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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

Analysis of maximum voltage transient of JT-60SA toroidal field coils in case of fast discharge

Novello, L.*; Cara, P.*; Coletti, A.*; Gaio, E.*; Maistrello, A.*; Matsukawa, Makoto; Philipps, G.*; Tomarchio, V.*; Yamauchi, Kunihito

IEEE Transactions on Applied Superconductivity, 26(2), p.4700507_1 - 4700507_7, 2016/03

https://doi.org/10.1109/TASC.2016.2521321

Times Cited Count：7 Percentile：39.28(Engineering, Electrical & Electronic)

Journal Articles

Interactions between anionic complex species of actinides and negatively charged mineral surfaces

Yamaguchi, Tetsuji; Nakayama, Shinichi; Yoshida, Takahiro

Radiochimica Acta, 92(9-11), p.677 - 682, 2004/12

https://doi.org/10.1524/ract.92.9.677.55009

Times Cited Count：6 Percentile：40.51(Chemistry, Inorganic & Nuclear)

Adsorption of actinides onto negatively charged mineral surfaces was investigated under conditions that actinides were predominantly present as anionic complex species: Th(CO $_{3}$ ) $_{5}$ $^{6-}$ , Am(CO $_{3}$ ) $_{3}$ $^{3-}$ , Np(CO $_{3}$ ) $_{2}$ (OH) $_{2}$ $^{2-}$ , UO $_{2}$ (OH) $_{4}$ $^{2-}$ , NpO $_{2}$ (OH) $_{2}$ $^{-}$ , Sn(OH) $_{5}$ $^{-}$ and Pb(OH) $_{3}$ $^{-}$ . These solutions were left to stand for 2 days to confirm these elements stable in dissolved state, and then contacted with minerals, -Al $_{2}$ O $_{3}$ or SiO $_{2}$ (AEROSIL, specific surface area: 10 $^{5}$ m $^{2}$ kg $^{-1}$ ). After desired contact time for 2 days or more, the solutions were ultra-filtered through 10 $^{4}$ -molecular-weight cutoff Millipore filters and the concentrations of the elements in the filtrates were determined. The sorption experiments were performed at room temperature (25 $^{circ}$ C) under Ar. Distribution coefficients decreased with the increasing pH and with increasing carbonate concentrations. The monotonous decrease in the distribution coefficients in the investigated pH range suggests that the electrostatic repulsion was a dominant interaction between anionic complex species of actinides and negatively charged mineral surfaces.

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：12.39(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

Structure evolution and corresponding electrical properties in weakly bound Co-C60 mixture

Sakai, Seiji; Naramoto, Hiroshi; Xu, Y.; Priyanto, T. H.; Lavrentiev, V.; Narumi, Kazumasa

Materials Research Society Symposium Proceedings, Vol.788, p.L11.49.1 - L11.49.6, 2004/00

https://doi.org/10.1557/PROC-788-L11.49

Mixture films between cobalt and C $_{60}$ (CoxC $_{60}$ , x = 0.5-700) were prepared by co-evaporation technique under UHV conditions. The composition-dependent features of dilatation and downshift of Raman peak suggest that the mixtures are composed of cobalt particles and a C $_{60}$ -based phase in which certain number of cobalt atoms are coordinated with C $_{60}$ molecules. It is deduced that the equilibrated number of cobalt atoms in the C $_{60}$ -based phase is 4 atoms per C $_{60}$ molecule and in which an electron transfer occurs from a cobalt atom to a C $_{60}$ molecule. The evaluation of their temperature dependences reveals that: (1) The mixtures with x 4 are thermally activated-type, and their conductive nature can be attributed to the C $_{60}$ -based phase. Further (2) the mixtures between 4 x 60 are also thermally activated, however, the electron hopping process between the isolated cobalt particles is supposed to be operative (variable-range-hopping). And (3) in the mixtures with x 60 which corresponds to a percolation threshold for cobalt particles, the system changes into metallic conduction.

Journal Articles

Study of residual stress for c/c composite by neutron scattering

Baba, Shinichi; Ishihara, Masahiro; Minakawa, Nobuaki; Suzuki, Junichi

Proceedings of International Conference on Advanced Technology in Experimental Mechanics 2003 (ATEM '03) (CD-ROM), 4 Pages, 2003/09

The aim of the present paper is to clarify the residual stress occuring in the c/c composite to improve the manufacturing process. The residual stress was measured by a neutron diffraction method using the RESA in the JRR-3M of JAERI in this study. As a results of the residual stress measurment, it was found that the residual stress of the ring type c/c composite is the comporessive stress, and the macroscopic residual strain/stress is absorbed mainly microstructural change such as pore shape change.

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：21.20(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

Structure and electrical characterization of VN $_{x}$ prepared by reactive pulsed laser deposition

Dai, Z.*; Miyashita, Atsumi; Yamamoto, Shunya; Narumi, Kazumasa; Naramoto, Hiroshi

Journal of Physics; Condensed Matter, 11(3), p.733 - 740, 1999/00

https://doi.org/10.1088/0953-8984/11/3/012

Times Cited Count：2 Percentile：16.44(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Change in electrical resistivity of nuclear graphite and carbon materials during low cycle fatigue

Eto, Motokuni; Konishi, Takashi*

Tanso, (186), p.30 - 35, 1999/00

https://doi.org/10.7209/tanso.1999.30

no abstracts in English

Journal Articles

Electrical insulation design and monitoring of the ITER magnet system

Yoshida, Kiyoshi; ; R.Gallix*; S.Sadakov*; R.Vieira*; J.Stoner*; C.Sborchia*

Fusion Technology 1998, 1, p.807 - 810, 1998/00

no abstracts in English

Journal Articles

Experimental results at pulse test facility(PTF) of butt joint used in ITER CS model coil outer module

Koizumi, Norikiyo; ; Nunoya, Yoshihiko; Takahashi, Yoshikazu; Ando, Toshinari; Tsuji, Hiroshi; P.Michael*; A.Zhukovsky*; J.D.Hale*; R.Lations*; et al.

Proc. of Int. Cryogenic Engineering Conf. (ICEC17), p.523 - 526, 1998/00

no abstracts in English

Journal Articles