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Journal Articles

Activity report of the task group of radiation protection about wastes containing natural radioactive nuclides

Saito, Tatsuo; Kobayashi, Shinichi*; Zaitsu, Tomohisa*; Shimo, Michikuni*; Fumoto, Hiromichi*

Hoken Butsuri (Internet), 55(2), p.86 - 91, 2020/06

Safety cases for disposal of uranium bearing waste and NORM with uranium has not yet been fully developed in Japan, because of safety assessment of extraordinary long timespan and uncertainty in unexpected incidents with uncompleted radon impact evaluation measures arising from uranium waste disposal facility in far future. Our task group of radiation protection for wastes with natural radioactive nuclides studied some safety cases with disposal of uranium bearing waste and NORM in terms of nuclides, U-235, U-238 and their progenies, and comprehensively discussed the current state of their disposal in comparison to the ideas of international organizations such as ICRP and IAEA. We developed our ideas for long term uncertainty and radon with the knowledge of experts in each related area of direction, repeating discussions, focusing out the orientation of each directions, and outlined the recommendations with our suggestions of solving important issues in the future to be addressed.

Journal Articles

Effect of magnetism on lattice dynamics in SrFe$$_2$$As$$_2$$ using high-resolution inelastic X-ray scattering

Murai, Naoki*; Fukuda, Tatsuo; Kobayashi, Tatsuya*; Nakajima, Masamichi*; Uchiyama, Hiroshi*; Ishikawa, Daisuke*; Tsutsui, Satoshi*; Nakamura, Hiroki; Machida, Masahiko; Miyasaka, Shigeki*; et al.

Physical Review B, 93(2), p.020301_1 - 020301_5, 2016/01

 Times Cited Count:7 Percentile:41.71(Materials Science, Multidisciplinary)

Journal Articles

Pressure-temperature-field phase diagram in the ferromagnet U$$_3$$P$$_4$$

Araki, Shingo*; Hayashida, Minami*; Nishiumi, Naoto*; Manabe, Hiroki*; Ikeda, Yoichi*; Kobayashi, Tatsuo*; Murata, Keizo*; Inada, Yoshihiko*; Wi$'s$niewski, P.*; Aoki, Dai*; et al.

Journal of the Physical Society of Japan, 84(2), p.024705_1 - 024705_8, 2015/02

 Times Cited Count:7 Percentile:54.9(Physics, Multidisciplinary)

Journal Articles

Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of an atmospheric dispersion model with an improved deposition scheme and oceanic dispersion model

Katata, Genki; Chino, Masamichi; Kobayashi, Takuya; Terada, Hiroaki; Ota, Masakazu; Nagai, Haruyasu; Kajino, Mizuo*; Draxler, R.*; Hort, M.*; Malo, A.*; et al.

Atmospheric Chemistry and Physics, 15(2), p.1029 - 1070, 2015/01

 Times Cited Count:167 Percentile:99(Environmental Sciences)

We estimated a detailed time trend of atmospheric releases during the Fukushima Dai-ichi Power Station (FNPS1) accident by combining environmental monitoring data with coupling simulation of atmospheric model of WSPEEDI-II, and oceanic dispersion model of SEA-GEARN-FDM. The new scheme of dry and fogwater depositions, in-cloud scavenging, cloud condensation nuclei activity, and wet scavenging by ice phase for radioactive iodine gas and other particles was incorporated into WSPEEDI-II. The results revealed that the major releases of radionuclides occurred in the following periods: afternoon on 12 March when the wet venting and hydrogen explosion at Unit 1, morning on 13 March after the venting event at Unit 3, midnight on 14 March when three-time openings of SRV were conducted at Unit 2, morning and night on 15 March, and morning on 16 March.

Journal Articles

Metamagnetic transition of itinerant ferromagnet U$$_3$$P$$_4$$ under high pressure

Araki, Shingo*; Hayashida, Minami*; Nishiumi, Naoto*; Manabe, Hiroki*; Ikeda, Yoichi*; Kobayashi, Tatsuo*; Murata, Keizo*; Inada, Yoshihiko*; Wi$'s$niewski, P.*; Aoki, Dai*; et al.

JPS Conference Proceedings (Internet), 3, p.011081_1 - 011081_6, 2014/06

Journal Articles

Achievement of 500 keV negative ion beam acceleration on JT-60U negative-ion-based neutral beam injector

Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.

Nuclear Fusion, 51(8), p.083049_1 - 083049_8, 2011/08

 Times Cited Count:42 Percentile:88.1(Physics, Fluids & Plasmas)

Hydrogen negative ion beams of 490 keV, 3 A and 510 keV, 1 A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 2 m$$^{2}$$ for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m$$^{2}$$). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60SA and ITER.

Journal Articles

Demonstration of 500 keV beam acceleration on JT-60 negative-ion-based neutral beam injector

Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Hydrogen negative ion beams of 490keV, 3A and 510 keV, 1A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of $$sim$$ 2 m$$^{2}$$ for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m$$^{2}$$). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60 SA and ITER.

JAEA Reports

Application study on low alkaline cementitious materials for deep geological repository of high level radioactive wastes, 2; Organization of previous finding and understanding of material properties of low alkaline cement (Joint research)

Kobayashi, Yasushi; Yamada, Tsutomu; Naito, Morimasa; Yui, Mikazu; Nakayama, Masashi; Sato, Haruo; Nishida, Takahiro*; Hironaga, Michihiko*; Yamamoto, Takeshi*; Sugiyama, Daisuke*; et al.

JAEA-Research 2009-013, 70 Pages, 2009/06

JAEA-Research-2009-013.pdf:8.85MB

Cementitious materials will be used to ensure construction and operational safety and work efficiency in a deep geological repository. The low alkaline cement has been developed to reduce uncertainties due to hyper alkaline for the long-term safety performance of the repository system. Functions of cementitious material required in each phase of repository construction, operation and closure were summarized in a separate report entitled "Application Study on Low Alkaline Cementitious Materials for Deep Geological Repository of High Level Radioactive Wastes (Phase I) "In this report, properties of low alkaline cement/concrete which have been developed both at home and abroad, and recipes of the low alkaline concrete taken account of application to the repository component have been investigated. Fresh and hardened properties of the low alkaline cement are equivalent to the OPC and the low alkaline cement has an advantage over OPC in terms of leaching resistance. The HFSC developed by JAEA, which belongs to a pozzolanic type low alkaline cement will be able to apply to the shotcrete and the lining concrete by choosing an adequate recipe. Clarification of influences of the chemical composition of groundwater on leachate properties of the hydrates, examination of pH measurement of cement leachate, evaluation of corrosion behavior of rebar embedded in the HFSC concrete are raised as open questions for future activities.

JAEA Reports

Application study on low alkaline cementitious materials for deep geological repository of high level radioactive wastes, 1; Requirements for use of cementitious materials in deep geological repository system (Joint research)

Kobayashi, Yasushi; Yamada, Tsutomu; Naito, Morimasa; Yui, Mikazu; Nakayama, Masashi; Sato, Haruo; Nishida, Takahiro*; Hironaga, Michihiko*; Yamamoto, Takeshi*; Sugiyama, Daisuke*; et al.

JAEA-Research 2008-112, 43 Pages, 2009/03

JAEA-Research-2008-112.pdf:4.58MB

In deep geological repository, use of cementitious material for rock support, lining, and grouting is essential for construction and operation and possibly raises in groundwater pH due to leachate from the cements. Since this hyperalkaline condition may lead to degradation of barriers, there is concern that it gives significant impact on long-term safety performance of the repository system. Because of these backgrounds, developments of low alkaline cement have been conducted both at home and abroad. JAEA is now planning to conduct an in-situ test for shotcreting using low alkaline cement at the Horonobe URL. On the other hand, CRIEPI has studied and developed cementitious materials for disposal of radioactive wastes. This joint research report summarizes requirements and expected performance of cementitious materials in repository taking account of surrounding conditions in each stage of the repository program so as to reflect them to further development of the low alkaline cement.

Journal Articles

Recent R&D activities of negative-ion-based ion source for JT-60SA

Ikeda, Yoshitaka; Hanada, Masaya; Kamada, Masaki; Kobayashi, Kaoru; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Inoue, Takashi; Honda, Atsushi; Kawai, Mikito; et al.

IEEE Transactions on Plasma Science, 36(4), p.1519 - 1529, 2008/08

 Times Cited Count:8 Percentile:34.65(Physics, Fluids & Plasmas)

The JT-60SA N-NBI system is required to inject 10 MW for 100 s at 500 keV. Three key issues should be solved for the JT-60SA N-NBI ion source. One is to improve the voltage holding capability. Recent R&D tests suggested that the accelerator with a large area of grids may need a high margin in the design of electric field and a long time for conditioning. The second issue is to reduce the grid power loading. It was found that some beamlets were strongly deflected due to beamlet-beamlet interaction and strike on the grounded grid. The grids are to be designed by taking account of beamlet-beamlet interaction in three-dimensional simulation. Third is to maintain the D- production for 100 s. A simple cooling structure is proposed for the active cooled plasma grid, where a key is the temperature gradient on the plasma grid for uniform D- production. The modified N-NBI ion source will start on JT-60SA in 2015.

Journal Articles

High-quality single crystal growth and physical properties in a ferromagnet UIr

Yamamoto, Etsuji; Haga, Yoshinori; Ikeda, Shugo; Matsuda, Tatsuma; Akazawa, Teruhiko*; Kotegawa, Hisashi*; Kobayashi, Tatsuo*; Onuki, Yoshichika*

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e123 - e125, 2007/03

no abstracts in English

Journal Articles

Tomonaga-Luttinger liquid in a quasi-one-dimensional $$S$$ = 1 antiferromagnet observed by specific heat measurements

Hagiwara, Masayuki*; Tsujii, Hiroyuki*; Rotundu, C. R.*; Andraka, B.*; Takano, Yasumasa*; Tateiwa, Naoyuki; Kobayashi, Tatsuo*; Suzuki, Takafumi*; Suga, Seiichiro*

Physical Review Letters, 96(14), p.147203_1 - 147203_4, 2006/04

 Times Cited Count:18 Percentile:68.78(Physics, Multidisciplinary)

Specific-heat experiments on single crystals of the $$S$$ = 1 quasi-one-dimensional bond-alternating antiferromagnet Ni(C$$_9$$H$$_{24}$$N$$_4$$)(NO$$_2$$)(ClO$$_4$$) (NTENP) have been performed in magnetic fields applied both parallel and perpendicular to the spin chains. We have found for the parallel field configuration that the magnetic specific heat ($$C_{rm mag}$$) is proportional to temperature ($$T$$) above a critical field $$H_c$$, at which the energy gap vanishes, in a temperature region above that of the long-range ordered state. The ratio $$C_{rm mag}$$ = $$T$$ increases as the magnetic field approaches $$H_c$$ from above. The data are in good quantitative agreement with the prediction of the $$c$$=1 conformal field theory in conjunction with the velocity of the excitations calculated by a numerical diagonalization, providing conclusive evidence for a Tomonaga-Luttinger liquid.

Journal Articles

Change of the Fermi surface across the critical pressure in CeIn$$_3$$; The de Haas-van Alphen study under pressure

Settai, Rikio*; Kubo, Tetsuo*; Shiromoto, Tomoyuki*; Honda, Daisuke*; Shishido, Hiroaki*; Sugiyama, Kiyohiro*; Haga, Yoshinori; Matsuda, Tatsuma; Betsuyaku, Kiyoshi*; Harima, Hisatomo*; et al.

Journal of the Physical Society of Japan, 74(11), p.3016 - 3026, 2005/11

 Times Cited Count:50 Percentile:12.02(Physics, Multidisciplinary)

We have studied a change of the Fermi surface in an antiferromagnet CeIn$$_3$$ via the de Haas-van Alphen experiment under pressure up to 3 GPa. With increasing pressure P, the Neel temperature $$T_N$$=10 K decreases and becomes zero at a critical pressure Pc $$simeq$$2.6 GPa. In the pressure region $$P > P_c$$, we have observed a large main Fermi surface named a, which indicates that the electronic state of 4 f electron in CeIn$$_3$$ changes from localized to itinerant at Pc, as observed in the similar antiferromagnets CeRh$$_2$$Si$$_2$$ and CeRhIn$$_5$$. The cyclotron effective mass $$m_c^*$$ of this main Fermi surface is extremely enhanced around Pc: $$m_c^*$$ $$simeq$$60 $$m_0$$ at 2.7 GPa for the magnetic field along the $$<$$100$$>$$ direction.

Journal Articles

Single crystal growth and fermi surface properties of an antiferromagnet UPdGa$$_5$$

Ikeda, Shugo; Matsuda, Tatsuma; Haga, Yoshinori; Yamamoto, Etsuji; Nakashima, Miho*; Kirita, Shingo*; Kobayashi, Tatsuo*; Hedo, Masato*; Uwatoko, Yoshiya*; Yamagami, Hiroshi*; et al.

Journal of the Physical Society of Japan, 74(8), p.2277 - 2281, 2005/08

 Times Cited Count:10 Percentile:54.78(Physics, Multidisciplinary)

We have succeeded in growing a high-quality single crystal of an antiferromagnet UPdGa$$_5$$ by the Ga-flux method with the off-stoichiometric composition of U : Pd : Ga = 1 : 2 : 7.3. The electronic state has been investigated by the de Haas-van Alphen experiment, indicating the similar cylindrical Fermi surfaces as in an antiferromagnet UPtGa$$_5$$. We have also studied the pressure effect by measuring the electrical resistivity. The N$$acute{rm e}$$el temperature decreases with increasing pressure and becomes zero at 3.1 GPa. The antiferromagnetic state is changed into the paramagnetic state above 3.1 GPa.

Journal Articles

Magnetism of uranium dioxide UO$$_{2}$$ under high pressure

Sakai, Hironori; Kato, Harukazu; Tokunaga, Yo; Kambe, Shinsaku; Walstedt, R. E.; Nakamura, Akio; Tateiwa, Naoyuki*; Kobayashi, Tatsuo*

Journal of Magnetism and Magnetic Materials, 272-276(Suppl.), p.e413 - e414, 2004/05

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

The d.c. magnetization of insulating UO$$_{2}$$ under high pressure up to about 1 GPa has been measured using a piston-cylinder cell. Pressure-induced weak ferromagnetism was found to appear at low pressure (about 0.2 GPa). Both the remanent magnetization and the coercive force increase as pressure increases. This weak ferromagnetism may come from spin canting or from uncompensated moments around grain boundaries.

Journal Articles

Heat-capacity anomalies at $$T_{sc}$$ and $$T^*$$ in the ferromagnetic superconductor UGe$$_2$$

Tateiwa, Naoyuki*; Kobayashi, Tatsuo*; Amaya, Kiichi*; Haga, Yoshinori; Settai, Rikio*; Onuki, Yoshichika

Physical Review B, 69(18), p.180513_1 - 180513_4, 2004/05

 Times Cited Count:40 Percentile:83.1(Materials Science, Multidisciplinary)

We have investigated the specific heat under high pressure in the ferromagnetic superconductor UGe$$_2$$. Specific heat anomalies at the characteristic temperatures $$T_{sc}$$, the superconducting transition temperature, and $$T^*$$ were directly observed from the high-pressure specific heat measurement. The low-temperature electronic specific heat coefficient increases with increasing pressure, corresponding to the formation of heavy-fermion state near the critical pressure.

JAEA Reports

Power distributions in the High Temperature Engineering Test Reactor (HTTR) by measuring gross gamma ray from the fuel assemblies

Nojiri, Naoki; Shimakawa, Satoshi; Takamatsu, Kuniyoshi; Ishii, Yoshiki; Kawano, Shuichi; Kobayashi, Shoichi; Kawamoto, Taiki; Iyoku, Tatsuo

JAERI-Tech 2003-086, 136 Pages, 2003/11

JAERI-Tech-2003-086.pdf:8.67MB

To provide a basis for determination of the actual core power distribution, The power distribution experiments by measuring gross gamma ray emitted from fission products in the fuel assemblies were performed. The fuel assemblies were not spent condition but in-service condition. The averaged burn up was about 4,400 MWD/t. The gamma ray of a fuel assembly was measured with a GM counter under a temporary fuel withdrawing situation from the core during shutdown state. Uncertainties of the determination were from 3 to 6 percent in axial distribution per one fuel compact and within about 4 percent in radial and axial distribution of the core per one fuel assembly. It was concluded that the power distribution of the HTTR is almost equivalent to the expected power-profile shaping. Calculation of gamma ray distribution was performed by ORIGEN-2 code based the power distribution obtained by the Monte Carlo MVP code. The calculation results show good agreement with the experimental ones. The method, procedure, analysis, correction, determination and comparison are described in this report.

Journal Articles

Site-specific phonon density of states discerned using electronic states

Seto, Makoto; Kitao, Shinji*; Kobayashi, Yasuhiro*; Haruki, Rie*; Yoda, Yoshitaka*; Mitsui, Takaya; Ishikawa, Tatsuo*

Physical Review Letters, 91(18), p.185505_1 - 185505_4, 2003/10

 Times Cited Count:31 Percentile:79.13(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Pressure-induced weak ferromagnetism in uranium dioxide, UO$$_{2}$$

Sakai, Hironori; Kato, Harukazu; Tokunaga, Yo; Kambe, Shinsaku; Walstedt, R. E.; Nakamura, Akio; Tateiwa, Naoyuki*; Kobayashi, Tatsuo*

Journal of Physics; Condensed Matter, 15(28), p.S2035 - S2037, 2003/07

 Times Cited Count:1 Percentile:8.89(Physics, Condensed Matter)

The cubic-fluorite type uranium dioxide UO$$_2$$ is an ionically bounded insulator with localized magnetic moments of U$$^{4+}$$ (5$$f^{2}$$) ions. Under atmospheric pressure, UO$$_2$$ exhibits a first order antiferromagnetic transition at $$T_{rm N}$$=30.8 K accompanied by a small lattice distortion. In order to clarify the interrelation between QQ and exchange interactions in this system, we performed d.c. magnetization measurement under high pressure up to about 1 GPa by a piston-cylinder-type cramped cell. From the d.c. magnetization measurements under high pressure ($$ge$$ 0.1 GPa), it is found that UO$$_2$$ shows a weak-ferromagnetic-like transition at $$sim$$ 30 K, where the transition temperature is almost independent of external pressure up to 1 GPa. The ferromagnetic component per uranium atom is very small ($$sim 0.05 mu_{rm B}$$), although its component is dependent of pressure. This small ferromagnetic component may come from a canted antiferromagnetic ordering.

JAEA Reports

Conceptual Design Phase II of Disposal Facility below the Generaly used Depth for RI Laboratory and so on

Kobayashi, Wataru*; Nakagawa, Tatsuo*; Mukunoki, Atsushi*; Goto, Kikuji*

JNC TJ8400 2003-044, 85 Pages, 2003/02

JNC-TJ8400-2003-044.pdf:1.47MB

Radioisotopes, nuclear fuel materials, and so on have been used in the various fields such as the research activities of universities and research institutes or the treatment and diagnosis of the medical institutes. It is necessary to treat and dispose of radioactive wastes safely and economically. A fundamental examination was carried out in the Conceptual Design Phase I of Disposal Facility below the generally used Depth for RI Laboratory Wastes and so on in last year. Based on the latest wastes data, the reevaluation of the facility design and the safety evaluation were enforced toward the examination result in last year. And it was examined about the operation procedure that includes wastes reception and disposal place closing. Furthermore, economic evaluation about the disposal was enforced.

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