燮 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.8

The permeation behavior of hydrogen through the oxide layer on the modified Zircaloy-4 (Zry-4) alloy was investigated. The modified Zry-4 was prepared by changing the chemical composition of standard Zry-4. The tin content of Zry-4 (1.5 wt%) reduced to 0.5 wt% and alloying elements such as Si, 0, and Nb were newly added from 0.01 wt% to 0.2 wt%. The oxide layers were grown in a static autoclave at 360℃ under the pressure of 2660 psi for 150 days. Permeation behaviors were characterized by measuring the time lag (t_L) of hydrogen permeation in the oxide. After the steady state of permeation flux, Fick's law was used to calculate the diffusivity of hydrogen in the modified Zry-4 specimens. The diffusivity of hydrogen in 0.5Sn-0.1Nb-0.1Fe-0.2Cr-0.2O-Zr specimen (1.26×10^-8 ㎠/s) turned out to be lower than that in 1.5Sn-0.2Fe-0.1Cr-0.1O-0.01Si-Zr and Zry-4 specimens. It was shown from the oxide structural investigation that the hydrogen diffusivity is dependant on the amount of tetragonal phase in the zirconium oxide; the phase transition of the oxide from tetragonal to monoclinic was found in 150 days exposure and the 0.5Sn-0.1Nb-0.1Fe-0.2Cr-0.2O-Zr specimen showed higher amount of tetragonal phase than the 1.5Sn-0.2Fe0.1Cr-0.1O-0.01Si-Zr specimen and Zry-4. In addition to the oxide structural study, effects of the microstructure of zirconium alloy such as precipitates and grain boundaries on the diffusivity and solubility of hydrogen were studied.

Investigation of NH₄OH on Zircaloy-4 Surfaces Using Electron Emission Spectroscopy

Jung, Hye-Yoon,Kang, Yong-Cheol Korean Chemical Society 2007 Bulletin of the Korean Chemical Society Vol.28 No.10

The interaction of ammonium hydroxide (NH4OH) with zircaloy-4 (Zry-4) was investigated using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) methods. In order to study the surface chemistry of NH4OH/Zry-4 system, the binding energies of N1s, O1s and Zr3d electrons were monitored. The N1s peak intensity was remarkably increased by following cycles of Ar+ sputtering of NH4OH dosed Zry-4 surface at room temperature. Because the nitrogen stayed under the subsurface region was diffused out onto the Zry-4 surface after oxygen concentration was decreased. These could be occurred after the surface oxygen was diffused into the bulk or desorbed out from the surface until Ar+ fluence was 6.0 × 1016 Ar+/cm2 then the surface was relatively atomic deficient state. The O1s peak intensity was decreased by stepwise Ar+ sputtering. After many cycles of Ar+ sputtering, the peak intensities of Zr3d peaks did not change much but the shape of the peak clearly did change. This implies that the oxidation state of zirconium was changed during stepwise Ar+ sputtering of NH4OH/Zry-4. The Zr3d peak intensity of zirconium nitride (ZrNx) increased as the intensity of N1s (from zirconium nitride) increased but the Zr3d peak intensity of zirconium oxide (ZrOx) decreased due to the depopulation of the oxygen species on the surface region. We also observed that the peak intensity of Zr4+ was nearly same after Ar+ sputtering processes but the peak intensity of metallic zirconium increased compared to that of before the sputtering process was performed.

Laser Powder Bed Fusion Additive Manufacturing of Recycled Zircaloy-4

Soung Yeoul Ahn,Sang Guk Jeong,Eun Seong Kim,Suk Hoon Kang,Jungho Choe,Joo Young Ryu,Dae Woon Choi,Jin Seok Lee,Jung‑Wook Cho,Takayoshi Nakano,Hyoung Seop Kim 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.9

Interest in Zircaloy-4 scrap recycling has increased in recent years. Zircaloy-4’s high melting temperature and powder reactivitypose significant challenges for metal additive manufacturing (MAM). In this study, Zircaloy-4 parts were built usinglaser powder bed fusion MAM for the first time. The reactivity of the Zircaloy-4 powder was successfully suppressed duringthe entire manufacturing process. The mechanical properties of the printed Zircaloy-4 were evaluated at room temperatureand reactor operating temperature of 316 °C. Remarkable yield strengths at both temperatures were obtained. This studywill serve as a starting point for safe Zircaloy-4 additive manufacturing.

핵연료 지지격자 성형을 위한 Zircaloy-4와 Zirlo 판재의 성형한계도 예측

서윤미(Yunmi Seo),현홍철(Hong Chul Hyun),이형일(Hyungyil Lee),김낙수(Naksoo Kim) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.8

본 연구에서는 핵연료 지지격자체의 재료인 Zircaloy-4 와 Zirlo 판재의 이론적 성형한계 예측모델을 제시했다. 먼저 인장시험 및 이방성시험으로 응력-변형률곡선과 이방성계수를 획득했으며, NUMISHEET 96을 따르는 돔장출시험으로 두 재료의 실험적 성형한계도들을 얻었다. 이론적 성형한계도는 성형한계모델과 항복조건의 영향을 받는다. Swift 확산네킹이론, Marciniak-Kuczynski 의 재료결함 모델, Storen-Rice 의 정점이론을 이용해 부변형률이 양인 구간에서의 성형한계 곡선을 구했으며, 부변형률이 음인 구간에는 Hill 의 국부네킹 이론을 적용했다. 또한 재료이방성을 고려하기 위해 Hill 48, Hosford 79 항복조건을 사용 했다. Swift 확산네킹모델 (Hill 48 항복조건 적용)과 Hill 모델은 각각 변형률비가 양과 음인 영역에 대해 Zircaloy-4의 성형한계도를 비교적 정확히 예측하며, Zirlo의 성형한계도는 Hosford 79 항복조건 (a = 8)을 적용한 Storen-Rice 모델로 나타낼 수 있다. In this work, we investigated the theoretical forming limit models for Zircaloy-4 and Zirlo used for spacer grid of nuclear fuel rods. Tensile and anisotropy tests were performed to obtain stress-strain curves and anisotropic coefficients. The experimental forming limit diagrams (FLD) for two materials were obtained by dome stretching tests following NUMISHEET 96. Theoretical FLD depends on FL models and yield criteria. To obtain the right hand side (RHS) of FLD, we applied the FL models (Swift’s diffuse necking, M-K theory, S-R vertex theory) to Zircaloy-4 and Zirlo sheets. Hill’s local necking theory was adopted for the left hand side (LHS) of FLD. To consider the anisotropy of sheets, the yield criteria of Hill and Hosford were applied. Comparing the predicted curves with the experimental data, we found that the RHS of FLD for Zircaloy-4 can be described by the Swift model (with the Hill’s criterion), while the LHS of the FLD can be explained by Hill model. The FLD for Zirlo can be explained by the S-R model and the Hosford’s criterion (a = 8).

Neutron irradiation performance of Zircaloy-4 under research reactor operating conditions

Jin, Hyun Ju,Kim, Tae Kyu Elsevier 2015 Annals of nuclear energy Vol.75 No.-

<P><B>Abstract</B></P> <P>Since more than 60% of operating research reactors in the world are over 40years old, aging management for their core structural components is one of the key issues faced to ensure life extension, reliability, and safe operation of these research reactors. To manage the aging process, a prediction for the irradiation behavior of the structural materials of the major components is required to avoid unplanned outages, and to enhance the safe and reliable operation. For this, the establishment of improved material properties for irradiated core structural materials in research reactors is essential. Zircaloy-4 is widely used as nuclear core structural materials such as fuel cladding and guide tubes due to its very low absorption cross-section of thermal neutrons, good mechanical property and corrosion resistance. In research reactors, Zircaloy-4 is subjected to relatively high neutron fluence and low temperature conditions compared with commercial reactors. Under such operating conditions, irradiation behaviors such as irradiation-induced dislocation, microstructural changes and irradiation growth in Zircaloy-4 were reviewed. In addition, irradiation-induced mechanical property changes obtained by a post irradiation examination were examined. This review will assist in the design as well as understanding of the irradiation behavior of Zircaloy-4 based core components in research reactors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Neutron irradiation performance of Zircaloy-4 in research reactor environment. </LI> <LI> Microstructure evolution during irradiation. </LI> <LI> Characteristics of irradiation growth. </LI> <LI> Irradiation induced mechanical property change is examined. </LI> </UL> </P>

The Effects of Ar-ion Bombardment and Annealing of D2O/Zircaloy-4 Surfaces Using XPS and UPS

Kyung-Sun Oh,Yong-Cheol Kang* 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.8

The surface chemistry of D2O dosed Zircaloy-4 (Zry-4) surface followed by Ar-ion bombardment and annealing was studied by means of X-ray photoelectron spectroscopy (XPS) and Ultraviolet photoelectron spectroscopy (UPS). In the XPS study, Ar-ion bombardment caused decrease of the oxygen on the surface region of Zry-4 and therefore led to change the oxidation states of the zirconium from oxide to metallic form. In addition, oxidation states of zirconium were changed to lower oxidation states of zirconium due to depopulation of oxygen on the surface region by annealing. Up to about 787 K, the bulk oxygen diffused out to the subsurface region and after this temperature, the oxygen on the surface of Zry-4 was depopulated. UPS study showed that the valence band spectrum of the D2O exposed Zry-4 exhibited a dominant peak at around 13 eV and no clear Fermi edge was detected. After stepwise Ar+ sputtering processes, the decrease of the oxygen on the surface of Zry-4 led to suppress the dominant peak around 13 eV, the peak around 9 eV and develop a new peak of the metallic Zr 4d state (20.5-21.0 eV) at the Fermi level.

단순전단 시험법 구축 및 바우싱거효과를 고려한 경화거동 예측

김동욱(Dongwook Kim),방성식(Sungsik Bang),김민수(Minsoo Kim),이형일(Hyungyil Lee),김낙수(Naksoo Kim) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.10

본 연구에서는 zircaloy-4 판재에 대해 바우싱거 효과를 고려한 경화거동 예측모델을 구축했다. 금속소재 가공에서 인장 후 압축 시 항복응력이 감소한다. 이에 스프링백 해석 시 바우싱거 효과를 반드시 고려해야 한다. Simple shear 시험에서 적정 시편크기 및 적정 조임토크에 대한 결정법을 제시했다. 5 가지 재료에 대한 simple shear 시험을 통해 응력-변형률 곡선을 구했다. 또한 유한요소해석을 활용해 simple shear 하중-변위 곡선으로부터 유효응력-변형률 곡선으로 변환과정을 소개했다. 등방/운동성 경화 조합모델을 활용해 simple shear 순/역방향 시험을 모사했다. 이때 각 경화계수에 따른 하중-변위 곡선 변화를 관찰하고, zircaloy-4에 대한 경화계수를 결정했다. In this study we establish a process to predict hardening behavior considering the Bauschinger effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Bauschinger effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with FEA. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.