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Tanaka, Taiki*; Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Boll, R. A.*; Brewer, N. T.*; Van Cleve, S.*; Dean, D. J.*; Ishizawa, Satoshi*; et al.
Physical Review Letters, 124(5), p.052502_1 - 052502_6, 2020/02
Times Cited Count：19 Percentile：81.08(Physics, Multidisciplinary)Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Aoyagi, Mitsuhiro; Matsuba, Kenichi; Kamiyama, Kenji
Nuclear Engineering and Design, 334, p.90 - 95, 2018/08
Times Cited Count：9 Percentile：62.99(Nuclear Science & Technology)Two-phase flow through porous media must be well understood to develop a severe accident analysis code not only for light water reactor but also sodium-cooled fast reactor. When a core disruptive accident occurs in sodium-cooled fast reactor, the fuel inside the core become melted and interacts with the coolant. As a result, gas-liquid two-phase flow will be formed in the debris bed, which may have porous nature depending on the cooling process. In such condition, the local porosity and its distribution are very important to characterize two-phase flow field in the porous media. In this study, X-ray radiography was applied to measure the local porosity in the packed bed of spheres. The radial profiles were estimated from the chordal profiles measured by the X-ray method and compared with the previous porosity model. In addition, the void fraction radial profiles were also obtained in air-water two-phase flow.
Murakami, Hiroaki; Ashizawa, Masaomi*; Tanaka, Kazuhiro*
Oyo Chishitsu, 59(1), p.2 - 12, 2018/04
This study describes the features of fractures and their fillings along with the long-term behavior of their hydrogeological structures in an underground environment based on the results of a geological investigation conducted at an underground facility in northern Kyushu. Fractures were classified into five groups on the basis of fracture orientation: A, B, C, D, and low-angle groups. The genesis of all fractures is the cooling process of granodiorite pluton. Almost all of the water-conducting fractures are included in the B group. Because a number of fracture fillings in the B group are filled by prehnite and crushed fragments of epidote and quartz, the fractures in this group alternated sealing and re-opening. The fracture characteristics in the B group are follow as: accompanying many alteration halos, long trace length, and cutting off other fractures. These results indicate that fractures in the B group have possibly functioned as pathways for groundwater flow in the long term.
Nakata, Hisakazu; Hayashi, Hirokazu; Amazawa, Hiroya; Sakai, Akihiro
JAEA-Technology 2017-031, 41 Pages, 2018/01
JAEA-Technology-2017-031.pdf:5.27MB
JAEA plans to install disposal facilities for radioactive waste arising from research institutes. It must meet the technical standards specified in the relevant rule. One technical standard is that the disposal facilities shall be performance so as not to be left with the voids after the backfilling with soil. Additionally, the rule also requires this radioactive waste be enclosed in a container in which no harmful voids remain. In order to contribute to the development of a method that adapts the disposal facilities to these technical standards, JAEA adopts a waste conditioning artifice that aims for reducing a quantity of voidage in each waste container by a vibration filling method using sandy soil, providing with average void ratios inside the disposal facilities being adequately controlled. In this reports, filling property tests are conducted in the light of filling sand characteristics, types of metal waste and vibration conditions.
Nb and 
Ta for chemical studies of element 105, Db, using the GARIS gas-jet systemHuang, M.*; Haba, Hiromitsu*; Murakami, Masashi*; Asai, Masato; Kaji, Daiya*; Kanaya, Jumpei*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Kikutani, Yuki*; Komori, Yukiko*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 304(2), p.845 - 849, 2015/05
Times Cited Count：3 Percentile：25.85(Chemistry, Analytical)A technique to utilize radioisotopes of Nb and Ta was developed for chemical studies of element 105, Db, by coupling a gas-jet transport system to the RIKEN gas-filled recoil ion separator (GARIS). The short-lived Nb and Ta were produced with nuclear reactions using a 
F beam whose energy was the same as that to produce 
Db. Then, they were separated with GARIS and extracted to a chemistry laboratory with the gas-jet transport system. By changing only magnetic field of GARIS and inserting an energy degrader and a shutter for recoil ions, we could deliver the Nb and Ta to a chemistry device for Db without changing other experimental conditions.
Hotta, Takashi
Physica B; Condensed Matter, 378-380, p.51 - 53, 2006/05
Times Cited Count：4 Percentile：22.76(Physics, Condensed Matter)In order to clarify what types of spin and orbital fluctuations dominate over low-temperature electronic properties of Pr-based filled skutterudites, we evaluate multipole susceptibility based on a multiorbital Anderson model constructed from a 
- coupling scheme. It is found that magnetic and quadrupole fluctuations are dominant at low temperatures. When we further include the effect of rattling as dynamical Jahn-Teller phonons, there remain quadrupole and octupole fluctuations, which may induce exotic superconducting pairing.
Hotta, Takashi
Physical Review Letters, 96(19), p.197201_1 - 197201_4, 2006/05
Times Cited Count：40 Percentile：81.37(Physics, Multidisciplinary)A mechanism of non-magnetic Kondo effect is proposed on the basis of a multiorbital Anderson model coupled with dynamical Jahn-Teller (JT) phonons. An electron system coupled dynamically with JT phonons has a vibronic ground state with double degeneracy due to clockwise and anti-clockwise rotational modes with entropy of 
. When a temperature is lower than a characteristic energy to turn the rotational direction, the rotational degree of freedom is eventually suppressed and the corresponding entropy is released, leading to quasi-Kondo behavior. We discuss possible relevance of this quasi-Kondo phenomenon to electronic properties of filled skutterudites.
Hotta, Takashi
Journal of the Physical Society of Japan, 74(9), p.2425 - 2429, 2005/09
Times Cited Count：26 Percentile：73.62(Physics, Multidisciplinary)In order to clarify exotic multipole properties of filled skutterudites, we evaluate multipole susceptibility for 
=1
5, where is the local 
-electron number, on the basis of a multiorbital Anderson model constructed using the - coupling scheme. For =1, magnetic fluctuations dominate over low-temperature electronic properties, while for =2 and 4, electronic states are dominated by both magnetic and quadrupole fluctuations. For =3 and 5, octupole fluctuations are found to be significant, depending on the crystalline electric field potential. We discuss possible relevance of the results to actual materials.
-electron systems with filled skutterudite structureHotta, Takashi
Journal of the Physical Society of Japan, 74(4), p.1275 - 1288, 2005/04
Times Cited Count：25 Percentile：72.91(Physics, Multidisciplinary)In order to understand electronic properties of filled skutterudite materials, the Anderson model is analyzed by using the numerical renormalization group method to evaluate magnetic susceptibility and entropy of electron for each case of =113, where is the number of electrons per rare-earth ion. For the 
-electron system corresponding to the Pr-based filled skutterudite, it is found that magnetic fluctuations significantly remain at low temperatures, even when the ground state is 
singlet, if 
triplet is the excited state with small excitation energy. By analyzing an orbital degenerate Hubbard model constructed based on the - coupling scheme, we find that anisotropic Cooper-pair mediated by magnetic fluctuations appears in a limited region in which the singlet and triplet ground states are interchanged.
TiO
pebble bed from the core of JMTRIkeshima, Yoshiaki; Ishida, Takuya*; Tsuchiya, Kunihiko; Tomita, Kenji; Ebisawa, Hiroyuki; Magome, Hirokatsu; Nakamichi, Masaru*; Kitajima, Toshio; Kawamura, Hiroshi
JAERI-Tech 2005-005, 37 Pages, 2005/02
JAERI-Tech-2005-005.pdf:7.59MB
no abstracts in English
Hotta, Takashi
Physical Review Letters, 94(6), p.067003_1 - 067003_4, 2005/02
Times Cited Count：15 Percentile：62.72(Physics, Multidisciplinary)In order to clarify magnetic properties of filled skutterudites, we analyze the Anderson model including seven orbitals hybridized with an 
conduction band using a numerical technique. For =2 corresponding to Pr-based filled skutterudites, where is the local -electron number, even if the ground state is a singlet, there remain significant magnetic fluctuations from a triplet state with a small excitation energy. This result can be understood by the fact that -electron states are clearly distinguished as itinerant and localized ones in the filled skutterudite structure. This picture also explains the complex results for -electron magnetic susceptibility and entropy for =113.
P-NMR study of the uranium-based filled skutterudite compound UFe
P
Tokunaga, Yo; Matsuda, Tatsuma; Sakai, Hironori; Kato, Harukazu*; Kambe, Shinsaku; Walstedt, R. E.; Haga, Yoshinori; Onuki, Yoshichika; Yasuoka, Hiroshi
Physical Review B, 71(4), p.045124_1 - 045124_5, 2005/01
Times Cited Count：10 Percentile：42.74(Materials Science, Multidisciplinary)P NMR measurements have been performed on the uranium-based ferromagnetic insulator UFeP with 
K. The field-orientation dependence of the hyperfine interaction has been measured using a single crystal, and the results compared with a point-dipolar field calculation assuming local moments at the U sites. We have also measured the field and temperature dependence of the nuclear spin-lattice relaxation rate (
) in several fields between 1.0 and 5.5 T at temperatures between 1.4 and 300 K. The results are discussed on the basis of a localized picture for the uranium 5f electrons.
Enoeda, Mikio; Kosaku, Yasuo; Hatano, Toshihisa; Kuroda, Toshimasa*; Miki, Nobuharu*; Homma, Takashi; Akiba, Masato; Konishi, Satoshi; Nakamura, Hirofumi; Kawamura, Yoshinori; et al.
Nuclear Fusion, 43(12), p.1837 - 1844, 2003/12
Times Cited Count：101 Percentile：93.45(Physics, Fluids & Plasmas)no abstracts in English
TiUchida, Munenori*; Ishitsuka, Etsuo; Kawamura, Hiroshi
Fusion Engineering and Design, 69(1-4), p.499 - 503, 2003/09
Times Cited Count：26 Percentile：82.89(Nuclear Science & Technology)no abstracts in English
TiO
pebble bed under neutron irradiationKawamura, Hiroshi; Kikukawa, Akihiro*; Tsuchiya, Kunihiko; Yamada, Hirokazu*; Nakamichi, Masaru; Ishitsuka, Etsuo; Enoeda, Mikio; Ito, Haruhiko
Fusion Engineering and Design, 69(1-4), p.263 - 267, 2003/09
Times Cited Count：3 Percentile：25.79(Nuclear Science & Technology)no abstracts in English
TiO pebble bed for a demo blanketHatano, Toshihisa; Enoeda, Mikio; Suzuki, Satoshi; Kosaku, Yasuo; Akiba, Masato
Fusion Science and Technology, 44(1), p.94 - 98, 2003/07
Times Cited Count：24 Percentile：81.86(Nuclear Science & Technology)no abstracts in English
PIshii, Kenji; Inami, Toshiya; Murakami, Yoichi; Hao, L.*; Iwasa, Kazuaki*; Kogi, Masafumi*; Aoki, Yuji*; Sugawara, Hitoshi*; Sato, Hideyuki*; Imada, Shin*; et al.
Physica B; Condensed Matter, 329-333(1-4), p.467 - 468, 2003/05
Times Cited Count：6 Percentile：35.62(Physics, Condensed Matter)Resonant x-ray scattering study was carried out to investigate an anomalous ordered state (
= 6.5 K) in the filled skutterudite PrFeP. At the Pr-
absorption edge, we observed resonant features in 
= odd reflections, which are forbidden in the 
structure above . Because these reflections contain the difference of anomalous scattering factor between two Pr atoms in the unit cell, and the ordered state is attributed to the ordering of two different electronic states of Pr.
Kawamura, Yoshinori; Konishi, Satoshi; Nishi, Masataka
Fusion Engineering and Design, 58-59, p.389 - 394, 2001/11
Times Cited Count：26 Percentile：85.07(Nuclear Science & Technology)no abstracts in English
tritium recovery experiments of blanket in-pile mockup with LiTiO pebble bed in JapanTsuchiya, Kunihiko; Nakamichi, Masaru; Nagao, Yoshiharu; Enoeda, Mikio; Osaki, Toshio*; Tanaka, Satoru*; Kawamura, Hiroshi
Journal of Nuclear Science and Technology, 38(11), p.996 - 1003, 2001/11
Times Cited Count：23 Percentile：82.42(Nuclear Science & Technology)no abstracts in English
