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Shibata, Taiju; Ishihara, Masahiro; Motohashi, Yoshinobu*; Ito, Tsutomu*; Baba, Shinichi; Kikuchi, Makoto*
Materials Transactions, 45(8), p.2580 - 2583, 2004/08
Times Cited Count：3 Percentile：26.38(Materials Science, Multidisciplinary)Fast neutrons (energy 
1.6
10
J) were irradiated to tetragonal zirconia polycrystals containing 3 mol% yttria (3Y-TZP) at the fluence levels of 2.510
(Light irradiation) and 4.310 (Heavy irradiation) m
. The irradiation caused no significant swelling in the 3Y-TZP specimens. After the neutron irradiation, superplastic characteristics were examined by tensile tests at a temperature range from 1623 to 1773 K with initial strain rates ranging from 5.010
to 1.6710s
. It was found that the elongation to fracture of the irradiated specimens was quite small in comparison with the unirradiated ones. The apparent activation energy for the superplastic flow of the irradiated 3Y-TZP was fairly high, i.e., 781 and 693 kJ・mol for Light and Heavy irradiations, respectively. Atomic displacement damages and defects in the 3Y-TZP caused by the irradiation were thought to be main causes of these property changes.
Yamashita, Toshiyuki; Kuramoto, Kenichi; Shirasu, Noriko; Nakano, Yoshihiro; Akie, Hiroshi; Nagashima, Hisao; Kimura, Yasuhiko; Omichi, Toshihiko*
Journal of Nuclear Materials, 320(1-2), p.126 - 132, 2003/07
Times Cited Count：10 Percentile：55.56(Materials Science, Multidisciplinary)Two irradiation tests on the rock-like oxide (ROX) fuels, small disk-shape fuel targets and pellet-type fuels, were performed in order to clarify in-pile irradiation stabilities. Swelling, fractional fission gas release (FGR) and phase change were examined by puncture test, profilometry and ceramography. YSZ single-phase fuel showed an excellent irradiation behavior, ie. low fission gas release (less than 3%), negligible swelling and no appreciable restructuring. The particle dispersed fuels showed lower swelling and higher fission gas release than those of mechanically blended fuels. Spinel decomposition and subsequence restructuring in the spinel matrix fuels was observed for the first time in the present investigation. It would be possible to reduce the FGR of the spinel matrix fuels, if the maximum fuels temperature is limited below 1700 K where neither spinel decomposition nor restructuring was observed. Damaged area of spinel matrix due to fission fragment irradiation seemed to be confined to thin layers around the surface of YSZ particles.
Motohashi, Yoshinobu*; Kobayashi, Tomokazu*; Harjo, S.*; Sakuma, Takaaki*; Shibata, Taiju; Ishihara, Masahiro; Baba, Shinichi; Hoshiya, Taiji
Nuclear Instruments and Methods in Physics Research B, 206, p.144 - 147, 2003/05
Times Cited Count：4 Percentile：33.44(Instruments & Instrumentation)The 3mol% yttria containing tetragonal zirconia polycrystals(3Y-TZP) were irradiated using 130MeV Zr
ions in the TANDEM accelerator facility at Tokai Research Establishment, JAERI. Irradiation was performed with the fluence of 3.510
and 2.110
ions/m
. Residual stress and changes in mechanical properties caused by the ion irradiation and the effects of the subsequent annealing are studied. The occurrence of compressive residual stresses and increases in hardness and fracture toughness were found at the surface regions of as-irradiated specimens. It was found from the subsequent annealing that these quantities decreased gradually with raising the annealing temperature and returned to that of un-irradiated state at around 1173K. A most probable cause of the increases in the hardness and fracture toughness after the irradiation may, therefore, be the residual compressive stresses left in the irradiated surface region.
Nakajima, Kunihisa; Omichi, Toshihiko*; Arai, Yasuo
Journal of Nuclear Materials, 304(2-3), p.176 - 181, 2002/08
Times Cited Count：3 Percentile：22.77(Materials Science, Multidisciplinary)The oxygen potentials of two type urania-yttria solid solutions, one is the solid solution expressed as nearly U
Y
O
and the other is nearly stoichiometric solid solution, are investigated by use of a mass spectrometer combined with a Knudsen cell. The oxygen potentials for the nearly stoichiometric specimens are much higher than those for pure urania with similar stoichiometry. On the other hand, the oxygen potentials for fully reduced specimens almost agree with those for pure urania having the same oxygen deficiencis.
Yamashita, Toshiyuki; Kuramoto, Kenichi; Akie, Hiroshi; Nakano, Yoshihiro; Shirasu, Noriko; Nakamura, Takehiko; Kusagaya, Kazuyuki*; Omichi, Toshihiko*
Journal of Nuclear Science and Technology, 39(8), p.865 - 871, 2002/08
Times Cited Count：26 Percentile：81.73(Nuclear Science & Technology)Research on the plutonium rock-like oxide (ROX) fuels and their once-through burning in light water reactors has been performed to establish an option for utilizing and disposing effectively the excess plutonium. The ROX fuel is a sort of the inert matrix fuels and consists of mineral-like compounds such as yttria stabilized zirconia, spinel and corundum. A particle-dispersed fuel was devised to reduce damage by heavy fission fragments. Some preliminary results on swelling, fractional gas release and microstructure change for five ROX fuels were obtained from the irradiation test and successive post-irradiation examinations. Inherent disadvantages of the Pu-ROX fuel cores could be improved by adding 238U or 232Th as resonant materials, and all improved cores showed a nearly the same characteristics as the conventional UO2 core during transient conditions. The threshold enthalpy of the ROX fuel rod failure was found to be comparable to the fresh UO2 rod by pulse-irradiation tests simulating reactivity initiated accident conditions.
C.Degueldre*; Takano, Masahide; Omichi, Toshihiko; Fukuda, Kosaku; P.Heimgartner*; T.Graber*
JAERI-Research 97-087, 19 Pages, 1997/11
JAERI-Research-97-087.pdf:0.87MB
no abstracts in English
