Shun Sekimoto

Accurate determination of chlorine, bromine, and iodine in sedimentary rock reference samples by radiochemical neutron activation analysis and a detailed comparison with inductively coupled plasma mass spectrometry literature data.

Trace amounts of three halogens (chlorine, bromine, and iodine) were determined using radiochemical neutron activation analysis (RNAA) for nine sedimentary rocks and three rhyolite samples. To obtain high-quality analytical data, the radiochemical procedure of RNAA was improved by lowering the background in gamma-ray spectrometry and completing the chemical procedure more rapidly than in conventional procedures. A comparison of the RNAA data of Br and I with corresponding inductively coupled plasma mass spectrometry (ICPMS) literature data revealed that the values obtained by ICPMS coupled with pyrohydrolysis preconcentration were systematically lower than the RNAA data for some reference samples, suggesting that the quantitative collection of Br and I cannot always be achieved by the pyrohydrolysis for some solid samples. The RNAA data of three halogens can classify sedimentary rock reference samples into two groups (the samples from inland water and those from seawater), implying the geochemical significance of halogen data.

Application of neutron activation analysis to micro gram scale of solid samples

An instrumental neutron activation analysis (INAA) procedure for analyzing extremely small samples was developed and applied to two kinds of extraterrestrial samples. A few mg of the Allende meteorite as well as the JB-1 basalt can work well as a reference sample for a relative method. To evaluate the applicability of this INAA procedure, detection limits are presented and compared with the elemental contents in a potential sample to be analyzed. The possibility of reuse of neutron-irradiated samples for mass spectrometry was noted by indicating degree of increase in isotopic abundance for noble gas and long-lived radioactive nuclides.

Multielemental analysis of Korean geological reference samples by INAA, ICP-AES and ICP-MS

Six Korean geological reference samples (KB-1, KGB-1, KT-1, KD-1, KG-1 and KG-2) prepared by Korea Institutes of Geoscience and Mineral Resources were analyzed by using INAA, ICP-AES and ICP-MS. Some elements could be determined by both INAA and non-INAA methods (ICP-AES and ICP-MS), and these data are consistent with each other. This study confirms that a combination of ICP-AES and ICP-MS is comparable to INAA in determining a wide range of major, minor and trace elements in geological materials.

Neutron activation analysis of iron meteorites

A simple and effective instrumental neutron activation analysis for iron meteorites is presented in this study. In order to design the analytical procedure, self-absorption of gamma-rays on samples, interfering nuclides and their respective reactions were examined. Seventeen elements (Fe, Co, Ni, Cu, Ga, Ge, As, Mo, Ru, Rh, Sb, W, Re, Os, Ir, Pt and Au) could be nondestructively determined in Canyon Diablo and Cape York iron meteorites. Our data of these two iron meteorites are consistent with the corresponding literature values. This study confirms that our analytical procedure with INAA is simple and effective in classification of iron meteorites.

Measurements of the neutron activation cross sections for Bi and Co at 386 MeV.

Neutron activation cross sections for Bi and Co at 386 MeV were measured by activation method. A quasi-monoenergetic neutron beam was produced using the (7)Li(p,n) reaction. The energy spectrum of these neutrons has a high-energy peak (386 MeV) and a low-energy tail. Two neutron beams, 0° and 25° from the proton beam axis, were used for sample irradiation, enabling a correction for the contribution of the low-energy neutrons. The neutron-induced activation cross sections were estimated by subtracting the reaction rates of irradiated samples for 25° irradiation from those of 0° irradiation. The measured cross sections were compared with the findings of other studies, evaluated in relation to nuclear data files and the calculated data by Particle and Heavy Ion Transport code System code.

Unique extraction behavior of americium and curium in a system of TBP and calcium nitrate hydrate melt

Extraction of Am(III) and Cm(III) between tri-n-butyl phosphate solution and molten calcium nitrate hydrate Ca(NO3)2RH2O was investigated radiochemically. In the range of water content R = 3.5-8.0, the distribution ratio was found to increase with the decrease of water activity. The dependence of the distribution ratios on the water activity in the hydrate melt changes at around log aH2O = −0.4, which corresponds to R = 5.0. The extraction behavior of Am(III) and Cm(III) was systematically discussed with the reported data of trivalent lanthanides.

Measurements of the neutron activation cross sections for Bi at 287 and 370 MeV

Abstract We present cross section measurements for neutron-induced activation of Bi, at 287 and 370 MeV. These values were derived from the activation method using a quasi-monoenergetic neutron field based on the 7Li(p,n) reaction. In separate experiments, samples were irradiated with neutrons derived from 7Li(p,n) reaction at either 0º or 30º for proton beam axis. This approach allows the subtraction of the low energy neutron components. The measured cross sections are compared with the findings of other studies, and evaluated in relation to nuclear data files.

Observation of attachment ratio of fission products on solution aerosol

Attachment behavior of fission products to solution aerosols has been observed to elucidate the role of chemical effects in the generation mechanism of fission-product aerosols. Primary aerosols generated from aqueous solution of sodium chloride or ammonium sulfate were passed through a fission-product chamber, and radioactive aerosols were generated by attaching fission products to the primary aerosol particles. Attachment ratios of the fission products on aerosols were estimated from activity measurements. It was found that the attachment ratio of the sodium chloride solution aerosol is larger than that of the ammonium sulfate solution aerosol.

Volume Reduction of Radioactive Concrete in Nuclear Facilities by Chemical Extraction Methods on Long-Lived Radioactive Nuclides

Leaching yields from an activated aggregate, removal yields from leachate, and overall mass balance relevant to the chemical procedure were investigated on radionuclides of 59Fe, 60Co, and 152Eu to reduce volume of radioactive waste used in a nuclear reactor facility. The radioactive nuclides were leached with 7 M HNO3 from the aggregate, then the 7 M HNO3 solution was mixed with NaOH or NH3 water to remove the nuclides as a precipitate. 70–80% of 60Co and 60–70% of 152Eu were leached from an activated aggregate. 100% of 59Fe, more than 99% of 60Co, and 94–98 % of 152Eu were removed as a precipitate at pH higher than 4, 7, and 6, respectively. Removal rates became lower at pH lower than 4 for 59Fe, 7 for 60Co, and 6 for 152Eu. It is basically possible to separate 60Co and 152Eu from precipitate of Fe at pH ∼ 4. The further separation to reduce volume of waste is not practical, because 20% of 60Co and 152Eu contained in the precipitate. 93% of volume reduction was achieved with one-step separation.Copyright

Fission cross-section measurements of 237Np, 242m Am, and 245Cm with lead slowing-down neutron spectrometer

The cross sections for neutron-induced fission of 237Np, Am, and 245Cm have been measured in the energy range from 0.1 eV to 2 keV using the lead slowing-down neutron spectrometer at the Research Reactor Institute, Kyoto University. The fission cross sections were deduced relative to those for 235U(n,f) and 10B(n,a). The cross section for 237Np(n,f) was obtained with the experimental uncertainty of about 20% in the energy region below 25 eV and typically 13% above this energy. The experimental uncertainties for 242m Am and 245Cm were, respectively, of the order of 14% and 9% in the entire energy region.