Nakamura, Shoji; Shibahara, Yuji*; Endo, Shunsuke; Kimura, Atsushi
Journal of Nuclear Science and Technology, 58(10), p.1061 - 1070, 2021/10
In a well-thermalized neutron field, it is principally possible to drive a thermal-neutron capture cross-section without considering an epithermal neutron component. This was demonstrated by a neutron activation method using the graphite thermal column (TC-Pn) of the Kyoto University Research Reactor. First, in order to confirm that the graphite thermal column was a well-thermalized neutron field, neutron irradiation was performed with neutron flux monitors: Au, Co, Sc, Cu, and Mo. The TC-Pn was confirmed to be extremely thermalized on the basis of Westcott's convention, because the thermal-neutron flux component took a constant value regardless of the sensitivity of each flux monitor to epithermal neutrons. Next, as a demonstration, the thermal-neutron capture cross section of Ta(n,)Ta reaction was measured using the graphite thermal column, and then derived to be 20.50.4 barn, which supported the evaluated value of 20.40.3 barn. The Ta nuclide could be useful as a flux monitor that complements the sensitivity between Au and Mo monitors.
Nishi, Tsuyoshi; Takano, Masahide; Ito, Akinori; Akabori, Mitsuo; Minato, Kazuo; Kizaki, Minoru
JAERI-Tech 2005-051, 13 Pages, 2005/09
An apparatus has been developed to measure the thermal diffusivities of minor actinide (MA) compounds. By installing the laser flash apparatus in a glove box with highly purified inert gas atmosphere, the thermal diffusivities measurement of MA compounds of -decay nuclides was enabled. A new sample holder has been also developed to measure the thermal diffusivities of very small samples. The performance of this new apparatus was confirmed by measuring the thermal diffusivities of small samples of tantalum, nickel and cerium oxides. The thermal diffusivity values obtained in this work agreed well with the literature values and the values measured by a conventional thermal diffusivities measurement apparatus. Accordingly, this apparatus was found to be useful for thermal diffusivities measurement of MA compounds.
Li, J.-F.*; Kawai, Masayoshi*; Kikuchi, Kenji; Igarashi, Tadashi*; Kurishita, Hiroaki*; Watanabe, Ryuzo*; Kawasaki, Akira*
Journal of Nuclear Materials, 321(2-3), p.129 - 134, 2003/09
For the development of tantalum-clad tungsten targets for spallation neutron sources, the bonding strength of tantalum-tungsten interface was investigated by means of an easy-to-use and miniaturized small punch (SP) test, in which a punching load is vertically applied to the center of a jointed disk. Cracks initiated and propagated in the tungsten side for all the samples hot-isostatically pressed (HIPed) at temperatures from 1673 to 2073 K, whereas nocrack and debonding were observed in the interface, indicating that the jointed interface is strongly bonded. The re-crystallization of tungsten occurs and results in its strength reduction, consequently the crack-initiating load decreases with HIPing temperature. The finite element analysis of the measured SP testing results shows that the maximum bonding strength can exceed 1000 MPa. The present study shows that SP test is suitable for the strength evaluation of jointed tantalum-tungsten interfaces.
Kawai, Masayoshi*; Furusaka, Michihiro; Li, J.-F.*; Kawasaki, Akira*; Yamamura, Tsutomu*; Mehmood, M.*; Kurishita, Hiroaki*; Kikuchi, Kenji; Takenaka, Nobuyuki*; Kiyanagi, Yoshiaki*; et al.
Proceedings of ICANS-XVI, Volume 3, p.1087 - 1096, 2003/07
In order to establish the technique fabricating a thin target slab with a real size, thin tantalum-clad tungsten slab with a hole for a thermocouple was fabricated with the high-precision machinery techniques and the HIP'ing method. The ultrasonic diagnostic showed that tantalum and tungsten bond was perfect. The HIP optimum condition was certified by means of the small punch test as already reported. The electrolytic coating technique in a molten salt was developed to make a thinner tantalum cladding on a tungsten target with a complicated shape, in order to reduce radioactivity from tantalum in an irradiated target.
Kawai, Masayoshi*; Furusaka, Michihiro*; Kikuchi, Kenji; Kurishita, Hiroaki*; Watanabe, Ryuzo*; Li, J.*; Sugimoto, Katsuhisa*; Yamamura, Tsutomu*; Hiraoka, Yutaka*; Abe, Katsunori*; et al.
Journal of Nuclear Materials, 318, p.35 - 55, 2003/05
R&D works for MW class solid target composed of tungsten to produce pulsed intense neutron source has been made in order to construct a future scattering facility. Three methods were investigated to prevent corrosion of tungsten from water; those are hipping, brazing and electric coating in molten salt bath. Hipping condition was optimized to be 1500 degree C in the previous work: here small punch test shows highest load for crack initiation of hipped materials at the boundary of W/Ta. The basic techniques for the other two methods were developed. Erosion test showed that uncovered W is susceptible of flowing water velocity. At high velocity w is easy to be eroded. For solid target design slab type and rod type targets were studied. As long as the optimized neutron performance is concerned, 1MW solid target is better than mercury target.
Mehmood, M.*; Kawaguchi, Nobuaki*; Maekawa, Hideki*; Sato, Yuzuru*; Yamamura, Tsutomu*; Kawai, Masayoshi*; Kikuchi, Kenji
Materials Transactions, 44(2), p.259 - 267, 2003/02
Electrochemical study has been carried out on the electro-deposition of tantalum in LiF-NaF-CaF melt containing KTaF at 700C. This has been done for determining the mechanistic features for preparing electrolytic coating of tantalum on nickel and tungsten substrates. Electro-deposition of metallic tantalum occurs primarily by electro-reduction of Ta(V). Pure metallic tantalum without any entrapped salt is successfully deposited on tungsten by galvanostatic polarization at reasonably low current densities. An additional feature on nickel is the formation of an intermetallic compound at potential 0.25V nobler than that of pure tantalum as a result of underpotential deposition of tantalum. This intermetallic compound covers the surface within a short time followed by deposition of pure tantalum, although intermetallic compound keeps growing at the interface of pure tantalum deposit and the substrate as a result of diffusion.
*; *; *; *; *; Nishi, Masataka; Yoshida, Kiyoshi; Isono, Takaaki; Tsuji, Hiroshi
Teion Kogaku, 32(4), p.167 - 172, 1997/00
no abstracts in English
Shiwaku, Hideaki; Yoda, Yoshitaka*; Harami, Taikan; *; Ono, Hideo
JAERI-Research 94-032, 44 Pages, 1994/11
no abstracts in English
Inoue, Takashi; *; Ohara, Yoshihiro; Okumura, Yoshikazu; M.Bacal*; P.Berlemont*
Plasma Sources Sci. Technol., 1, p.75 - 81, 1992/00
no abstracts in English
Kaneya, Yusuke*; Asai, Masato; Sato, Tetsuya; Tomitsuka, Tomohiro; Tsukada, Kazuaki; Toyoshima, Atsushi; Mitsukai, Akina; Makii, Hiroyuki; Hirose, Kentaro; Osa, Akihiko; et al.
no journal, ,
To study the influence of the valence 7p electronic orbital on chemical properties of lawrencium, a measurement of the adsorption enthalpy of lawrencium was carried out. A new method using a surface ionization technique coupled to an on-line isotope separator was developed, which enabled one to measure temperature dependence of lawrencium surface adsorption on a metallic tantalum surface at high temperature up to 2800 K. The temperature dependences of adsorption of lawrencium as well as various lanthanide elements were investigated with this method, and the adsorption enthalpy of lawrencium was successfully extracted.