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Cs discharge from a forested catchmentSakuma, Kazuyuki; Hayashi, Seiji*; Yoshimura, Kazuya; Kurikami, Hiroshi; Malins, A.; Funaki, Hironori; Tsuji, Hideki*; Kobayashi, Takamaru*; Kitamura, Akihiro; Iijima, Kazuki
Water Resources Research, 58(8), p.e2021WR031181_1 - e2021WR031181_16, 2022/08
Times Cited Count：2 Percentile：39.28(Environmental Sciences)Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Wakai, Takashi; Kobayashi, Sumio; Kato, Shoichi; Ando, Masanori; Takasho, Hideki*
Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 7 Pages, 2017/07
This paper describes a thermal fatigue test on a structural model with a dissimilar welded joint. In the present design of JSFR, there may be dissimilar welded joints between ferritic and austenitic steels especially in IHX and SG. Creep-fatigue is one of the most important failure modes in JSFR components. However, the creep-fatigue damage evaluation method has not been established for dissimilar welded joint. To investigate the evaluation method, structural test will be needed for verification. Therefore, a thermal fatigue test on a thick-wall cylinder with a circumferential dissimilar welded joint between Mod.9Cr-1Mo steel and 304SS was performed. Since the coefficients of thermal expansion of these steels were significantly different, buttering layer of Ni base alloy was installed between them. After the completion of the test, deep cracks were observed at the HAZ in 304SS, as well as at HAZ in Mod.9Cr-1Mo steel. There were many tiny surface cracks in BM of 304SS. According to the fatigue damage evaluation based on the finite element analysis results, the largest fatigue damage was calculated at HAZ in 304SS. Large fatigue damage was also estimated at BM of 304SS. Fatigue cracks were observed at HAZ and BM of 304SS in the test, so that analytical results are in a good agreement with the observations. However, though relatively small fatigue damage was estimated at HAZ in Mod.9Cr-1Mo steel, deep fatigue cracks were observed in the test. To identify the cause of such a discrepancy between the test and calculations, we performed a series of finite element analyses. Some metallurgical investigations were also performed.
Ono, Ayako; Tanaka, Masaaki; Kobayashi, Jun; Kamide, Hideki
Mechanical Engineering Journal (Internet), 4(1), p.16-00217_1 - 16-00217_15, 2017/02
In the design of the Advanced Sodium-cooled Fast Reactor in Japan, the Reynolds number in the primary hot leg (H/L) piping reaches 4.2
10
. Furthermore, a short elbow is used in the H/L piping to achieve a compact plant layout. In the H/L piping, flow-induced vibration is a concern due to the excitation force caused by pressure fluctuation in the short elbow. In this report, the influence of inlet velocity condition on the unsteady velocity characteristics in the short elbow was studied by controlling the flow patterns at the elbow inlet. Measured velocity distributions indicated that the inlet velocity profiles affected a circumferential secondary flow, which then affected an area of flow separation at the elbow. It was also found that the velocity fluctuation at low frequency components observed upstream of the elbow could remain in downstream of the elbow though its intensity was attenuated.
Kobayashi, Jun; Ezure, Toshiki; Tanaka, Masaaki; Kamide, Hideki
Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 5 Pages, 2016/11
JAEA has been conducting a design study for an advanced large-scale sodium-cooled fast reactor (SFR). Hot sodium from the fuel subassembly can mix with the cold sodium from the control rod (CR) channel at the bottom of Upper Internal Structure (UIS). Temperature fluctuation due to the fluid mixing at the core outlet may cause high cycle thermal fatigue at the bottom of UIS. JAEA had performed a water experiment to examine countermeasures for the significant temperature fluctuation generated at the bottom of SFRs UIS. Meanwhile, a self-actuated shutdown system (SASS) is equipped in a backup control rod (BCR) channel to ensure reactor shutdown. The BCR guide tubes have a flow guide structure "flow-collector" to provide reliable operation of SASS. Flow-collector may affect the thermal mixing behavior at the bottom of the UIS. This study has investigated the influence of the flow- collector on characteristics of the temperature fluctuation around the BCR channels.
Ono, Ayako; Kamide, Hideki; Kobayashi, Jun; Doda, Norihiro; Watanabe, Osamu*
Journal of Nuclear Science and Technology, 53(9), p.1385 - 1396, 2016/09
Times Cited Count：11 Percentile：71.62(Nuclear Science & Technology)Decay heat removal by natural circulation is a significant passive safety measure of a fast reactor against station blackout. The decay heat removal system (DHRS) of the loop type sodium fast reactor being designed in Japan comprises a direct reactor auxiliary cooling system and primary reactor auxiliary cooling system (PRACS). The thermal hydraulic phenomena in the plant under natural circulation conditions need to be understood for establishing a reliable natural circulation driven DHRS. In this study, sodium experiments were conducted using a plant dynamic test loop to understand the thermal-hydraulic phenomena considering natural circulation in the plant. The experiments simulating the scram transient confirmed that PRACS started up smoothly under natural circulation, and the simulated core was stably cooled after the scram. Moreover, the experiments varying the pressure loss coefficients of the loop as the experimental parameters showed robustness of the PRACS.
Ikuta, Masafumi*; Niwa, Masakazu; Danhara, Toru*; Yamashita, Toru*; Maruyama, Seiji*; Kamataki, Takanobu*; Kobayashi, Tetsuo*; Kurosawa, Hideki*; Kokubu, Yoko; Hirata, Takafumi*
Chishitsugaku Zasshi, 122(3), p.89 - 107, 2016/03
We carried out mineral composition analysis, morphological classification of volcanic glass shards and refractive index measurements of the glass shards and orthopyroxene from the eruption products from Sakurajima volcano. In this study, refractive indexes of hydrated and non-hydrated parts within each individual glass shard were measured separately. This measurements in consideration of hydration in glass shards made possible distinct discrimination of the pumice samples from the three eruption events of Bunmei, An-ei, and Taisho. Pumice layers in the core samples obtained from the southern part of the Miyazaki Plain were also identified as the Sakurajima-Bunmei tephra by the above mentioned analyses, and also by the data of radiocarbon dating for coaly materials included in the pumice layers. Occurrences of the pumice layers suggest that the Sakurajima-Bunmei tephra could have reached the southern part of Miyazaki Plain as pumice falls.
Kobayashi, Jun; Tanaka, Masaaki; Ohno, Shuji; Ohshima, Hiroyuki; Kamide, Hideki
Proceedings of 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16) (USB Flash Drive), p.6664 - 6677, 2015/08
Numerical simulation is recognized an essential tool for the physical phenomena analysis and plant design study of a sodium-cooled fast reactor (SFR). In order to enhance credibility of the numerical results in the activities for plant design by using numerical simulations, it is recognized that verification and validation (V&V) process is very important. In this study, experiments for planar triple parallel jets mixing phenomena conducted in JAEA were proposed as benchmark problems for the code validation in the area of thermal striping study in the SFR development.
Tomita, Masanori*; Matsumoto, Hideki*; Funayama, Tomoo; Yokota, Yuichiro; Otsuka, Kensuke*; Maeda, Munetoshi*; Kobayashi, Yasuhiko
Life Sciences in Space Research, 6, p.36 - 43, 2015/07
A radiation-induced bystander response is generally known as a cellular response induced in unirradiated cell by receiving bystander signaling factors released from directly irradiated cells of a cell population. Bystander responses induced by high-LET heavy ions at low fluence are an important problem concerning the health of astronauts in the space environment. Here we set out NO-mediated bystander signal transductions induced by high-LET heavy-ion microbeam irradiation in normal human fibroblasts. Our findings suggest that Akt- and NF-
B-dependent signaling pathway involving COX-2 plays an important role in the NO-mediated high-LET heavy-ion-induced bystander responses. Additionally, COX-2 may be used as a molecular marker of high-LET heavy-ion-induced bystander cells, which are distinguish form directly irradiated cells.
Kobayashi, Jun; Ezure, Toshiki; Kamide, Hideki; Oyama, Kazuhiro*; Watanabe, Osamu*
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05
A column type upper internal structure (UIS) is installed in the upper plenum of reactor vessel in JSFR. High cycle thermal fatigue may occur at the bottom plate (CIP) of the UIS where the hot sodium from the fuel subassembly can mix with the cold sodium from the control rod channel and the blanket fuel subassembly. We have been conducted a water experiment using a reactor upper plenum model to grasp the thermal-hydraulic phenomena around control rod (CR) channels, and to obtain countermeasures for significant temperature fluctuation on the CIP. The experimental apparatus has 1/3 scale and 60
sector model of the reactor upper plenum. By the experiment, characteristics of fluid temperature fluctuation between the handling head of the assemblies and the CIP are measured and countermeasure for the significant temperature fluctuation generation will be discussed on the influence of the distance from the handling head outlet to the lower surface of the CIP.
Matsumoto, Hideki*; Tomita, Masanori*; Otsuka, Kensuke*; Hatashita, Masanori*; Maeda, Munetoshi*; Funayama, Tomoo; Yokota, Yuichiro; Suzuki, Michiyo; Sakashita, Tetsuya; Ikeda, Hiroko; et al.
JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 76, 2015/03
The objective of this project is to elucidate molecular mechanisms for the induction of radioadaptive response through radiation-induced bystander responses induced by irradiation with heavy ion microbeams in JAEA. We found that the adaptive response was induced by Ar (520 MeV 
Ar
) microbeam-irradiation of a limited number of cells, followed by the broad beam-irradiation and that the adaptive response was almost completely suppressed by the addition of carboxy-PTIO, as a nitric oxide (NO) scavenger. In addition, we found several genes induced specifically and preferentially when radioadaptive response could be induced. We confirmed that 
expression was specifically induced only when radioadaptive response could be induced. Our findings strongly suggested that radioadaptive response can be induced by NO-mediated bystander responses evoked by irradiation with heavy ion microbeams.
Tomita, Masanori*; Matsumoto, Hideki*; Otsuka, Kensuke*; Funayama, Tomoo; Yokota, Yuichiro; Suzuki, Michiyo; Sakashita, Tetsuya; Kobayashi, Yasuhiko
JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 77, 2015/03
Radiation-induced bystander responses are defined as responses in cells that have not been directly targeted by radiation but are in the neighborhood of cells that have been directly exposed. In this study, we aim to clarify a role of bystander response to sustain the homeostasis of damaged tissue using heavy-ion microbeams. We established the heavy-ion microbeam irradiation method to a 3D cultured human epidermis. Using this method, a viable cell rate of the 3D cultured human epidermis irradiated with 260 MeV 
Ne-ion microbeams or broadbeams was analyzed by the MTT method.
Aizawa, Kosuke; Kobayashi, Jun; Onojima, Takamitsu; Tanaka, Masaaki; Ohno, Shuji; Kamide, Hideki; Nagasawa, Kazuyoshi*
Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 13 Pages, 2014/12
Thermal striping phenomenon is one of the most important issues in an advanced loop type sodium cooled reactor JSFR. Temperature fluctuation caused by mixing of fluids at different temperature from the control rod channels and the core fuel assemblies may touch the Core Instrument Plane (CIP) at bottom of the Upper Internal Structure (UIS) and cause high cycle thermal fatigue there. In JAEA, the 1/3-scaled Five Jets Water Test (FIWAT) has been performed in order to investigate thermal striping phenomena around the CIP. In the FIWAT, the test section was simulating a control rod channel, adjacent four fuel subassemblies and a part of the CIP. The flow rate ratio and the absolute velocity of hot jets as the reference experimental condition were equal to that of the JSFR and a third of JSFR, respectively. In the experiment, it was shown that the fluid temperature fluctuation characteristics around the structure depended on the flow rate ratio. The temperature fluctuation which showed sudden decrease and recovery like a spike form was intermittently observed in the fluid near the structure. The amplitude of such spike-like temperature fluctuation in the fluid was much mitigated on the structure surface.
Ono, Ayako; Tanaka, Masaaki; Kobayashi, Jun; Kamide, Hideki
Proceedings of 9th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-9) (CD-ROM), 7 Pages, 2014/11
Kimura, Nobuyuki; Kobayashi, Jun; Kameyama, Yuri*; Nagasawa, Kazuyoshi*; Ezure, Toshiki; Ono, Ayako; Kamide, Hideki
JAEA-Research 2014-009, 104 Pages, 2014/07
JAEA-Research-2014-009.pdf:15.23MBJAEA-Research-2014-009-appendix(CD-ROM).pdf:17.88MB
In this study, water experiments (WATLON) were carried out to clarify the unsteady behavior of heat transfer under wall jet condition in the mixing tee. In experiments, heat transfer coefficients between fluid and wall in the mixing region were obtained from temperature measurements using thermocouples (movable tree type in fluid and embedded type in wall). To clarify the relation between the local velocity and the wall temperature, those were measured simultaneously by the Particle Image Velocimetry (PIV) and the thermocouple measurement, respectively. Sampling time of the velocity by the PIV and the temperature by the thermocouple were synchronized in the measurement. The experimental results showed that the heat transfer coefficient was from 2 - 6 time larger than the reference value predicted by the Dittus-Boelter correlation in straight pipes and was increased as the local velocity near the wall.
Ono, Ayako; Tanaka, Masaaki; Kobayashi, Jun; Kamide, Hideki
Proceedings of 22nd International Conference on Nuclear Engineering (ICONE-22) (DVD-ROM), 10 Pages, 2014/07
The fluid structures in the short-elbow whose curvature radius equals to its diameter were examined with varying the inlet condition. The velocity profile and turbulence intensity at the elbow inlet were changed by various perforated plate. It was found that the inlet condition affect to the flow structure in the elbow and the low frequent velocity fluctuation remained downstream of the elbow.
Ono, Ayako; Kobayashi, Jun; Kamide, Hideki; Watanabe, Osamu*
Proceedings of 8th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-8) (USB Flash Drive), 10 Pages, 2012/12
Fully natural circulation system is adopted in a decay heat removal system (DHRS) of Japan Sodium Cooled Fast Reactor. The DHRS of JSFR consists of one unit of DRACS and two units of PRACS. In this study, the sodium experiments were conducted using a sodium test loop PLANDTL in order to investigate the effect of operation mode on transient behavior of thermal hydraulic in PRACS loop. The experimental results revealed the effect of increasing heat removal capacity of PRACS and the forced flow operation in PRACS loop on the thermal transient and natural circulation behavior in PRACS loop.
Kobayashi, Jun; Kimura, Nobuyuki; Tobita, Akira; Kamide, Hideki
JAEA-Research 2012-014, 40 Pages, 2012/07
JAEA-Research-2012-014.pdf:7.8MB
As the temperatures difference between the control rod channels and the core fuel subassemblies is around 100 C centigrade, temperature fluctuation due to the fluid mixing at the core outlet may cause high cycle thermal fatigue at the bottom of upper internal structure (UIS) in JSFR. Then, a water experiment was conducted using an 1/3 scale 60 sector model. As a result, thermal striping phenomena in the region between the fuel subassembly outlet and the bottom of the UIS were grasped. The modified geometry of the UIS bottom and the handling head of the primary CR channel was created so as to suppress the cold jets from the CR channels. The comparison of measured temperature fluctuations around the CR channels revealed that the modified geometry was effective to decrease the temperature fluctuation intensity and amplitude in the sensitive frequency band to the stress conversion.
nanocomposite electrocatalyst; An in situ electrochemical X-ray absorption fine structure studyMasuda, Takuya*; Fukumitsu, Hitoshi*; Fugane, Keisuke*; Togasaki, Hirotaka*; Matsumura, Daiju; Tamura, Kazuhisa; Nishihata, Yasuo; Yoshikawa, Hideki*; Kobayashi, Keisuke*; Mori, Toshiyuki*; et al.
Journal of Physical Chemistry C, 116(18), p.10098 - 10102, 2012/05
Times Cited Count：118 Percentile：93.76(Chemistry, Physical)In situ electrochemical X-ray absorption fine structure (XAFS) measurements were performed at the Pt L
and Ce L edges of the Pt-CeO/C catalyst, which was prepared by a combined process of precipitation and coimpregnation methods, as well as at the Pt L edge of the conventional Pt/C catalyst in oxygen-saturated H
SO
solution to clarify the role of CeO in the reduction of the overpotential for the oxygen reduction reaction (ORR) at the Pt-CeO nanocomposite compared with the conventional Pt/C catalyst. XAFS measurements clearly show that the enhancement of ORR activity is attributed to the inhibition of Pt oxide formation by the CeO layer, of which Ce
was oxidized to Ce
instead of Pt at the Pt oxide formation potential.
Kobayashi, Masaki*; Niwa, Hideharu*; Harada, Yoshihisa*; Horiba, Koji*; Oshima, Masaharu*; Ofuchi, Hironori*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; et al.
Journal of Power Sources, 196(20), p.8346 - 8351, 2011/10
Times Cited Count：32 Percentile：67.33(Chemistry, Physical)The electronic structure of Co atoms in CoPc-based carbon catalysts, which were prepared by pyrolyzing a mixture of CoPc and phenol resin polymer up to 1000
C, has been investigated using XAFS analysis and HXPES. The Co K XAFS spectra show that most of the Co atoms are in the metallic state and small quantities of oxidized Co components are present in the samples even after acid washing to remove Co atoms. Based on the difference in probing depth between XAFS and HXPES, it was found that after acid washing, the surface region with the aggregated Co clusters is primarily composed of metallic Co. Since the electrochemical properties remain almost unchanged even after the acid washing process, the residual metallic and oxidized Co atoms themselves will hardly contribute to the ORR activity of the CoPc-based carbon cathode catalysts, implying that the active sites of the CoPc-based catalysts primarily consist of light elements such as C and N.
