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Journal Articles

Development of methods for reprocessing and reuse of tritium breeder materials in broader approach activities

Hoshino, Tsuyoshi

Journal of Nuclear Materials, 442(1-3), p.S425 - S428, 2013/11

 Times Cited Count:4 Percentile:32.98(Materials Science, Multidisciplinary)

Development of reprocessing and reuse of this spent breeder including unburned $$^{6}$$Li is important from viewpoint of effective utilization $$^{6}$$Li as a limited resource. This activity has been started between Japan and the EU in the Broader Approach activities. The effect of solvent on dissolution of Li$$_{2}$$TiO$$_{3}$$ powder was evaluated. Li$$_{2}$$TiO$$_{3}$$ powder with 99.9% purity was prepared as a starting powder. Solubility of Li was evaluated from the measurement result of the Li content in solution by ICP (inductively coupled plasma) atomic emission spectrometry. Peroxide hydrogen (H$$_{2}$$O$$_{2}$$) was selected as solvent. Most of Li$$_{2}$$TiO$$_{3}$$ was soluble in room temperature, and then the solubility of Li were larger than 90%.

Journal Articles

Preliminary characterization of plasma-sintered beryllides as advanced neutron multipliers

Nakamichi, Masaru; Kim, Jae-Hwan; Munakata, Kenzo*; Shibayama, Tamaki*; Miyamoto, Mitsutaka*

Journal of Nuclear Materials, 442(1-3), p.S465 - S471, 2013/11

 Times Cited Count:11 Percentile:64.89(Materials Science, Multidisciplinary)

Journal Articles

The Effect of sintering time on synthesis of plasma sintered beryllides

Kim, Jae-Hwan; Nakamichi, Masaru

Journal of Nuclear Materials, 442(1-3), p.S461 - S464, 2013/11

 Times Cited Count:16 Percentile:77.2(Materials Science, Multidisciplinary)

Journal Articles

Irradiation response in weldment and HIP joint of reduced activation ferritic/martensitic steel, F82H

Hirose, Takanori; Sokolov, M. A.*; Ando, Masami; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Stoller, R. E.*; Odette, G. R.*

Journal of Nuclear Materials, 442(1-3), p.S557 - S561, 2013/11

 Times Cited Count:9 Percentile:58.11(Materials Science, Multidisciplinary)

Journal Articles

First-principles thermodynamic calculations of diffusion characteristics of impurities in $$gamma$$-iron

Tsuru, Tomohito; Kaji, Yoshiyuki

Journal of Nuclear Materials, 442(1-3), p.S684 - S687, 2013/11

 Times Cited Count:5 Percentile:39.25(Materials Science, Multidisciplinary)

Since the solute impurities have an effect on the embrittlement through segregation under irradiation, the solute stability of impurity elements is of considerable importance. In the present study, the diffusion characteristics of large-radius impurities in $$gamma$$-Fe are investigated by first principles calculations. According to the classical diffusion and transition state theories, diffusion coefficient were evaluated nonempirically. The vacancy formation energy and binding energy between impurity and vacancy were obtained by first principles density functional theory (DFT) calculations. And the migration energy was calculated by nudged elastic band method collaborated with DFT. Consequently, it is confirmed that the binding energy between large-radius impurity and vacancy is larger than that with equivalent size of the solvent element, and that the migration enthalpies of these impurities are quite small compared with self diffusion.

Journal Articles

An Atomistic modeling of He bubble stability at grain boundaries in alpha-Fe

Suzudo, Tomoaki; Tsuru, Tomohito; Yamaguchi, Masatake; Kaburaki, Hideo

Journal of Nuclear Materials, 442(1-3), p.S655 - S659, 2013/11

 Times Cited Count:6 Percentile:44.86(Materials Science, Multidisciplinary)

He bubbles at grain boundaries (GBs) may lead materials to serious embrittlement, but the mechanism of the nucleation of such bubbles is not well-understood. In the present paper, we analyzed the stability of various He-vacancy clusters, which are precursors of He bubbles, at several kinds of grain boundaries of alpha-Fe using a set of empirical potentials. We found that the dissociation energy of vacancy from He-vacancy clusters at GBs is generally less than that for the intragranular counterparts, and that the He-to-vacancy ratio in equilibrium for various GB cases becomes larger in comparison with the intragranular case. The results obtained here are useful for kinetic models of He bubble nucleation.

Journal Articles

Microsegregation in a F82H plate

Sakasegawa, Hideo; Tanigawa, Hiroyasu

Journal of Nuclear Materials, 442(1-3), p.S18 - S22, 2013/11

 Times Cited Count:0 Percentile:0.01(Materials Science, Multidisciplinary)

Through the Broader Approach (BA) activity in Japan, F82H-BA07 heat of 5 tons prepared applying electrosrag remelting (ESR) has been studied as a step toward a larger-scale melting about 20 tons. From the result of elemental mapping images using electron probe microanalysis (EPMA), micro-segregation of at least four metallic elements such as chromium, tungsten, vanadium and manganese was found as stripes parallel to the hot rolling direction. In the case of tungsten segregation, the maximum difference of content was about 1.0 wt% between the observed stripes. This difference could cause differences in nano-metric structures between stripes, and affect mechanical properties. In this presentation, we discuss how much micro-segregation should be decreased considering effects of micro-segregation on nano-metric structures and mechanical properties in addition to the result of optimization of homogenizing condition.

Journal Articles

Application of master curve method to the evaluation of fracture toughness of F82H steels

Kim, B. J.; Kasada, Ryuta*; Kimura, Akihiko*; Wakai, Eiichi; Tanigawa, Hiroyasu

Journal of Nuclear Materials, 442(1-3), p.S38 - S42, 2013/11

 Times Cited Count:11 Percentile:67.96(Materials Science, Multidisciplinary)

Journal Articles

Effect of cation exchange on hydrogen adsorption property of mordenite for isotope separation

Kawamura, Yoshinori; Iwai, Yasunori; Munakata, Kenzo*; Yamanishi, Toshihiko

Journal of Nuclear Materials, 442(1-3), p.S455 - S460, 2013/11

 Times Cited Count:11 Percentile:64.89(Materials Science, Multidisciplinary)

Zeolite easily exchanges its cation to another. In this work, synthetic mordenite type zeolite (Na-MOR) was used as start material. And, its cation (Na$$^{+}$$) has been exchanged by Li$$^{+}$$, K$$^{+}$$, Mg$$^{2+}$$ and Ca$$^{2+}$$. Then, adsorption capacities of H$$_{2}$$ and D$$_{2}$$ on them were investigated at 77 K, 159 K, 175 K and 195 K. Adsorption capacities on Li-MOR and Ca-MOR became larger than that on Na-MOR at low pressure range. Oppositely, that on K-MOR became smaller. In case of alkaline metal, cation with small atomic number may lead to large adsorption capacity.

Journal Articles

Development of high-grade VPS-tungsten coatings on F82H reduced activation steel

Tokunaga, Tomonori*; Watanabe, Hideo*; Yoshida, Naoaki*; Nagasaka, Takuya*; Kasada, Ryuta*; Lee, Y.-J.*; Kimura, Akihiko*; Tokitani, Masayuki*; Mitsuhara, Masatoshi*; Hinoki, Tatsuya*; et al.

Journal of Nuclear Materials, 442(1-3), p.S287 - S291, 2013/11

 Times Cited Count:10 Percentile:61.83(Materials Science, Multidisciplinary)

Journal Articles

Mechanical properties of friction stir welded 11Cr-ferritic/martensitic steel

Yano, Yasuhide; Sato, Yutaka*; Sekio, Yoshihiro; Otsuka, Satoshi; Kaito, Takeji; Ogawa, Ryuichiro; Kokawa, Hiroyuki*

Journal of Nuclear Materials, 442(1-3), p.S524 - S528, 2013/09

 Times Cited Count:14 Percentile:73.01(Materials Science, Multidisciplinary)

Friction stir welding was applied to the wrapper tube materials, 11Cr-ferritic/martensitic steel, intended for fast reactors and defect-free welds were successfully produced. Then, the mechanical and microstructural properties of the friction stir welded steel were investigated. The hardness values of the stir zone were about 550 Hv, and they had hardly any dependence on the rotational speed, although they were much higher than that of the base material. However, tensile strengths and elongations of the stir zones were better at 298 K, compared to those of the base material. These excellent tensile properties were attributable to the fine grain formation during friction stir welding. A part of this study is the result of "Friction stir welding of the wrapper tube materials for Na fast reactors" carried out under the Strategic Promotion Program for Basic Nuclear Research by the Ministry of Education, Culture, Sports, Science and Technology of Japan.

Journal Articles

Microstructure and high-temperature strength of high Cr ODS tempered martensitic steels

Otsuka, Satoshi; Kaito, Takeji; Tanno, Takashi; Yano, Yasuhide; Koyama, Shinichi; Tanaka, Kenya

Journal of Nuclear Materials, 442(1-3), p.S89 - S94, 2013/09

 Times Cited Count:14 Percentile:73.01(Materials Science, Multidisciplinary)

The manufacturing tests of 11-12Cr ODS tempered martensitic steels were carried out, and their ferritic/martensitic duplex structures were quantitatively evaluated by three types of methods, i.e. high temperature XRD, EPMA and metallography. It was demonstrated that excessive formation of residual-alpha ferrite provided by increasing Cr can be suppressed by appropriately controlling the concentration of ferrite-forming element and austenite-forming element on the basis of the parameter "chemical driving force of $$alpha$$ to $$gamma$$ reverse transformation" as a useful indication. The 11Cr-ODS steel containing a small portion of residual-alpha ferrite was successfully manufactured. In the as-received condition, this 11Cr-ODS steel is shown to have the satisfactory creep strength and ductility as high as the 9Cr-ODS steel while 0.2% proof strength at 973K is lower than in the 9Cr-ODS steel.

Journal Articles

Engineering design of contact-type liquid level sensor for measuring thickness validation of liquid lithium jet in IFMIF/EVEDA lithium test loop

Kanemura, Takuji; Kondo, Hiroo; Suzuki, Sachiko*; Hoashi, Eiji*; Yamaoka, Nobuo*; Horiike, Hiroshi*; Furukawa, Tomohiro; Ida, Mizuho; Nakamura, Kazuyuki; Matsushita, Izuru*; et al.

Fusion Science and Technology, 62(1), p.258 - 264, 2012/07

 Times Cited Count:4 Percentile:32.44(Nuclear Science & Technology)

In the Engineering Validation and Engineering Design Activities (EVEDA) project of the International Fusion Materials Irradiation Facility (IFMIF), which is one of the Broader Approach (BA) activities, thickness variation of a liquid lithium (Li) jet simulating the IFMIF Li target is planned to be measured in the EVEDA Li Test Loop (ELTL). For this purpose, a contact-type liquid level sensor was developed, which can detect contacts between a probe and Li. Analysis of the contact signals yields average jet thickness and amplitude distribution. One of the key development requirements is to drive the probe by 0.1 mm step with positioning accuracy of 0.01 mm under the vacuum condition of 10$$^{-3}$$Pa. To satisfy such a requirement, the sensor's own weight load and moment load were calculated, and based on those calculation results a powerful motor and a friction-reduced ball screw were selected and strong structure was adopted. We have successfully completed the design work of the sensor.

Journal Articles

Pd/ZrO$$_{2}$$ catalyst for the oxidation process of tritiated organic substances produced in fusion plants

Iwai, Yasunori; Sato, Katsumi; Yamanishi, Toshihiko

Fusion Science and Technology, 62(1), p.83 - 88, 2012/07

 Times Cited Count:3 Percentile:25.35(Nuclear Science & Technology)

In case of a fire accident in a fusion plant, some tritiated organic substances will be produced. We have developed a Pd/ZrO$$_{2}$$ catalyst applicable for the oxidation of the tritiated organic substances. Overall reaction rate constant of tritiated methane oxidation over palladium catalyst in a flow-through system were determined as a function of space velocity from 1200 to 7000 h$$^{-1}$$, methane concentration in carrier from 0.004 to 100 ppm, temperature of catalyst from 473 to 673 K. The Pd/ZrO$$_{2}$$ catalysts initially showed the large overall reaction rate constants in the whole tested temperature range. However the constants were gradually decreased when the catalysts were continuously used for the tritiated methane oxidation. The decrease has been explained as the layers of produced water formed on the surface of the catalyst plays the obstacle role of reactant transport onto noble metal deposited on the catalyst. The overall reaction rate constant was dependent on the space velocity and independent on the methane concentration in the reactant mixture.

Journal Articles

Overview of materials research and IFMIF-EVEDA under the Broader Approach framework

Nishitani, Takeo; Tanigawa, Hiroyasu; Yamanishi, Toshihiko; Clement Lorenzo, S.*; Baluc, N.*; Hayashi, Kimio; Nakajima, Noriyoshi*; Kimura, Haruyuki; Sugimoto, Masayoshi; Heidinger, R.*; et al.

Fusion Science and Technology, 62(1), p.210 - 218, 2012/07

 Times Cited Count:3 Percentile:25.35(Nuclear Science & Technology)

Recent progress in the material related researches and the IFMIF/EVEDA project, which are carried out under the Broader Approach (BA) framework, is reported. In the International Fusion Energy Research Center (IFERC) project of BA, the R&D building was completed March 2010 at the Rokkasho BA site. R&Ds on reduced activation ferritic/ martensitic (RAFM) steels as structural material, SiC/SiC composites as a flow channel insert material and/or alternative structural material, advanced tritium breeders and neutron multipliers, and tritium technology relevant to the DEMO operational condition are progressed in Japan and EU. In the IFMIF/EVEDA project, the fabrication of the injector for the IFMIF prototype accelerator was completed at the CEA Saclay, and the first proton beam was obtained in May, 2011. The IFMIF lithium target test loop was completed in March 2011, and a lithium flow of 5 m/s was obtained.

Journal Articles

IFMIF/EVEDA; Adjustment of scope and recent technical achievements

Garin, P.*; Sugimoto, Masayoshi; IFMIF/EVEDA Integrated Project Team

Fusion Science and Technology, 62(1), p.219 - 225, 2012/07

 Times Cited Count:8 Percentile:53.19(Nuclear Science & Technology)

IFMIF aims at generating material database for DEMO and future power plants, and Engineering Design and Engineering Validation Activities have been conducted since mid 2007 under the Broader Approach Agreement. So far the main efforts were focused on the validation work to provide information for the engineering design of IFMIF. In December 2010, new scope of the project was accepted to prioritize the validation of accelerator prototype and to extend the duration of its validation test up to mid 2017, while the other activities shall be completed in mid 2013 as the primary plan. The goal of engineering design has been modified to prepare the Intermediate design report. However, a big earthquake in Japan caused to shift project schedule, especially lithium test loop completed in early 2011. Nevertheless major components development has been continued, e.g. first operation of ion injector has been conducted. This article summarizes status of all activities and future plan of the project.

Journal Articles

Effects of carbon impurity on microstructural evolution in irradiated $$alpha$$-iron

Abe, Yosuke; Suzudo, Tomoaki; Jitsukawa, Shiro; Tsuru, Tomohito; Tsukada, Takashi

Fusion Science and Technology, 62(1), p.139 - 144, 2012/07

 Times Cited Count:10 Percentile:60.98(Nuclear Science & Technology)

Static and dynamic interactions between SIA loops and carbon impurities as a major impurity in $$alpha$$-iron was studied using atomic-scale computer simulations to clarify possible mechanisms of trapping of SIA loops by carbon impurities. It was found that bindings of carbon-vacancy complexes with SIA loops are so strong when they locate inside the loop habit plane. This situation would be realized below $$sim$$450 K at which carbon-vacancy complexes become to dissociate. At higher temperatures, it can be expected that the dissociated interstitial carbon atoms tend to migrate towards the loop periphery due to the internal stress field associated with SIA loops, and this could attribute to the continuous 1D motion of SIA loops with dragging impurities as observed by experiments. A long-term microstructural evolution induced by radiation damage was also simulated by taking into account the trapping and detrapping rates of SIA loops deduced from the knowledge obtained in this study.

Journal Articles

Adsorption behavior of hydrogen and deuterium on natural mordenite adsorbents at 77 K

Munakata, Kenzo*; Kawamura, Yoshinori

Fusion Science and Technology, 62(1), p.71 - 76, 2012/07

 Times Cited Count:6 Percentile:44.18(Nuclear Science & Technology)

Cryogenic adsorption is effective for the recovery of low-concentration hydrogen isotopes from bulk helium gases. As the result of screening test, it has been found out that a natural mordenite has a quite high adsorption capacity for H$$_{2}$$ and D$$_{2}$$ under the helium atmosphere at 77 K. In this work, the adsorption rates of hydrogen isotopes for the mordenite were quantified by analyzing breakthrough curves obtained in experiments. Evaluated effective pore diffusivities suggest that the mordenite is promising for the recovery of low concentration hydrogen isotopes from the helium bulk gas.

Journal Articles

Analysis of test matrix and design status of test modules of IFMIF

Wakai, Eiichi; Kikuchi, Takayuki; Yokomine, Takehiko*; Yamamoto, Michiyoshi; Soldaini, M.*; Polato, A.*

Fusion Science and Technology, 62(1), p.246 - 251, 2012/07

 Times Cited Count:6 Percentile:44.18(Nuclear Science & Technology)

Oral presentation

Evaluation of creep properties of welded joint for reduced activation ferritic/martenstic steel

Nakata, Toshiya; Tanigawa, Hiroyasu; Kimura, Kazuhiro*

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23 (Records 1-20 displayed on this page)