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Journal Articles

A Study on stress measurement of weld part using double exposure method

Suzuki, Kenji*; Kura, Komoe*; Miura, Yasufumi*; Shiro, Ayumi*; Toyokawa, Hidenori*; Saji, Choji*; Kajiwara, Kentaro*; Shobu, Takahisa

Zairyo, 71(12), p.1005 - 1012, 2022/12

This paper describes a stress measurement from a welded part of an austenitic stainless steel using synchrotron X-rays. Difficulty measuring the X-ray stress of the welded part is caused by the broadening of the diffraction spot in the radial and circumferential directions. The bending strains of the rectangular bar made of the welded part were measured using synchrotron white X-rays and the double exposure method. To improve the energy resolution, monochromatic synchrotron X-ray of 70 keV was used. The diffraction pattern showed the sharp arc like a pattern from texture material. The diffraction profile was obtained from the integral of the diffraction intensity in the direction of the circumference. The diffraction angle was determined using the double exposure method. As a result, the distribution of the residual stresses of the welded part could be measured.

Journal Articles

Research and development for commercialization of high temperature gas-cooled reactors; Contribution to carbon neutrality

Shinohara, Masanori; Sumita, Junya; Inaba, Yoshitomo; Shibata, Taiju

Dai-59-Kai X Sen Zairyo Kyodo Ni Kansuru Toronkai Koen Rombunshu, p.22 - 28, 2022/11

no abstracts in English

Journal Articles

Electronic structure-based modeling of dislocation motion and its application to nanoscale mechanics

Tsuru, Tomohito

Zairyo, 71(8), p.660 - 665, 2022/08

The dynamic behavior of individual defects at the nanoscale plays an important role in understanding the mechanical properties of highly controlled materials and the nature of their mechanical functions. The purpose of this study is to reveal the origin of the mechanical properties from the electronic structure calculations of dislocation core. In this paper, we propose a modeling that describes the slip bahavior based on the kink mechanism for alloys with a body-centered cubic lattice structure (BCC) that shows a unusual temperature dependence on mechanical properties. In addition, we introduce analytical model to understand the role of alloying elements on dislocation motion from the electronic structure and predict mechanical properties.

Journal Articles

Effects of a corrosion inhibitor on the corrosion of steels under thin solution layers

Momma, Yuichiro*; Sakairi, Masatoshi*; Ueno, Fumiyoshi; Otani, Kyohei

Zairyo To Kankyo, 71(5), p.133 - 137, 2022/05

The effect of the corrosion inhibitor on the corrosion of steel under a thin solution layer was investigated. As a result of forming a thin solution layer with a thickness of 1.0-0.2 mm on the specimen, adding a mixed solution of sodium molybdate and aluminum lactate as a corrosion inhibitor, and performing electrochemical measurement, the corrosion inhibitor suppresses the anodic reaction. And in the thin solution layer, it was suggested that the morphology of the protective layer structure by the corrosion inhibitor changed according to the amount of liquid as compared with the bulk immersion.

Journal Articles

Stress measurements of quasi-coarse grained material using double exposure method with high-energy monochromatic X-rays

Suzuki, Kenji*; Yamada, Minami*; Shiro, Ayumi*; Shobu, Takahisa; Toyokawa, Hidenori*; Saji, Choji*

Zairyo, 71(4), p.347 - 353, 2022/04

We have already succeeded in the residual stress of aluminum alloys using the double exposure method (DEM) with 30 keV synchrotron radiation X-rays. However, the DEM has not be applied in the range of high-energy synchrotron X-rays. In this study, the stress measurements of a shrink-fitted ring using the DEM with synchrotron monochromatic X-rays beyond about 70 keV were performed. A CdTe pixel detector and a CCD camera were used as a detector. The shrink-fitted specimen of SUS304 was quasi-coarse grains of 43 micro-meters, and the diffraction rings were spotty. Despite quasi-coarse grains, it was possible to measure the stresses of the shrink-fitted specimen using the DEM. As a result, the DEM is excellent method to measures the stress for coarse grained materials. In addition, it is better to make the length between the detection positions longer to improve precision of the DEM. On the other hand, it was ineffective to increase the positions of detection.

Journal Articles

${it In situ}$ observation of recrystallization of aluminum single crystals using synchrotron radiation monochromatic X-rays

Shiro, Ayumi*; Shobu, Takahisa; Okada, Tatsuya*

Zairyo, 71(4), p.354 - 360, 2022/04

Recrystallization process of an aluminum (Al) single crystal was observed in situ using synchrotron X-rays. Al single-crystalline samples were deformed in tension along a $$<$$111$$>$$ direction to a strain of 8%, and were subsequently annealed at 753 K. The changes in the shape and intensity of diffraction spots were analyzed using a two-dimensional detector. A diffraction spot from the deformation matrix had three peaks which reflected a sub-grained microstructure of the sample. The ${it in situ}$ observation during annealing unveiled the appearance of diffraction spots from a recrystallized grain at 330.8 s. As the diffraction spots from the recrystallized grain became larger, the diffraction spots from the deformation matrix gradually disappeared. The application of the X-ray topography method revealed the crystal orientation variation in a recrystallized grain in order of 0.001 degree.

Journal Articles

Effect of $$^{90}$$Sr dissolved solution on corrosion potential of type 316L stainless steel

Aoyama, Takahito; Kato, Chiaki; Sato, Tomonori; Sano, Naruto; Yamashita, Naoki; Ueno, Fumiyoshi

Zairyo To Kankyo, 71(4), p.110 - 115, 2022/04

no abstracts in English

Journal Articles

Electrochemical behavior of carbon steels under thickness-controlled solution layer

Momma, Yuichiro*; Sakairi, Masatoshi*; Ueno, Fumiyoshi; Otani, Kyohei

Zairyo To Kankyo, 71(4), p.121 - 125, 2022/04

The effect of solution layer thickness on the atmospheric corrosion of carbon steel was investigated using novel devices fabricated by a 3D printer. These novel devices allowed us to control the solution layer thickness precisely. Potentiodynamic polarization measurements were performed under thickness-controlled solution layer, and oxygen diffusion limiting current density ($$j_{rm lim}$$) and anodic current density ($$j_{rm anode}$$) were measured. As the solution layer become thinner, $$j_{rm lim}$$ increased and $$j_{rm anode}$$ decreased. This result indicates that corrosion accelerates when the solution layer becomes thinner. The diffusion coefficient of oxygen was calculated as 3.20$$times$$10$$^{-5}$$ cm$$^{2}$$ s$$^{-1}$$ from the relationship between $$j_{rm lim}$$ and solution layer thickness, and the critical diffusion thickness was estimated to be 0.87 mm.

Journal Articles

Polarization characteristics and evaluation of corrosion rate of stainless steel in nitric acid solution containing $$^{237}$$Np

Irisawa, Eriko; Kato, Chiaki; Yamashita, Naoki; Sano, Naruto

Zairyo To Kankyo, 71(3), p.70 - 74, 2022/03

In order to evaluate the corrosion of stainless steels used in spent nuclear fuel reprocessing facilities, the immersion corrosion tests and polarization measurements were performed using R-SUS304ULC stainless steel in nitric acid solution containing a kind of radionuclides, $$^{237}$$Np. At temperatures above 328 K, the corrosion potential was higher than that in nitric acid solution and was near the transpassive region. From the comparison between the corrosion amount calculated by the immersion corrosion tests and the polarization resistance, the values of $$k$$=0.018-0.025 V were obtained as a conversion factor, and the possibility of calculating the corrosion amount from the electrochemical measurement was examined.

Journal Articles

Effect of oxygen concentration on corrosion rate of carbon steel in air/solution alternating condition

Otani, Kyohei; Ueno, Fumiyoshi; Kato, Chiaki

Zairyo To Kankyo, 71(2), p.40 - 45, 2022/02

The purpose of this study is to investigate the effect of oxygen concentration in the air on the corrosion rate of carbon steel in an air/solution alternating environment in the low oxygen concentration range and to clarify the corrosion rate and corrosion mechanism of carbon steel depending on the oxygen concentration in air by the mass change of specimens before and after the corrosion test and observing the iron rust layer formed on the surface of carbon steel. The corrosion rate increases with increasing oxygen concentration in the air, and the gradient of the corrosion rate decreases gradually. The maximum erosion depth increased with increasing oxygen concentration except for the case of 1% oxygen concentration, however, the maximum erosion depth for 1% oxygen concentration was larger than that for 5% air oxygen concentration.

Journal Articles

Corrosion of carbon steel in the simulated air/solution interface environment

Otani, Kyohei; Kato, Chiaki

Zairyo To Kankyo, 70(12), p.480 - 486, 2021/12

This is a comprehensive paper of the corrosion of carbon steel in air/solution alternating condition. From cross-sectional observation and analysis of the iron rust layer formed on the surface of carbon steel in the alternating condition, it was found that a multilayered iron rust layer composed of red rust layer ($$gamma$$-FeOOH), rust crust layer (Fe$$_{3}$$O$$_{4}$$), inner crystal (Fe$$_{3}$$O$$_{4}$$), and inner rust layer was formed on carbon steel. The multi-layered iron rust layer would accelerate the cathodic oxygen reduction reaction, and the reason why the corrosion rate of the carbon steel in the alternating condition was accelerated. The effect of artificial seawater (ASW) composition on the corrosion rate of carbon steel in air/solution alternating condition was investigated. It was found that the corrosion rate increased with increasing concentration from pure water to 200 times diluted ASW, and decreased with increasing concentration from 20 times diluted ASW to no diluted ASW. The Mg and Ca ions in ASW precipitated on the reaction interface and formed a metal cation layer, which inhibited the oxygen reduction reaction, and thus the corrosion of carbon steel was inhibited in the highly concentrated ASW.

Journal Articles

Radiolysis effects, which should be taken into account for safe decommissioning of Fukushima-Daiichi Nuclear Power Station

Hata, Kuniki

Zairyo To Kankyo, 70(12), p.468 - 473, 2021/12

In order to estimate corrosive environment in the contaminated water at Fukushima Daiichi Nuclear Power Station, effects of oxidants, such as H$$_{2}$$O$$_{2}$$, which were generated from water radiolysis, should be taken into account due to the irradiation field in the reactor building. The process of water radiolysis and the amounts of these oxidants can change depending on the conditions of water and types of radiation. After the accident, a variety of factors, which can affect water radiolysis, such as seawater constituents, surface of oxides, and $$alpha$$-radionuclides, had been discussed. In this paper, these effects on radiolysis are reviewed for the better understanding of the corrosive environment in the contaminated water.

Journal Articles

A Task of microbiologically influenced corrosion in Fukushima Daiichi Decommissioning

Wakai, Satoshi*; Hirano, Shinichi*; Ueno, Fumiyoshi; Okamoto, Akihiro*

Zairyo To Kankyo, 70(12), p.491 - 496, 2021/12

After Fukushima Daiichi Nuclear Power Station accident, various corrosion mitigating activities have been treated, and severe corrosion incident have never taken placed. On the other hand, the facilities were exposed sea water, and some of them have continuously exposed to ground water. The exposure of metal materials to environmental water has a risk of microbiologically influenced corrosion (MIC). In this paper, we summarize the latest knowledge of MIC and the task of MIC in the decommissioning of Fukushima Daiichi Nuclear Power Station.

Journal Articles

Time dependence of corrosion behavior on Ta in NaOH solutions

Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi

Zairyo To Kankyo, 70(6), p.192 - 198, 2021/06

The time dependence of corrosion behavior on tantalum used in nuclear fuel reprocessing equipment in sodium hydroxide solution was investigated by immersion corrosion tests, and the mechanism of aging change was discussed from surface observations and electrochemical measurements. The immersion tests were carried out at room temperature with NaOH concentrations ranging from 1 to 7 mol/L and immersion times ranging from 24 to 168 hr, respectively. The corrosion rate increased with NaOH concentration, but peaked with immersion time and then decreased. The time to peak of corrosion rate was shorter with higher NaOH concentration. The SEM observations and Raman analysis at the surface of the specimens that were cleaned and weighed after the immersion test did not show any film formation. On the other hand, the polarization resistance showed a constant value or an increase after a decrease immediately after immersion. It is suggested that the change in corrosion rate is affected by the formation of film by immersion, since the value of polarization resistance is almost the same as the sum of film resistance and charge transfer resistance. The film was considered to be mainly Na$$_{8}$$Ta$$_{6}$$O$$_{19}$$ formed by the dissolution of Ta.

Journal Articles

Synthesis of a Si-Al gel as a starting material of aluminosilicate solids

Sato, Junya; Shiota, Kenji*; Takaoka, Masaki*

Zairyo, 70(5), p.406 - 411, 2021/05

An aluminosilicate solid is an inorganic material that has the property of immobilizing heavy metals or radionuclides in the matrix. In this study, aluminosilicates with a Si/Al molar ratio of 0.5 was synthesized from a chemical reagent in order to produce aluminosilicate solids with a low Si/Al molar ratio, which were expected to improve the immobilization of heavy metals and radionuclides contained in the matrix. The synthesized Si-Al gel with a Si/Al molar ratio of 0.5 had little impurity content and was in an amorphous phase. In addition, the compressive strength of the aluminosilicate solid produced by the synthesized Si-Al gel showed a 5 MPa or more, confirming that it can be used as a raw material for aluminosilicate solids. The aluminosilicate solid with a Si/Al molar ratio of 1.25 had a dense surface structure from the result of BSE images and had the highest compressive strength among all samples.

Journal Articles

Corrosion resistance and oxide film structure of stainless steels and Ni-based alloys under sulfuric decomposition gas at high temperature

Hirota, Noriaki; Takeda, Kiyoko*; Tachibana, Yukio; Masaki, Yasuhiro*

Zairyo To Kankyo, 70(3), p.68 - 76, 2021/03

Corrosion resistance of stainless steels and Ni-based alloys were evaluated in a sulfuric acid decomposition gas at high temperature. The evaluation were carried out in an environment simulated in the sulfuric acid decomposition reaction vessel for thermochemical hydrogen production process (IS process). Their corrosion films were also analyzed for better understanding of the corrosion behavior. As a result, after 100 hour corrosion test, Ni-based alloy containing 2.4% Si showed good corrosion resistance. Ferritic stainless steel containing 3% Al (3Al-Ferrite) showed better corrosion resistance. Its corrosion rate was lower than that of SiC (0.1mm/year), which is a candidate material for the sulfuric acid decomposition reaction vessel. On the other hand, Ni-based alloy pre-filmed with Al$$_{2}$$O$$_{3}$$ is prepared as the relative corrosion film of 3Al-Ferrite. Its corrosion rate was significantly higher than that of 3Al-Ferrite. As the result of EPMA analysis of these oxide films, Ni-based alloy containing 2.4% Si formed Si oxide film which had some cracks after the long term corrosion test. Therefore S penetrated into grain boundaries of the matrix through the oxide film. 3Al-Ferrite formed a thin and uniform Al$$_{2}$$O$$_{3}$$ film, and the penetration of S into the grain boundaries was not observed. Al$$_{2}$$O$$_{3}$$ pre-film of Ni-based alloy also showed S penetration in the matrix because the Al$$_{2}$$O$$_{3}$$ pre-film had many small defects originally. The corrosion oxide film of 3Al-Ferrite consisted of only $$alpha$$-Al$$_{2}$$O$$_{3}$$, while the Al$$_{2}$$O$$_{3}$$ pre-film consist of $$alpha$$-Al$$_{2}$$O$$_{3}$$ and $$gamma$$-Al$$_{2}$$O$$_{3}$$. Those results suggest that the better corrosion resistance of 3Al-Ferrite is due to the uniform formation of dense $$alpha$$-Al$$_{2}$$O$$_{3}$$ film at the early stage of the corrosion.

Journal Articles

Effect of seawater components on corrosion rate of steel in air/solution alternating condition

Otani, Kyohei; Tsukada, Takashi; Ueno, Fumiyoshi; Kato, Chiaki

Zairyo To Kankyo, 69(9), p.246 - 252, 2020/09

The purpose of this study was to investigate the effect of artificial sea water concentration on the corrosion rate of carbon steel under air/solution alternating condition, and to clarify the corrosion mechanism of carbon steel that changes with artificial seawater concentration. Mass measurements showed that the corrosion rate of carbon steel in the alternating condition accelerates with increasing concentration in the concentration region between deionized water to 200 times diluted artificial seawater (ASW), and the corrosion rate decreases with increasing concentration in the concentration region between 20 times diluted ASW to undiluted ASW. It can be considered that the reason why the carbon steel corrosion was suppressed in highly concentrated artificial seawater would Mg ions and Ca ions in the artificial seawater precipitate and cover on the surface due to the increase in pH near the surface by oxygen reduction reaction.

Journal Articles

Aim for computational science on corrosion problems and prompt approach for corrosion of 1F decommissioning in JSCE

Yamamoto, Masahiro

Zairyo To Kankyo 2020 Koenshu (CD-ROM), p.9 - 16, 2020/05

The author has been continuing research and development for corrosion science for about forty years. One of the main targets of his research is applying computational science techniques on corrosion problems. The results are briefly introduced in this article. Also, the author organized some workshop for corrosion problems of 1F decommissioning procedure for several years. Such activities are evaluated for receiving the society award in JSCE.

Journal Articles

Characterization of microstructures by X-ray diffraction line profile analysis, 2; Line profile analysis using synchrotron radiation

Shobu, Takahisa; Shiro, Ayumi*; Yoshida, Yutaka*

Zairyo, 69(4), p.343 - 347, 2020/04

Dislocation density is a very important physical quantity in the evaluation of fatigue of metallic materials. Generally, the dislocation density is evaluated by a scanning electron microscope. Recently, a method generated the dislocation density from the width of the X-ray diffraction profile has been proposed. In this study, we report the application of this technology to synchrotron radiation. Five diffraction profiles were obtained with a two-dimensional detector during tensile loading of the austenitic stainless steel SUS316L, and the dislocation density was calculated from the line profile analysis. As a result, the dislocation density increased sharply after plastic deformation, and the value was in good agreement with the result separately measured with a scanning electron microscope. In the future, it is expected that the line profile analysis will contribute to the elucidation of the mechanism of fatigue fracture by measuring the dislocation density from the local area in materials.

409 (Records 1-20 displayed on this page)