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Nagase, Fumihisa
Annals of Nuclear Energy, 171, p.109052_1 - 109052_8, 2022/06
Times Cited Count：2 Percentile：50.96(Nuclear Science & Technology)The fracture threshold of the fuel decreases if the oxidized Zr alloy cladding is strongly constrained by the spacer grid during quenching in a loss-of-coolant accident. Therefore, the estimation of realistic levels of the axial constraint has been a subject of significant interest on fuel safety. In this study, a test assembly consisting of a PWR-type simulated fuel segment and a 3
3 grid piece was heated in steam, cooled, and quenched, and the axial constraint force on the fuel segment was measured. The constraint force of the Zircaloy grid gradually decreased with temperature. Once the Zircaloy grid was heated to 
1060 K, the reduced constraint force had difficulty recovering, and thus the maximum constraint force during cooling and quenching was 
10 N. The constraint force was clearly reduced at 1070 K during the tests with the Inconel grid. However, the reduced constraint force partially recovered during cooling. As a result, the maximum constraint force during cooling and quenching was 20 to 50 N for the Inconel grid. In conclusion, oxidation, ballooning, rupture, or eutectic formation would not generally cause an extremely strong constraint, as predicted by previous studies, at the grid position.
Ozawa, Masaaki*; Amaya, Masaki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 19(4), p.185 - 200, 2020/12
no abstracts in English
/SiC interfaceMiyashita, Atsumi; Yoshikawa, Masahito; Kano, Takuma; Onuma, Toshiharu*; Sakai, Takayuki*; Iwasawa, Misako*; Soneda, Naoki*
Annual Report of the Earth Simulator Center April 2004 - March 2005, p.287 - 291, 2005/12
Silicon carbide semiconductor device is expected to be used under a severe environment like the nuclear reactor and the space environment. On the semiconductor device interface, the electric charge state of the defect decides an electric characteristic. To emulate interfacial structure the 
interface structure is generated and the electronic geometry is decided by the first-principle molecular dynamics simulation with the earth simulator. The amorphous interface structure is made by medium-scale model of about 400 atoms. The heating temperature is 4000K, the heating time is 3.0ps, the speed of rapid cooling is -1000K/ps, and SiC movable layers in the interface are assumed to be 4 layers. In temperature 2200K the 
terminal was opened to make the layer more amorphous. The model has almost abrupt interface, however, some defects energy levels were still observed in the band gap. The energy levels are originated from interfacial oxygen. The localized electronic distribution of the dangling bond causes defect energy levels.
Nagase, Fumihisa; Tanimoto, Masataka*; Uetsuka, Hiroshi
IAEA-TECDOC-1320, p.270 - 278, 2002/11
With a view to obtaining basic data for evaluating high burnup fuel behavior under LOCA conditions, a systematic research program is being conducted at JAERI. High-temperature oxidation tests with non-irradiated cladding have been performed to investigate separate effects of pre-oxidation and pre-hydriding on the oxidation kinetics. "Integral thermal shock tests" have been conducted simulating a LOCA condition to examine the influence of pre-hydriding on failure-bearing capability of oxidized cladding upon quenching. Test results showed almost no influence of absorbed hydrogen on the threshold value for oxidation amount under no axial restraint condition. On the other hand, it was shown that the threshold value is reduced by absorbed hydrogen for the restraint condition.
Nagase, Fumihisa; Otomo, Takashi; Tanimoto, Masataka*; Uetsuka, Hiroshi
Proceedings of the 2000 International Topical Meeting on LWR Fuel Performance (CD-ROM), 15 Pages, 2000/04
no abstracts in English
; ;
Ika Kikaigaku, 57(2), p.59 - 64, 1987/02
no abstracts in English
; Sasuga, Tsuneo; ;
Ika Kikaigaku, 56(3), p.102 - 107, 1986/00
no abstracts in English
; ;
J.Appl.Polym.Sci., 32, p.5669 - 5671, 1986/00
Times Cited Count：7 Percentile：68.33(Polymer Science)no abstracts in English
Narukawa, Takafumi; Yamaguchi, Akira*; Jang, S.*; Amaya, Masaki
no journal, ,
no abstracts in English
Narukawa, Takafumi; Uehara, Hiroyuki; Amaya, Masaki
no journal, ,
no abstracts in English
Narukawa, Takafumi
no journal, ,
no abstracts in English
