Kenji Tomura

Determination of rare-earth elements in rock samples by neutron activation analysis with a lithium-drifted germanium detector after chemical group-separation

Abstract A lithium-drifted germanium detector combined with chemical group-separation has been utilized for the determination of rare-earth elements (La, Ce, Nd, Sm, Eu, Gd, Tb, Tm, Yb and Lu) in rock samples by neutron activation. This procedure has the advantage of a low background level which cannot be attained in the non-destructive method. The combination of the Ge(Li) detector and chemical group-separation also offers a distinct simplification in the correction of contributions from other nuclides. For optimum utility of a Ge(Li) detector in neutron activation analysis, chemical group-separations are recommended.

Cl, Br and I in igneous standard rocks

Abstract Radiochemical neutron activation analysis (RNAA) and isotope dilution mass spectrometry (IDMS) are applied to the determination of Cl, Br and I in igneous standard rocks. Seventeen different standard samples of igneous rocks distributed by the Geological Survey of Japan (GSJ) and by the Association National de la Recherche Technique (ANRT) in France were investigated. The Cl contents range from 10 to 1000 ppm, Br from 0.05 to 2.5 ppm, and I from 5 to 100 ppb. In this study, four standard samples for Cl, eight for Br, and six for I were newly determined. The analytical results between RNAA and IDMS are in good agreement within one standard deviation. The halogen contents are found to be well correlated for Cl and Br, but less clearly for I. Halogens generally are enriched in rhyolites in the volcanic rock series while they are depleted in plutonic rock series, especially in granite.

MULTIELEMENT NEUTRON ACTIVATION ANALYSIS OF HUMAN SCALP HAIR A LOCAL POPULATION SURVEY IN THE TOKYO METROPOLITAN AREA

Applying instrumental neutron activation analysis, multielement analysis of human hair was carried out to elucidate the levels of various trace element concentrations in hair of local population in the Tokyo metropolitan area. 202 hair samples were collected from the inhabitants classified by sex and five age groups. Using several combinations of irradiation time, cooling time and counting time, forty elements were quantitatively analyzed. The method of analysis for data including samples under detection limit is discussed, assuming that the frequanecy distribution of trace element contents in hair is log-normal.

Activation and tracer techniques for study of metallofullerenes

Advantages and uniqueness of radiochemical techniques in fullerene studies are pointed out. Some experimental data are presented on metallofullerenes production yields, HPLC elution behaviors of Y, La, Gd containing fullerenes, encapsulation of a new metal in the carbon cage, stability of the carbon cage against recoil energy, and the distribution of metallofullerenes among various organs of rats.

New Lanthanoid Metallofullerenes and their HPLC Elution Behavior

Abstract HPLC behaviors of metallofullerenes of 14 lanthanoid elements were studied by use of radiotracers, and the species of some of the metallofullerenes were identified by mass spectroscopy. From the HPLC elution behaviors, 14 lanthanoid elements forming metallofullerenes were found to be grouped into two, namely, Sm, Eu, Tm and Yb as one group and the rest of the elements as another. Some new species of metallofullerenes like La@C74, and M@Cn (M=Eu, Tm, Yb; n=74, 82, 84, 88, 90, 92, 94) have been identified. The observed retention times of metallofullerenes are discussed in terms of the number of carbon atoms of the cage and from consideration of the electron donor and acceptor relation between the fullerene species and the HPLC stationary phases.

RAPID DETERMINATION OF DYSPROSIUM IN ROCK SAMPLES BY NEUTRON ACTIVATION ANALYSIS WITH A Ge(Li) DETECTOR AFTER CHEMICAL SEPARATION.

Abstract A neutron activation method for the rapid determination of dysprosium in rocks, based on simple chemical separation and γ-spectrometry with a lithiumdrifted germanium detector, is described. The 94.7-keV photopeak of dysprosium-165 (2.3 h half-life) was measured. Several geochemical standard rocks covering a variety of rock types were analyzed. The detection limit was 0.005 μg of dysprosium. A precision of ±4.7% was obtained on 7 separate analyses of a basalt standard rock. The accuracy of the method is discussed.

Neutron activation analysis of scandium

Abstract A neutron activation method is proposed for the determination of trace quantities of scandium, down to submicrogram level, in rocks, ores and meteorites. The sample and standard are irradiated intermittently for a total of 30 h, at a neutron flux of 5·10 11 n/cm 2 /sec; the radiochemical separation consists essentially of a one-step anion exchange. The induced γ-activity of 40 Sc, 85 days, isolated from the sample is measured and compared with that of a standard. The chemical yield averages 85% and there is a considerable saving of time in the radiochemical work. Results are quoted for the scandium contents of 2 standard rocks, cassiterite and several stony meteorites. Details of conflicting nuclear reactions are also given.

Determination of trace manganese in high-purity iron by instrumental neutron activation analysis using a thermal column

Instrumental neutron activation analysis was developed to determine trace manganese in highly purified iron. This method is based on an irradiation at a well-thermalized position in a thermal column and fast neutron interference correction by extrapolating56Mn activities at poorly thermalized positions. An iron reference standard material containing 0.03 ppm Mn can be analyzed by this method. The present method is applicable to the determination of trace elements the atomic numbers of which are 1 or 2 lower than those of the matrix element.

Neutron dosimetry for fission track dating at irradiation facilities of a TRIGA type reactor

Abstract The neutron fluence at irradiation facilities in various positions of the TRIGA Mark II reactor (Institute for Atomic Energy, Rikkyo University, Japan) was estimated using gold metal monitors. Westcotts g-value of Lu-176, which was calculated from the sub-cadmium Lu-177/Lu-176m activation ratio assuming a Maxwellian distribution of neutron velocity, was also presented for tentative estimation of apparent neutron temperature. Westcotts g-value data were used for the comparison of the reaction rate of fission tracks in the sub-cadmium neutron energy region with that calculated using the conventional flux measured using gold metal monitors. The data at these facilities were reasonably comparable with each other and were also correlated to the previous data for irradiation facilities of other type reactors, JRR-2 and JRR-4 (JAERI, Tokai, Japan). Furthermore, they have been compared to data obtained by using the dosimeter glass, NBS-SRM 962a, pre-irradiated in the NBSR reactor (U.S.A.). These results contribute to the understanding of inter-reactor and/or inter-laboratory comparison and standardization of fission track ages.

Determination of trace elements in carbonates by instrumental neutron activation analysis

A systematic non-destructive determination of eighteen trace elements (F, Na, Cl, Sc, Mn, Zn, Br, Sr, I, Ba, La, Ce, Sm, Eu, Tb, Yb, Th and U) in carbonate samples by thermal neutron activation analysis was developed. Three 0.2–0.5g samples were irradiated for 15 sec (in the case of determination of F), for 3 min (in the case of Na, Cl, Mn, Sr and I) and for 60 hrs (in the case of Sc, Zn, Br, Ba, La, Ce, Sm, Eu, Tb, Yb, Th and U) in the TRIGA MARK II Reactor at a thermal neutron flux of 5·1011 n·cm−2·sec−1 (15 sec and 3 min irradiation) and 1.5·1012n·cm−2·sec−1 (60 hrs irradiation), respectively. According to the half life of the nuclides formed, the activities were measured with a Ge(Li) spectrometer as follows,20F∶15 sec counting after 20–25 sec cooling,24Na,38Cl,56Mn,87mSr and128I∶600 sec couting after 30–120 min cooling,82Br,140La,153Sm,175Yb and239Np (daughter of239U)∶3000 sec counting after 1 week cooling,46Sc,65Zn,131Ba,141Ce,152Eu,160Tb and233Pa (daughter of233Th)∶5000 sec counting after 1 month cooling. The errors due to the fluctuation of the neutron flux and the counting geometry were minimized by the use of calcium determined previously with EDTA-titration as an internal standard. The interferences from24Mg(n, p)24Na and235U(n, fission) reactions were corrected by the activities produced by the reactions in unit weight of magnesium and uranium, and their concentrations in samples measured experimentally. The data of Na, Mn, Zn and Sr were compared with the results obtained by atomic absorption analysis.