RADIOISOTOPES
Online ISSN : 1884-4111
Print ISSN : 0033-8303
ISSN-L : 0033-8303
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Volume 57, Issue 9
Displaying 1-4 of 4 articles from this issue
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Articles
  • Determination of the Anisotropic Emission Factor for Neutrons from 241Am-Be Source
    Munehiko KOWATARI, Isamu ONUMA, Yoshihiko TANIMURA, Katsuya KAWASAKI, ...
    Article type: Articles
    2008 Volume 57 Issue 9 Pages 559-569
    Published: 2008
    Released on J-STAGE: September 29, 2008
    DOIhttps://doi.org/10.3769/radioisotopes.57.559
    JOURNAL FREE ACCESS
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    The neutron standard field using an 241Am-Be neutron source has been widely used for the routine calibration of neutron dosemeters. The parameters concerning the neutron field should be well defined for proper calibration. The neutron fluence rate at the calibration point is one of the most essential parameters. Although the neutron fluence rate at the calibration point is obtained by the source strength and the distance from the center of the source to the calibration point, an additional correction factor for an anisotropic emission from the source should be adopted. Neutrons are emitted isotropically from the source, but the scattering of neutrons with source and encapsulation materials are inevitable. As a result of this effect, the distribution of the neutron fluence rate at the calibration point is expected to be variable with the angle of the source. This effect is defined as an anisotropic emission from the neutron source and expressed by an anisotropic factor, FI(θ), the ratio of the neutron fluence rate at the calibration point with the angle θ to that calculated by assuming isotropic emission at the same distance from the center of the source.
    For the proper calibration of the neutron dosemeters used in the Japan Atomic Energy Agency(JAEA), the anisotropic factor FI(90) from an 241Am-Be neutron source was experimentally determined using the precision long counter. Before the determination of the anisotropic factor of the 241Am-Be source with the protection case, the measured angular distribution from the X3 type 241Am-Be source was compared with the result obtained by other researchers and with the Monte Carlo calculation using MCNP-4C, for the verification of the method the authors adopted.
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  • Radiolytic Degradation of Hexabromocyclododecane in Waste Water from Thermal Insulation-Treatment Factory with Gamma Ray Irradiation
    Xing-Zheng WU, Keisuke TORIYAMA, Tomoaki HARII, Yoshio KATOH, Tetsuo T ...
    Article type: Articles
    2008 Volume 57 Issue 9 Pages 571-577
    Published: 2008
    Released on J-STAGE: September 29, 2008
    DOIhttps://doi.org/10.3769/radioisotopes.57.571
    JOURNAL FREE ACCESS
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    Radiolytic, and radiolytic/biological decompositions of hexabromocyclododecane(HBCD) in primary and ultimate waste waters from a thermal insulation-treatment process and a factory of polyester process are studied with gamma ray irradiation. Concentrations and degradation ratios of HBCD, and Br− concentrations are determined before and after gamma ray irradiation. Also, total organic carbon(TOC), chemical oxygen demand(COD), and biochemical oxygen demand(BOD) are determined to evaluate the decomposition of total organic compounds. As a result, about 72.5% of HBCD in ultimate waste water were decomposed with dose of 100kGy. Furthermore, about 98% of HBCD, nearly all organic compounds were removed after the combination of radiolytic/biological treatments.
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Review Article
Applications of Stable Isotopes in Life Sciences
  • Lead and Strontium Stable Isotope Measurements by Using a High Lateral Resolution Secondary Ion Mass Spectrometer(NanoSIMS)
    Yuji SANO
    Article type: Review Article
    2008 Volume 57 Issue 9 Pages 579-591
    Published: 2008
    Released on J-STAGE: September 29, 2008
    DOIhttps://doi.org/10.3769/radioisotopes.57.579
    JOURNAL FREE ACCESS
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    The method of Pb and Sr isotope measurements at about 5μm resolution was developed by using a high lateral resolution secondary ion mass spectrometer(NanoSIMS NS50). Since the both elements have radiogenic nuclides such as 206Pb, 207Pb, and 87Sr, natural variations of isotopic ratios are large. It is possible to detect a meaningful variation in a terrestrial sample, even though the experimental error is relatively large. In the case of monazite U-Pb dating, a 4 nA O− primary beam was used to sputter the sample and secondary positive ions were extracted for mass analysis using a Mattauch-Herzog geometry. The multi-collector system was modified to detect 140Ce+, 204Pb+, 206Pb+, 238U16O+, and 238U16O2+ ions simultaneously. Based on the monazite standard from North-Central Madagascar, we have determined the 206Pb/238U ratios of samples. 207Pb/206Pb ratios were measured by a magnet scanning with a single collector mode. 44 monazite grains extracted from a sedimentary rock in Taiwan were analyzed. Observed ages were consistent with the U-Th-Pb chemical ages by EPMA. Then NanoSIMS has been used to measure 87Sr/86Sr ratios in natural calcium carbonate samples. Multi-collector system was adjusted to detect 43Ca+, 80Ca2+, 86Sr+, and 87Sr+ ions at the same time. Magnetic field was scanning for the EM#4 counter to detect 85Rb+, 86Sr+ and 87Sr+, while the EM#4b can measure 86Sr+, 87Sr+, and 88Sr+, respectively. Repeated analyses of a coral skeleton standard(JCp-1) show that 87Sr/86Sr ratio agrees well with the seawater signature, after the series of corrections such as Ca dimer, 87Rb, and a mass bias estimated by 88Sr/86Sr ratio. The method is applied to an otolith from ayu (Plecoglossus altivelis altivelis) collected from the Yodo river, Japan. The spatial variation of 87Sr/86Sr ratios was consistent with amphidromous migration of the fish, namely, born in the lake and grown in the coastal sea and finally collected in a river.
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