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Journal Articles

Conceptual study of a plutonium burner high temperature gas-cooled reactor with high nuclear proliferation resistance

Goto, Minoru; Demachi, Kazuyuki*; Ueta, Shohei; Nakano, Masaaki*; Honda, Masaki*; Tachibana, Yukio; Inaba, Yoshitomo; Aihara, Jun; Fukaya, Yuji; Tsuji, Nobumasa*; et al.

Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.507 - 513, 2015/09

A concept of a plutonium burner HTGR named as Clean Burn, which has a high nuclear proliferation resistance, had been proposed by Japan Atomic Energy Agency. In addition to the high nuclear proliferation resistance, in order to enhance the safety, we propose to introduce PuO$$_{2}$$-YSZ TRISO fuel with ZrC coating to the Clean Burn. In this study, we conduct fabrication tests aiming to establish the basic technologies for fabrication of PuO$$_{2}$$-YSZ TRISO fuel with ZrC coating. Additionally, we conduct a quantitative evaluation of the security for the safety, a design of the fuel and the reactor core, and a safety evaluation for the Clean Burn to confirm the feasibility. This study is conducted by The University of Tokyo, Japan Atomic Energy Agency, Fuji Electric Co., Ltd., and Nuclear Fuel Industries, Ltd. It was started in FY2014 and will be completed in FY2017, and the first year of the implementation was on schedule.

Journal Articles

Microscopic evidence for long-range magnetic ordering in the $$Gamma$$$$_{8}$$ ground quartet systems Sm$$Tr$$$$_{2}$$Al$$_{20}$$ ($$Tr$$: Ti, V, Cr)

Ito, Takashi; Higemoto, Wataru; Ninomiya, Kazuhiko; Sakai, Akito*; Nakatsuji, Satoru*

Journal of the Physical Society of Japan, 81(Suppl.B), p.SB050_1 - SB050_4, 2012/12

Recently, $$RT_2$$Al$$_{20}$$ compounds ($$R$$: rare earth, $$T$$: transition metal) have attracted much attention due to interesting physical properties closely related to their caged-structure. Each $$R$$ ion is confined in a Frank-Kasper cage consisting of 16 Al atoms and the large coordination number leads to strong $$c$$-$$f$$ hybridization. In addition, the Frank-Kasper cage allows various multipole degrees of freedom for the $$f$$-electrons at low $$T$$ because of a highly symmetric crystalline-electric-field (CEF). Among the $$RT_2$$Al$$_{20}$$ series, Pr$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V) and Sm$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V, Cr) exhibit both these features. The $$Gamma_3$$ ground doublet systems Pr$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V) show a phase transition at $$T_O$$ = 2.0K (Ti) and 0.6K (V). The order parameter is believed to be an electric quadrupole active in the $$Gamma_3$$ subspace. A possibility of the quadrupole Kondo effect has been discussed based on characteristic $$T$$-dependence in specific heat, resistivity, and magnetic susceptibility. The $$Gamma_8$$ ground quartet systems Sm$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V, Cr) also exhibit a phase transition at $$T_O$$ = 6.4K (Ti), 2.3K (V), and 1.8K (Cr). A nuclear specific heat study in SmTi$$_2$$Al$$_{20}$$ suggests that the primary order parameter is a magnetic dipole in spite of field-insensitive nature of the phase boundary. A possible importance of a secondarily ordered octupole moment was discussed. We here present a microscopic study of PrTi$$_2$$Al$$_{20}$$ and Sm$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V, Cr) using muon spin relaxation. In PrTi$$_2$$Al$$_{20}$$, no additional local field was observed in the ordered phase. This strongly supports the quadrupole ordering scenario. On the other hand, an appearance of a coherent local field was observed below $$T_O$$ in Sm$$T_2$$Al$$_{20}$$. This is consistent with the primary magnetic dipole ordering. The frequency distribution suggests that the magnetic structure is possibly different between the Sm$$T_2$$Al$$_{20}$$ compounds.

Journal Articles

$$mu$$SR evidence of nonmagnetic order and $$^{141}$$Pr hyperfine-enhanced nuclear magnetism in the cubic $$Gamma_3$$ ground doublet system PrTi$$_2$$Al$$_{20}$$

Ito, Takashi; Higemoto, Wataru; Ninomiya, Kazuhiko; Luetkens, H.*; Baines, C.*; Sakai, Akito*; Nakatsuji, Satoru*

Journal of the Physical Society of Japan, 80(11), p.113703_1 - 113703_4, 2011/11

 Times Cited Count:29 Percentile:78.95(Physics, Multidisciplinary)

Journal Articles

Oxidation of element 102, nobelium, with flow electrolytic column chromatography on an atom-at-a-time scale

Toyoshima, Atsushi; Kasamatsu, Yoshitaka*; Tsukada, Kazuaki; Asai, Masato; Kitatsuji, Yoshihiro; Ishii, Yasuo; Tome, Hayato; Nishinaka, Ichiro; Haba, Hiromitsu*; Oe, Kazuhiro*; et al.

Journal of the American Chemical Society, 131(26), p.9180 - 9181, 2009/07

 Times Cited Count:13 Percentile:45.68(Chemistry, Multidisciplinary)

We report here on the successful oxidation of element 102, nobelium (No), on an atom-at-a-time scale in 0.1 M $$alpha$$-hydroxyisobutyric acid ($$alpha$$-HIB) solution using newly developed flow electrolytic column chromatography. It is found that the most stable No$$^{2+}$$ is oxidized to No$$^{3+}$$ within 3 min and that the oxidized No complex with $$alpha$$-HIB holds the trivalent state in the column above the applied potential of 1.0 V.

Journal Articles

Effects of chemical bonding character on pressure-induced structural changes of liquid metals and semiconductors

Hattori, Takanori; Tsuji, Kazuhiko*

Materia, 47(10), p.507 - 512, 2008/10

We investigate pressure-induced structural changes in liquids of tetrahedrally bonded materials by a synchrotron X-ray diffraction. The liquids show various structural changes, depending on their ionic characters in the chemical bonds. The liquids with a small ionic character, such as GaSb, InSb, InAs, show continuous structural changes over a wide pressure region of about 20 GPa. In contrast, those with a large ionic character, such as CdTe, AgI, show drastic structural changes within a narrow pressure region of $$sim$$ 2 GPa. We discuss the effect of the ionicity on the pressure-induced structural changes in liquid and compare the effect with that in the crystalline phases.

Journal Articles

A Study of air ingress and its prevention in HTGR

Yan, X.; Takeda, Tetsuaki; Nishihara, Tetsuo; Ohashi, Kazutaka; Kunitomi, Kazuhiko; Tsuji, Nobumasa*

Nuclear Technology, 163(3), p.401 - 415, 2008/09

 Times Cited Count:10 Percentile:58.26(Nuclear Science & Technology)

A rupture of primary piping in HTGR represents a design basis event. In such a loss of coolant event a safety issue remains graphite oxidation damage to fuel and core should major air ingress take place through the breached primary boundary. The present study deals with the two most probable cases of air ingress. The first results from rupture of a standpipe. A design change proposed in the vessel top structure intends to rule out any probability of a standpipe rupture. The feasibility of the modified structure is evaluated. The second case results from rupture of a main coolant pipe. Experiment and analysis are performed to gain understanding of the multi-phased air ingress phenomena and accordingly a new mechanism of sustained counter-air diffusion is proposed that is fully passive and effective in preventing major air ingress in the event of main coolant pipe rupture. The results of the present study may lead to improved safety and economic design of the HTGR.

Journal Articles

Structural and electronic properties of liquid InAs under pressure

Shimojo, Fuyuki*; Miyata, Yasuhisa*; Sugahara, Takayuki*; Hattori, Takanori; Tsuji, Kazuhiko*

Journal of Physics; Conference Series, 98, p.042016_1 - 042016_4, 2008/00

 Times Cited Count:0 Percentile:0.05

The structural and bonding properties of liquid InAs under pressure are investigated by ab initio molecular-dynamics simulations. The calculated structure factors are in good agreement with the recent X-ray diffraction measurements over a wide range of pressure. It is shown that the pressure dependence of the spatial correlation between atoms depends on the species of atomic pairs reflecting the strength of the covalent bonding. A detailed investigation of the pair distribution functions confirms that different pressure-induced structural changes occur below and above 6-10 GPa. It is suggested that such structural changes are related to the reduction of the covalent nature under pressure.

Journal Articles

Pressure-induced structural change of liquid InAs and the systematics of liquid III-V compounds

Hattori, Takanori; Tsuji, Kazuhiko*; Miyata, Yasuhisa*; Sugahara, Takayuki*; Shimojo, Fuyuki*

Physical Review B, 76(14), p.144206_1 - 144206_10, 2007/10

 Times Cited Count:6 Percentile:32.45(Materials Science, Multidisciplinary)

To understand the pressure-induced structural changes of liquid III-V compounds systematically, the pressure dependence of liquid InAs was investigated using the synchrotron X-ray diffraction and an $textit{ab initio}$ molecular dynamics simulation (AIMD). The X-ray diffraction experiments revealed that the liquid changes its compression behavior from a nearly uniform type to a nonuniform one around 9 GPa. Corresponding to this change, the coordination number CN, which is maintained up to 9 GPa, markedly increases from 6.0 to 7.5. The AIMD simulation revealed that this change is related to the change in the pressure dependence of all three pair correlations. In particular, a marked change is observed in the As-As correlation; in the low pressure region the position of the first peak in $$g_{rm AsAs}(r)$$, $$r_{rm AsAs}$$, increases with maintaining the CN$$_{rm AsAs}$$, but in the high pressure region the $$r_{rm AsAs}$$ stops increasing and the CN$$_{rm AsAs}$$ begins to increase. The results for InAs are compared with those for GaSb and InSb and the systematics of the pressure-induced structural change of liquid III-V compounds are dicussed.

Journal Articles

Pressure dependence of the structure of liquid Sn up to 19.4 GPa

Narushima, Takashi*; Hattori, Takanori; Kinoshita, Tomohiro*; Hinzmann, A*; Tsuji, Kazuhiko*

Physical Review B, 76(10), p.104204_1 - 104204_8, 2007/09

 Times Cited Count:24 Percentile:68.56(Materials Science, Multidisciplinary)

The structure of liquid Sn was investigated up to 19.4 GPa by synchrotron X-ray diffraction. Upon compression up to about 3-6 GPa, the structural features, which reflect the anisotropic local structure become less prominent; i.e., the hump on the high-$$Q$$ side of the first peak in the structure factor $$S(Q)$$ becomes smaller, the position of the second peak relative to that of the first peak in $$S(Q)$$, $$Q_{2}/Q_{1}$$, decreases, and the coordination number, CN, increases. These features indicate that the liquid structure changes toward a simple liquid metal upon compression. However, at higher pressures, the structural parameters nearly unchanged. The parameters in this pressure range are still deviated from their respective values for simple liquid metals. These findings suggest that, contrary to previous expectations, the liquid does not monotonically approach a simple liquid metal, but takes a relatively stable intermediate form with an anisotropic local structure before approaching a simple liquid metal. The high-pressure behavior of liquid Sn is compared to those of liquid Si and liquid Ge and the systematics in liquid group 14 elements are discussed.

Journal Articles

Pressure-induced structural changes in liquid III-V compounds

Hattori, Takanori; Taga, Naohito*; Takasugi, Yukinobu*; Kinoshita, Tomohiro*; Narushima, Takashi*; Tsuji, Kazuhiko*; Kikegawa, Takumi*

Photon Factory Activity Report 2005, Part A, p.42 - 43, 2006/11

no abstracts in English

Journal Articles

Pressure-induced structural change of liquid CdTe up to 23.5GPa

Hattori, Takanori; Kinoshita, Tomohiro*; Narushima, Takashi*; Tsuji, Kazuhiko*; Katayama, Yoshinori

Physical Review B, 73(5), p.054203_1 - 054203_9, 2006/02

 Times Cited Count:22 Percentile:68.31(Materials Science, Multidisciplinary)

The structure of liquid CdTe was investigated at pressures up to 23.5GPa using synchrotron X-ray diffraction. The structure factor, S(Q), and the pair distribution function, g(r), drastically change in two pressure regions, 1.8-3.0 GPa and 7.0-9.0 GPa, accompanied with marked increase in the average coordination number, CN. These findings suggest that there exists at least three stable liquid forms below 23.5GPa. The pressure interval of the structural change is much smaller compared to other liquids of tetrahedrally bonded materials. Comparing the shapes of S(Q) and g(r), and other structural parameters with the respective data for the reference materials reveals that the lowest- and intermediate-pressure forms have the same local structures as the crystalline counterpart (zinc-blende-like local structure and a NaCl-like local structure), while the highest-pressure form has a different local structure from that in the crystalline form.

Journal Articles

Design study on passive cooling system of the Gas Turbine High Temperature Reactor (GTHTR300)

Katanishi, Shoji; Kunitomi, Kazuhiko; Tsuji, Nobumasa*; Maekawa, Isamu*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(3), p.257 - 267, 2004/09

no abstracts in English

Journal Articles

X-ray structural studies on elemental liquids under high pressures

Katayama, Yoshinori; Tsuji, Kazuhiko*

Journal of Physics; Condensed Matter, 15(36), p.6085 - 6103, 2003/09

 Times Cited Count:81 Percentile:93.05(Physics, Condensed Matter)

X-ray structural studies on several elemental liquids under high pressure are reviewed. Combination of synchrotron radiation sources and large volume presses enables us to carry out in-situ structural measurements on liquids at high pressures up to several GPa. The measurements have revealed that compressions of liquid alkali metals are almost uniform, whereas those of liquids that have covalent components in bonding are mostly anisotropic. In some elements, different types of volume dependence of the nearest neighbour distances are observed in different pressure ranges. This behaviour suggests that the liquid phase can be divided in regions. Although most of the observed structural changes are continuous, a discovery of an abrupt structural change in liquid phosphorus, which is completed over a pressure range of less than 0.05 GPa around 1GPa and 1050 $$^{circ}$$C, supports existence of a first-order liquid-liquid phase transition.

Journal Articles

X-ray diffraction study on structural change in liquid selenium under high pressure

Katayama, Yoshinori; Mizutani, Takeshi; Utsumi, Wataru; Shimomura, Osamu; Tsuji, Kazuhiko*

Physica Status Solidi (B), 223(2), p.401 - 404, 2001/01

 Times Cited Count:18 Percentile:67.54(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Structural studies of metallic fluids at SPring-8

Tamura, Kozaburo*; Inui, Masanori*; Tsuji, Kazuhiko*; Funakoshi, Kenichi*; Utsumi, Wataru

Nihon Kessho Gakkai-Shi, 42(1), p.33 - 40, 2000/02

no abstracts in English

Journal Articles

EXAFS study on liquid selenium and liquid tellurium under high pressure

Katayama, Yoshinori; Shimomura, Osamu; Tsuji, Kazuhiko*

Journal of Non-Crystalline Solids, 250-252(Part2), p.537 - 541, 1999/08

no abstracts in English

Journal Articles

High temperature research beamline (BL04B1) at SPring-8

Utsumi, Wataru; Funakoshi, Kenichi*; Urakawa, Satoru*; Irifune, Tetsuo*; Tamura, Kozaburo*; Inui, Masanori*; Tsuji, Kazuhiko*; Shimomura, Osamu

Hoshako, 12(1), p.17 - 23, 1999/02

no abstracts in English

Journal Articles

Amorphization from the quenched high-pressure phase in III-V and II-VI compounds

Mori, Yuki*; Kato, Sayuri*; Mori, Hiroko*; Katayama, Yoshinori; Tsuji, Kazuhiko*

Review of High Pressure Science and Technology, 7, p.353 - 355, 1998/03

The temperature dependence of phase transitions in GaSb, AlSb, GaAs, GaP, InAs, ZnSe, and CdTe are studied by X-ray diffraction measurements under pressure upto 30 GPa at temperatures of 90-300K. The phase transitions depend on paths in a pressure-temperature phase diagram. The structure of the recovered phase after decompression depends on the ionicity in bonding: amorphous for small ionicity, the stable zincblende structure for large ionicity, and microcrystalline or moderate ionicity. These results are discussed by using a configuration-coordinate model.

Journal Articles

Effect of pressure on hopping conduction in amorphous Ge alloys

Toda, Naohiro*; Katayama, Yoshinori; Tsuji, Kazuhiko*

Review of High Pressure Science and Technology, 7, p.647 - 649, 1998/03

The electrical conductivity $$sigma$$ has been measured at pressures $$P$$ to 8 GPa and temperatures $$T$$ of 77-300K in evaporated amorphous Ge (a-Ge), a-Ge-Cu alloys and a-Ge-Al alloys. The $$T$$ dependence of $$sigma$$ is well described by a power lw at low temperatures below 150 K, which is expemcted from a multi-phonon tunneling transition process model with weak electron-lattice coupling, rather than the Mott's variable range hopping conduction model. The exponent $$n$$ in the power law changes with increasing pressure. For both a-Ge$$_{1-x}$$Cu$$_{x}$$ and a-Ge$$_{1-x}$$Al$$_{x}$$ alloys, d(ln $$n$$)/d$$P$$ show positive values in the low pressure region and negative values in the high pressure region. Results are discussed from several hopping conduction models.

Journal Articles

Structure of liquid rubidium and liquid sodium under pressure

Morimoto, Yoshiki*; Kato, Sayuri*; Toda, Naohiro*; Katayama, Yoshinori; Tsuji, Kazuhiko*; Yaoita, Kenichi*; Shimomura, Osamu

Review of High Pressure Science and Technology, 7, p.245 - 247, 1998/03

X-ray diffraction for liquid Rb and liquid Na has been measured under pressure up to 6 GPa using synchrotron radiation. Volume dependences of static structure factor $$S(Q)$$ and pair distribution function $$g(r)$$ were obtained to the volume range $$nu(=V/V_{0})$$ of 0.52 for liquid Rb and $$nu$$ of 0.73 for liquid Na to investigate the effect of the electronic change on the structure of liquid metals. With increasing pressure, the peaks of $$S(Q)$$ of both liquid Rb and liquid Na shift towards higher $$Q$$, and the heights of the first peak increase. Theses volume dependences of the structural data are compared with those for other metals under pressure and expanded fluids.

52 (Records 1-20 displayed on this page)