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Shinozaki, Masaru; Aita, Takahiro; Iso, Takahito*; Odakura, Manabu*; Haginoya, Masahiro*; Kadowaki, Hiroyuki*; Kobayashi, Shingo*; Inagawa, Takumu*; Morimoto, Taisei*; Iso, Hidetoshi; et al.
JAEA-Technology 2021-043, 100 Pages, 2022/03
JAEA-Technology-2021-043.pdf:7.49MB
It is planned that the MOX (Mixed Oxide) from the decommissioned facilities in Nuclear Fuel Cycle Engineering Laboratories is going to be consolidated and stored stably and safely for a long term in Plutonium Fuel Production Facility of the Plutonium Fuel Development Center of Nuclear Fuel Cycle Engineering Laboratories. For this purpose, it is necessary to pelletize nuclear fuel materials in the facility and store them in the assembly storage (hereinafter referred to as "waste packaging work") to secure storage space in the plutonium material storage. As a countermeasure to reduce the facility risk in this waste packing work, it was decided to construct a new powder weighing and homogenization mixing facility to physically limit the amount (batch size) of nuclear fuel materials handled at the entrance of the process. In order to secure the installation space for the new facility in the powder preparation room (1) (FP-101), the pre-dismantling temporary waste storage facility 3 (FPG-03a, b, c) was dismantled and removed. This facility consists of a granulating and sizing facility, an additive mixing facility, and a receiving and delivering guided facility, which started to be used from January 1993, and was discontinued on February 3, 2012 and became a waste facility. Subsequently, the dismantling and removal of the interior equipment was carried out by pellet fabrication section for glove operation to reduce the amount of hold-up, and before the main dismantling and removal, there was almost no interior equipment except for large machinery. This report describes the dismantling and removal of the glove box and some interior equipment and peripherals of the facility, as well as the Green House setup method, dismantling and removal procedures, and issues specific to powder process equipment (dust, etc.).
Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.
High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02
As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950
C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.
Nozaki, Mikito*; Watanabe, Kenta*; Yamada, Takahiro*; Shih, H.-A.*; Nakazawa, Satoshi*; Anda, Yoshiharu*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; Hosoi, Takuji*; Shimura, Takayoshi*; et al.
Japanese Journal of Applied Physics, 57(6S3), p.06KA02_1 - 06KA02_7, 2018/06
Times Cited Count：21 Percentile：66.94(Physics, Applied)We fabricated AlON dielectric films by repeating thin AlN deposition and in situ O
oxidation for AlGaN/GaN MOS-HFETs. Uniform nitrogen distribution is achievable by the proposed ALD-based process and that nitrogen concentration can be precisely controlled by changing AlN thickness (ALD cycle number) in each step. It was found that AlON films grown by ALD system offers significant advantages in terms of practical application while keeping superior Vth stability and electrical properties at the insulator/AlGaN interface in AlGaN/GaN MOS-HFETs.
Yamada, Takahiro*; Watanabe, Kenta*; Nozaki, Mikito*; Shih, H.-A.*; Nakazawa, Satoshi*; Anda, Yoshiharu*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; Hosoi, Takuji*; Shimura, Takayoshi*; et al.
Japanese Journal of Applied Physics, 57(6S3), p.06KA07_1 - 06KA07_6, 2018/06
Times Cited Count：6 Percentile：27.37(Physics, Applied)Thermal oxidation of AlGaN surface and its impact on the electrical properties of AlGaN/GaN MOS capacitors were investigated by means of synchrotron radiation photoelectron spectroscopy (SR-PES), atomic force microscopy (AFM) and C-V measurements. SR-PES analysis revealed that the AlGaN surface is oxidized even at low temperature of 400C, in contrast to no oxide formation on GaN surface. However, since no noticeable change in the surface morphology was observed at temperatures up to 800C, it can be concluded that an ultrathin oxide overlayer is formed on the AlGaN surface. On the other hand, for the oxidation treatments above 850C, the formation of small oxide grains was observed over the entire area of the AlGaN surface, and the growth of oxide grains significantly degraded the surface morphology. Therefore, the AlGaN/GaN MOS capacitors were fabricated on the AlGaN surface oxidized at moderate temperatures up to 800C. While we have confirmed that relatively good interface properties are obtained for direct AlON deposition without oxidation treatment, it was found that the oxidation treatment at 400C leads to further improvement of interface properties and reduction of C-V hysteresis.
/AlON stacked gate dielectrics for AlGaN/GaN MOS heterojunction field-effect transistorsWatanabe, Kenta*; Terashima, Daiki*; Nozaki, Mikito*; Yamada, Takahiro*; Nakazawa, Satoshi*; Ishida, Masahiro*; Anda, Yoshiharu*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; Hosoi, Takuji*; et al.
Japanese Journal of Applied Physics, 57(6S3), p.06KA03_1 - 06KA03_6, 2018/06
Times Cited Count：11 Percentile：45.59(Physics, Applied)The advantage of SiO/AlON stacked gate dielectrics over SiO, AlON and AlO single dielectric layers was demonstrated. Our systematic research revealed that the optimized stacked structure with 3.3-nm-thick AlON interlayer is beneficial in terms of superior interface quality, reduced gate leakage current and C-V hysteresis for next-generation high frequency and high power AlGaN/GaN MOS-HFETs.
/GaN stacks for high-quality GaN-based metal-oxide-semiconductor devices with improved gate dielectric reliabilityYamada, Takahiro*; Watanabe, Kenta*; Nozaki, Mikito*; Yamada, Hisashi*; Takahashi, Tokio*; Shimizu, Mitsuaki*; Yoshigoe, Akitaka; Hosoi, Takuji*; Shimura, Takayoshi*; Watanabe, Heiji*
Applied Physics Express, 11(1), p.015701_1 - 015701_4, 2018/01
Times Cited Count：45 Percentile：85.43(Physics, Applied)A simple and feasible method for fabricating high-quality and highly reliable GaN-based metal-oxide-semiconductor (MOS) devices was developed on the basis of systematic physical and electrical characterizations. Chemical vapor deposition of SiO films directly onto GaN substrates forming Ga-oxide interlayers was used to fabricate SiO/GaO
/GaN stacked structures. Although well-behaved hysteresis-free GaN-MOS capacitors with extremely low interface state density below 10
cm
eV
were obtained by post-deposition annealing, Ga diffusion into overlying SiO layers severely degraded the insulating property and dielectric breakdown characteristics of the MOS devices. However, this problem was found to be solved by employing rapid thermal processing, leading to superior performance of the GaN-MOS devices in terms of interface quality, insulating property and gate dielectric reliability.
Watanabe, Kenta*; Nozaki, Mikito*; Yamada, Takahiro*; Nakazawa, Satoshi*; Anda, Yoshiharu*; Ishida, Masahiro*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; Hosoi, Takuji*; Shimura, Takayoshi*; et al.
Applied Physics Letters, 111(4), p.042102_1 - 042102_5, 2017/07
Times Cited Count：17 Percentile：59.59(Physics, Applied)AlGaN/GaN HFET (hetero-junction field-effect transitor) has gained much attention as next-generation high frequency and high power devices. In this study, we systematically investigated the interface reaction between Al-based dielectrics (AlO and AlON) and AlGaN layer during deposition and post-deposition annealing (PDA), and revealed high thermal stability of AlON/AlGaN interface.
Yamada, Takahiro*; Ito, Joyo*; Asahara, Ryohei*; Watanabe, Kenta*; Nozaki, Mikito*; Nakazawa, Satoshi*; Anda, Yoshiharu*; Ishida, Masahiro*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; et al.
Journal of Applied Physics, 121(3), p.035303_1 - 035303_9, 2017/01
Times Cited Count：75 Percentile：92.36(Physics, Applied)Initial oxidation of GaN(0001) epilayers and subsequent growth of thermal oxides in dry oxygen ambient were investigated by means of X-ray photoelectron spectroscopy, spectroscopic ellipsometry, atomic force microscopy and X-ray diffraction measurements. It was found that, whereas initial oxide formation tends to saturate at temperatures below 800C, selective growth of small oxide grains proceeds at dislocations in the epilayers, followed by noticeable grain growth leading to rough surface morphology at higher oxidation temperatures. This indicates that oxide growth and its morphology are crucially dependent on the defect density in the GaN epilayers. Structural characterizations also revealed that polycrystalline 
- and 
-phase GaO grains in an epitaxial relation with the GaN substrate are formed from the initial stage of the oxide growth. On the basis of these experimental findings, we also developed a comprehensive model for GaN oxidation mediated by nitrogen removal and mass transport.
Asahara, Ryohei*; Nozaki, Mikito*; Yamada, Takahiro*; Ito, Joyo*; Nakazawa, Satoshi*; Ishida, Masahiro*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; Hosoi, Takuji*; Shimura, Takayoshi*; et al.
Applied Physics Express, 9(10), p.101002_1 - 101002_4, 2016/10
Times Cited Count：42 Percentile：83.27(Physics, Applied)The superior physical and electrical properties of AlON gate dielectrics on AlGaN/GaN substrates in terms of thermal stability, reliability, and interface quality were demonstrated by direct AlON deposition and subsequent annealing. Nitrogen incorporation into alumina was proven to be beneficial both for suppressing intermixing at the insulator/AlGaN interface and reducing the number of electrical defects in AlO films. Consequently, we achieved high-quality AlON/AlGaN/GaN metal-oxide-semiconductor capacitors with improved stability against charge injection and a reduced interface state density as low as 1.2
10
cmeV. The impact of nitrogen incorporation into the insulator was discussed on the basis of experimental findings.
Miwa, Shuhei; Osaka, Masahiko; Nozaki, Takahiro*; Arima, Tatsumi*; Idemitsu, Kazuya*
Journal of Nuclear Materials, 465, p.840 - 842, 2015/10
Times Cited Count：1 Percentile：9.15(Materials Science, Multidisciplinary)Oxygen potential of a prototypic Mo-cermet fuel containing PuO
was experimentally determined. It was shown that the oxygen potentials of Mo-cermet fuel containing PuO were the same as those of pure PuO. It was also confirmed that the gradual oxidation of the Mo matrix occurred only above the oxygen potential of Mo/MoO. It is concluded that the oxidation-reduction behavior of the Mo-cermet fuel can be evaluated individually for each phase of actinides oxide and Mo matrix. Better phase structures of the Mo-cermet fuel for taking full advantage of the oxidation-reduction controllability were suggested by the confinement of the actinides oxide phase with Mo.
Oguri, Hidetomo; Hasegawa, Kazuo; Ito, Takashi; Chishiro, Etsuji; Hirano, Koichiro; Morishita, Takatoshi; Shinozaki, Shinichi; Ao, Hiroyuki; Okoshi, Kiyonori; Kondo, Yasuhiro; et al.
Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.389 - 393, 2014/10
no abstracts in English
Futatsukawa, Kenta*; Ito, Yuichi; Kikuzawa, Nobuhiro; Kobayashi, Tetsuya*; Sato, Fumiaki; Shinozaki, Shinichi; Suzuki, Takahiro*; Fang, Z.*; Fukui, Yuji*; Michizono, Shinichiro*
Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1126 - 1129, 2014/06
no abstracts in English
Futatsukawa, Kenta*; Ikegami, Masanori*; Ito, Yuichi; Kikuzawa, Nobuhiro; Sato, Fumiaki; Shinozaki, Shinichi; Suzuki, Takahiro*; Chishiro, Etsuji; Hirano, Koichiro; Fang, Z.*; et al.
Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1149 - 1153, 2014/06
no abstracts in English
Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi; Kojima, Kazutoshi*; Nozaki, Shinji*
Proceedings of SPIE, Vol.8725 (CD-ROM), 8 Pages, 2013/06
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology)Iwamoto, Naoya*; Koizumi, Atsushi*; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi; Kojima, Kazutoshi*; Koike, Shumpei*; Uchida, Kazuo*; Nozaki, Shinji*
Materials Science Forum, 717-720, p.267 - 270, 2012/05
Times Cited Count：1 Percentile：53.05(Materials Science, Multidisciplinary)In this study, we carried out an attempt to identify the defects responsible for the degraded charge collection efficiency of the 6H-SiC p
n diode irradiated with 1 MeV electrons by the alpha particle induced charge transient spectroscopy. To form defects in the SiC crystal, one of the diodes was irradiated with 1 MeV electrons at a fluence of 110
/cm
. Collected charges of the diodes were measured in room temperature using 5.486 MeV alpha particles from 
Am source. After the electron irradiation, the collected charge of the diode at a reverse bias of 100 V decreased to 84% of its initial value. In order to investigate the relationship between degradation of collected charge and defects in detail, time-dependent collected charges of the diodes were measured in temperature ranges from 170 K to 310 K. As a result, two distinct peaks labeled X
and X are found for the electron-irradiated diode, and their activation energies are estimated to be 0.30 and 0.47 eV, respectively. These two peaks are considered to correspond to the defect levels introduced by the electron irradiation. In particular, when the diodes are used in room temperature, X is more critical to the charge collection than X.
Makino, Takahiro; Iwamoto, Naoya*; Onoda, Shinobu; Oshima, Takeshi; Kojima, Kazutoshi*; Nozaki, Shinji*
Materials Science Forum, 717-720, p.469 - 472, 2012/05
Times Cited Count：1 Percentile：53.05(Materials Science, Multidisciplinary)The peak amplitude of ion induced transient current in n-type 6H-SiC MOS capacitors decreased as the number of incident ions increased and the decrease was recovered to the initial value by applying a positive bias at +1 V. In addition, we monitored a change in the capacitance for the MOS capacitors during ion irradiation. The capacitances increase as the number of incident ion increase. Thus, the result obtained in this study indicates that the depletion layer decreased as the increasing number of incident ions and saturated. Since the number of incident ions at the peak current saturation corresponds to the saturation of the capacitance, we can conclude that the decrease in peak current comes from the decrease in the depletion layer. In addition, the generation of electron-hole pairs by incident ion may result in the formation of an inversion layer. This would have the effect of shielding the charge carriers from the applied bias further reducing the depletion layer width.
n diode irradiated with high-energy electronsIwamoto, Naoya; Koizumi, Atsushi*; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi; Kojima, Kazutoshi*; Koike, Shumpei*; Uchida, Kazuo*; Nozaki, Shinji*
IEEE Transactions on Nuclear Science, 58(6), p.3328 - 3332, 2011/12
Times Cited Count：5 Percentile：37.41(Engineering, Electrical & Electronic)no abstracts in English
Oshima, Takeshi; Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Deki, Manato; Nozaki, Shinji*
AIP Conference Proceedings 1336, p.660 - 664, 2011/05
Times Cited Count：1 Percentile：47.51(Physics, Applied)Metal-Oxide-Semiconductor (MOS) capacitors were fabricated on n-type 4H- and 6H-SiC epitaxial layers, and transient currents induced in SiC MOS capacitors by ion incidence were investigated. Transient Ion Beam Induced Current (TIBIC) measurements were performed using 15 MeV oxygen ions. As a result, the TIBIC peak height decreased with increasing number of incident ions. For example, the TIBIC signal peak for a 4H-SiC MOS capacitor at a reverse bias of 15 V was 0.18 mA at the beginning. The peak decreased to be 0.10 mA after 1800 ion irradiation. After that, the forward bias of 1 V was applied to the MOS capacitor and the TIBIC measurements were carried out under the same conditions. As a result, the peak height was recovered to be 0.18 mA. In general, the response of charge de-trapping by deep levels in wide bandgap semiconductors is very slow and they act as fixed charge. Since dense electron-hole pairs are generated by ion incident and holes move to the SiO/SiC interface by the electric field (applied reverse bias). Therefore, the decrease in TIBIC signal peak can be interpreted in terms of the recombination of negatively charged acceptor type deep levels with ion induced holes.
-raysOshima, Takeshi; Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Nozaki, Shinji*; Kojima, Kazutoshi*
Materials Science Forum, 679-680, p.362 - 365, 2011/03
Times Cited Count：1 Percentile：56.01(Engineering, Multidisciplinary)Charge induced in the 6H-Silicon Carbide (SiC) n Metal-Oxide-Semiconductor (MOS) capacitors by 15 MeV oxygen ion microbeams was evaluated using Transient Ion Beam Induced Current (TIBIC) before and after -ray irradiations. With increasing number of incident ions, the peak height of TIBIC signals decreases and the fall time increases. The decrease in TIBIC peak finally saturated. The peak height of the TIBIC signal can be refreshed to its original shape by applying a positive bias of + 1V to the oxide electrode. This result can be explained in terms of the existence of deep hole traps. Small decrease in both TIBIC signal peak and collected charge was observed due to -ray irradiation.
Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi; Kojima, Kazutoshi*; Koizumi, Atsushi*; Uchida, Kazuo*; Nozaki, Shinji*
IEEE Transactions on Nuclear Science, 58(1), p.305 - 313, 2011/02
Times Cited Count：10 Percentile：59.30(Engineering, Electrical & Electronic)no abstracts in English
