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Journal Articles

Crystal and magnetic structures of double hexagonal close-packed iron deuteride

Saito, Hiroyuki*; Machida, Akihiko*; Iizuka, Riko*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Sato, Toyoto*; Orimo, Shinichi*; Aoki, Katsutoshi*

Scientific Reports (Internet), 10, p.9934_1 - 9934_8, 2020/06

 Times Cited Count:0 Percentile:100(Multidisciplinary Sciences)

Neutron powder diffraction profiles were collected for iron deuteride (FeDx) while the temperature decreased from 1023 to 300 K for a pressure range of 4-6 GPa. The $$varepsilon$$' deuteride with a double hexagonal close-packed (dhcp) structure, which coexisted with other stable or metastable deutrides at each temperature and pressure condition, formed solid solutions with a composition of FeD$$_{0.68(1)}$$ at 673 K and 6.1 GPa and FeD$$_{0.74(1)}$$ at 603 K and 4.8 GPa. Upon stepwise cooling to 300 K, the D-content x increased to a stoichiometric value of 1.0 to form monodeuteride FeD$$_{1.0}$$. In the dhcp FeD$$_{1.0}$$ at 300 K and 4.2 GPa, dissolved D atoms fully occupied the octahedral interstitial sites, slightly displaced from the octahedral centers in the dhcp metal lattice, and the dhcp sequence of close-packed Fe planes contained hcp-stacking faults at 12%. Magnetic moments with 2.11 $$pm$$ 0.06 B/Fe-atom aligned ferromagnetically in parallel on the Fe planes.

Journal Articles

Hexagonal close-packed iron hydride behind the conventional phase diagram

Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Sato, Toyoto*; Orimo, Shinichi*; Aoki, Katsutoshi*

Scientific Reports (Internet), 9(1), p.12290_1 - 12290_9, 2019/08

 Times Cited Count:3 Percentile:34.9(Multidisciplinary Sciences)

Hexagonal close-packed iron hydride, hcp FeHx, is absent from the conventional phase diagram of the Fe-H system, although hcp metallic Fe exists stably over extensive temperature ($$T$$) and pressure ($$P$$) conditions, including those corresponding to the Earth's inner core. ${{it In situ}}$ X-ray and neutron diffraction measurements at temperatures ranging from 298 to 1073 K and H pressures ranging from 4 to 7 GPa revealed that the hcp hydride was formed for FeH$$_{x}$$ compositions when $$x < 0.6$$. Hydrogen atoms occupied the octahedral interstitial sites of the host metal lattice both partially and randomly. The hcp hydride exhibited a H-induced volume expansion of 2.48(5) $AA $^{3}$$/H-atom, which was larger than that of the face-centered cubic (fcc) hydride. The hcp hydride showed an increase in $$x$$ with $$T$$, whereas the fcc hydride showed a corresponding decrease. The present study provides guidance for further investigations of the Fe-H system over an extensive $$x$$-$$T$$-$$P$$ region.

Journal Articles

In-situ measurement of electrical conductivity of solution within crevice of stainless steel in high temperature and high purity water

Soma, Yasutaka; Komatsu, Atsushi; Ueno, Fumiyoshi

Zairyo To Kankyo, 67(9), p.381 - 385, 2018/09

In-situ measurement of electrical conductivity of solution within crevice of SUS316L stainless steel in 288$$^{circ}$$C water has been conducted with newly developed electrochemical sensor system. The sensor measures local electrical conductivity of crevice solution beneath the electrode ($$kappa$$$$_{crev}$$) with electrochemical impedance method. The sensors were installed at different positions within tapered crevice of SUS316L stainless steel. The crevice specimen with the sensors were immerged into 288$$^{circ}$$C, 8 MPa, pure oxygen saturated high purity water for 100 h. $$kappa$$$$_{crev}$$ at a position with crevice gap of $$approx$$59.3$$mu$$m was 8-11$$mu$$S/cm, least deviate from conductivity of 288$$^{circ}$$C pure water (4.4$$mu$$S/cm) and no localized corrosion occurred. On the contrary, $$kappa$$$$_{crev}$$ at a position with crevice gap of $$approx$$4.4$$mu$$m increased with time and showed maximum value of $$approx$$1600$$mu$$S/cm at 70 h. Localized corrosion occurred in the vicinity of this position. Thermodynamic equilibrium calculation showed $$kappa$$$$_{crev}$$ of 1600$$mu$$S/cm being equivalent to pH of 3 to 3.7. It can be concluded that acidification occurred in tight crevice even under high purity bulk water and resulted in localized corrosion.

Journal Articles

Localized corrosion in crevice of SUS316 stainless steel in oxygenated high temperature and high purity water

Soma, Yasutaka; Ueno, Fumiyoshi

Zairyo To Kankyo, 67(5), p.222 - 228, 2018/05

Localized corrosion in crevice of SUS316 stainless steel after immersion in 288$$^{circ}$$C high purity water with dissolved oxygen concentration of 32 ppm for 100 h was analyzed. Two different types of localized corrosion initiated on grain boundary and inclusions. The former initiated on grain boundary and oxide grown into grain matrix. The oxidized area showed duplex structure composed of microcrystalline FeCr$$_{2}$$O$$_{4}$$ and island-shaped residual metals. The latter initiated on inclusions containing Ca and S and microcrystalline FeCr$$_{2}$$O$$_{4}$$ grown into metal matrix. These localized corrosion occurred selectively in oxygen depleted area indicated formation of macroscopic corrosion cell with the corroded area as anode and surrounding oxygenated area as cathode.

Journal Articles

Effect of dissolved gas on mechanical property of sheath material of mineral insulated cables under high temperature and pressure water

Takeuchi, Tomoaki; Nakano, Hiroko; Uehara, Toshiaki; Tsuchiya, Kunihiko

Nuclear Materials and Energy (Internet), 9, p.451 - 454, 2016/12

 Times Cited Count:1 Percentile:83.2(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Electrical conductivity and potential response within crevice of stainless steel in high temperature water under cyclic deaerated and aerated condition

Soma, Yasutaka; Kato, Chiaki; Ueno, Fumiyoshi

Fushoku Boshoku Kyokai Dai-63-Kai Zairyo To Kankyo Toronkai Koenshu, p.253 - 256, 2016/10

Contribution of corrosion to advance of stress corrosion cracking (SCC) of stainless steel in high temperature water must be assessed because serious corrosion can be found within SCC of light water reactors. The corrosion took the form of both intergranular and grain-matrix attack indicate aggressive corrosion condition was formed in the crevice of the SCC. We have investigated the crevice environment electrochemically and found that local electrical conductivity of the crevice solution at satisfactory narrow crevice gap having more than 100 times higher than that of bulk solution. In this research we assessed effect of cyclic deaerated and aerated bulk solution to the crevice environment. The result showed that electrical conductivity of the crevice solution under the deaerated bulk solution increased more than 10times by injection of pure oxygen suggest that the dissolved oxygen caused aggressive corrosion condition within the crevice.

JAEA Reports

Performance test of ex-core high temperature and high pressure water loop test equipment (Contract research)

Nakano, Hiroko; Uehara, Toshiaki; Takeuchi, Tomoaki; Shibata, Hiroshi; Nakamura, Jinichi; Matsui, Yoshinori; Tsuchiya, Kunihiko

JAEA-Technology 2015-049, 61 Pages, 2016/03


In Japan Atomic Energy Agency, we started a research and development so as to monitor the Nuclear Plant Facilities situations during a severe accident, such as a radiation-resistant monitoring camera under a severe accident, a radiation resistant in-water transmission system for conveying the information in-core and a heat-resistant signal cable. As part of advance in a heat-resistant signal cable, we maintained to ex-core high-temperature and pressure water loop test equipment which can be simulated conditions of BWRs and PWRs for evaluation reliability and property of construction sheath materials. This equipment consists of Autoclave, water conditioning tank, water pump, high-pressure metering pump, preheater, heat exchanger and pure water purification equipment. This report describes the basic design and the results of performance tests of construction machinery and tools of ex-core high-temperature and pressure water loop test equipment.

Journal Articles

True Boundary for the formation of homoleptic transition-metal hydride complexes

Takagi, Shigeyuki*; Iijima, Yuki*; Sato, Toyoto*; Saito, Hiroyuki; Ikeda, Kazutaka*; Otomo, Toshiya*; Miwa, Kazutoshi*; Ikeshoji, Tamio*; Aoki, Katsutoshi*; Orimo, Shinichi*

Angewandte Chemie; International Edition, 54(19), p.5650 - 5653, 2015/05

 Times Cited Count:23 Percentile:29.5(Chemistry, Multidisciplinary)

Journal Articles

Design and performance of high-pressure PLANET beamline at pulsed neutron source at J-PARC

Hattori, Takanori; Sano, Asami; Arima, Hiroshi*; Komatsu, Kazuki*; Yamada, Akihiro*; Inamura, Yasuhiro; Nakatani, Takeshi; Seto, Yusuke*; Nagai, Takaya*; Utsumi, Wataru; et al.

Nuclear Instruments and Methods in Physics Research A, 780, p.55 - 67, 2015/04

 Times Cited Count:40 Percentile:1.21(Instruments & Instrumentation)

PLANET is a time-of-flight (ToF) neutron beamline dedicated to high-pressure and high-temperature experiments. The large six-axis multi-anvil high-pressure press designed for ToF neutron diffraction experiments enables routine data collection at high pressures and high temperatures up to 10 GPa and 2000 K, respectively. To obtain clean data, the beamline is equipped with the incident slits and receiving collimators to eliminate parasitic scattering from the high-pressure cell assembly. The high performance of the diffractometer for the resolution ($$Delta$$ $$d$$/$$d$$ $$sim$$ 0.6%) and the accessible $$d$$-spacing range (0.2-8.4 ${AA}$) together with low-parasitic scattering characteristics enables precise structure determination of crystals and liquids under high pressure and temperature conditions.

Journal Articles

Six-axis multi-anvil press for high-pressure, high-temperature neutron diffraction experiments

Sano, Asami; Hattori, Takanori; Arima, Hiroshi*; Yamada, Akihiro*; Tabata, Satoshi*; Kondo, Masahiro*; Nakamura, Akihiro*; Kagi, Hiroyuki*; Yagi, Takehiko*

Review of Scientific Instruments, 85(11), p.113905_1 - 113905_8, 2014/11

 Times Cited Count:23 Percentile:21.21(Instruments & Instrumentation)

We developed a six-axis multi-anvil press, ATSUHIME, for high-pressure and high-temperature in situ time-of-flight neutron powder diffraction experiments. The press has six orthogonally oriented hydraulic rams that operate individually to compress a cubic sample assembly. Experiments indicate that the press can generate pressures up to 9.3 GPa and temperatures up to 2000 K using a 6-6-type cell assembly, with available sample volume of about 50 mm $$^{3}$$. Using a 6-8-type cell assembly, the available conditions expand to 16 GPa and 1273 K. Combination of the six-axis press and the collimation devices realized high-quality diffraction pattern with no contamination from the heater or the sample container surrounding the sample. This press constitutes a new tool for using neutron diffraction to study the structures of crystals and liquids under high pressures and temperatures.

Journal Articles

Recent progress on solution chemistry of actinides studied by time-resolved laser-induced fluorescence spectroscopy

Kimura, Takaumi; Kirishima, Akira*; Arisaka, Makoto

Kidorui, (47), p.43 - 56, 2005/11

no abstracts in English

Journal Articles

Synthesis of Al$$_{x}$$Ga$$_{1-x}$$N and InN crystals under high pressures

Saito, Hiroyuki; Utsumi, Wataru; Kaneko, Hiroshi*; Aoki, Katsutoshi

Proceedings of Joint 20th AIRAPT - 43rd EHPRG International Conference on High Pressure Science and Technology (CD-ROM), 4 Pages, 2005/06

We have performed synthesis studies of various III-V nitrides crystals, key materials for optoelectronic and high-power/frequency devices, using a cubic-anvil-type large volume high-pressure apparatus combined with in situ X-ray diffraction. Polly-crystallines of Al$$_{x}$$Ga$$_{1-x}$$N alloys covering a composition range of 0 $$leq$$ x $$leq$$ 1 were synthesized by a solid-phase reaction under high pressure. In situ X-ray diffraction profiles were measured to observe the alloying process, which started at around 800$$^{circ}$$C under 6.0 GPa. Single crystal of Al$$_{0.1}$$Ga$$_{0.9}$$N was also successfully obtained by slow cooling of its melt from 2400$$^{circ}$$C at 6.5 GPa. For InN, its phase diagram was determined under high P-T conditions up to 20GPa and 2000$$^{circ}$$C based on the in situ observations, which demonstrates that 19GPa and 1900$$^{circ}$$C are needed for its congruent melting.

Journal Articles

In-core ECP sensor designed for the IASCC experiments at JMTR

Tsukada, Takashi; Miwa, Yukio; Ugachi, Hirokazu; Matsui, Yoshinori; Itabashi, Yukio; Nagata, Nobuaki*; Dozaki, Koji*

Proceedings of International Conference on Water Chemistry of Nuclear Reactor Systems (CD-ROM), 5 Pages, 2004/10

IASCC initiation and propagation tests will be performed on the per-irradiated specimen in the Japan Materials Testing Reactor (JMTR). Since in core, the radiolysis of water causes a generation of various kind of radical species and some oxidizing species such as hydrogen peroxide, the water chemistry in irradiation capsules must be assessed by measurements of the electrochemical corrosion potential (ECP). For the in-core measurement of ECP in JMTR, we fabricated and tested the Fe/Fe$$_{3}$$O$$_{4}$$ type ECP sensor. After the fabrication, the function of each sensor was examined in high temperature water by out-of-core thermal cycling and high temperature holding tests.

Journal Articles

Synthesis of Al$$_{x}$$Ga$$_{1-x}$$N alloy by solid-phase reaction under high pressure

Saito, Hiroyuki; Utsumi, Wataru; Kaneko, Hiroshi*; Aoki, Katsutoshi

Japanese Journal of Applied Physics, Part 2, 43(7B), p.L981 - L983, 2004/07

 Times Cited Count:4 Percentile:78.82(Physics, Applied)

Bulk specimens of Al$$_{x}$$Ga$$_{1-x}$$N alloys covering a composition range of 0$$leq$$${it x}$$$leq$$1 were synthesized by a solid-phase reaction under high pressure. ${it In situ}$ X-ray diffraction profiles were measured to observe the alloying process, which began at around 800$$^{circ}$$C under 6.0 GPa. SEM observation and X-ray analysis of the recovered specimen indicated a uniform distribution of Al and Ga and continuous variations of the lattice constants against the composition, which implies that a solid solution of AlN and GaN is formed regardless of atomic composition.

Journal Articles

Modification of cooling water system to high pressure in PBEF (Particle Beam Engineering test Facility)

Dairaku, Masayuki; Ezato, Koichiro; Suzuki, Satoshi; Akiba, Masato; Imai, Tsuyoshi

KEK Proceedings 2003-16 (CD-ROM), 4 Pages, 2004/02

no abstracts in English

Journal Articles

Instrumental development for spectroscopic speciation of f-elements in hydrothermal solutions; Luminescence properties of lanthanide(III) ions

Kimura, Takaumi; Nagaishi, Ryuji; Arisaka, Makoto*; Ozaki, Takuo; Yoshida, Zenko

Radiochimica Acta, 90(9-11), p.715 - 719, 2002/11

 Times Cited Count:15 Percentile:29.36(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

The State and trend of IASCC study

Tsukada, Takashi

Nippon Yosetsu Kyokai "Genshiryoku Kozo Kiki No Zairyo, Sekkei, Seko, Kensa Ni Kansuru Koshukai" Tekisuto, 40 Pages, 2002/00

no abstracts in English

Journal Articles

Aging degradation of light water reactor materials; Reactor internal and pressure vessel materials

Tsukada, Takashi; Ebine, Noriya

Nippon AEM Gakkai-Shi, 9(2), p.171 - 177, 2001/06

no abstracts in English

JAEA Reports

Development of quick-responce area-averaged void fraction meter

Watanabe, Hironori; Iguchi, Tadashi; Kimura, Mamoru; Anoda, Yoshinari

JAERI-Research 2000-043, 77 Pages, 2000/11


no abstracts in English

JAEA Reports


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JNC-TY6400 2000-013, 102 Pages, 2000/02



62 (Records 1-20 displayed on this page)