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Ishidera, Takamitsu; Okazaki, Mitsuhiro*; Yamada, Yoshihide*; Tomura, Tsutomu*; Shibutani, Sanae*
Journal of Nuclear Science and Technology, 60(5), p.536 - 546, 2023/05
The distribution coefficient (
) value of radionuclides is an important parameter in the radionuclide migration analysis in the safety assessment of the geological disposal of high-level radioactive waste. The values must be extensively evaluated especially under conditions where they might be decreased to improve the reliability of safety assessment. In this study, the pH dependence of the values for Sn and Nb on montmorillonite was evaluated using batch sorption experiments at neutral to alkaline pH, which might be caused by the leaching of cementitious materials and the corrosion of carbon steel. The values were determined in the range 8 
pH 12 by the experiments and were found to decrease with increasing pH. A model calculation using a thermodynamic sorption model was conducted on the measured pH dependence of the values. Two different sorption sites were required to describe the pH dependence of the values of Sn in the model calculation, whereas one sorption site was considered predominant in the sorption of Nb.
Tomiyasu, Keisuke*; Ito, Naoko*; Okazaki, Ryuji*; Takahashi, Yuki*; Onodera, Mitsugi*; Iwasa, Kazuaki*; Nojima, Tsutomu*; Aoyama, Takuya*; Ogushi, Kenya*; Ishikawa, Yoshihisa*; et al.
Advanced Quantum Technologies (Internet), 1(3), p.1800057_1 - 1800057_7, 2018/12
Spin-state transition, also known as spin crossover, plays a key role in diverse systems. In theory, the boundary range between the low- and high-spin states is expected to enrich the transition and give rise to unusual physical states. However, no compound that realizes a nearly degenerate critical range as the ground state without requiring special external conditions has yet been experimentally identified. This study reports that the Sc substitution in LaCoO3 destabilizes its nonmagnetic low-spin state and generates an anomalous paramagnetic state accompanied by the enhancement of transport gap and magneto-lattice-expansion as well as the contraction of Co-O distance with the increase of electron site transfer. These phenomena are not well described by the mixture of conventional low- and high-spin states, but by their quantum superposition occurring on the verge of a spin-state transition.
Kato, Masaji*; Nara, Yoshitaka*; Okazaki, Yuki*; Kono, Masanori*; Sato, Toshinori; Sato, Tsutomu*; Takahashi, Manabu*
Materials Transactions, 59(9), p.1427 - 1432, 2018/09
Times Cited Count：6 Percentile：32.61(Materials Science, Multidisciplinary)To ensure the safe geological disposal of radioactive waste, it is important to determine the permeability (hydraulic conductivity) of clays. The transient pulse method is suitable for low-permeability materials because it requires a relatively short time to determine their permeability. Upstream pore pressure typically increases in the measurement conducted via the transient pulse method. However, this procedure cannot be used to determine the permeability of clays due to the increase in pore pressure. Therefore, the transient pulse method has never been applied to determine clay permeability. In this study, we applied the transient pulse method to a clay sample to determine its permeability while decreasing the downstream pore pressure.
Kato, Masaji*; Nara, Yoshitaka*; Okazaki, Yuki*; Kono, Masanori*; Sato, Toshinori; Sato, Tsutomu*; Takahashi, Manabu*
Zairyo, 67(3), p.318 - 323, 2018/03
To ensure the safe geological disposal of radioactive wastes, it is important to determine the permeability of clays. The transient pulse test is suitable to apply to the low permeability materials, because it takes relatively short term to determine the permeability. Usually we increase the upstream pore pressure in the measurement with the transient pulse test. However, it is impossible to determine the permeability of clay in this procedure because of the increase of pore pressure. Therefore, the transient pulse test has never been applied to the determination of permeability of clays. In this study, we tried to apply the transient pulse test to a clay obtained in Mizunami Underground Research Laboratory to determine the permeability with decreasing the downstream pore pressure. It was clarified that the transient pulse test with decreasing downstream pore pressure is appropriate from the measurements of granite and sandstone. It was shown that the permeability of a clay was determined by the transient pulse test with decreasing the downstream pore pressure, which agreed with the permeability determined from the falling head test. The measurement time of the transient pulse test is much shorter than that of the falling head test. It is concluded that the transient pulse test is appropriate for the determination of the permeability of clays.
-ray Spectrometry of Environmental Samples Collected in FukushimaSaegusa, Jun; Yoda, Tomoyuki; Maeda, Satoshi; Okazaki, Tsutomu; Otani, Shuichi; Yamaguchi, Toshio; Kurita, Yoshiyuki; Hasumi, Atsushi; Yonezawa, Chushiro*; Takeishi, Minoru
Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1078 - 1085, 2017/11
After the nuclear accident at the Fukushima Daiichi Nuclear Power Plant in March 2011, the Japan Atomic Energy Agency has newly set up a laboratory for radioactivity analysis in Fukushima. At the laboratory, radioactivity concentrations of environmental samples such as soil, water, dust filter, plant, etc., approximately 1,000 samples in a month, are measured with high-resolution -ray spectrometry systems. The systems employ n-type HPGe detectors from Ortec. Since September 2012, characterization and upgrade of the systems have been performed aimed at enhancing reliability of analysis and convenience of customers. Resolving both systematic and technical issues, the laboratory has been accredited the ISO/IEC 17025 standard as a testing laboratory for radioactivity analysis.
Ishii, Yasuo; Takahashi, Hiroaki; Tachi, Yukio; Tomura, Tsutomu*; Nemoto, Kazuaki*; Okazaki, Mitsuhiro*
no journal, ,
Am(III) diffusion experiment were performed by reservoir depletion (RD) test method coupled with thin layer ID profile fitting in 0.1 or 0.5M NaCl / 0.05M NaHCO
- bentonite (kunipia-F) system. The Kd values were also measured using batch technique in the same experimental conditions. In an ordinary ID profile acquisition cutting the bentonite by scraper, the compacted bentonite sample can be cut into 100 
m thick slices. Using this technique, it was possible to divide the ID profile into 10 m and therefore, to analyze diffusion distance layer larger than 50 m.
Ishii, Yasuo; Tomura, Tsutomu; Nemoto, Kazuaki; Okazaki, Mitsuhiro; Tachi, Yukio
no journal, ,
Am(III) diffusion experiment were performed by reservoir depletion (RD) test method coupled with thin layer ID profile fitting.
Saegusa, Jun; Nagayama, Takehiro; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Takeishi, Minoru
no journal, ,
In the process of -ray spectrometry analyses for radioactivity measurements, the coincidence summing effect needs to be considered. In this study, the concidence summing correction factors for 605 and 796 keV -rays from various standard volume sources were evaluated based on the peak-to-total (P/T) ratio method. The results were compared with the values directly obtained from the measurements of these sources containing certified amount of 
Cs nuclide.
Nagayama, Takehiro; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Saegusa, Jun
no journal, ,
no abstracts in English
Saegusa, Jun; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Takeishi, Minoru
no journal, ,
no abstracts in English
Kurita, Yoshiyuki; Okazaki, Tsutomu; Maeda, Satoshi; Yoda, Tomoyuki; Saegusa, Jun
no journal, ,
no abstracts in English
Maeda, Satoshi; Yoda, Tomoyuki; Okazaki, Tsutomu; Saegusa, Jun
no journal, ,
no abstracts in English
Kurita, Yoshiyuki; Okazaki, Tsutomu; Maeda, Satoshi; Yoda, Tomoyuki; Saegusa, Jun
no journal, ,
no abstracts in English
Saegusa, Jun; Yanagisawa, Kayo; Yamaguchi, Toshio; Manabe, Sachi; Yoda, Tomoyuki; Maeda, Satoshi; Utsumi, Azusa; Shibamichi, Masaru; Ejiri, Akira; Kurita, Yoshiyuki; et al.
no journal, ,
no abstracts in English
Maeda, Satoshi; Yoda, Tomoyuki; Okazaki, Tsutomu; Otani, Shuichi; Saegusa, Jun
no journal, ,
no abstracts in English
Kato, Masaji*; Nara, Yoshitaka*; Okazaki, Yuki*; Kono, Masanori*; Sato, Toshinori; Sato, Tsutomu*; Fukuda, Daisuke*; Takahashi, Manabu*
no journal, ,
Hydraulic aperture of fracture with in-filling minerals in granite are estimated using result of hydraulic test.
Nara, Yoshitaka*; Kato, Masaji*; Okazaki, Yuki*; Kono, Masanori*; Fukuda, Daisuke*; Sato, Tsutomu*; Sato, Toshinori; Takahashi, Manabu*
no journal, ,
Change of permeability in macro-fractured granite under flow of water including clays was observed. The result indicated that permeability decreased 3 to 4 orders of magnitude due to filling of clay to macro-fracture in granite.
Ishidera, Takamitsu; Hamamoto, Takafumi*; Okazaki, Mitsuhiro*; Yamada, Yoshihide*; Tomura, Tsutomu*
no journal, ,
no abstracts in English
