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Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Kubota, Takumi*; Kimuro, Shingo*; Amano, Yuki; Miyakawa, Kazuya; Iwatsuki, Teruki; Mizuno, Takashi; Sasaki, Takayuki*; et al.
Chemosphere, 168, p.798 - 806, 2017/02
Times Cited Count：3 Percentile：10.21(Environmental Sciences)For better understanding of the migration behavior of minor actinides (MA) in deep groundwater, the interaction of doped rare earth elements (REEs) and components in Horonobe deep groundwater was studied. Appx. 10 ppb of rare earth elements, i.e., Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm and Yb were doped to the sample groundwater collected from a packed sections in borehole drilled from 140 m depth experiment drift of Horonobe underground research laboratory (URL), Hokkaido, Japan. Then, that groundwater was sequentially filtrated by 0.2 micron pore filter, 10 kDa, 3 kDa and 1 kDa of nominal molecular weight limit (NMWL) ultrafilters by keeping inert condition. After that, the filtrate solutions were analyzed by ICP-MS to determine the concentrations of retained REEs at each filtration steps, while the used filters were analyzed by the neutron activation analysis (NAA) and TOF-SIMS element mapping to know the amount and chemical speciation of trapped fraction of the REEs on each filter. A remarkable relation between the retention ratios of REEs in the filtrate solutions and the ionic radius was observed, i.e., smaller rare earth element solves more in liquid phase under the Horonobe groundwater condition. NAA and TOF-SIMS analyses revealed that certain portions of REEs were trapped by 0.2 micron pore filters as rare earth phosphates which corresponded with the predicted predominant species by a chemical equilibrium calculation for the Horonobe groundwater condition, while small portions of colloidal REEs were trapped by 10 kDa and 3 kDa NMWL ultrafilters. The result suggested that phosphate anion plays an important role in the chemical behavior of REEs in saline (seawater based) groundwater, which could be referred for the prediction of migration behavior of trivalent actinide released from the repository of radioactive waste in far future.
Shimojo, Kojiro; Aoyagi, Noboru; Saito, Takumi*; Okamura, Hiroyuki; Kubota, Fukiko*; Goto, Masahiro*; Naganawa, Hirochika
Analytical Sciences, 30(2), p.263 - 269, 2014/02
Times Cited Count：49 Percentile：86.18(Chemistry, Analytical)Osaka, Masahiko; Konashi, Kenji*; Hayashi, Hirokazu; Li, D.*; Homma, Yoshiya*; Yamamura, Tomoo*; Sato, Isamu; Miwa, Shuhei; Sekimoto, Shun*; Kubota, Takumi*; et al.
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 5 Pages, 2011/12
Summer schools for future experts have successfully been completed under Japan Actinide Network (J-ACTINET) for the purpose of development of human resources who are expected to be engaged in every areas of actinide-research/engineering. The first summer school was held in Ibaraki-area in August 2009, followed by the second one in Kansai-area in August 2010. Two summer schools have focused on actual experiences of actinides in actinide-research fields for university students and young researchers/engineers as an introductory course of actinide-researches. Several quasi actinide-handling experiences at the actinide-research fields have attracted attentions of participants at the first school in Ibaraki-area. The actual experiments using actinides-containing solutions have been carried out at the second school in Kansai-area. Future summer schools will be held every year for the sustainable human resource development in various actinide-research fields.
Kubota, Takumi*; Nakano, Tomoko*; Amano, Hikaru; Suzuki, Takashi; Mahara, Yasunori*
JAEA-Conf 2008-003, p.36 - 39, 2008/04
In analysis of environmental iodine, samples containing low I-129 and low iodine amount are subject to contamination from reagents and apparatus. We measured the isotopic ratio of I-129/I-127 in brine that was collected at Mobara in Chiba prefecture and was characterized as having a high iodine concentration and a low isotopic ratio. The results, however, showed high isotopic ratios. We suspected that the contamination was caused by using halogen containing reagents because the samples treated with Cl-form anion exchange resin in iodine extraction process were strongly contaminated. In this study, we have conducted halogen-free extraction processes such as ion exchange and solvent extraction whose recovery has been investigated with 
spectrometry of I-126 produced through photonuclear reaction with the KURRI LINAC. The total iodine recovery through ion exchange with NO
-form anion exchange resin and solvent extraction with dodecane was more than 80%.
Sasaki, Takayuki*; Kubo, Shintaro*; Kobayashi, Taishi*; Kirishima, Akira*; Kimura, Takaumi; Kubota, Takumi*; Takagi, Ikuji*; Moriyama, Hirotake*
Journal of Nuclear and Radiochemical Sciences, 6(1), p.51 - 54, 2005/07
no abstracts in English
Kubota, Takumi*; Nakano, Tomoko*; Amano, Hikaru; Suzuki, Takashi; Mahara, Yasunori*
no journal, ,
no abstracts in English
Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki; Mizuno, Takashi; Kubota, Takumi*; Sasaki, Takayuki*; Sato, Nobuaki*
no journal, ,
For understanding of the migration behavior of minor actinides (MA) in groundwater, the interaction of rare earth elements and suspended matters contained in Horonobe deep groundwater was studied. From this chemical analog study, it is suggested that the migration behavior of MA in the Horonobe groundwater system seems to be regulated by the formation of phosphate precipitation and small percentage of MA would be carried in the groundwater as pseudo colloids like MA-humic substance complex.
Amano, Yuki; Amamiya, Hiroki; Murakami, Hiroaki; Iwatsuki, Teruki; Terashima, Motoki; Mizuno, Takashi; Kirishima, Akira*; Kuno, Atsushi*; Sasaki, Takayuki*; Kubota, Takumi*; et al.
no journal, ,
no abstracts in English
Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki; Mizuno, Takashi; Kubota, Takumi*; Sasaki, Takayuki*; Sato, Nobuaki*
no journal, ,
no abstracts in English
Kokami, Takayuki*; Sasaki, Takayuki*; Amamiya, Hiroki; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki; Mizuno, Takashi; Kubota, Takumi*; Kirishima, Akira*
no journal, ,
no abstracts in English
Kowatari, Munehiko; Kubota, Takumi*; Shibahara, Yuji*; Fujii, Toshiyuki*; Takamiya, Koichi*; Mizuno, Satoshi*; Yamana, Hajimu*
no journal, ,
Instead of conventional Ge semiconductor detectors and NaI(Tl) scintillation spectrometers, an application of a CZT whose crystal has the dimension of 1 cm cubic semiconductor to the in-situ environmental radio-activity measurement was attempted in deeply affected areas in Fukushima region. A CZT detector does not have such a high resolution of peaks, comparing a Ge detector. However, it is found that a CZT has enough characteristics to properly determine radio-activity of 
Cs and 
Cs in soil, throughout the in-situ measurement campaign in deeply affected area within 5 km from the Fukushima Dai-ichi Nuclear Power Plant, where dose rates exceed 50 
Sv h
. Results of radioactivity concentration in soil ranged between 1 and 500 kBq m
and seem consistent to those obtained by the air-borne measurement.
Kowatari, Munehiko; Kubota, Takumi*; Shibahara, Yuji*; Fujii, Toshiyuki*; Takamiya, Koichi*; Mizuno, Satoshi*; Yamana, Hajimu*
no journal, ,
For the purpose of determining a surface deposition density on soil for radio-cesiums, a CdZnTe (CZT) semiconductor detector whose crystal has dimensions of 1 cm cubic was applied to the in situ environmental radio-activity measurement in deeply contaminated areas in Fukushima region. Even in high dose rate areas where pulse height spectra weren't able to be properly obtained by the conventional high purity Ge semiconductor detector, proper pulse height spectra were obtained by the CZT detector with certain accuracy. Results of deposition density on soil for Cs and Cs derived from net peak areas by the CZT detector seemed consistent, comparing with those measured by the Japanese government. Air kerma rates were estimated by the same pulse height spectra for determining surface deposition density on soil for radio-cesiums and found to be almost the same values as obtained by the NaI(Tl) scintillation survey-meter.
