Ito, Takashi; Higemoto, Wataru; Koda, Akihiro*; Shimomura, Koichiro*
Applied Physics Letters, 115(19), p.192103_1 - 192103_4, 2019/11
Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Sato, Toyoto*; Orimo, Shinichi*; Aoki, Katsutoshi*
Scientific Reports (Internet), 9(1), p.12290_1 - 12290_9, 2019/08
Hexagonal close-packed iron hydride, hcp FeHx, is absent from the conventional phase diagram of the Fe-H system, although hcp metallic Fe exists stably over extensive temperature () and pressure () conditions, including those corresponding to the Earth's inner core. X-ray and neutron diffraction measurements at temperatures ranging from 298 to 1073 K and H pressures ranging from 4 to 7 GPa revealed that the hcp hydride was formed for FeH compositions when . Hydrogen atoms occupied the octahedral interstitial sites of the host metal lattice both partially and randomly. The hcp hydride exhibited a H-induced volume expansion of 2.48(5) /H-atom, which was larger than that of the face-centered cubic (fcc) hydride. The hcp hydride showed an increase in with , whereas the fcc hydride showed a corresponding decrease. The present study provides guidance for further investigations of the Fe-H system over an extensive -- region.
Oi, Motoki; Teshigawara, Makoto; Harada, Masahide; Ikeda, Yujiro
Journal of Nuclear Science and Technology, 56(7), p.573 - 579, 2019/07
In pulsed neutron sources, a neutron absorber called decoupler is attached to the moderator to sharpen the neutron pulses for achieving good neutron energy resolutions. Cadmium and boron carbide (BC) are widely used as the decoupler materials. However, it is difficult to use BC in MW-class spallation neutron sources owing to high burn-up, which decreases cut-off energy and increase of helium gas swelling. To solve these issues, we introduce the concept of pre-decoupler to reduce neutron absorption in the BC decoupler, which is sandwiched by appropriate neutron absorption materials. Then, we study impacts of the pre-decouplers on BC decoupler in terms of burn-up by performing simplified model calculations. It is shown that neutron absorption in BC is reduced by 60% by using a Cd pre-decoupler without neutron intensity penalty. Moreover, helium gas swelling in BC is restrained to be one-third of the value when not using the pre-decoupler.
Klotz, S.*; Casula, M.*; Komatsu, Kazuki*; Machida, Shinichi*; Hattori, Takanori
Physical Review B, 100(2), p.020101_1 - 020101_5, 2019/07
Ytterbium dihydride (YbH) shows a well-known transition at 16 GPa from a CaH-type structure to a high-pressure (high-) phase with Yb at hcp sites and unknown H-positions. Here, we report its complete structure determination by neutron diffraction at 34 GPa. Hydrogen(deuterium) is located at 2 and 2 positions of space group , thus forming a high-symmetry "collapsed" close-packed lattice. The transition is sluggish and can be seen as a transfer of 1/2 of the hydrogen atoms from strongly corrugated H-layers to interstitial sites of the Yb-lattice. We demonstrate by first-principles calculations that the transition is related to a change from a completely filled -electron configuration to a fractional -hole (0.25 h) occupation in the high- phase. The charge transfer closes the gap at the transition and leads to a metallic ground state with sizeable electron-phonon interaction involving out-of-plane vibrational modes of interstitial hydrogen.
Ono, Hitomi*; Takenaka, Keisuke*; Kita, Tomoaki*; Taniguchi, Masashi*; Matsumura, Daiju; Nishihata, Yasuo; Hino, Ryutaro; Reinecke, E.-A.*; Takase, Kazuyuki*; Tanaka, Hirohisa*
E-Journal of Advanced Maintenance (Internet), 11(1), p.40 - 45, 2019/05
Sato, Hiroyuki; Ohashi, Hirofumi
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05
To establish a probabilistic approach for assessment of toxic gas leakage accidents in a H plant, the present study focusses on development of an uncertainty analysis method for toxic gas concentration in a control room. The method consists of 6 steps; (1) Identification of uncertainty factors, (2) derivation of variable parameters, (3) identification of uncertainties in variable parameters, (4) identification of important factors considering the sensitivity analysis results and expert opinions, (5) uncertainty propagation analysis, (6) assessment of uncertainty analysis results. The method is then applied to representative toxic gas leakage accidents in a H plant by IS process coupled to the HTTR. The results obtained in the study leads us to the conclusion that the suggested method can successfully characterize and quantify uncertainties in the toxic gas concentration in control room.
Hidaka, Akihide; Himi, Masashi*; Addad, Y.*
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
no abstracts in English
Kumagai, Yuta; Fidalgo, A. B.*; Jonsson, M.*
Journal of Physical Chemistry C, 123(15), p.9919 - 9925, 2019/04
Radiation-induced oxidative dissolution of uranium dioxide (UO) is one of the most important chemical processes of U driven by redox reactions. We have examined the effect of UO stoichiometry on the oxidative dissolution of UO induced by hydrogen peroxide (HO) and -ray irradiation. By comparing the reaction kinetics of HO between stoichiometric UO and hyper-stoichiometric UO, we observed a significant difference in reaction speed and U dissolution kinetics. The stoichiometric UO reacted with HO much faster than the hyper-stoichiometric UO. The U dissolution from UO was initially much lower than that from UO, but gradually increased as the oxidation by HO proceeded. The -ray irradiation induced the U dissolution that is analogous to the kinetics by the exposure to a low concentration (0.2 mM) of HO. The exposure to higher HO concentrations caused lower U dissolution and resulted in deviation from the U dissolution behavior by -ray irradiation.
Inagaki, Yoshiyuki; Sakaba, Nariaki
Shokubai, 61(2), p.92 - 96, 2019/04
The outline of the membrane IS process to produce hydrogen by thermochemical water splitting using solar heat at around 650C is described. The membrane technology has been applied to the three main reaction of the IS process to lower the reaction temperature and reduce the amount of circulation materials in the process. The key component technologies such as catalysts, membranes and corrosion resistant materials have been developed. The study was supported in part by the Council for Science, Technology and Innovation, Cross-ministerial Strategic Innovation Promotion Program, "Energy Carrier".
Irisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu
QST-M-16; QST Takasaki Annual Report 2017, P. 63, 2019/03
no abstracts in English
Carnevali, P. B. M.*; Schulz, F.*; Castelle, C. J.*; Kantor, R. S.*; Shih, P. M.*; Sharon, I.*; Santini, J.*; Olm, M. R.*; Amano, Yuki; Thomas, B. C.*; et al.
Nature Communications (Internet), 10, p.463_1 - 463_15, 2019/01
Shinto, Katsuhiro; Okoshi, Kiyonori; Shibata, Takanori*; Nammo, Kesao*; Ikegami, Kiyoshi*; Takagi, Akira*; Namekawa, Yuya*; Ueno, Akira; Oguri, Hidetomo
AIP Conference Proceedings 2052, p.050002_1 - 050002_7, 2018/12
In the 2017/2018 campaign, the J-PARC cesiated rf-driven negative hydrogen (H) ion source producing H beam with the beam current of 47 mA accomplished three long-term operations more than 2,000 hours without any serious issues. On the final day of this campaign, the ion source produced an H beam current of 72 mA so that the linac commissioning group could demonstrate the beam current of 60 mA at the linac exit. We are also conducting an endurance test of a J-PARC-made antenna at a test bench. The antenna achieved the operation time approximately 1,400 hours.
Ebihara, Kenichi; Yamaguchi, Masatake; Tsuru, Tomohito; Itakura, Mitsuhiro
Keikinzoku, 68(11), p.596 - 602, 2018/11
Hydrogen embrittlement (HE) is considered as one cause of stress corrosion cracking. HE is a serious problem in the development of high strength aluminum alloy as with steels. For understanding HE, it is inevitable to know hydrogen trapping states in the alloys and it can be identified using thermal desorption spectrometry of H. In this study, we numerically simulated thermal desorption spectra of hydrogen in aluminum for a cylindrical and a plate specimens and interpreted the desorption peaks included in them on the basis of the trap site concentration and the trap energy. As a result, we found that the peak at the lowest-temperature side can result from grain boundaries and confirmed that the reported interpretation for other peaks is reasonable. We also obtained the result showing the possibility that the trap site concentration of defects changes during heating the specimens. This result may give a suggestion for the interpretation of temperature desorption spectra of steels.
Ftterer, M. A.*; Li, F.*; Gougar, H.*; Edwards, L.*; Pouchon, M. A.*; Kim, M. H.*; Carr, F.*; Sato, Hiroyuki
Proceedings of 9th International Topical Meeting on High Temperature Reactor Technology (HTR 2018) (USB Flash Drive), 12 Pages, 2018/10
This paper provides an update on the international effort in the development of the VHTR system pursued through international collaboration between 8 countries in the GIF and an outlook on future R&D. The versatility of the VHTR enables it to be designed with inherent safety characteristics and optimized for both electric and non-electric applications, in particular for cogeneration of heat and power. Recent highlights from the four currently active GIF VHTR R&D projects are provided and placed into the context of the related national programs. Based on VHTR's relatively high technology readiness level, orientations for future R&D are outlined and will contribute to further enhancing the system's market readiness level.
Yamauchi, Akihiro*; Amaya, Masaki
Proceedings of Annual Topical Meeting on Reactor Fuel Performance (TopFuel 2018) (Internet), 7 Pages, 2018/10
Differential scanning calorimetry (DSC) measurements on pre-hydrided cold worked, stress relieved and recrystallized Zry-4 cladding were performed in a temperature range between 50 and 600C in order to elucidate the effect of final heat treatment at fabrication of Zircaloy-4 (Zry-4) cladding on the terminal solid solubility during the dissolution of zirconium hydrides at heating up (TSSD). Obtained DSC curves and Metallography indicate that the initial state of hydrides affects the dissolution behavior of hydride. The Arrhenius plots of the TSSD temperatures and hydrogen contents obtained from this study revealed that cold worked samples exhibited the largest TSSD and followed by stress relieved and recrystallized samples. The results of this study indicated that the difference in microstructure due to final heat treatment at fabrication of Zry-4 cladding affects the dissolution behavior of hydrides.
Yamazaki, Saishun; Pshenichnikov, A.; Pham, V. H.; Nagae, Yuji; Kurata, Masaki; Tokushima, Kazuyuki*; Aomi, Masaki*; Sakamoto, Kan*
Proceedings of Annual Topical Meeting on Reactor Fuel Performance (TopFuel 2018) (Internet), 8 Pages, 2018/10
It is predictively evaluated that degradation of fuel assembly proceeded in a certain steam-starved condition at the early stage of a SA at 1F unit 2 (BWR). As for PWR fuel assembly, effective steam flow rate was properly indicated by normalizing to a unit of g-HO/sec/rod which is used as an important parameter for evaluating fuel degradation progression. Due to the inhomogeneous configuration of BWR fuel assembly, the difference of Zry oxidation and hydrogen uptake between the inside and outside of the channel box cannot be properly evaluated by this normalization. Instead of g-HO/sec/rod, proper evaluation unit for BWR configuration is necessary. To accumulate Zry oxidation and hydrogen uptake data for steam-starved conditions, high temperature oxidation tests were performed using a simulated BWR fuel bundle sample. The use of equivalent diameter of the cross section of BWR fuel assembly was proposed for normalization of effective steam flow rate.
Ebihara, Kenichi; Saito, Kei*; Takai, Kenichi*
"Suiso Zeika No Kihon Yoin To Tokusei Hyoka" Kenkyukai Hokokusho, p.57 - 61, 2018/09
no abstracts in English
Shinto, Katsuhiro; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Shibata, Takanori*; Nammo, Kesao*; Namekawa, Yuya*; Ueno, Akira; Oguri, Hidetomo
AIP Conference Proceedings 2011, p.050018_1 - 050018_3, 2018/09
Shinto, Katsuhiro; Shibata, Takanori*; Miura, Akihiko; Miyao, Tomoaki*; Wada, Motoi*
AIP Conference Proceedings 2011, p.080016_1 - 080016_3, 2018/09
Shibata, Takanori*; Shinto, Katsuhiro; Takagi, Akira*; Oguri, Hidetomo; Ikegami, Kiyoshi*; Okoshi, Kiyonori; Nammo, Kesao*; Naito, Fujio*
AIP Conference Proceedings 2011, p.020008_1 - 020008_3, 2018/09