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Journal Articles

Oxygen potential of neodymium-doped U $_{0.817}$ Pu $_{0.180}$ Am $_{0.003}$ O $_{2 pm x}$ uranium-plutonium-americium mixed oxides at 1573, 1773, and 1873 K

Vauchy, R.; Sunaoshi, Takeo*; Hirooka, Shun; Nakamichi, Shinya; Murakami, Tatsutoshi; Kato, Masato

Journal of Nuclear Materials, 580, p.154416_1 - 154416_11, 2023/07

https://doi.org/10.1016/j.jnucmat.2023.154416

Times Cited Count：4 Percentile：98.08(Materials Science, Multidisciplinary)

Journal Articles

Oxygen potential, oxygen diffusion, and defect equilibria in UO $_{2 pm x}$

Watanabe, Masashi; Kato, Masato

Frontiers in Nuclear Engineering (Internet), 1, p.1082324_1 - 1082324_9, 2023/01

https://doi.org/10.3389/fnuen.2022.1082324

Since the oxygen potential and the oxygen coefficient of UO $_{2}$ have a significant impact on fuel performance, many experimental data have been obtained. However, experimental data of the oxygen potential and the oxygen diffusion coefficient in the high temperature region above 1673 K are very limited. In the present study, we aimed to obtain these data and analyze them by defect chemistry. The oxygen potentials and the oxygen chemical diffusion coefficient of UO $_{2}$ were measured by the gas equilibrium method in the near stoichiometric region at temperatures ranging from 1673 to 1873 K. A data set of oxygen potentials was made together with literature data and analyzed by defect chemistry. The oxygen potential of UO $_{2}$ was determined as a function of O/U ratio and temperature, and an equation representing the relationship was derived. The oxygen chemical diffusion coefficient values obtained in this study were reasonably close to the literature values. The oxygen partial pressure dependence of the oxygen chemical diffusion coefficients was predicted from the evaluated results of the oxygen potential data, but no clear dependence was observed.

Journal Articles

Oxygen potential measurement of (U,Pu,Am)O $_{2 pm x}$ and (U,Pu,Am,Np)O $_{2 pm x}$

Hirooka, Shun; Matsumoto, Taku; Kato, Masato; Sunaoshi, Takeo*; Uno, Hiroki*; Yamada, Tadahisa*

Journal of Nuclear Materials, 542, p.152424_1 - 152424_9, 2020/12

https://doi.org/10.1016/j.jnucmat.2020.152424

Times Cited Count：6 Percentile：60.71(Materials Science, Multidisciplinary)

The measurement of oxygen potential was conducted at 1,673, 1,773, and 1,873 K for (U $_{0.623}$ Pu $_{0.350}$ Am $_{0.027}$ )O $_{2}$ and at 1,873 and 1,923 K for (U $_{0.553}$ Pu $_{0.285}$ Am $_{0.015}$ Np $_{0.147}$ )O $_{2}$ by using a thermo-gravimeter and an oxygen sensor. Am inclusion in terms of substituting the U significantly increased the oxygen potential. Similarly, the inclusion of Np as a substitute for U increased the oxygen potential; however, the effect was not as large as that with the Pu or Am addition at the same rate. The results were analyzed via defect chemistry and certain defect formations were suggested in the reducing region and the near-stoichiometric region by plotting the relationship between PO $_{2}$ and the deviation from the stoichiometry. The equilibrium constants of the defect reactions were arranged to reproduce the experiment such that Am/Np contents were included in the entropy with coefficients fitting the experimental data.

Journal Articles

Tuning strain-induced -to- martensitic transformation of biomedical Co-Cr-Mo alloys by introducing parent phase lattice defects

Mori, Manami*; Yamanaka, Kenta*; Sato, Shigeo*; Tsubaki, Shinki*; Sato, Kozue*; Kumagai, Masayoshi*; Imafuku, Muneyuki*; Shobu, Takahisa; Chiba, Akihiko*

Journal of the Mechanical Behavior of Biomedical Materials, 90, p.523 - 529, 2019/02

https://doi.org/10.1016/j.jmbbm.2018.10.038

Times Cited Count：19 Percentile：71.16(Engineering, Biomedical)

Journal Articles

Recent studies for structural integrity evaluation and defect inspection of J-PARC spallation neutron source target vessel

Wakui, Takashi; Wakai, Eiichi; Naoe, Takashi; Shintaku, Yohei*; Li, T.*; Murakami, Kazuya*; Kanomata, Kenichi*; Kogawa, Hiroyuki; Haga, Katsuhiro; Takada, Hiroshi; et al.

Journal of Nuclear Materials, 506, p.3 - 11, 2018/08

https://doi.org/10.1016/j.jnucmat.2018.02.030

Times Cited Count：3 Percentile：30.05(Materials Science, Multidisciplinary)

The mercury target vessel is designed as multi-walled structure with thin wall (min. 3 mm), and assembled by welding. In order to estimate the structural integrity of the vessel, it is important to measure the defects in welding accurately. For nondestructive tests of the welding, radiographic testing is applicable but it is difficult to detect for some defect shapes. Therefore it is effective to do ultrasonic testing together with it. Because ultrasonic methods prescribed in JIS inspect on the plate with more than 6 mm in thickness, these methods couldn't be applied as the inspection on the vessel with thin walls. In order to develop effective method, we carried out measurements using some testing method on samples with small defect whose size is specified. In the case of the latest phased array method, measured value agreed with actual size. It was found that this method was applicable to detect defects in the thin-walled structure for which accurate inspection was difficult so far.

Journal Articles

Infrared spectroscopic study of OH defects in monazite

Abe, Takeyasu; Kuribayashi, Takahiro*; Nakamura, Michihiko*

European Journal of Mineralogy, 29(6), p.949 - 957, 2017/12

https://doi.org/10.1127/ejm/2017/0029-2663

Times Cited Count：2 Percentile：6.21(Mineralogy)

Polarised infrared spectra of synthetic single crystals and radiation-damaged natural samples were collected to examine hydroxyl incorporation in monazite. The IR spectra of pure synthetic monazite contain two OH stretching bands at 3163 and 3335 cm $^{-1}$ with contrasting bandwidths of 40 and 90 cm $^{-1}$ , respectively. The two OH bands show strong pleochroism and dominant infrared absorption in the Y direction. The IR spectra of natural monazite contains a weak pleochroic OH band centered around 3400 cm $^{-1}$ with a bandwidth of more than 200 cm $^{-1}$ . During step-heating experiments, this broad OH band split into several bands, and these bands differ from those observed in the spectra of synthetic samples. The OH stretching signals in the spectra of both natural and synthetic samples disappeared after heating at 1000 $^{circ}$ C. Based on these results, OH defects in natural monazite arise because of secondary hydration facilitated by radiation damage, as in the case of natural zircon and xenotime.

Journal Articles

Defect chemistry and basic properties of non-stoichiometric PuO $_{2}$

Kato, Masato; Nakamura, Hiroki; Watanabe, Masashi; Matsumoto, Taku; Machida, Masahiko

Defect and Diffusion Forum, 375, p.57 - 70, 2017/05

http://doi.org/10.4028/www.scientific.net/DDF.375.57

The basic properties of PuO $_{2-x}$ were reviewed, and the equilibrium defects in PuO $_{2-x}$ were evaluated from the experimental data of the oxygen potential and electrical conductivity as well as the Ab-initio calculation results. Consistency among various properties was confirmed, and the mechanistic models for thermal property representations were derived.

Journal Articles

Defect engineering in silicon carbide; Single photon sources, quantum sensors and RF emitters

Kraus, H.; Simin, D.*; Fuchs, F.*; Onoda, Shinobu; Makino, Takahiro; Dyakonov, V.*; Oshima, Takeshi

Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.176 - 179, 2015/11

Journal Articles

Diffusion of tritium in intermetallic compound -LiAl; Relation to the defect structure

Sugai, Hiroyuki

Solid State Ionics, 177(39-40), p.3507 - 3512, 2007/01

https://doi.org/10.1016/j.ssi.2006.10.012

The diffusion coefficient and its activation energy (116.3 11.7 kJ/mol) of tritium in an intermetallic compound -LiAl are determined at temperatures from 700 to 848 K. Though the present result for the diffusion coefficient is almost the same as that reported previously, the present result for the activation energy turns out nearly twice of that (64.9 3.8 kJ/mol). The present result for the activation energy is consistent with the systematics that an increase of lithium concentration in Al-Li systems increases the activation energy, but the previous result is not. Furthermore, a consideration of the crystal structure and defect structure suggests that tritium diffuses and is impeded by the attractive interaction with lithium atom at lithium sublattices.

Journal Articles

Diffusion of tritium in intermetallic compound -LiAl; Relation to the defect structure

Sugai, Hiroyuki

Solid State Ionics, 177(39-40), p.3507 - 3512, 2007/01

https://doi.org/10.1016/j.ssi.2006.10.012

Times Cited Count：3 Percentile：17.87(Chemistry, Physical)

The diffusion coefficients and its activation energy (103.79.5 kJ/mol) for tritium in intermetallic compound -LiAl are determined at temperatures from 699 to 886 K. Though the present result for the diffusion coefficient is almost the same as that reported earlier, the activation energy turns out nearly twice of that (64.93.8 kJ/mol) reported earlier. On the basis of the crystal structure and defect structure, the large activation energy of this study suggest that tritium diffuses interstitially and is impeded by an attractive interaction with lithium atoms in lithium sublattices.

Journal Articles

Oxygen potential and defect structure of oxygen-excess pyrochlore Ce $_{2}$ Zr $_{2}$ O $_{7+x}$

Otobe, Haruyoshi; Nakamura, Akio; Yamashita, Toshiyuki; Minato, Kazuo

Journal of Physics and Chemistry of Solids, 66(2-4), p.329 - 334, 2005/02

https://doi.org/10.1016/j.jpcs.2004.07.015

Times Cited Count：23 Percentile：65.92(Chemistry, Multidisciplinary)

Pyrochlore-type (P-type) zirconias have been attracting significant research interest as disposable forms of high-level radioactive waste. In this work, we have clarified the oxygen potentials (g(O $_{2}$ )) vs. oxygen nonstoichiometry (x) and temperature relations of P-type Ce $_{2}$ Zr $_{2}$ O $_{7+x}$ by the emf method and determined the lattice parameters (a0) with respect to x by XRD method.

Journal Articles

FT-IR study on interaction of irradiated deuteron with defects in Li $_{2}$ O

Tanigawa, Hisashi; Tanaka, Satoru*; Enoeda, Mikio; Akiba, Masato

Journal of Nuclear Materials, 329-333(2), p.1291 - 1294, 2004/08

https://doi.org/10.1016/j.jnucmat.2004.04.228

Times Cited Count：4 Percentile：29.26(Materials Science, Multidisciplinary)

In order to elucidate the interaction of hydrogen isotopes with irradiation defects, infrared absorption spectroscopy was conducted for a single crystal of Li $_{2}$ O. Using FT-IR, O-D stretching vibration from the bulk Li $_{2}$ O was observed under deutron irradiation. Under and after the irradiation, several peaks were observed in the O-D stretching vibration region and these peaks had different dependence on conditions of the irradiation. From the observed behaviour of the peaks, it was suggested that most of the irradiated deutron existed in Li $_{2}$ O without O-D bonding because of interaction with the defects.

Journal Articles

Hydrogen migration in electron irradiated Pd based dilute alloys around the 50 K anomaly

Yamakawa, Koji*; Chimi, Yasuhiro; Ishikawa, Norito; Iwase, Akihiro*

Journal of Alloys and Compounds, 370(1-2), p.211 - 216, 2004/05

https://doi.org/10.1016/j.jallcom.2003.09.037

Times Cited Count：1 Percentile：12.44(Chemistry, Physical)

The migration of hydrogen in Pd-1at.% Fe-H and Pd-1at.% Ag-H alloys is investigated by electrical resistivity measurement around 50 K. The disordered hydrogen atoms are introduced by electron irradiation with 0.5 MeV electrons below 15 K. The disordered atoms order by migration of hydrogen atoms during the heating-up of the specimens. The recovery curves of electrical resistivity have two sub-stages for electron irradiated specimens and one stage for fast cooled specimens. The migration energy of hydrogen is obtained from the kinetic analysis of the resistivity change due to the ordering, using the cross-cut method for the electron irradiated specimen and fast cooled specimen. The obtained value of the migration energy for the low temperature stage is smaller than that for the high temperature stage. The value for the high temperature stage is similar to the energy for the case of fast cooling. The difference between the hydrogen atoms disordered by irradiation and that by fast cooling is discussed for Pd based alloys.

Journal Articles

Defect production and radiation annealing in platinum irradiated with high-energy heavy ions

Chimi, Yasuhiro; Iwase, Akihiro; Iwata, Tadao*

Nuclear Instruments and Methods in Physics Research B, 209, p.159 - 164, 2003/08

https://doi.org/10.1016/S0168-583X(02)02009-8

Times Cited Count：2 Percentile：21.31(Instruments & Instrumentation)

Accumulation of defects during energetic ion irradiation below 10K in platinum thin films is studied by electrical resistivity measurements. Experimental results are analyzed by using a model which describes the production and selective radiation annealing of defects. For high-energy (100MeV) heavy ion irradiations, radiation annealing process due to electronic excitation is found mainly at the initial stage of irradiation. From the defect accumulation curve and defect recovery spectra, the effective temperature corresponding to the lattice agitation induced by electronic excitation is estimated.

Journal Articles

Irradiation effects on thermal expansion of SiC/SiC composite materials

Ishihara, Masahiro; Baba, Shinichi; Hoshiya, Taiji; Shikama, Tatsuo*

Journal of Nuclear Materials, 307-311(Part2), p.1168 - 1172, 2002/12

https://doi.org/10.1016/S0022-3115(02)01056-5

Times Cited Count：5 Percentile：34.58(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Irradiation effects on MgB $_{2}$ bulk samples and formation of columner defects on high-Tc supercoductor

Okayasu, Satoru; Sasase, Masato; Hojo, Kiichi; Chimi, Yasuhiro; Iwase, Akihiro; Ikeda, Hiroshi*; Yoshizaki, Ryozo*; Kambara, Tadashi*; Sato, H.*; Hamatani, Yutaro*; et al.

Physica C, 382(1), p.104 - 107, 2002/10

https://doi.org/10.1016/S0921-4534(02)01206-6

Times Cited Count：28 Percentile：75.41(Physics, Applied)

no abstracts in English

Journal Articles