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Wakai, Eiichi; Takada, Fumiki; Takaya, Shigeru; Kato, Shoichi; Kitazawa, Sin-iti; Okubo, Nariaki; Suzudo, Tomoaki; Fujii, Kimio; Yoshitake, Tsunemitsu; Kaji, Yoshiyuki; et al.
no journal, ,
no abstracts in English
Kawamura, Makoto; Yanagawa, Harunaga*; Okubo, Hiroo*; Oi, Takao; Kawachi, Susumu; Inagaki, Manabu
no journal, ,
We showed the concept of the total system performance assessment. Based on the concept, we examined and integrated information about the significant impact of the natural phenomena exerted on geological environment conditions and HLW disposal system environmental condition for groundwater scenarios.
Mitsui, Seiichiro; Oe, Toshiaki*; Inagaki, Yaohiro*; Okubo, Takahiro*; Kurosawa, Susumu*; Goto, Takahiro*; Inagaki, Manabu*; Ishiguro, Katsuhiko*; Takase, Hiroyasu*; Takahashi, Hirokazu*
no journal, ,
In order to develop robust performance assessment models, we have been preparing an information basis regarding glass properties and glass dissolution/alteration processes under disposal conditions as a part of NUMO-JAEA joint project. Our iterative working process for the preparation of the information basis comprises five steps: (1) integration of current knowledge; (2) development of glass dissolution scenarios based on current knowledge; (3) development of conceptual model; (4) sensitivity analyses to evaluate relative importance of relevant processes and associated uncertainties; and (5) identification of future R&D issues towards further improvement of the information basis. The current status will be presented in this talk.
Okubo, Manabu*; Onitsuka, Takashi*; Fukumoto, Kenichi*; Suzudo, Tomoaki
no journal, ,
In structural materials of fast breeder and fusion rectors, vacancies produced by radiation displacements are clustered and form voids. Experimental evidence indicates that the voids become obstacles of dislocation motion and cause hardening of the materials, but the detailed mechanism of the hardening has not been clear. In the current study, we perform molecular dynamics simulation of the interaction between a screw dislocation and a void to clarify the radiation hardening mechanism. Our results clearly show that the screw dislocation is pinned between the center of the void and its rear interface.
Onitsuka, Takashi*; Okubo, Manabu*; Fukumoto, Kenichi*; Suzudo, Tomoaki
no journal, ,
Many of BCC metals are used as structural materials in nuclear devices. A possible cause of embrittlement of such metals under neutron radiation is accumulation of lattice defects that hamper the dislocation motions. Molecular dynamics have been used for the analyses of such dislocation motions, but interaction mechanism between the lattice defects and screw dislocation are still unclear. In this talk, we utilize molecular dynamics and analyze the interaction between void and screw dislocation in BCC Fe.
Onitsuka, Takashi*; Okubo, Manabu*; Suzudo, Tomoaki; Fukumoto, Kenichi*
no journal, ,
Reactor structural materials such as pressure vessels become brittle under neutron irradiation. It is widely known that a cause of such phenomenon could be formation of extended lattice defects under irradiation such as voids that become obstacles for dislocation motion, but we do not know the strength of these obstacles accurately enough for establishing a quantitative model. In the present study, we choose pure iron as a substitute of steel and numerically simulate the interaction between screw dislocation and a void using molecular dynamics method. Especially, we analyze the critical shear stress.
Ookubo, Manabu; Shimizu, Ryo; Hatori, Masakazu; Kobayashi, Takanori; Uekura, Ryoichi
no journal, ,
Under the circumstances where the fuel is disposed in the reactor core and the furnace fuel storage tank during the decommissioning measures of "Monju" where the decay heat is at an extremely low level, while preventing the sodium from being frozen by the preheater heater, It is desirable to continue operation of cooling the dissipated heat released into the compartment by ventilating air conditioning equipment. However, the operation of ventilation air conditioning equipment is designed for normal operation of nuclear reactors, and it is necessary to review the proper operation according to the situation at the stage of decommissioning. In this report, we will summarize the relationship between the actual load and the capacity of the ventilating and air conditioning equipment based on the past operation data and report on the status of consideration on rational ventilation air conditioning equipment operation at the decommissioning stage.