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Tomiyasu, Kunihiko; Sugiyama, Tomoyuki; Fuketa, Toyoshi
Journal of Nuclear Science and Technology, 44(5), p.733 - 742, 2007/05
Times Cited Count：23 Percentile：79.85(Nuclear Science & Technology)In order to investigate the influence of hydrogen embrittlement on fuel failure under reactivity-initiated accident (RIA) conditions, pulse irradiation experiments were performed with unirradiated fuel rods at the NSRR. The present study demonstrated hydride-assisted PCMI failure which has been observed in high burnup fuel experiments. The fuel enthalpy at failure was lower when the cladding had thicker hydride rim where surface cracks were easily generated. It indicates that the failure limit is highly correlated with the stress intensity factor assuming that the crack depth is equivalent to the hydride rim thickness. Hence we conclude that hydride rim formation is the primary factor of decreasing the failure limit for high burnup fuels. Based on the experimental results together with an analysis on cladding mechanical state during PCMI, the present study suggests a process of through-wall crack generation which is originated with brittle cracking within the hydride rim.
Fuketa, Toyoshi; Sugiyama, Tomoyuki; Umeda, Miki; Tomiyasu, Kunihiko; Sasajima, Hideo
Proceedings of 2006 International Meeting on LWR Fuel Performance (TopFuel 2006) (CD-ROM), p.273 - 277, 2006/10
By using pulse-irradiation capability of the NSRR, JAEA continues to perform experiments simulating fuel behaviour during reactivity-initiated accidents (RIAs). The recently-tested fuels include those irradiated in European PWRs and have burnups of 67 to 79 MWd/kgU. Cladding materials of these tested rods are Zirlo, M5, MDA and NDA. The tests resulting in the PCMI failure indicate that the fuel enthalpy at failure correlates closely with the thickness of the hydride rim, and in turn with the oxide layer thickness. Fission gas release during the RIA transient is highly dependent on the peak fuel enthalpy, and a higher enthalpy causes a larger fission gas release. Pellets with a larger grain size may have a suppression effect on the release. When DNB occurs during the transient, the large cladding deformation is caused by the increase of the rod internal pressure in combination with the decreased yield stress of the cladding at an elevated temperature. In the phase of the PCMI, the deformation is driven only by solid thermal expansion of fuel pellets.
Fuketa, Toyoshi; Nakamura, Takehiko; Nagase, Fumihisa; Nakamura, Jinichi; Suzuki, Motoe; Sasajima, Hideo; Sugiyama, Tomoyuki; Amaya, Masaki; Kudo, Tamotsu; Chuto, Toshinori; et al.
JAEA-Review 2006-004, 226 Pages, 2006/03
JAEA-Review-2006-004.pdf:34.43MB
Fuel Safety Research Meeting 2005, which was organized by the Japan Atomic Energy Agency was held on March 2-3, 2005 at Toshi Center Hotel, Tokyo. The purposes of the meeting are to present and discuss the results of experiments and analyses on reactor fuel safety and to exchange views and experiences among the participants. The technical topics of the meeting covered the status of fuel safety research activities, fuel behavior under Reactivity Initiated Accident (RIA) and Loss of coolant accident (LOCA) conditions, high fuel behavior, and radionuclide release under severe accident conditions. This summary contains all the abstracts and sheets of viewgraph presented in the meeting.
Tomiyasu, Kunihiko; Sugiyama, Tomoyuki; Nakamura, Takehiko; Fuketa, Toyoshi
JAERI-Research 2005-022, 128 Pages, 2005/09
JAERI-Research-2005-022.pdf:16.11MB
In order to clarify the driving force of PCMI failure on high burnup fuels and the influence of hydrogen embrittlement on failure limit under RIA conditions, simulated-RIA experiments were performed on fresh fuel rods in the NSRR. The driving force was restricted only to thermal expansion of pellet by using fresh pellets, and fresh claddings were pre-hydrided to simulate hydrogen absorption of high burnup fuels. In seven experiments, test rods resulted in PCMI failure, which was observed on high burnup fuels, in terms of transient behavior and fracture configuration. It indicates that the driving force is sufficiently explained with thermal expansion of pellet and a contribution of fission gas is small. Many incipient cracks were generated in the outer surface of the cladding, and they stopped at the boundary between hydride rim and metallic layer. It suggests that a toughness of metallic region except hydride rim has particular importantance for failure limit. Fuel enthalpy at failure correlates with the thickness of hydride rim, and tends to decrease with thicker hydride rim.
Sugiyama, Tomoyuki; Tomiyasu, Kunihiko; Sasajima, Hideo; Umeda, Miki; Nagase, Fumihisa; Fuketa, Toyoshi; Okawara, Masami; Honda, Junichi
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no abstracts in English
Tomiyasu, Kunihiko; Sugiyama, Tomoyuki; Nakamura, Takehiko; Fuketa, Toyoshi; Muramatsu, Yasuyuki
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no abstracts in English
Umeda, Miki; Sugiyama, Tomoyuki; Tomiyasu, Kunihiko; Sasajima, Hideo; Nagase, Fumihisa; Fuketa, Toyoshi; Kurosawa, Shingo; Kaminaga, Norihisa
no journal, ,
no abstracts in English
