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Otsuka, Satoshi; Shizukawa, Yuta; Tanno, Takashi; Imagawa, Yuya; Hashidate, Ryuta; Yano, Yasuhide; Onizawa, Takashi; Kaito, Takeji; Onuma, Masato*; Mitsuhara, Masatoshi*; et al.
Journal of Nuclear Science and Technology, 60(3), p.288 - 298, 2023/03
Times Cited Count：4 Percentile：78.52(Nuclear Science & Technology)JAEA has been developing 9Cr-oxide dispersion strengthened (ODS) tempered martensitic steel(TMS) as a candidate material for the fuel cladding tubes of sodium-cooled fast reactors(SFRs). The reliable prediction of in-reactor creep-rupture strength is critical for implementing the 9Cr-ODS TMS cladding tube in the SFR. This study investigated the quantitative correlation between the creep properties of 9Cr-ODS TMS at 700 
C and the dispersions of nanosized oxides by analyzing the creep data and the material's nanostructure. The possibility of deriving a formula for estimating the in-reactor creep properties of 9Cr-ODS TMSs based on an analysis of the nanostructure of neutron-irradiated 9Cr-ODS TMSs was also discussed. The creep properties of 9Cr-ODS TMS at 700 C closely correlated with the dispersion of nanosized oxide particles. The correlation between creep-rupture lives and nanosized oxide particle dispersion was determined using existing creep models. The elucidation of correlation between the stress exponent of secondary creep rate and the nanostructure is essential to enhance future modeling reliability and formulation.
Mitsuhara, Masatoshi*; Kurino, Koichi*; Yano, Yasuhide; Otsuka, Satoshi; Toyama, Takeshi*; Onuma, Masato*; Nakashima, Hideharu*
Tetsu To Hagane, 109(3), p.189 - 200, 2023/03
Times Cited Count：0 Percentile：0(Metallurgy & Metallurgical Engineering)Oxide Dispersion Strengthened (ODS) ferritic steel, a candidate material for fast reactor fuel cladding, has low thermal expansion, good thermal conductivity, and excellent resistance to irradiation damage and high temperature strength. The origin of the excellent high-temperature strength lies in the dispersion of fine oxides. In this study, creep tests at 700 or 750C, which are close to the operating temperatures of fast reactors, and high-temperature tensile tests at 900 to 1350 C, which simulate accident conditions, were conducted on 9Cr ODS ferritic steels, M11 and MP23, and 12Cr ODS ferritic steel, F14, to confirm the growth behavior of oxides. In the M11 and F14 creep test samples, there was little oxide growth or decrease in number density from the initial state, indicating that dispersion strengthening by oxides was effective during deformation. After creep deformation of F14, the development of dislocation substructures such as dislocation walls and subgrain boundaries was hardly observed, and mobile dislocations were homogeneously distributed in the grains. The dislocation density increased with increasing stress during the creep test. In the high-temperature ring tensile tests of MP23 and F14, the strength of both steels decreased at higher temperatures. In MP23, elongation decreased with increasing test temperature from 900 to 1100 C, but increased at 1200 C, decreased drastically at 1250 C, and increased again at 1300 C. In F14, elongation decreased with increasing temperature. It was inferred that the formation of the 
-ferrite phase was responsible for this complex change in mechanical properties of MP23 from 1200 to 1300 C.
Kusano, Kanya*; Ichimoto, Kiyoshi*; Ishii, Mamoru*; Miyoshi, Yoshizumi*; Yoden, Shigeo*; Akiyoshi, Hideharu*; Asai, Ayumi*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Goto, Tadanori*; et al.
Earth, Planets and Space (Internet), 73(1), p.159_1 - 159_29, 2021/12
Times Cited Count：6 Percentile：51.19(Geosciences, Multidisciplinary)The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.
Se
ultrathin films on van der Waals ferromagnet CrSiTe
Kato, Takemi*; Sugawara, Katsuaki*; Ito, Naohiro*; Yamauchi, Kunihiko*; Sato, Takumi*; Oguchi, Tamio*; Takahashi, Takashi*; Shiomi, Yuki*; Saito, Eiji; Sato, Takafumi*
Physical Review Materials (Internet), 4(8), p.084202_1 - 084202_6, 2020/08
Times Cited Count：4 Percentile：20.66(Materials Science, Multidisciplinary)Iwasaki, Yuma*; Sawada, Ryoto*; Stanev, V.*; Ishida, Masahiko*; Kirihara, Akihiro*; Omori, Yasutomo*; Someya, Hiroko*; Takeuchi, Ichiro*; Saito, Eiji; Yorozu, Shinichi*
npj Computational Materials (Internet), 5, p.103_1 - 103_6, 2019/10
Times Cited Count：47 Percentile：87.87(Chemistry, Physical)Hirobe, Daichi*; Sato, Masahiro*; Hagihara, Masato*; Shiomi, Yuki*; Masuda, Takatsugu*; Saito, Eiji
Physical Review Letters, 123(11), p.117202_1 - 117202_7, 2019/09
Times Cited Count：14 Percentile：65.02(Physics, Multidisciplinary)Iwasaki, Yuma*; Takeuchi, Ichiro*; Stanev, V.*; Gilad Kusne, A.*; Ishida, Masahiko*; Kirihara, Akihiro*; Ihara, Kazuki*; Sawada, Ryoto*; Terashima, Koichi*; Someya, Hiroko*; et al.
Scientific Reports (Internet), 9, p.2751_1 - 2751_7, 2019/02
Times Cited Count：61 Percentile：92.99(Multidisciplinary Sciences)Akiyoshi, Hideharu*; Kadowaki, Masanao; Nakamura, Haruna*; Sugita, Takafumi*; Hirooka, Toshihiko*; Harada, Yayoi*; Mizuno, Akira*
Journal of Geophysical Research; Atmospheres, 123(22), p.12523 - 12542, 2018/11
Times Cited Count：1 Percentile：2.87(Meteorology & Atmospheric Sciences)A reduction of the total ozone over the southern tip of South America lasting 3 weeks occurred in November 2009. Analyses of the ERA-Interim reanalysis data and the total ozone observed by the Ozone Monitoring Instrument indicate that the total ozone reduction event was caused by a migration of the polar vortex toward the South American continent at the time of the vortex breakup. The vortex migration is associated with an enhanced wave flux from the troposphere at 120-150W and 50-60S to the west of the South American continent to the stratosphere over the southern part of the continent, which led to a large negative geopotential height anomaly in the lower stratosphere. In November, a blocking event was diagnosed from the 500-hPa geopotential height over the west of the South American continent. These results suggest a relation between the long-lasting reduction of the total ozone over the southern tip of South America and the blocking phenomenon in the troposphere of the Southern Hemisphere through wave propagation from the blocking region in 2009. Analysis of the total ozone anomaly for 50-60S and 65-75W over the southern tip of South America in November for 1979-2015 indicates that the negative ozone anomaly in November 2009 was one of the largest anomalies in this 37-year period and was associated with the large negative geopotential height anomaly in the lower stratosphere. Analyses of dynamical fields were also conducted for other years with large geopotential height anomalies.
Yagmur, A.*; Uchida, Kenichi*; Ihara, Kazuki*; Ioka, Ikuo; Kikkawa, Takashi*; Ono, Madoka*; Endo, Junichi*; Kashiwagi, Kimiaki*; Nakashima, Tetsuya*; Kirihara, Akihiro*; et al.
Applied Physics Letters, 109(24), p.243902_1 - 243902_4, 2016/12
Times Cited Count：3 Percentile：14.94(Physics, Applied)Thermoelectric devices based on the spin Seebeck effect (SSE) were irradiated with gamma (
) rays with the total dose of around 3
10
Gy in order to investigate the -radiation resistance of the devices. To demonstrate this, Pt/Ni
Zn
Fe
O
/Glass and Pt/Bi
Y
Fe
O
/Gd
GaO SSE devices were used. We confirmed that the thermoelectric, magnetic, and structural properties of the SSE devices are not affected by the -ray irradiation. This result demonstrates that SSE devices are applicable to thermoelectric generation even in high radiation environments.
Uchida, Kenichi*; Adachi, Hiroto; Kikkawa, Takashi*; Kirihara, Akihiro*; Ishida, Masahiko*; Yorozu, Shinichi*; Maekawa, Sadamichi; Saito, Eiji*
Proceedings of the IEEE, 104(10), p.1946 - 1973, 2016/10
Times Cited Count：213 Percentile：99.2(Engineering, Electrical & Electronic)Kirihara, Akihiro*; Kondo, Koichi*; Ishida, Masahiko*; Ihara, Kazuki*; Iwasaki, Yuma*; Someya, Hiroko*; Matsuba, Asuka*; Uchida, Kenichi*; Saito, Eiji; Yamamoto, Naoharu*; et al.
Scientific Reports (Internet), 6, p.23114_1 - 23114_7, 2016/03
Times Cited Count：62 Percentile：90.69(Multidisciplinary Sciences)Heat-flow sensing is expected to be an important technological component of smart thermal management in the future. Conventionally, the thermoelectric (TE) conversion technique, which is based on the Seebeck effect, has been used to measure a heat flow by converting the flow into electric voltage. However, for ubiquitous heat-flow visualization, thin and flexible sensors with extremely low thermal resistance are highly desired. Recently, another type of TE effect, the longitudinal spin Seebeck effect (LSSE), has aroused great interest because the LSSE potentially offers favourable features for TE applications such as simple thin-film device structures. Here we demonstrate an LSSE-based flexible TE sheet that is especially suitable for a heat-flow sensing application. This TE sheet contained a NiZnFeO
film which was formed on a flexible plastic sheet using a spray-coating method known as ferrite plating. The experimental results suggest that the ferrite-plated film, which has a columnar crystal structure aligned perpendicular to the film plane, functions as a unique one-dimensional spin- current conductor suitable for bendable LSSE-based sensors. This newly developed thin TE sheet may be attached to differently shaped heat sources without obstructing an innate heat flux, paving the way to versatile heat-flow measurements and management.
Yokoi, Naoto*; Ishihara, Masafumi*; Sato, Koji*; Saito, Eiji
Physical Review D, 93(2), p.026002_1 - 026002_6, 2016/01
Times Cited Count：16 Percentile：60.37(Astronomy & Astrophysics)Niizeki, Tomohiko*; Kikkawa, Takashi*; Uchida, Kenichi*; Oka, Mineto*; Suzuki, Kazuya*; Yanagihara, Hideto*; Kita, Eiji*; Saito, Eiji
AIP Advances (Internet), 5(5), p.053603_1 - 053603_6, 2015/05
Times Cited Count：39 Percentile：81.57(Nanoscience & Nanotechnology)Iwasawa, Yuzuru*; Abe, Yutaka*; Kaneko, Akiko*; Kanagawa, Tetsuya*; Saito, Shimpei*; Matsuo, Eiji*; Ebihara, Kenichi; Sakaba, Hiroshi*; Koyama, Kazuya*; Nariai, Hideki*
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 7 Pages, 2015/05
For the safety design in which heat is properly removed from the molten fuel after the core disruptive accident in a sodium-cooled fast reactor, the estimation of the breakup behavior of molten fuel discharged into the coolant like a jet is desired. In order to investigate the influence of viscocity on the jet behavior, we simulated a jet discharged into a coolant using the three-dimensional lattice Boltzmann model for two-phase fluid, and examined the influence of Ohnesorge number and Reynolds number on the jet behavior. As a result, we made clear that it is necessary to consider viscosity of the coolant as well as that of the jet for the estimation of jet behavior.
Matsuo, Eiji*; Abe, Yutaka*; Iwasawa, Yuzuru*; Ebihara, Kenichi; Koyama, Kazuya*
Nihon Kikai Gakkai Rombunshu (Internet), 81(822), p.14-00409_1 - 14-00409_20, 2015/02
In order to understand the jet breakup behavior of the molten core material into coolant during a core disruptive accident (CDA) for a sodium-cooled fast reactor (SFR), we simulated the jet breakup due to the hydrodynamic interaction using the lattice Boltzmann method (LBM). The applicability of the LBM to the jet breakup simulation was validated by comparison with our experimental data. In addition, the influence of several dimensionless numbers such as Weber number and Froude number was examined using the LBM. As a result, we validated applicability of the LBM to the jet breakup simulation, and found that the jet breakup length is independent of Froude number and in good agreement with the Epstein's correlation when the jet interface becomes unstable.
Shiomi, Yuki*; Nomura, Kentaro*; Kajiwara, Yosuke*; Eto, Kazuma*; Novak, M.*; Segawa, Koji*; Ando, Yoichi*; Saito, Eiji
Physical Review Letters, 113(19), p.196601_1 - 196601_5, 2014/11
Times Cited Count：272 Percentile：99.03(Physics, Multidisciplinary)-ray for improvement neutron emission profile measurementUchida, Yuki*; Takada, Eiji*; Fujisaki, Akihiro*; Isobe, Mitsutaka*; Ogawa, Kunihiro*; Shinohara, Koji; Tomita, Hideki*; Kawarabayashi, Jun*; Iguchi, Tetsuo*
Review of Scientific Instruments, 85(11), p.11E118_1 - 11E118_4, 2014/11
Times Cited Count：9 Percentile：40.01(Instruments & Instrumentation)Uchida, Kenichi*; Ishida, Masahiko*; Kikkawa, Takashi*; Kirihara, Akihiro*; Murakami, Tomoo*; Saito, Eiji
Journal of Physics; Condensed Matter, 26(34), p.343202_1 - 343202_15, 2014/08
Times Cited Count：203 Percentile：84.49(Physics, Condensed Matter)Sanada, Yukihisa; Takamura, Yoshihide; Urabe, Yoshimi; Tsuchida, Kiyofumi; Nishizawa, Yukiyasu; Yamada, Tsutomu; Sato, Yoshiharu; Hirayama, Hirokatsu; Nishihara, Katsuya; Imura, Mitsuo; et al.
JAEA-Research 2014-005, 67 Pages, 2014/05
JAEA-Research-2014-005.pdf:52.68MB
Distribution of radiocesium existing on the waterbed such as lake or pond was concerned about at the present that passed for two years by an accident. Here, the direct measurement technique of the radiocesium concentration (in-situ measurement technique) was developed. This method was used an plastic scintillation detector (p-Scanner). This detector carried out quick measurement of a large area. In addition, the count-rate of p-Scanner was converted to the radiocesium concentration (Ba/kg-wet) by comparative measurement of -ray spectrometer. We applied the technique to the agricultural pond in Fukushima and made a map of distribution of radiocesium concentration.
Harries, J.; Iwayama, Hiroshi*; Okihara, Lisa*; Nagasono, Mitsuru*; Shigemasa, Eiji*
JPS Conference Proceedings (Internet), 1, p.013083_1 - 013083_6, 2014/03
