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Yoshida, Hisao*; Yamamoto, Akira*; Hosokawa, Saburo*; Yamazoe, Seiji*; Kikkawa, Soichi*; Hara, Kenji*; Nakamura, Mitsutaka; Kamazawa, Kazuya*; Tanaka, Tsunehiro*
Topics in Catalysis, 64(9-12), p.660 - 671, 2021/08
Times Cited Count：2 Percentile：11.54(Chemistry, Applied)
O
by 
inelastic neutron scattering and their reactivity with ethyleneYamazoe, Seiji*; Yamamoto, Akira*; Hosokawa, Saburo*; Fukuda, Ryoichi*; Hara, Kenji*; Nakamura, Mitsutaka; Kamazawa, Kazuya*; Tsukuda, Tatsuya*; Yoshida, Hisao*; Tanaka, Tsunehiro*
Catalysis Science & Technology, 11(1), p.116 - 123, 2021/01
Times Cited Count：6 Percentile：34.43(Chemistry, Physical)SiO
(GPS) scintillator-based alpha imaging detector for rapid plutonium detection in high-radon environmentsMorishita, Yuki; Izaki, Kenji; Kaneko, Junichi*; Yamamoto, Seiichi*; Higuchi, Mikio*; Torii, Tatsuo
IEEE Transactions on Nuclear Science, 67(10), p.2203 - 2208, 2020/10
Times Cited Count：9 Percentile：71.58(Engineering, Electrical & Electronic)We developed a GdSiO (GPS) scintillator-based alpha imaging detector and demonstrated its effectiveness by evaluating actual Pu particle and 
Rn progeny. The GPS scintillator plate was prepared by a sintering method. The outer dimensions of the GPS scintillator plate were 5 
5 cm, and the scintillator layer was approximately 50 
m on a 3-mm-thick high-transparency glass. The plate was optically coupled to a position-sensitive photomultiplier tube with silicone grease. The developed imaging detector exhibited good uniformity. Pu particle activities were accurately evaluated at 14 different positions, and the difference in activity was within 6%. Radon-222 (Rn) progeny counts were reduced by 65.3% by applying an energy window. Although the Pu/Rn progeny activity ratio was 1/51, the Pu particle was successfully identified among Rn progeny within the 5 min-measurement time. The imaging detector has an excellent ability for detecting Pu among Rn progeny. Thus, this detector is useful for alpha contamination monitoring in high-radon-background environments.
Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Hoshi, Katsuya; Torii, Tatsuo
Radiation Measurements, 112, p.1 - 5, 2018/05
Times Cited Count：17 Percentile：85.18(Nuclear Science & Technology)To detect plutonium isotopes (
Pu, 
Pu, and 
Pu) in a field of high beta and 
background, an alpha particle detector with low beta and -ray sensitivity is required. Therefore, we optimized the thickness of the GAGG scintillator for alpha particle detection in a field of high beta and background. We prepared three GAGG scintillators with thicknesses of 0.05 mm, 0.07 mm, and 0.1 mm. Each of the GAGG scintillators was coupled optically to the SiPM array, which was used as the photodetector. Alpha, beta, and rays were irradiated onto the developed alpha particle detector, and their spectra were obtained. All GAGG scintillators used in this study were not sensitive to rays with a dose rate of 1 mSv/h. The beta count of the 0.05-mm-thick GAGG was only 1/100 that of the 0.1-mm-thick GAGG. Therefore, the 0.05-mm-thick GAGG scintillator is promising from the viewpoint of detecting plutonium contamination in a field with high beta and background.
Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Nemoto, Norio
Radiation Measurements, 103, p.33 - 38, 2017/08
Times Cited Count：14 Percentile：78.05(Nuclear Science & Technology)Nuclear fuel materials, such as uranium and plutonium (Pu), are handled at nuclear fuel facilities. There are a contamination source of Pu in tight spaces that cannot be directly measured by a ZnS(Ag) scintillation detector, such as interspace between a glovebox window and a platform, pipe flange, port cover of vinyl bag, and filter interspaces. Therefore, we developed a new imaging detector called a flexible alpha camera that enables to identify the Pu contamination for tight spaces at work sites. The thickness of the flexible alpha camera was only 
1/5 of the ZnS(Ag) scintillation detector, and its efficiency for 4-pi direction was 42.7% for 5.5-MeV alpha particles. Minimal detectable activity (MDA) was 0.014 Bq. Four types of PuO sample, removed from a duct, Bag-In/Bag-Out port, glovebox glove, and vinyl sheet, were measured by the flexible alpha camera and the PuO particle was automatically identified. Using the flexible alpha camera, the Pu contamination source can be quickly detected, preventing the spread of contamination.
Yamashita, Takuya; Nagae, Yuji; Kikuchi, Koichi*; Yamamoto, Kenji*
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 8 Pages, 2017/04
Yamashita, Takuya; Wakai, Takashi; Onizawa, Takashi; Sato, Kenichiro*; Yamamoto, Kenji*
Journal of Pressure Vessel Technology, 138(6), p.061407_1 - 061407_6, 2016/12
Times Cited Count：0 Percentile：0(Engineering, Mechanical)Yamashita, Takuya; Nagae, Yuji; Sato, Kenichiro*; Yamamoto, Kenji*
Journal of Pressure Vessel Technology, 138(2), p.024501_1 - 024501_7, 2016/04
Times Cited Count：0 Percentile：0(Engineering, Mechanical)Nagae, Yuji; Yamamoto, Kenji*; Otani, Tomomi*
Proceedings of 2015 ASME Pressure Vessels and Piping Conference (PVP 2015) (Internet), 7 Pages, 2015/07
Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Toi, Kohei*; Tsubota, Yoichi*; Higuchi, Mikio*
Nuclear Instruments and Methods in Physics Research A, 764, p.383 - 386, 2014/11
Times Cited Count：36 Percentile：93.56(Instruments & Instrumentation)Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Toi, Kohei*; Tsubota, Yoichi*
Nuclear Instruments and Methods in Physics Research A, 747, p.81 - 86, 2014/05
Times Cited Count：40 Percentile：94.83(Instruments & Instrumentation)Alpha particles are monitored for detecting nuclear fuel material (i.e., plutonium and uranium) at nuclear fuel facilities. In this study, we developed a new alpha-particle imaging system by combining an Si-PM array, which is insensitive to noise, with a Ce-doped GdAlGaO
(GAGG) scintillator, and evaluated our developed system's fundamental performance. The scintillator was 0.1-mm thick, and the light guide was 3.0 mm thick. An 
Am source was used for all the measurements. We evaluated the spatial resolution by taking an image of a resolution chart. A 1.6 lp/mm slit was clearly resolved, and the spatial resolution was estimated to be less than 0.6-mm FWHM. The energy resolution was 13% FWHM. A slight distortion was observed in the image, and the uniformity near its center was within 24%. We conclude that our developed alpha-particle imaging system is promising for plutonium detection at nuclear fuel facilities.
Wakai, Takashi; Nagae, Yuji; Takaya, Shigeru; Obara, Satoshi; Date, Shingo*; Yamamoto, Kenji*; Kikuchi, Koichi*; Sato, Kenichiro*
Tainetsu Kinzoku Zairyo Dai-123-Iinkai Kenkyu Hokoku, 52(2), p.147 - 159, 2011/07
By employing high-Cr ferritic steels to the structural materials for JSFR, a compact plant designing can be achieved. It contributes to reduce the construction cost and to enhance the freedom of designing. Among the high-Cr ferritic steels, modified 9Cr-1Mo steel (compatible to ASTM A335 P91) is a candidate of the structural material for the demonstration facility of JSFR, because the steel has superior microstructure stability at elevated temperature for long time. However, remarkable creep strength degradation has been observed in the welded joint of high-Cr ferritic steels, especially in long-term region. It is known as "Type-IV damage". In the elevated temperature designing for the fast reactors, such creep strength degradation must be taken into account properly. Therefore, the creep strength assessment procedure and the allowable stress for the welded joints made of modified 9Cr-1Mo steel have been proposed. In this study, (1) a series of creep rupture tests to verify the validity of the creep strength assessment procedure was performed. (2) Applicability of the creep strength assessment procedure to the creep fatigue strength assessment of the welded joints made of modified 9Cr-1Mo steel was investigated. (3) Metallurgical examinations of creep ruptured specimens were carried out to confirm the contribution of "Type-IV damage". As a result, it was demonstrated that the creep strength assessment procedure was validated using the long-term creep rupture test results less than 30,000h and that the creep strength assessment procedure was applicable to the creep-fatigue strength assessment based on some uniaxial creep-fatigue test results.
Seno, Kenji*; Tamura, Akinori*; Nishiyama, Seiji*; *; Fuse, Masato*; *; *; *
JNC TJ5410 2004-011, 3606 Pages, 2004/03
JNC-TJ5410-2004-011-1.pdf:87.3MBJNC-TJ5410-2004-011-2.pdf:27.58MBJNC-TJ5410-2004-011-3.pdf:14.8MBJNC-TJ5410-2004-011-4.pdf:10.25MB
This is the work that has operated basic design, concerning excavation for the underground facilities to perform the studies on engineering technologu at deep underground (east and west shafts, a ventilation shaft, horizontal research drifts) as a part of the Horonobe Deep Underground Research Plan.
*; Yasu, Takami; Shoji, Kenji; Fukushima, Isao; *; Shibuya, Jun; ; ; Yamamoto, Masao
PNC TN8440 87-190, 35 Pages, 1987/08
no abstracts in English
Aoki, Kenji; Shimizu, Kazuyuki; Yamamoto, Masahiko; Takeuchi, Kenji; Hiyama, Hisao; Iwasaki, Shogo
no journal, ,
no abstracts in English
Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Toi, Kohei*; Tsubota, Yoichi*
no journal, ,
Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Toi, Kohei*; Tsubota, Yoichi*; Higuchi, Mikio*
no journal, ,
Nagae, Yuji; Sato, Kenichiro*; Yamamoto, Kenji*
no journal, ,
no abstracts in English
Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Nemoto, Norio; Kashimuta, Yoshio*
no journal, ,
Nuclear fuel materials such as uranium and plutonium were handled at a nuclear fuel facility. Early detection of a contamination due to these materials is important to prevent internal exposure of workers. ZnS(Ag) scintillation detector has been widely used to detect these materials by measuring alpha-particles. It cannot directly measure narrow space. ZnS(Ag) scintillation detector does not have an ability to distinguish nuclear fuel materials from naturally occurring alpha emitters such as radon daughters. To solve this problem, we developed a new imaging detector named "flexible alpha camera". We actually measured plutonium specimen and radon daughters by the flexible alpha camera. In the result of 2-dimensional distribution, plutonium specimen was imaged as point. Spatial resolution of plutonium specimen was only 0.36 mm FWHM. Plutonium was distinguished from radon daughters based on differences of 2-dimensional distribution and energy by using the flexible alpha camera.
Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*
no journal, ,
Spectroscopy of alpha particles is necessary to distinguish plutonium isotopes from radon progeny. We previously developed an alpha particle imaging detector by combining a 0.1-mm-thick GAGG scintillator with a silicon photomultiplier (SiPM). This detector had better energy resolution than the ZnS(Ag) scintillator-based alpha particle detector. However, it had 
or sensitivity because the GAGG scintillator was too thick compared with the range of 5.5 MeV 
particles. Therefore, it is difficult to measure alpha particles from plutonium in a field with high and background. To solve this problem, we optimized the thickness of GAGG scintillator by comparing three GAGG scintillators with thicknesses of 0.05 mm, 0.07 mm, and 0.1 mm. Each of the GAGG scintillators was optically coupled to SiPM, which was used as the photodetector. The peak channels and energy resolutions for 5.5 MeV alpha particles of three GAGG scintillators were compared. Also, the count rates of particles of the GAGG scintillators were evaluated by using a 
Sr source. The peak channel of the 0.05-mm-thick GAGG scintillator was 1.6x higher than that of the 0.1-mm-thick GAGG scintillator and 3.7x higher than that of the plastic scintillator. The 0.05-mm-thick GAGG scintillator had the best energy resolution of 11.6 % FWHM and the lowest count rate of 0.2 cpm among the three GAGG scintillators.
