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A PRELIMINARY EVALUATION OF UNPROTECTED LOSS-OF-FLOW ACCIDENT FOR A PROTOTYPE FAST-BREEDER REACTOR
TOHRU SUZUKI,Yoshiharu Tobita,KENICHI KAWADA,HIROTAKA TAGAMI,JOJI SOGABE,KENICHI MATSUBA,KEI ITO,HIROYUKI OHSHIMA 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.3
In the original licensing application for the prototype fast-breeder reactor, MONJU, the event progression during an unprotected loss of flow (ULOF), which is one of the technically inconceivable events postulated beyond design basis, was evaluated. Through this evaluation, it was confirmed that radiological consequences could be suitably limited even if mechanical energy was released. Following the Fukushima-Daiichi accident, a new nuclear safety regulation has become effective in Japan. The conformity of MONJU to this new regulation should hence be investigated. The objectives of the present study are to conduct a preliminary evaluation of ULOF for MONJU, reflecting the knowledge obtained after the original licensing application through CABRI experiments and EAGLE projects, and to gain the prospect of in-vessel retention for the conformity of MONJU to the new regulation. The preliminary evaluation in the present study showed that no significant mechanical energy release would take place, and that thermal failure of the reactor vessel could be avoided by the stable cooling of disrupted-core materials. This result suggests that the prospect of in-vessel retention against ULOF, which lies within the bounds of the original licensing evaluation and conforms to the new nuclear safety regulation, will be gained.
Bending Strength of Textured Alumina Prepared by Slip Casting in a Strong Magnetic Field
Suzuki Tohru S.,Uchikoshi Tetsuo,Morita Koji,Hirage Keijiro,Sakka Yoshio 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
The mechanical properties of ceramics materials can be tailored by designing their microstructures. We have reported that development of texture can be controlled by slip casting in a strong magnetic field followed by heating even for diamagnetic ceramics such as alumina. A strong magnetic field of 12T was applied to the suspension indcuding alumina powder to rotate each particle during slip casting. The sintering was conducted at the desired temperature in air without a magnetic field. C-axis of alumina was parallel to the magnetic field. Bending strength of textured alumina depended on the direction of oriented microstructure.
Suzuki, Ginga,Shimizu, Satoshi,Torii, Mana,Tokue, Ai,Ying, Guo,Yoshinari, Masao,Hoshi, Noriyuki,Kimoto, Katsuhiko,Miura, Hiromi,Hayakawa, Tohru,Ohkubo, Chikahiro The Korean Academy of Prosthodonitics 2020 The Journal of Advanced Prosthodontics Vol.12 No.6
PURPOSE. This study evaluated the availability of multi-directionally forged (MDF) titanium (Ti) as a component of removable partial dentures (RPDs). MDF-Ti remarkably improved the mechanical properties of RPDs due to its ultrafine-grained structure. MATERIALS AND METHODS. The wear resistance, plaque adhesion, and machinability of MDF-Ti were tested. As controls, commercially pure (CP) titanium was used for wear, plaque adhesion, and machinability tests. For wear resistance, the volume losses of the titanium teeth before and after wear tests were evaluated. Plaque adhesion was evaluated by the assay of Streptococcus mutans. In the machinability test, samples were cut and ground by a steel fissure bur and carborundum (SiC) point. An unpaired t-test was employed for the analysis of the significant differences between MDF-Ti and the control in the results for each test. RESULTS. Wear resistance and plaque adherence of MDF-Ti similar to those of CP-Ti (P>.05) were indicated. MDF-Ti exhibited significantly larger volume loss than CP-Ti in all conditions except 100/30,000 g/rpm in machinability tests (P<.05). CONCLUSION. Although the wear resistance and plaque adherence of MDF-Ti were comparable to those of controls, MDF-Ti showed better machinability than did CP-Ti. MDF-Ti could be used as a framework material for RPDs.
Kenichi Kawada,Tohru Suzuki 한국원자력학회 2021 Nuclear Engineering and Technology Vol.53 No.12
To improve the capability of the SAS4A code, which simulates the initiating phase of core disruptiveaccidents for MOX-fueled Sodium-cooled Fast Reactors (SFRs), the authors have investigated in detail thephysical phenomena under unprotected loss-of-flow (ULOF) conditions in a previous paper (Kawada andSuzuki, 2020) [1]. As the conclusion of the last article, fuel stub motion, in which the residual fuel pelletswould move toward the core central region after fuel pin disruption, was identified as one of the keyphenomena to be appropriately simulated for the initiating phase of ULOF. In the present paper, based on the analysis of the experimental data, the behaviors related to the stubmotion were evaluated and quantified by the author from scratch. A simple model describing fuel stubmotion, which was not modeled in the previous SAS4A code, was newly proposed. The applicability ofthe proposed model was validated through a series of analyses for the CABRI experiments, by which thestub motion would be represented with reasonable conservativeness for the reactivity evaluation ofdisrupted core
Fabrication of Alumina Free-standing Objects by Electrophoretic Deposition
Uchikoshi Tetsuo,Furumi Seiichi,Suzuki Tohru S.,Sakka Yoshio 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
The coating of conductive polypyrrole (Ppy) on nonconductive ceramic substrates was performed by polymerization of pyrrole (Py) in an aqueous solution. The Ppy film was characterized by scanning electron microscopy and conductivity measurements. Electrophoretic deposition of bimodal alumina suspension prepared with a phosphate ester was performed using Ppy film as a cathode. Fabrication of alumina ceramics with irregular shapes or complicated patterns were also attempted by sintering the deposits together with the Ppy coated substrates in air.
Characteristics of Self-Leveling Behavior of Debris Beds in a Series of Experiments
Songbai Cheng,Hidemasa Yamano,Tohru Suzuki,Yoshiharu Tobita,Yuya Nakamura,Bin Zhang,Tatsuya Matsumoto,Koju Morita 한국원자력학회 2013 Nuclear Engineering and Technology Vol.45 No.3
During a hypothetical core-disruptive accident (CDA) in a sodium-cooled fast reactor (SFR), degraded core materials can form roughly conically-shaped debris beds over the core-support structure and/or in the lower inlet plenum of the reactor vessel from rapid quenching and fragmentation of the core material pool. However, coolant boiling may ultimately lead to leveling of the debris bed, which is crucial to the relocation of the molten core and heat-removal capability of the debris bed. To clarify the mechanisms underlying this self-leveling behavior, a large number of experiments were performed within a variety of conditions in recent years, under the constructive collaboration between the Japan Atomic Energy Agency (JAEA)and Kyushu University (Japan). The present contribution synthesizes and gives detailed comparative analyses of those experiments. Effects of various experimental parameters that may have potential influence on the leveling process, such as boiling mode, particle size, particle density, particle shape, bubbling rate, water depth and column geometry, were investigated, thus giving a large palette of favorable data for the better understanding of CDAs, and improved verifications of computer models developed in advanced fast reactor safety analysis codes.
Sakka Yoshio,Saito Sho,Honda Atsushi,Suzuki Tohru S.,Moriyoshi Yusuke 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
We have demonstrated that textured nanocomposites can be fabricated by slip casting followed by partial oxidation. reaction sintering of mixed suspensions of and SiC powders in a high magnetic field. The sintered density was changed by the degree of oxidation at 1200C and 1300C. The degree of orientation of alumina in the nanocomposite was examined on the basis of the X-ray diffraction patterns and scanning electron micrographs. It is confirmed that aluminaoriented nanocomposites were fabricated. The three-point bending strength at room temperature was observed for the nanocomposites.
The Production of Xylitol by Enzymatic Hydrolysis of Agricultural Wastes
Kazuhiro Takamizawa,Lien Ha Tran,Masanori Yogo,Hiroshi Ojima,Keiichi Kawai,Tohru Suzuki,Osamu Idota 한국생물공학회 2004 Biotechnology and Bioprocess Engineering Vol.9 No.3
Agricultural waste products, beech wood and walnut shells, were hydrolyzed at 40oC using mixed crude enzymes produced by Penicillium sp. AHT-1 and Rhizomucor pusillus HHT-1. D-xylose, 4.1 g and 15.1 g was produced from the hydrolysis of 100 g of beech wood and walnut shells, respectively. For xylitol production, Candida tropicalis IFO0618 and the waste product hydrolyzed solutions were used. The effects on xylitol production, of adding glucose as a NADPH source, D-xylose and yeast extract, were examined. Finally, a 50% yield of xylitol was obtained by using the beech wood hydrolyzed solution with the addition of 1% yeast extract and 1% glucose at an initial concentration.
Taguchi, Satoru,Fukuhara, Hiroshi,Kakutani, Shigenori,Takeshima, Yuta,Miyazaki, Hideyo,Suzuki, Motofumi,Fujimura, Tetsuya,Nakagawa, Tohru,Igawa, Yasuhiko,Kume, Haruki,Homma, Yukio Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.24
Background: Adjuvant androgen deprivation therapy (ADT) is a treatment option for prostate cancer (PC) patients after radical prostatectomy (RP). Although it can achieve a good progression-free survival rate, some patients still develop clinical metastasis. We here investigated risk factors of clinical metastasis in post-prostatectomy patients who received immediate adjuvant ADT. Materials and Methods: We identified 197 patients with non-metastatic PC who underwent RP at our institution between 2000 and 2012, followed by adjuvant ADT. The associations of various clinicopathologic factors with clinical metastasis (primary endpoint) and cancer-specific survival (secondary endpoint) were assessed. Multivariate analysis was conducted using a Cox proportional hazards model. Median follow-up was 87 months after RP. Results: Nine (4.6%) patients developed clinical metastasis and six (3.0%) died from PC. Eight of nine metastatic patients had a pathologic Gleason score (GS) 9 and developed bone metastasis, while the remaining one had pathologic GS 7 and developed metastasis only to para-aortic lymph nodes. On multivariate analyses, pathologic GS ${\geq}9$ and regional lymph node metastasis (pN1) were independent predictors of clinical metastasis and pathologic GS ${\geq}9$ was an independent predictor of cancer-specific death. Conclusions: Pathologic GS ${\geq}9$ and pN1 were independent predictors of clinical metastasis in post-prostatectomy patients who received immediate adjuvant ADT. Furthermore, pathologic GS ${\geq}9$ was an indispensable condition for bone metastasis, which may imply that patients with GS ${\leq}8$ on adjuvant ADT are unlikely to develop bone metastasis.