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Journal Articles

Study on the relation between the crystal structure and thermal stability of FeUO$$_{4}$$ and CrUO$$_{4}$$

Akiyama, Daisuke*; Kusaka, Ryoji; Kumagai, Yuta; Nakada, Masami; Watanabe, Masayuki; Okamoto, Yoshihiro; Nagai, Takayuki; Sato, Nobuaki*; Kirishima, Akira*

Journal of Nuclear Materials, 568, p.153847_1 - 153847_10, 2022/09

FeUO$$_{4}$$, CrUO$$_{4}$$, and Fe$$_{x}$$Cr$$_{1-x}$$UO$$_{4}$$ are monouranates containing pentavalent U. Even though these compounds have similar crystal structures, their formation conditions and thermal stability are significantly different. To determine the factors causing the difference in thermal stability between FeUO$$_{4}$$ and CrUO$$_{4}$$, their crystal structures were evaluated in detail. A Raman band was observed at 700 cm$$^{-1}$$ in all the samples. This Raman band was derived from the stretching vibration of the O-U-O axis band, indicating that Fe$$_{x}$$Cr$$_{1-x}$$UO$$_{4}$$ was composed of a uranyl-like structure in its lattice regardless of its "x"' value. M$"o$ssbauer measurements indicated that the Fe in FeUO$$_{4}$$ and Fe$$_{x}$$Cr$$_{1-x}$$UO$$_{4}$$ were trivalent. Furthermore, Fe$$_{x}$$Cr$$_{1-x}$$UO$$_{4}$$ lost its symmetry around Fe$$^{mathrm{III}}$$ with increasing electron densities around Fe$$^{mathrm{III}}$$, as the abundance of Cr increased. These results suggested no significant structural differences between FeUO$$_{4}$$ and CrUO$$_{4}$$. Thermogravimetric measurements for UO$$_{2}$$, FeUO$$_{4}$$, and CrUO$$_{4}$$ showed that the temperature at which FeUO$$_{4}$$ decomposed under an oxidizing condition (approximately 800 $$^{circ}$$C) was significantly lower than the temperature at which the decomposition of CrUO$$_{4}$$ started (approximately 1250 $$^{circ}$$C). Based on these results, we concluded that the decomposition of FeUO$$_{4}$$ was triggered by an ``in-crystal'' redox reaction, i.e., Fe$$^{mathrm{III}}$$ $${+}$$ U$$^{mathrm{V}}$$ $$rightarrow$$ Fe$$^{mathrm{II}}$$ $${+}$$ U$$^{mathrm{VI}}$$, which would not occur in the CrUO$$_{4}$$ lattice because Cr$$^{mathrm{III}}$$ could never be reduced under the investigated condition. Finally, the existence of Cr$$^{mathrm{III}}$$ in FexCr$$_{1-x}$$UO$$_{4}$$ effectively suppressed the decomposition of the Fe$$_{x}$$Cr$$_{1-x}$$UO$$_{4}$$ crystal, even at a very low Cr content.

Journal Articles

Atomistic modeling of hardening in spinodally-decomposed Fe-Cr binary alloys

Suzudo, Tomoaki; Takamizawa, Hisashi; Nishiyama, Yutaka; Caro, A.*; Toyama, Takeshi*; Nagai, Yasuyoshi*

Journal of Nuclear Materials, 540, p.152306_1 - 152306_10, 2020/11

 Times Cited Count:5 Percentile:70.64(Materials Science, Multidisciplinary)

Spinodal decomposition in thermally aged Fe-Cr alloys leads to significant hardening, which is the direct cause of the so-called 475C-embrittlement. To illustrate how spinodal decomposition induces hardening by atomistic interactions, we conducted a series of numerical simulations as well as reference experiments. The numerical results indicated that the hardness scales linearly with the short-range order (SRO) parameter, while the experimental result reproduced this relationship within statistical error. Both seemingly suggest that neighboring Cr-Cr atomic pairs essentially cause hardening, because SRO is by definition uniquely dependent on the appearance probability of such pairs. A further numerical investigation supported this notion, as it suggests that the dominant cause of hardening is the pinning effect of dislocations passing over such Cr-Cr pairs.

Journal Articles

Difference between Cr and Ni K-edge XANES spectra of rust layers formed on Fe-based binary alloys exposed to Cl-rich environment

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Materials Transactions, 46(1), p.136 - 139, 2005/01

 Times Cited Count:2 Percentile:26.67(Materials Science, Multidisciplinary)

The rust layer formed on weathering steel possesses a strong protective ability against corrosives in an atmosphere. This ability is related to the structure of the rust layer. The difference in the protective ability of a rust layer in a Cl-rich environment between conventional weathering steel containing Cr and advanced weathering steel containing Ni is believed to be caused by the differences in local structural and chemical properties between alloying elements, Cr and Ni, in the rust layer. In order to examine the effect of these alloying elements on the structure of the rust layer formed on steel in a Cl-rich environment, we have performed Cr and Ni K-edge X-ray absorption near-edge structure (XANES) measurements for the rust layer of Fe-Cr and Fe-Ni binary alloys exposed to a Cl-rich atmosphere using synchrotron radiation. The results of the Cr K-edge XANES measurements for the rust layer of Fe-Cr binary alloys show that the atomic geometry around Cr depends on the concentration of Cr. Therefore, it is expected that the local structure around Cr in the rust layer is unstable. On the other hand, from the results of the Ni K-edge XANES measurements for the rust layer of Fe-Ni binary alloys, Ni is considered to be positioned at a specific site in the crystal structure of a constituent of the rust layer, such as akagan$'e$ite or magnetite. As a consequence, Ni negligibly interacts with Cl$$^{-}$$ ions in the rust layer.

Journal Articles

Corrosion-erosion test of SS316 in flowing Pb-Bi

Kikuchi, Kenji; Kurata, Yuji; Saito, Shigeru; Futakawa, Masatoshi; Sasa, Toshinobu; Oigawa, Hiroyuki; Wakai, Eiichi; Miura, Kuniaki*

Journal of Nuclear Materials, 318(1-3), p.348 - 354, 2003/05

 Times Cited Count:27 Percentile:85.52(Materials Science, Multidisciplinary)

Corrosion test of austenitic stainless tube was done under the flowing Pb-Bi condition during 3000 hrs at 450$$^{circ}$$C. Specimen is 316SS produced as a tubing form with 13.8 mm outer diameter, 2 mm thickness and 40 cm length. During the operation, maximum temperature, temperature difference and flow velocity of Pb-Bi at the specimen were kept at 450$$^{circ}$$C, 50$$^{circ}$$C, and 1m/s, respectively. After the test, specimen and components of the loop were cut and examined by optical microscope, SEM, EDX, WDX and X-ray diffraction. Pb-Bi adhered on the surface of the specimen even after Pb-Bi was drained out to the storage tank from the circulating loop. Different results from a stagnant corrosion test were that the specimen surface became rough and the corrosion rate was maximally 0.1mm/3000hrs. And mass transfer from the high temperature to the lower temperature area was observed: crystals of Fe-Cr were found on the tube surface in low-temperature part. The size of crystal was 0.1 $$sim$$ 0.2 mm. The depositing crystal was ferrite grain and the chemical composition ratio (mass%) of Fe to Cr was 9:1.

Journal Articles

Microstructural evolution of Fe-Cr-W model alloys during Fe$$^{+}$$ ion irradiation

Wakai, Eiichi; Hishinuma, Akimichi; Abe, Hiroaki; Takaki, Seiichi*; Abiko, Kenji*

Materials Transactions, JIM, 41(9), p.1176 - 1179, 2000/09

no abstracts in English

Journal Articles

Damage structures and mechanical properties in high-purity Fe-9Cr alloy irradiated by neutrons

Wakai, Eiichi; Hishinuma, Akimichi; Usami, Koji; Kato, Yasushi*; Takaki, Seiichi*; Abiko, Kenji*

Materials Transactions, JIM, 41(9), p.1180 - 1183, 2000/09

no abstracts in English

Journal Articles

Stress measurement of sintered Fe-Cr/TiN composite material with X-ray and neutron diffraction methods

Takago, S.*; Sasaki, Toshihiko*; Minakawa, Nobuaki; Morii, Yukio; Hirose, Yukio*

Proceedings of 6th International Conference on Residual Stressess (ICRS-6), Vol.1, p.41 - 48, 2000/07

no abstracts in English

JAEA Reports

Post-lrradiation examination on Fe-15Cr-20Ni series model alloy irradiated by CMIR-2(1); Effect of defect sink and size of solute atom on radiation induced segregation(1)

; Yamagata, Ichiro; Donomae, Takako; Akasaka, Naoaki

JNC TN9400 2000-046, 24 Pages, 2000/02

JNC-TN9400-2000-046.pdf:1.1MB

lt is well known that solute atoms are segregated on surface, grain boundary, etc. and composition changed partially in irradiated austenitic stainless steel. For understanding radiation induced segregation (RIS), we adopt a Fe-15Cr-20Ni-x (x: Si, Mo) which is basically alloy system in PNC1520, and size of Si, Mo are different from matrix atoms to investigate RIS behaviors. The specimens were irradiated by "Joyo" fast reactor that irradiation condition is 3.5 $$times$$ 10$$^{26}$$ n/m$$^{2}$$ (E>0.1Mev) at 476$$^{circ}$$C. After irradiation, the specimen were observed and analyzed with EDS (Energy Dispersive X-ray Spectroscope) of 400kV TEM (Transmission Electron Microscope). The behavior of RIS depends on size of solute atoms of alloy. For example, oversized atoms are decreased and undersized atoms are increased in sink. RIS of voids are as same as or more than grain boundaries and smaller than precipitates. The void denuded zone was existed nearby G.B. in case of combinations between the grains from G.B.0ne of the reasons in this, the voids swepted by moving G.B. in radiation induced G.B. migration.

Journal Articles

Effects of neutron irradiation on tensile properties in high-purity Fe-(9-50)Cr and Fe-50Cr-xW alloys

Wakai, Eiichi; Hishinuma, Akimichi; Miwa, Yukio; Ouchi, Asao*; Isozaki, Seiichi*; Takaki, Seiichi*; Abiko, Kenji*

Materials Transactions, JIM, 41(1), p.136 - 140, 2000/01

no abstracts in English

Journal Articles

Phase transformation of high-purity Fe-50Cr-xW alloys during Fe$$^{+}$$ ion irradiation

Wakai, Eiichi; Hishinuma, Akimichi; Abe, Hiroaki; Miwa, Yukio; Takaki, Seiichi*; Abiko, Kenji*

Proc of Ultra-High-Purity Metallic-Base Materials (UHPM-98), p.35 - 45, 1998/00

no abstracts in English

Journal Articles

Effects of purity and Cr concentration on microstructural evolution in Fe-Cr alloys during electron irradiation

Wakai, Eiichi; Hishinuma, Akimichi; Kato, Yasushi*; *; *

Nihon Kinzoku Gakkai Koen Gaiyo, 1994 Shuki (Dai-115-Kai) Taikai, 0, p.488 - 494, 1994/00

no abstracts in English

Journal Articles

Crossover phenomenon in dynamical scaling of phase separation in Fe-Cr alloy

;

Physical Review Letters, 52(10), p.835 - 838, 1984/00

 Times Cited Count:136 Percentile:97.26(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Decomposition kinetics in iron-chromium alloys

;

Physica B; Condensed Matter, 120, p.392 - 396, 1983/00

no abstracts in English

Journal Articles

Neutron small-angle scattering study of the decomposition of an Fe-Cr alloy in the unstable state

;

Journal of the Physical Society of Japan, 51(2), p.347 - 348, 1982/00

 Times Cited Count:13 Percentile:79.77(Physics, Multidisciplinary)

no abstracts in English

JAEA Reports

Formation of Isolated Metal in a MatelicMelter for Vitrification of HLW

*; ; ; ; ; ;

JAERI-M 8574, 28 Pages, 1979/11

JAERI-M-8574.pdf:2.16MB

no abstracts in English

Oral presentation

Atomistic modeling of hardening in thermally-aged Fe-Cr binary alloys

Suzudo, Tomoaki; Nagai, Yasuyoshi*; Alfredo, C.*

no journal, , 

It is widely known that Fe-Cr binary alloys undergo spinodal decomposition when they are thermally aged, and that this microstructural evolution causes hardening and loss of ductility of the material. The present study is about the first attempt to tackle this problem by exploiting atomistic modeling techniques. We apply Monte Carlo simulation to creating spinodally-decomposed microstructure and molecular dynamics to simulating edge dislocations moving through this microstructure by imposing shearing deformation. We then measure the critical stress as a measure of hardness for many cases over the progress in spinodal decomposition, and succeed in reproducing an experimentally-discovered proportionality between the phase separation parameter and the hardening.

Oral presentation

Compatibility of Fe-Cr-Al alloys with liquid bismuth

Furukawa, Tomohiro; Takai, Toshihide; Watanabe, Shigeki*; Ishioka, Noriko*

no journal, , 

Authors have started the development of liquid bismuth target system for continuous production of therapeutic radionuclide astatine-211 as an application of liquid metal technology cultivated in above research and development, in recent years. Fe-Cr-Al alloy is one of the candidates of the target window in this system. In order to clarify the corrosion of the target window in pure liquid bismuth, the exposure test at elevated temperature was done for Fe-Cr-Al alloys and their references. The test was conducted under argon gas flow, i.e. saturated dissolved oxygen condition in theory. The temperature and exposure time were 500$$^{circ}$$C and 500 hours, respectively. Results of metallurgical examination after the exposure, it was concluded that the corrosion behavior was basically equivalent to that in lead-bismuth eutectic, which is the candidate coolant of heavy metal cooled fast reactors and accelerator driven systems.

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