Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Yamamoto, Masahiko; Kono, Soma; Saegusa, Yu; Kuno, Takehiko; Sekine, Megumi; Inoue, Naoko; Noro, Naoko; Rodriguez, D.; Yamaguchi, Tomoki; Stinett, J.*
Proceedings of INMM & ESARDA Joint Annual Meeting 2023 (Internet), 10 Pages, 2023/05
The gamma-ray measurement part of the Non-Destructive Assay (NDA) course of safeguards and nuclear material accountancy was developed to focus on gamma-ray measurement allotting two days out of five days. The lectures on the basic characteristics and detection methods and mechanism of gamma-ray detectors were provided as e-learnings which were developed. The part for hands-on exercises were implemented in JAEA facility. Participants have set up each gamma-ray detector, and performed measurements of uranium and the other gamma-ray emitting nuclides. Also, uranium-235 enrichment measurements have been performed. In addition, the participants trained with a handheld gamma-ray spectrometer, HM-5, that is popular for IAEA safeguards as the preparation in the measurement exercise of fresh fuel assemblies in JRR-3, a research reactor facility of JAEA. This paper reports on the development, implementation, and feedback from participants on gamma-ray measurement part of the NDA course.
Nishida, Satoru*; Nishino, Soichiro*; Sekine, Masahiko*; Oka, Yuki*; Harjo, S.; Kawasaki, Takuro; Suzuki, Hiroshi; Morii, Yukio*; Ishii, Yoshinobu*
Materials Transactions, 62(5), p.667 - 674, 2021/05
Times Cited Count：5 Percentile：41.35(Materials Science, Multidisciplinary)Tanaka, Kosuke; Miwa, Shuhei; Sato, Isamu; Hirosawa, Takashi; Sekine, Shinichi; Osaka, Masahiko; Obayashi, Hiroshi; Koyama, Shinichi
Journal of Nuclear Science and Technology, 51(7-8), p.876 - 885, 2014/07
Times Cited Count：5 Percentile：36.96(Nuclear Science & Technology)As a first step for obtaining experimental data on the effects of high-temperature chemical interaction on fission product (FP) release behavior, we focused on the dissolution of irradiated uranium plutonium mixed oxide (MOX) fuel by molten zircaloy (Zry), and carried out a heating test under the reducing atmosphere. Pieces of an irradiated MOX fuel pellet and cladding were subjected to the heating test at 2373 K for 5 min. The fractional release rate of cesium (specifically 
Cs) was monitored during the test and its release behavior was evaluated. The observation of microstructures and measurements of elemental distribution in the heated specimen were also performed. We demonstrated experimentally that the fuel dissolution by molten Zry accelerated the release of Cs from the fuel pellets.
Osaka, Masahiko; Tanaka, Kosuke; Sekine, Shinichi; Akutsu, Yoko; Suzuki, Tatsuya*; Mimura, Hitoshi*
Journal of Nuclear Materials, 427(1-3), p.384 - 388, 2012/08
Times Cited Count：4 Percentile：31.96(Materials Science, Multidisciplinary)Morphology-controlled synthesis of Mo compounds from a nitric acid solution by microwave heating was investigated for effective utilizations of Mo fission product from a high level nuclear waste. The microwave heating method was revealed to greatly accelerate crystallization and crystal growth of the synthesized powder. Addition of a small amount of Zr stabilized synthesis of a hexagonal-MoO
powder. Furthermore, the microwave heating with Zr-addition has synthesized a specific urchin-like shaped hexagonal-MoO crystal having a good crystallinity. The present methods would be useful for effective utilization of Mo from high level nuclear waste in terms of their practicability and ability to the morphology control.
Miwa, Shuhei; Osaka, Masahiko; Yoshimochi, Hiroshi; Tanaka, Kenya; Seki, Takayuki*; Sekine, Shinichi*
JNC TN9400 2005-023, 43 Pages, 2005/04
JNC-TN9400-2005-023.pdf:3.56MB
The effect of oxygen potential on the sintering behavior of MOX fuel containing Am (Am-MOX) was investigated. Green pellets of Am-MOX were prepared by a conventional powder metallurgical technique. For Am-MOX fuel pellets sintered at various oxygen potential conditions, density measurement, microstructural observation and elements analyses by EPMA were performed High density pellets having good structure were obtained due to oxygen potential change of sintering atmosphere from high oxygen potential to low oxygen potential at 800
C in the cooling process.For the pellets sintered at -520 kJ/mol, -390 kJ/mol and -340 kJ/mol, the sintered density increases with increase of oxygen potential up to -390 kJ/mol (threshold oxygen potential), then decreases above the threshold oxygen potential. This tendency is similar to that observed in the (U,Gd)O
system. The differences of sintering behavior for Am-MOX pellets which were observed by changing the oxygen potential were attributable to the difference of pore structure, which was supposed to be caused by the valence state of Am in the oxides. On the other hands, the grain size of Am-MOX pellet sintered at -520 kJ/mol was almost the same as that at -390 kJ/mol. Homogeneous distribution of U, Pu and Am was obtained at pellets sintered both -520 and -390 kJ/mol in these sintering conditions. For the pellets sintered at 1500C , 1600C , 1700C , the high dense pellets are obtained, therefore This results shows the the possibility of fabrication of good fuel pellets at lower temperature than 1700C
Sekine, Takashi; Maeda, Yukimoto; Aoyama, Takafumi; Ariyoshi, Masahiko
Nihon Genshiryoku Gakkai Wabun Rombunshi, 4(4), p.259 - 275, 2005/04
The MK-III upgrading project was completed in the experimental fast reactor JOYO to increase irradiation capability for irradiation tests. After modification work of cooling system, the system function tests were carried out between August 2001 and March 2003. As a result of these tests, it was confirmed that the performance of whole plant included the modified components, which were the intermediate heat exchanger (IHX) and the dump heat exchanger (DHX) etc., was satisfied with the design. The performance tests were carried out from June 2003 as the last phase of MK-III modification work. During the performance tests, the reactor power was raised step by step as 20%, 50%, 75%, 90% and 100% (140MWt), while confirming the nuclear and thermal characteristics of MK-III core and the heat removal capability of IHX and DHX. All performance tests was successfully carried out and it was confirmed that the performance of JOYO MK-III plant was satisfied with the design. Certificate of pre-use inspection about JOYO MK-III was conferred from Ministry of Education, Culture, Sports, Science and Technology in 27th November 2003 and the MK-III modification work was completed. This report shows the results of the system function tests and the performance tests of JOYO MK-III.
Osaka, Masahiko; Miwa, Shuhei; Mondo, Kenji; Ozaki, Yoko; Ishi, Yohei; Yoshimochi, Hiroshi; Seki, Takayuki*; Sekine, Shinichi*; Ishida, Takashi*; Tanaka, Kenya
JNC TN9400 2005-002, 40 Pages, 2005/03
JNC-TN9400-2005-002.pdf:2.43MB
An experimental investigation for the phase relation of (U,Pu,Am)O was performed with XRD, ceramography and DTA. Although lattice parameter tended to increase with increases of Am content and O/M ratio, its slope differed from that of (U,Pu)O. A drastic structural change was observed around O/M=1.98. Besides, many DTA peaks, which could never be seen in the case of (U,Pu)O, were observed above O/M=1.98.These results were interpreted with a hypothesis that all Am were trivalent and equivalent amount of U became pentavalent. The dependence of lattice parameter on Am content could be expressed well by using a model with ionic radii of each element. Also the structural change around O/M=1.98 could be explained as caused by valence states of each element. It was concluded from these interpretation that all Am in (U,Pu,Am)O were likely to exist as trivalent state.
Maeda, Yukimoto; Aoyama, Takafumi; Yoshida, Akihiro; Sekine, Takashi; Ariyoshi, Masahiko; Ito, Chikara; Masaaki, Nemoto; Murakami, Takanori; Isozaki, Kazunori; Hoshiba, Hideaki; et al.
JNC TN9410 2003-011, 197 Pages, 2004/03
JNC-TN9410-2003-011.pdf:10.26MB
MK-III performance tests began in June 2003 to fully characterize the upgraded core and heat transfer system. Then, the last pre-use inspection was finished in November 2003.This report summarize the result of each performance test.
Koyama, Shinichi; Osaka, Masahiko; Sekine, Takashi; Morozumi, Katsufumi; Namekawa, Takushi;
Journal of Nuclear Science and Technology, 40(2), p.998 - 1013, 2003/02
Times Cited Count：23 Percentile：80.7(Nuclear Science & Technology)None
Inoue, Masaki; ; ; ; Sekine, Takashi; Osaka, Masahiko
Journal of Nuclear Materials, 323(1), p.108 - 122, 2002/00
Times Cited Count：10 Percentile：56.43(Materials Science, Multidisciplinary)None
B
C for moderatorDonomae, Takako; Tachi, Yoshiaki; Onose, Shoji; Matsumoto, Shinichiro; Ito, Masahiko; Sekine, Manabu*
no journal, ,
no abstracts in English
Am
)OMiwa, Shuhei; Osaka, Masahiko; Mondo, Kenji; Ishi, Yohei; Yoshimochi, Hiroshi; Tanaka, Kenya; Seki, Takayuki*; Sekine, Shinichi*; Kurosaki, Ken*; Uno, Masayoshi*; et al.
no journal, ,
An experimental investigation on phase relation of (PuAm)O was carried out by X-ray diffraction (XRD) analysis, ceramography and Differential Thermal Analysis (DTA) for (PuAm)O having different O/M ratios from 1.90 to 2.00.
Osaka, Masahiko; Miwa, Shuhei; Tanaka, Kosuke; Sekine, Shinichi*
no journal, ,
Basic sintering tests of UO
/PuO-Mo cermet were carried out adding Ni and Pd as sintering additives. Optimal conditions to achieve high density cermet were pursured. This study intends to obtain basic knowledge about densification of Mo-cermet when metal impurities are included.
Miwa, Shuhei; Osaka, Masahiko; Tanaka, Kosuke; Ishi, Yohei; Tanaka, Kenya; Sekine, Shinichi*; Seki, Takayuki*
no journal, ,
R&D of advanced fuel containing minor actinide for use in fast reactors is described related to the composite fuel with MgO matrix. Fabrication tests of MgO composite fuels containing Am were done by a practical process that could be adapted to the presently used commercial manufacturing technology. Am-containing MgO composite fuels having good characteristics, i.e., having no defects, a high density, a homogeneous dispersion of host phase, were obtained.
Miwa, Shuhei; Osaka, Masahiko; Sato, Isamu; Hirosawa, Takashi; Tanaka, Kosuke; Sekine, Shinichi*; Ishida, Takashi*; Seki, Takayuki*; Kashimura, Naoki*
no journal, ,
no abstracts in English
Miwa, Shuhei; Osaka, Masahiko; Tanaka, Kosuke; Sekine, Shinichi*
no journal, ,
no abstracts in English
Iwata, Yoshihiro; Ito, Chikara; Sekine, Takashi; Osaka, Masahiko
no journal, ,
no abstracts in English
