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Journal Articles

Effect of copper addition on precipitation behavior near grain boundary in Al-Zn-Mg alloy

Matsuda, Kenji*; Yasumoto, Toru*; Bendo, A.*; Tsuchiya, Taiki*; Lee, S.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Marioara, C. D.*; Lervik, A.*; Holmestad, R.*; et al.

Materials Transactions, 60(8), p.1688 - 1696, 2019/08

 Times Cited Count:5 Percentile:46.2(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Characterisation of structural similarities of precipitates in Mg-Zn and Al-Zn-Mg alloys systems

Bendo, A.*; Maeda, Tomoyoshi*; Matsuda, Kenji*; Lervik, A.*; Holmestad, R.*; Marioara, C. D.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Toda, Hiroyuki*; Yamaguchi, Masatake; et al.

Philosophical Magazine, 99(21), p.2619 - 2635, 2019/07

 Times Cited Count:13 Percentile:83.11(Materials Science, Multidisciplinary)

Journal Articles

Measurement of temperature response of intermediate heat exchanger in heat application system abnormal simulating test using HTTR

Ono, Masato; Fujiwara, Yusuke; Honda, Yuki; Sato, Hiroyuki; Shimazaki, Yosuke; Tochio, Daisuke; Homma, Fumitaka; Sawahata, Hiroaki; Iigaki, Kazuhiko; Takada, Shoji

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 5 Pages, 2017/04

Japan Atomic Energy Agency (JAEA) has carried out research and developments towards nuclear heat utilization of High Temperature Gas-cooled Reactor (HTGR) using High Temperature Engineering Test Reactor (HTTR). The nuclear heat utilization systems connected to HTGR will be designed on the basis of non-nuclear-grade standards in terms of easier entry for the chemical plant companies and the construction economics of the systems. Therefore, it is necessary that the reactor operations continue even if abnormal events occur in the systems. Heat application system abnormal simulating test with HTTR was carried out in non-nuclear heating operation to focus on the thermal effect in order to obtain data of the transient temperature behavior of the metallic components in the Intermediate Heat Exchanger (IHX). The IHX is the key components to connect the HTTR with the heat application system. In the test, the coolant helium gas temperature was heated up to 120$$^{circ}$$C by the compression heat of the gas circulators in the HTTR under the ideal condition to focus on the heat transfer. The tests were conducted by decreasing the helium gas temperature stepwise by increasing the mass flow rate to the air cooler. The temperature responses of the IHX were investigated. For the components such as the heat transfer tubes and heat transfer enhancement plates of IHX, the temperature response was slower in the lower position in comparison with the higher position. The reason is considered that thermal load fluctuation is imposed in the secondary helium gas which flows from the top to the bottom in the heat transfer tubes of the IHX. The test data are useful to verify the numerical model of the safety evaluation code.

Journal Articles

Investigation of absorption characteristics for thermal-load fluctuation using HTTR

Tochio, Daisuke; Honda, Yuki; Sato, Hiroyuki; Sekita, Kenji; Homma, Fumitaka; Sawahata, Hiroaki; Takada, Shoji; Nakagawa, Shigeaki

Journal of Nuclear Science and Technology, 54(1), p.13 - 21, 2017/01

 Times Cited Count:1 Percentile:15.39(Nuclear Science & Technology)

GTHTR300C is designed and developed in JAEA. The reactor system is required to continue a stable and safety operation as well as a stable power supply in the case that thermal-load is fluctuated by the occurrence of abnormal event in the heat utilization system. Then, it is necessary to demonstrate that the thermal-load fluctuation should be absorbed by the reactor system so as to continue the stable and safety operation could be continued. The thermal-load fluctuation absorption tests without nuclear heating were planned and conducted in JAEA to clarify the absorption characteristic of thermal-load fluctuation mainly by the reactor and by the IHX. As the result it was revealed that the reactor has the larger absorption capacity of thermal-load fluctuation than expected one, and the IHX can be contributed to the absorption of the thermal-load fluctuation generated in the heat utilization system in the reactor system. It was confirmed from there result that the reactor and the IHX has effective absorption capacity of the thermal-load fluctuation generated in the heat utilization system. Moreover it was confirmed that the safety estimation code based on RELAP5/MOD3 can represents the thermal-load fluctuation absorption behavior conservatively.

JAEA Reports

HTTR thermal load fluctuation test (non-nuclear heating test); Confirmation of HTGR system response against temperature transient

Honda, Yuki; Tochio, Daisuke; Nakagawa, Shigeaki; Sekita, Kenji; Homma, Fumitaka; Sawahata, Hiroaki; Sato, Hiroyuki; Sakaba, Nariaki; Takada, Shoji

JAEA-Technology 2016-016, 16 Pages, 2016/08


A system analysis code is validated with the thermal-load fluctuation absorption test with nun-nuclear heating by using the High Temperature Engineering test Reactor (HTTR) to clarify the High Temperature Gas-cooled Reactor (HTGR) system response against temperature transient. The thermal-load fluctuation absorption test consists on the thermal load fluctuation tests (non-nuclear heating) and heat application system abnormal simulating test (non-nuclear heating). The HTGR reactor response against temperature transient is clarified in the thermal load fluctuation test (non-nuclear heating). The Intermediate Heat Exchanger (IHX) reactor response against temperature transient is clarified in the heat application system abnormal simulating test (non-nuclear heating). With the two HTTR non-nuclear heating test, HTGR system response against temperature transient is obtained.

Journal Articles

Operation and maintenance experience from the HTTR database

Shimizu, Atsushi; Furusawa, Takayuki; Homma, Fumitaka; Inoi, Hiroyuki; Umeda, Masayuki; Kondo, Masaaki; Isozaki, Minoru; Fujimoto, Nozomu; Iyoku, Tatsuo

Journal of Nuclear Science and Technology, 51(11-12), p.1444 - 1451, 2014/11

 Times Cited Count:1 Percentile:10.7(Nuclear Science & Technology)

JAEA has kept up a data-base system of operation and maintenance experiences of the HTTR. The objective of this system is to share the information obtained operation and maintenance experiences and to make use of lessons learned and knowledge into a design, construction and operation managements of the future HTGR. More than one thousand records have been registered into the system between 1997 and 2012. This paper describes the status of the data-base system, and provides suggestions for improvement from four experiences: (1) performance degradation of helium compressors; (2) malfunction of reserved shutdown system in reactivity control system; (3) maintenance experiences of emergency gas turbine generators; and (4) experiences of the Great East Japan Earthquake. These experiences are extracted from the system as important lessons learned to be expected to apply for design, construction and operation managements of future HTGR.

Journal Articles

Verification of nuclear calculation methodology and preliminary uncertainty quantification in a sodium-cooled fast reactor

Ikeda, Kazumi*; Homma, Yuto*; Moriwaki, Hiroyuki*; Oki, Shigeo

Proceedings of 2014 International Congress on the Advances in Nuclear Power Plants (ICAPP 2014) (CD-ROM), p.1175 - 1183, 2014/04

JAEA Reports

Integrity check of emergency generator for the HTTR after the Tohoku-Pacific Ocean Earthquake

Homma, Fumitaka; Inoi, Hiroyuki; Watanabe, Shuji; Fukutani, Koji*

JAEA-Technology 2013-034, 57 Pages, 2013/12


Emergency generator of HTTR started in the blackout occurred just after an Tohoku Pacific Ocean Earthquake on March 11, 2011 with an intensity of 5 upper on the Japanese seven stage seismic scale and its duration time was long. In addition, we suffer from multiple severe aftershocks just after the start of emergency generators. Emergency generator of HTTR was able to supply output electric power sufficiently and stably to required loads. We carried on integrity check of the emergency generator for the HTTR after the earthquake. In particular, we put emphasis on finding faults caused by thee earthquake shaking. As a result, we found that the erosion in a combustion liner, and the condition of erosion was very strange and rare. Therefore, we carried out investigations of causes of erosion, and change of specifications for combustion liner to prevent erosion. This measure improve the reliability for the further Large-Scale earthquake.

Journal Articles

Dipole strength distributions in $$^{56}$$Fe

Shizuma, Toshiyuki; Hayakawa, Takehito; Ogaki, Hideaki; Toyokawa, Hiroyuki*; Komatsubara, Tetsuro*; Kikuzawa, Nobuhiro; Inakura, Tsunenori*; Homma, Michio*; Nakada, Hitoshi*

Physical Review C, 87(2), p.024301_1 - 024301_7, 2013/02

 Times Cited Count:14 Percentile:70.65(Physics, Nuclear)

Electro-magnetic dipole transitions in $$^{56}$$Fe were measured in photon scattering experiments with a linearly polarized photon beam. The parity quantum numbers of the excited dipole states were determined by the intensity asymmetry of resonantly scattered $$gamma$$-rays with respect to the polarization plane of the incident photon beam. While the summed magnetic dipole ($$M1$$) strength was determined as $$Sigma B(M1)!uparrow=3.52(17)$$ $$mu_N^2$$ at excitation energies between 7 and 10 MeV, the summed electric dipole ($$E1$$) strength below 10 MeV was obtained as $$Sigma B(E1)!uparrow=78.0(15)times10^{-3},e^2{rm fm}^2$$. The observed $$M1$$ strength was compared with shell-model predictions in the $$pf$$-shell using the GXPF1J and KB3G effective interactions. In addition, the $$E1$$ strength was compared with random-phase approximation calculations with the Skyrme interaction.

Journal Articles

Anisotropic spin fluctuations in the heavy fermion systems; Case studies of CePd$$_5$$Al$$_2$$ and NpPd$$_5$$Al$$_2$$

Sakai, Hironori; Chudo, Hiroyuki; Tokunaga, Yo; Kambe, Shinsaku; Haga, Yoshinori; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*; Homma, Yoshiya*; Aoki, Dai*; et al.

Journal of the Physical Society of Japan, 81(Suppl.B), p.SB003_1 - SB003_6, 2012/12

 Times Cited Count:5 Percentile:40.99(Physics, Multidisciplinary)

In the so-called 115 family members with chemical formulae of Ce$$T$$In$$_5$$ ($$T$$=Co, Rh, Ir) and $$An$$$$T$$Ga$$_5$$ ($$An$$=U, Np, Pu), our analysis of the Knight shift and spin-lattice relaxation rates suggests that larger XY-type anisotropy in the antiferromagnetic spin fluctuations in the normal states would favor $$d$$-wave superconductivity with higher $$T_c$$. In order to examine this working hypothesis, the anisotropy ratios of antiferromagnetic fluctuations are derived from our NMR results for the superconductor NpPd$$_5$$Al$$_2$$ and antiferromagnet CePd$$_5$$Al$$_2$$, which are tetragonal compounds with a 115-related structure. CePd$$_5$$Al$$_2$$ shows Ising-type anisotropy, which is the same anisotropy as in the ordered state. On the other hand, NpPd$$_5$$Al$$_2$$ shows XY-type anisotropy just above $$T_c$$.

Journal Articles

Solid-state NMR study of actinide dioxides

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Chudo, Hiroyuki; Osaka, Masahiko; Miwa, Shuhei; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori; Homma, Yoshiya*

Materials Research Society Symposium Proceedings, Vol.1444, p.149 - 158, 2012/00

 Times Cited Count:0 Percentile:0.11

Besides the importance of AnO$$_2$$ series (An; U, Np, Pu, Am) as a nuclear fuel, the magnetic properties of these compounds at low temperatures are particularly interesting. Their surprisingly varied physical properties continue to be of interest for both theory and experiment. In this study, we have performed NMR studies for the series of actinide dioxides. On the basis of $$^{17}$$O-NMR studies, exotic magnetic orderings associated with multipole degrees of freedom on 5$$f$$ electrons have been identified in UO$$_2$$ (dipolar + quadrupolar ordering) and NpO$$_2$$ (octupolar + quadrupolar ordering), in contrast with the non-magnetic ground state of PuO$$_2$$. In AmO$$_2$$, our $$^{17}$$O-NMR data provide the first microscopic evidence for a phase transition as a bulk property in this system.

Journal Articles

$$^{237}$$Np nuclear relaxation rate in heavy fermion superconductor NpPd$$_5$$ Al$$_2$$

Chudo, Hiroyuki; Tokunaga, Yo; Kambe, Shinsaku; Sakai, Hironori; Haga, Yoshinori; Matsuda, Tatsuma; Onuki, Yoshichika; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; et al.

Physical Review B, 84(9), p.094402_1 - 094402_5, 2011/09

 Times Cited Count:6 Percentile:31.79(Materials Science, Multidisciplinary)

Journal Articles

NMR study on AmO$$_{2}$$; Comparison with UO$$_{2}$$ and NpO$$_{2}$$

Tokunaga, Yo; Nishi, Tsuyoshi; Kambe, Shinsaku; Nakada, Masami; Homma, Yoshiya*; Sakai, Hironori; Chudo, Hiroyuki

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA110_1 - SA110_3, 2011/07

 Times Cited Count:2 Percentile:21.57(Physics, Multidisciplinary)

We have successfully performed an $$^{17}$$O NMR for the first time on Americium dioxide (AmO$$_2$$). We observed a drastic broadening of the NMR spectrum, after a sudden drop of NMR signal intensity below $$T_0$$. These data provide the first microscopic evidence for a phase transition as a bulk property in this system. In the ordered state, we found a spectrum with a triangular line shape, which resembles neither that of UO$$_2$$ nor NpO$$_2$$. It is also suggested that there is considerable damage to the sample induced by self-radiation effects from the alpha decay of $$^{243}$$Am.

Journal Articles

Manipulation and electron-oscillation-measurement of laser accelerated electron beams

Kotaki, Hideyuki; Hayashi, Yukio; Kawase, Keigo; Mori, Michiaki; Kando, Masaki; Homma, Takayuki; Koga, J. K.; Daido, Hiroyuki; Bulanov, S. V.

Plasma Physics and Controlled Fusion, 53(1), p.014009_1 - 014009_7, 2011/01

 Times Cited Count:5 Percentile:26.23(Physics, Fluids & Plasmas)

Journal Articles

Intense and reproducible K$$_{alpha}$$ emissions from micron-sized Kr cluster target irradiated with intense femtosecond laser pulses

Hayashi, Yukio; Fukuda, Yuji; Faenov, A. Y.*; Kando, Masaki; Kawase, Keigo; Pikuz, T. A.*; Homma, Takayuki; Daido, Hiroyuki; Bulanov, S. V.

Japanese Journal of Applied Physics, 49(12), p.126401_1 - 126401_3, 2010/12

 Times Cited Count:11 Percentile:43.19(Physics, Applied)

Journal Articles

La substitution effect and hyperfine-enhanced $$^{141}$$Pr nuclear spin dynamics in PrPb$$_3$$; $$^{139}$$La NMR study in Pr$$_{0.97}$$La$$_{0.03}$$Pb$$_3$$

Tokunaga, Yo; Sakai, Hironori; Chudo, Hiroyuki; Kambe, Shinsaku; Yasuoka, Hiroshi; Suzuki, Hiroyuki*; Walstedt, R. E.*; Homma, Yoshiya*; Aoki, Dai*; Shiokawa, Yoshinobu*

Physical Review B, 82(10), p.104401_1 - 104401_6, 2010/09

 Times Cited Count:5 Percentile:28.15(Materials Science, Multidisciplinary)

$$^{139}$$La NMR studies have been performed on PrPb$$_3$$ substituted with 3% La. The temperature dependence of the local magnetic susceptibility around La ions has been extracted from the $$^{139}$$La Knight shift. These data show that the non-magnetic $$Gamma_3$$ crystalline-electric-field (CEF) ground state (GS) is preserved even at the nearest neighboring Pr ions, although their CEF level scheme is slightly modified due to the La substitution. On the other hand, the temperature dependence of the nuclear spin-lattice relaxation rate $$1/T_1$$ is found to be well reproduced by assuming the same CEF level scheme over a wide temperature range. However, $$1/T_1$$ shows a strong upturn below 10 K, which is not expected from the non-magnetic CEF GS. We show that the low temperature anomaly can be quantitatively understood in terms of a cross-relaxation process between $$^{141}$$Pr and $$^{139}$$La nuclear spins.

Journal Articles

Metrology of wide field of view nano-thickness foils' homogeneity by conventional and phase contrast soft X-ray imaging

Faenov, A. Y.; Pikuz, T.*; Fukuda, Yuji; Kando, Masaki; Kotaki, Hideyuki; Homma, Takayuki; Kawase, Keigo; Skobelev, I.*; Gasilov, S.*; Kawachi, Tetsuya; et al.

Japanese Journal of Applied Physics, 49(6), p.06GK03_1 - 06GK03_5, 2010/06

 Times Cited Count:8 Percentile:36.82(Physics, Applied)

Journal Articles

NMR evidence for the 8.5 K phase transition in americium dioxide

Tokunaga, Yo; Nishi, Tsuyoshi; Kambe, Shinsaku; Nakada, Masami; Ito, Akinori; Homma, Yoshiya*; Sakai, Hironori; Chudo, Hiroyuki

Journal of the Physical Society of Japan, 79(5), p.053705_1 - 053705_4, 2010/05

 Times Cited Count:14 Percentile:65.65(Physics, Multidisciplinary)

We report here the first NMR study of americium dioxide (AmO$$_2$$). More than 30 years ago, a phase transition was suggested to occur in this compound at 8.5 K based on magnetic susceptibility data, while no evidence had been obtained from microscopic measurements. We have prepared a powder sample of $$^{243}$$AmO$$_2$$ containing 90 at.% $$^{17}$$O and have performed $$^{17}$$O NMR at temperatures ranging from 1.5 K to 200 K. After a sudden drop of the $$^{17}$$O NMR signal intensity below 8.5 K, at 1.5 K we have observed an extremely broad spectrum covering a range of $$sim$$14 kOe in applied field. These data provide the first microscopic evidence for a phase transition as a bulk property in this system. In addition, the $$^{17}$$O NMR spectrum has been found to split into two peaks in the paramagnetic state, an effect which has not been reported for actinide dioxides studied up to now. We suggest that the splitting is induced by self-radiation damage from the alpha decay of $$^{243}$$Am.

Journal Articles

Anisotropic spin fluctuations in heavy-fermion superconductor NpPd$$_5$$Al$$_2$$

Chudo, Hiroyuki; Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Aoki, Dai*; Homma, Yoshiya*; Haga, Yoshinori; Matsuda, Tatsuma; Onuki, Yoshichika; Yasuoka, Hiroshi

Journal of the Physical Society of Japan, 79(5), p.053704_1 - 053704_4, 2010/05

 Times Cited Count:12 Percentile:62.18(Physics, Multidisciplinary)

We present $$^{27}$$Al NMR measurements of the Knight shift and nuclear spin-lattice relaxation rate 1/$$T$$$$_1$$ in the normal state for a single crystal of the heavy-fermion superconductor NpPd$$_5$$ Al$$_2$$ ($$T$$$$_{rm c}$$ = 4.9 K). We report here that 1/$$T$$$$_1$$ shows a large anisotropy with a different temperature dependence for $$H$$ $$parallel$$ $$a$$ and $$H$$ $$parallel$$ $$c.$$ 1/$$T$$$$_1$$ for $$H$$ $$parallel$$ $$c$$ shows a power-law temperature dependence $$sim$$$$T$$$$^{0.38}$$, while 1/$$T$$$$_1$$ for $$H$$ $$parallel$$ $$a$$ shows a $$T$$-linear dependence at low temperatures in fields well above $$H$$$$_{rm c2}$$. From the analysis of 1/$$T$$$$_1$$, $$XY$$-type anisotropy of AFM spin fluctuations is found to become prominent below 20 K.

Journal Articles

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

108 (Records 1-20 displayed on this page)