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Takahara, Shogo
no journal, ,
no abstracts in English
Sugiyama, Tomoyuki
no journal, ,
no abstracts in English
Takeda, Takeshi
no journal, ,
In this thermo-hydraulic research group, studies for upgrading of phenomena predictability of thermal-hydraulic safety analysis methodology are being conducted through the clarification of phenomena and the validation of analysis codes using LSTF facility in the first and second programs of OECD/NEA ROSA Project. Best-estimate (BE) code predicted break flow rate reasonably well through combination of appropriate models in post-test analysis of pressure vessel top break LOCA based on recent incident. Computational fluid dynamics code reproduced fluid temperature distribution by three-dimensional thermal-fluid analysis of temperature stratification experiment with ECCS injection. In addition, it was confirmed that BE code has remaining problems on predictability through blind analysis of intermediate-size break LOCA experiment based on risk-information.
Tonoike, Kotaro
no journal, ,
Criticality safety is important for fuel cycle facilities (FCFs) where nuclear materials of various kinds and a large quantity are being handled; therefore researches are conducted for prevention of anomaly, prevention of escalation, and mitigation of influence. Efforts have been focused, especially, on the prevention of anomaly due to difficulty of handling criticality accidents. Today, criticality safety design and evaluation of FCFs depends on computation using analysis codes and nuclear data, for which it is essential to validate that the computation is correct. Thus, JAEA has consistently performed acquisition of critical mass data by critical experiments, building models for validation, validation of analysis codes and nuclear data, and computation of basic criticality data. It is expected that new fuel design with higher fissile contents is going to be employed for more advanced utilization of light water reactors. JAEA will be engaged in researches on new criticality safety control methods such as the burn-up credit and/or the poison credit.
Iida, Yoshihisa
no journal, ,
Sorption of radionuclides on rocks is an important factor for safety assessments of geologic disposal of radioactive wastes. Batch sorption tests were conducted to study influence of salinity on the sorption of selenium and cesium on rocks under reducing environment of underground. The sorption ratio of selenium which forms low sorbable anionic species in groundwater was as high as cationic cesium, suggesting a specific bonding of selenium species with surface sites of rocks under anoxic conditions. The influence of salinity on the sorption of selenium was slightly negative, but was not remarkable.
Shibamoto, Yasuteru
no journal, ,
no abstracts in English
Chimi, Yasuhiro
no journal, ,
Regarding up-graded and long-term operations of commercial light water reactors (LWRs), proper managements against burnup extension of fuels and plant aging of the current LWRs are important issues. In the present study, in order to provide the technical information for the safety regulation of the Japanese government, safety research on the integrity of fuels and materials under simulated LWR water and irradiation conditions will be performed by means of irradiation tests using the Japan Materials Testing Reactor (JMTR), which will restart in FY 2011.
Katsuyama, Jinya
no journal, ,
Structural integrity of major components in LWR is assessed conservatively with sufficient safety margin by deterministic way based on current regulation. For further safe long-term operation, structural integrity should be assessed scientifically and rationally without unnecessary over-conservatism. For this purpose, probabilistic fracture mechanics (PFM) analysis codes have been developed for weld-overlay cladding of reactor pressure vessel (RPV), and welded joints of pressure boundary piping. The effect of cladding on weld residual stress and probability of crack initiation during pressurized thermal shock were evaluated by PFM analysis. It was shown that weld-overlay cladding of RPV should be considered for structural integrity assessment. For piping weld, uncertainty of weld residual stress distribution due to scatter of welding conditions were evaluated. Applicability of PFM analysis to quantify the safety margin for the piping integrity assessment related to SCC was shown.
Abe, Hitoshi; Kashima, Takao; Uchiyama, Gunzo
no journal, ,
To contribute on confirmation of safety of fuel cycle facilities, evaluation method for soundness of confinement capability of the facilities under fire accident has been investigated. Panel materials of glove-box and cable sheath materials were considered to be an examination object as the representative organic materials in the facilities. Combustion property data, such as mass loss rate of the materials and soot generation ratio, and clogging property data of HEPA filter with combustion of the materials were measured as a parameter with radiation heat given to the materials, supply flow rate to the materials and oxygen concentration in the supply flow. Furthermore, progress of rising differential pressure of HEPA filter under a scenario of fire accident was evaluated on the basis of these data.
