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  • Author or Editor: Y. Hatsukawa x
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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.

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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.

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Abstract  

Multiparameter coincidence g-ray spectrometry based on g-g coincidence is widely used in the field of nuclear structure studies, and has produced many succesful results. In this paper, feasibility of the method for neutron activation analysis of trace elements was studied. Particularly, a long-lived radioisotope 129I (T1/2 = 1.57.107 y) in algae samples and iridium in geological samples has been determined.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Y. Toh, M. Koizumi, M. Oshima, A. Kimura, Y. Hatsukawa, A. Osa, and J. Goto

Abstract  

In order to improve the sensitivity for the quantification of trace elements, we propose the combination of prompt gamma-ray analysis (PGA) and a multiple gamma-ray detection method. A new Ge detector system for multiple prompt gamma-ray analysis (MPGA) was constructed at the neutron guide-hall of the JRR-3M reactor of the Japan Atomic Energy Agency (JAEA). The first demonstration of this system was given with a plastic sample containing traces of cadmium. The quantification limit of cadmium in a plastic sample was found to be about 0.1 ppm.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Oshima, Y. Toh, Y. Hatsukawa, M. Koizumi, A. Kimura, A. Haraga, M. Ebihara, and K. Sushida

Abstract  

A new radionuclide quantification method is proposed on the basis of multiple gamma-ray detection, which is two or higher fold gamma-ray coincidence method. The coincidence method has so far been used for nuclear structure study. We apply this method for quantification of radioactive nuclei. The advantage of this method consists of high energy resolution and high sensitivity. It is successfully applied to nuclear waste analysis, neutron activation analysis and prompt gamma-ray analysis. The principle of the multiple gamma-ray detection method and future perspectives for an innovative pulsed neutron source and a new detector system will be presented.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: N. Shinohara, Y. Hatsukawa, K. Hata, N. Kohno, M. Andoh, H. Saleh, W. Charlton, T. Parish, and S. Raman

Abstract  

For nuclear transmutation of minor actinides, delayed neutron emission measurement for241Am was carried out in thermal neutron irradiation location. The neutron capture cross sections of241Am were also measured radiochemically. The transmutation process of241Am in reactor is discussed by calculating the yields of minor actinides with the nuclear data measured in this study and the evaluated values. The accelerator driven transmutation of minor actinides by high-flux neutrons from spallation reactions is also presented.

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Abstract  

To determine the cross sections of the135Cs(n,γ)136Cs reaction, a sample of135Cs included in a “standardized solution” of137Cs was used as a target and irradiated in a reactor. The ratio of the atom number of135Cs to that of137Cs was determined to be 0.89±0.03 with a quadrupole mass spectrometer. The thermal cross section and the resonance integral measured in this study were determined to be 8.3±0.3 and 38.1±2.6 b respectively.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Sekine, S. Ichikawa, A. Osa, M. Koizumi, H. Iimura, K. Tsukada, I. Nishinaka, Y. Hatsukawa, Y. Nagame, M. Asai, Y. Kojima, T. Hirose, M. Shibata, H. Yamamoto, and K. Kawade

Abstract  

Studies on the decay of unstable nuclei using the two on-line isotope separators of JAERI are reviewed for the past five years. With the previously established ion-source technique using mono-oxide ion formation in a thermal ion source, the new nuclides125Pr and127Pr have been identified in heavy-ion fusion residues. Further, with a newly developed gas-jet coupled thermal ion source, the new nuclides166Tb,165Gd,161Sm and236Am have been identified by bombarding238U and235U targets with a proton or6Li beam. Other studies, including off-line experiments, by decay spectroscopy, laser spectroscopy and Mössbauer spectroscopy are described.

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