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Journal Articles

Quantum paramagnet near spin-state transition

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.

Journal Articles

Application of the transient pulse method to measure clay permeability

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:3 Percentile:23.2(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.

Journal Articles

Application of transient pulse method to permeability measurement for clay

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.

Journal Articles

Establishment of a Laboratory for $$gamma$$-ray Spectrometry of Environmental Samples Collected in Fukushima

Saegusa, 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 $$gamma$$-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.

Oral presentation

Sorption / diffusion data aquisition method development for high sorbing americium in compacted bentonite

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$$_{3}$$ - 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 $$mu$$m thick slices. Using this technique, it was possible to divide the ID profile into 10 $$mu$$m and therefore, to analyze diffusion distance layer larger than 50 $$mu$$m.

Oral presentation

Development of sorption and diffusion data acquisition method in compacted bentonite, 2; Sorption and diffusion of am as functions of carbonate and salinity of porewater

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.

Oral presentation

Coincidence summing correction factors based on P/T method and reference source method for volume samples

Saegusa, Jun; Nagayama, Takehiro; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Takeishi, Minoru

no journal, , 

In the process of $$gamma$$-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 $$gamma$$-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 $$^{134}$$Cs nuclide.

Oral presentation

Reduction of environmental background count rates for Ge detectors at JAEA Fukushima Environmental Safety Center

Nagayama, Takehiro; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Saegusa, Jun

no journal, , 

no abstracts in English

Oral presentation

Validation of coincidence-summing correction based on the peak-to-total ratio

Saegusa, Jun; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Takeishi, Minoru

no journal, , 

no abstracts in English

Oral presentation

Survey of radiocesium accumulation in the building of Sasakino Analytical Laboratory, JAEA

Kurita, Yoshiyuki; Okazaki, Tsutomu; Maeda, Satoshi; Yoda, Tomoyuki; Saegusa, Jun

no journal, , 

no abstracts in English

Oral presentation

Findings obtained from daily check of mechanically cooled HPGe detectors

Maeda, Satoshi; Yoda, Tomoyuki; Okazaki, Tsutomu; Saegusa, Jun

no journal, , 

no abstracts in English

Oral presentation

Survey of radiocesium accumulation in the building of Sasakino Analytical Laboratory, JAEA

Kurita, Yoshiyuki; Okazaki, Tsutomu; Maeda, Satoshi; Yoda, Tomoyuki; Saegusa, Jun

no journal, , 

no abstracts in English

Oral presentation

Outline of Sasakino Analytical Laboratory, Fukushima Environmental Safety Center of JAEA

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

Oral presentation

Relationship between cooling temperature and energy shift of a mechanically-cooled Ge detector

Maeda, Satoshi; Yoda, Tomoyuki; Okazaki, Tsutomu; Otani, Shuichi; Saegusa, Jun

no journal, , 

no abstracts in English

Oral presentation

Estimation of hydraulic aperture of fracture with in-filling minerals in granite

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.

Oral presentation

Change of permeability in macro-fractured granite under flow of water including clays

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.

16 (Records 1-16 displayed on this page)
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