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structure transition under high pressureYamanaka, Takamitsu*; Nakamoto, Yuki*; Sakata, Masafumi*; Shimizu, Katsuya*; Hattori, Takanori
Physics and Chemistry of Minerals, 51(1), p.4_1 - 4_10, 2024/02
Times Cited Count：0 Percentile：0.34(Materials Science, Multidisciplinary)Neutron and synchrotron X-ray diffraction and electric conductivity measurements of FeTiO ilmenite were performed under pressures. Ilmenite structure is retained up to 28 GPa. Structure analysis revealed that FeO
and TiO are compressible and less compressible below 8 GPa, respectively. The resistivity is lowest along the Fe-Ti direction that has shortest interatomic distance among all the metal ion pairs. The resistivity in the direction normal to c-axis monotonically decreases with pressure, whereas that along c-axis shows hallow-shape with pressure. Maximum entropy analysis shows that electron configuration of Fe
(3
) is more strongly changed than Ti
(3
) under compression. The anisotropic electrical conductivity and non-uniform structure change of Fe-Ti interatomic distance can be explained by the possible spin transition from high-spin state to intermediate-spin state of Fe cation.
Fe
O
solid solutions under high-pressure and high-temperature conditionsYamanaka, Takamitsu*; Hirao, Naohisa*; Nakamoto, Yuki*; Mikouchi, Takashi*; Hattori, Takanori; Komatsu, Kazuki*; Mao, H.-K.*
Physics and Chemistry of Minerals, 49(10), p.41_1 - 41_14, 2022/10
Times Cited Count：0 Percentile：0.02(Materials Science, Multidisciplinary)Magnetic and crystal structure of MnFeO solid solutions under high-PT conditions are investigated by neutron diffraction and synchrotron M
ssbauer spectroscopy. The ferrimagnetic-paramagnetic transition and tetragonal-cubic transition of Mn
FeO spinel occur at 100
C and 180C, respectively, suggesting both the transitions are not coupled. The structure transition temperature decreases with pressure. Mssbauer experiments and neutron diffraction revealed that the Fe occupancy in tetrahedral site increases increase with pressure, suggesting MnFeO phase approaches inverse spinel. Magnetic structure refinement clarified paramagnetic and ferrimagnetic structure of MnFeO and MnFeO. These spinels transform into high-pressure orthorhombic phases at 18.4 and 14.0 GPa, respectively, indicating lower transition pressure with increasing Mn content.
FeO spinel and postspinel with elevating pressureYamanaka, Takamitsu*; Rahman, S.*; Nakamoto, Yuki*; Hattori, Takanori; Jang, B. G.*; Kim, D. Y.*; Mao, H.-K.*
Journal of Physics and Chemistry of Solids, 167, p.110721_1 - 110721_10, 2022/08
Times Cited Count：1 Percentile：15.7(Chemistry, Multidisciplinary)High-pressure neutron diffraction proved that MnFeO and MnFeO spinels transform into CaMnO-type structure above 18 GPa and 14 GPa, respectively. The transition pressure of MnFeO solutions decreases with increasing Mn content. Synchrotron X-ray M
ssbauer experiments revealed that Fe and Fe
distribution at the tetrahedral (A) and octahedral (B) sites in the spinel structure changes with pressure. MnFeO and MnFeO spinels are ferrimagnetic and the CaMnO-type phase is paramagnetic. The temperature dependence of resistivity indicates that both spinels are semiconductors wherein electrons hop between cations at the A and B sites. A pressure-induced shortening of B-B distance promoted conduction via greater electron mobility between adjacent B cations. The Fe and Fe occupancies at the B sites in MnFeO are much larger than those in MnFeO. The CaMnO-type phase is metallic. Theoretical calculation confirmed the metallic character and Fe d-orbitals strongly renormalized compared to Mn d-orbitals.
Hattori, Takamitsu
Radioisotopes, 63(8), p.399 - 403, 2014/08
From the view point of applying to laboratory exercise of radioactivity measurement by a Liquid Scintillation Counter (LSC), Vietnamese vodkas have specific features as measurement samples, for example, they are colorless, have high concentration of ethanol, and only very few organic materials are included. Investigation was made to make sure that the Vietnamese vodkas are appropriate or not as a measurement sample for the LSC exercise. Direct measurements of 
C without any chemical pre-treatment were made on both radioactive concentrations and specific activities of three kinds of Vietnamese vodka and also pure ethanol reagent. The LSC measurements reveal that estimated C concentration is proportional to ethanol concentration in samples and that specific activity of C shows good agreement among the Vietnamese vodkas and pure ethanol, as well as the reference value of 0.25 Bq/g of Carbon. Thus the conclusion is derived that the Vietnamese vodkas can be applied with high accuracy to the LSC exercise as measurement samples.
Sugimoto, Jun; Sakamoto, Ryuichi; Kushita, Kohei; Arai, Nobuyoshi; Hattori, Takamitsu; Matsuda, Kenji; Ikuta, Yuko; Sato, Koichi
Transactions of NESTet 2008 (CD-ROM), 6 Pages, 2008/05
Nuclear human resources development (HRD) in Japan has been identified as one of the most important issues these years in nuclear society, mostly due to the decrease of nuclear engineers in industries and students in universities, and to the difficulties of technical transfers. Nuclear Technology and Education Center (NuTEC) at Japan Atomic Energy Agency (JAEA) aims at comprehensive nuclear education and training activities, which cover (1) education and training for domestic nuclear engineers, (2) cooperation with universities and (3) international cooperation. The main feature of NuTEC's training programs is that the curricula places emphasis on the laboratory exercise with well-equipped training facilities and expertise of lecturers mostly from JAEA. The wide spectrum of cooperative activities have been pursued with universities, which includes newly developed remote-education system, and also with international organizations, such as with FNCA countries and IAEA.
Hattori, Takamitsu
Hoshasen Riyo Gijutsu Detabesu (Internet), 3 Pages, 2007/09
Liquid scintillation counter is widely used for measurements not only of such low energy 
-emitting radionuclides as 
H and C, but also middle to high energy -emitters and 
-emitters. The measurements can be achieved with high counting efficiencies and is applicable to high radioactivity samples. However, the quenching correction is required for quantitative evaluation because decrease in the counting efficiency always occurs by quenching effect.
Harada, Akio; Sato, Tadashi*; Nakajima, Kunihisa; Komuro, Yuichi; Shiraishi, Hirotsugu*; Hattori, Takamitsu; Ikuta, Yuko; Yachi, Shigeyasu; Kushita, Kohei
JAERI-Review 2005-026, 55 Pages, 2005/09
JAERI-Review-2005-026.pdf:1.95MB
This report provides an example of answers to the problems of the 37th Examination for the Chief Engineer of Nuclear Fuel. This examination was done as a national qualification in March 2005. Brief explanations or references are added to some answers.
