Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: K. Goto x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

57Fe Mössbauer spectroscopy was applied to the crystallization study of IR-transmitting calcium aluminate glass, 60CaO·32Al2O3·5Fe2O3·3Eu2O3, in which Fe(III) atoms occupy tetrahedral Al(III) sites. Heat treatment of calcium aluminate glass below and above the crystallization temperature causes the formation of mayenite, 12CaO·7Al2O3, and brownmillerite, 4CaO·Al2O3·Fe2O3, respectively. Mössbauer spectra of the glass ceramics indicate that Fe(III) atoms substitute Al(III) sites, having less covalent Fe(III)-O bonds and more distorted Fe(III)O4 tetrahedra than they do in the original glass. DTA revealed that crystallization of calcium aluminate glass is triggered by simultaneous cleavage of Ca-O and Al-O bonds.

Restricted access

Abstract  

The primary fragment mass-yield distribution for the asymmetric fission path in heavy nuclei, 233Pa, 239Np, 245Am and 249Bk at the excitation energy of ~20 MeV are experimentally constructed based on the intensities of total kinetic energies for individual mass splits. The results revealed an interesting phenomenon: in all the studied fissioning systems, the inner wings of the mass-yield distributions in the asymmetric fission path appear along the same mass-wall of A = 130 fragment mass. The asymmetric mass-yield distribution indicates the strong effect of structural shells in fragments on the final mass division process of the asymmetric fission path.

Restricted access

Abstract  

In this study, using neutron activation analysis with multi-parameter coincidence method which was developed at Japan Atomic Energy Agency (JAEA), a non-destructive, ultra-high sensitive multi-elemental determination has been realized. The multi-parameter coincidence method is carried out with an array of 19 germanium detectors, GEMINI-II. Using this system, very weak γ-rays emitted from trace amounts of elements can be detected. The iridium concentration has been determined by means of neutron activation analysis with multi-parameter coincidence method for Cuban sediment samples across the K/T boundary strata.

Restricted access

Abstract  

Low-energy photons produced by the Compton scattering from hydrogen increase the background in the lower-energy region of the gamma-ray spectrum. This results in an increase in the detection limit for trace elements. In multiple photon detection prompt gamma-ray analysis (MPGA), only those elements that simultaneously emit two or more prompt gamma-rays, which have cascade relation and are emitted within a short interval, can be measured. Therefore, the influence of hydrogen can be reduced. In this study, standard polymer and food samples are measured. The hydrogen background is reduced in MPGA.

Restricted access

Abstract  

A neutron beam line for multiple prompt gamma-ray analysis was constructed at the Japan Atomic Energy Agency. A detector system for the MPGA was constructed at the C2-3-2 beam line in January 2005. It comprised eight (upgraded in March 2007) clover Ge detectors with a BGO Compton suppressor. High efficiency detector system provides an advantage in terms of the detection limit of MPGA when compared to the result of PGA. The supermirror neutron bender was improved and a supermirror neutron guide was installed upstream of the sample position.

Restricted access

Abstract  

An isothermal chromatographic apparatus was developed for the on-line experiments of super heavy elements in gas phase. As a model of Rf, we investigated the gas phase chemistry of Zr and Hf chlorides. The dependence of the reaction efficiency on temperature was examined. It was found that about 80% of Zr and Hf reacted with chlorinating gas at 900 °C. Adsorption enthalpies of Zr and Hf chlorides were deduced from the isothermal chromatograph by the Monte Carlo simulation based on the microscopic model proposed by Zvára.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Toyoshima, K. Tsukada, H. Haba, M. Asai, S. Goto, K. Akiyama, I. Nishinaka, S. Ichikawa, Y. Nagame, and A. Shinohara

Abstract  

The anion exchange behavior of 255No produced by the 248Cm(12C,5n) reaction has been investigated in 11.5M HCl, 4M HCl and 8M HNO3 to deduce the behavior of 'primordial 257No' produced via 248Cm(18O,5n)261Rf 257No before anion exchange separation in the 261Rf experiment. It was found that 255No is mostly eluted from the anion exchange column with these solutions. The contribution of 'primordial 257No' to the -decay events of 261Rf in the 261Rf experiment was evaluated based on the present results.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Maruyama, D. Kaji, T. Kaneko, S. Goto, K. Tsukada, H. Haba, M. Asai, S. Ichikawa, Y. Nagame, and H. Kudo

Abstract  

Rapid chemical separation of berkelium is essential in order to measure the unknown isotope 252Bk. An anion exchange system of mineral acid and methanol was examined. An elution curve of Bk was obtained using 250Bk produced by the 248Cm+18O system and the 251Bk activity could be measured in the preliminary experiments. The whole chemical separation was completed within 30 minutes.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Goto, D. Kaji, I. Nishinaka, Y. Nagame, S. Ichikawa, K. Tsukada, M. Asai, H. Haba, S. Mitsuoka, K. Nishio, M. Sakama, Y. Zhao, K. Sueki, K. Tanikawa, K. Takamiya, H. Kudo, and H. Nakahara

Abstract  

To study the correlation between fragment mass distributions and shell structures of fission fragments, fragment mass and energy distributions in proton-induced fission of 232Th and uranium isotopes, 233,235,238U, were precisely measured using a double-TOF method. It was found that the lighter side of the heavier wing of asymmetric mass distributions shifts to larger fragment mass number corresponding to the N/Z value of the fissioning nucleus. The results are explained qualitatively by the change of the most probable mass number of fission fragments of Z = 50 proton-shell.

Restricted access