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Journal Articles

Development of experimental database for decay heat removal system of sodium-cooled fast reactor; Uncertainty evaluation of temperature measurement data in PLANDTL-2 experiment

Akimoto, Yuta; Ezure, Toshiki; Onojima, Takamitsu; Kurihara, Akikazu

Dai-25-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 5 Pages, 2021/07

In order to improve the reliability of the experimental database for a decay heat removal system in sodium-cooled fast reactors, uncertainty evaluation of temperature measurement data in thermal hydraulic experiments using sodium as the working fluid was investigated using the sodium experimental facility PLANDTL-2. In this study, an evaluation method of uncertainty due to the influence of the heat loss from the test section and the uncertainty of reference thermocouples was proposed for the relative calibration of thermocouples fixed inside the test section of PLANDTL-2. Moreover, the method has also been applied to the temperature measurement data of PLANDTL-2 experiment, and the confidence interval was evaluated to confirm the applicability of the method.

Journal Articles

Study on multi-dimensional core cooling behavior of sodium-cooled fast reactors under DRACS operating conditions

Ezure, Toshiki; Onojima, Takamitsu; Tanaka, Masaaki; Kobayashi, Jun; Kurihara, Akikazu; Kameyama, Yuri*

Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.3355 - 3363, 2019/08

Steady-state sodium experiments under the operating conditions of a decay heat removal system (DHRS) were carried out as part of the safety enhancement of sodium-cooled fast reactors using the PLANDTL 2 facility, which has 30 heated channels with electric heaters and 25 no-heated channels as the simulated core. In the experiments, a direct reactor auxiliary cooling system (DRACS) with a dipped type direct heat exchanger (DHX) in the upper plenum was used as the DHRS. This paper reports on the preliminary experimental results of the PLANDTL 2 experiments under the DRACS operating conditions without flow in the primary circuit, including the thermal hydraulic interactions between the upper plenum and the core under the DHX operating conditions and the resulting core cooling behavior from the outside of the multiple rows of the fuel assemblies

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 3; Progress report on NUMO-JAEA collaborative research in FY2013 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Kitamura, Akira; Yoshikawa, Hideki; Oda, Chie; Ishidera, Takamitsu; et al.

JAEA-Research 2014-030, 457 Pages, 2015/03

JAEA-Research-2014-030.pdf:199.23MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and post-closure performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, based on some examples of developing method of hydro-geological structure model, acquired knowledge are arranged using the tree diagram, and model uncertainty and its influence on the evaluation items were discussed. With regard to (2) study on scenario development, the developed approach for "defining conditions" has been reevaluated and improved from practical viewpoints. In addition, the uncertainty evaluation for the effect of use of cementitious material, as well as glass dissolution model, was conducted with analytical evaluation. With regard to (3) study on setting radionuclide migration parameters, based on survey of precedent procedures, multiple-approach for distribution coefficient of rocks was established, and the adequacy of the approach was confirmed though its application to sedimentary rock and granitic rock. Besides, an approach for solubility setting was developed including the procedure of selection of solubility limiting solid phase. The adequacy of the approach was confirmed though its application to key radionuclides.

Journal Articles

Novel findings obtained with the colony formation assay of normal human cells

Hamada, Nobuyuki*; Sakashita, Tetsuya; Hara, Takamitsu*; Fujimichi, Yuki*

Hoshasen Seibutsu Kenkyu, 49(3), p.318 - 331, 2014/09

Over the past half century, a colony formation assay has been most commonly used to evaluate cellular radiosensitivity. Our colony formation assay of primary normal human diploid fibroblasts and the analysis of the size and cell numbers in abortive colonies comprising $$<$$ 50 cells and clonogenic colonies comprising $$geq$$ 50 cells led to observations that can potentially answer a fundamental question of what is actually being evaluated in the colony formation assay, and a new phenomenon was also unveiled with the colony formation assay whereby the higher the dose the larger the size of colonies arising from irradiated primary normal human diploid ocular lens epithelial cells. This paper shall review these findings.

Journal Articles

A Branching process model for the analysis of abortive colony size distributions in carbon ion-irradiated normal human fibroblasts

Sakashita, Tetsuya; Hamada, Nobuyuki*; Kawaguchi, Isao*; Hara, Takamitsu*; Kobayashi, Yasuhiko; Saito, Kimiaki

Journal of Radiation Research, 55(3), p.423 - 431, 2014/02

 Times Cited Count:4 Percentile:26.46(Biology)

Our previous analysis with a branching process model showed that the relative cell death (RCD) in human fibroblasts can persist over 16 generations following irradiation with low linear energy transfer (LET) $$gamma$$-rays. Here we further set out to evaluate the RCD persistency in abortive colonies arising from normal human fibroblasts exposed to high-LET carbon ions (18.3 MeV/u, 108 keV/$$mu$$m). We found that the abortive colony size distribution determined by biological experiments follows the linear relationship on the log-log plot, and that the Monte Carlo simulation using the RCD probability estimated from such linear relationship well simulates the experimentally determined surviving fraction and the relative biological effectiveness (RBE). We identified the short-term phase and long-term phase for the persistent RCD, as was the case for $$gamma$$-irradiation.

Journal Articles

A Framework for analysis of abortive colony size distributions using a model of branching processes in irradiated normal human fibroblasts

Sakashita, Tetsuya; Hamada, Nobuyuki*; Kawaguchi, Isao*; Ouchi, Noriyuki; Hara, Takamitsu*; Kobayashi, Yasuhiko; Saito, Kimiaki

PLOS ONE (Internet), 8(7), p.e70291_1 - e70291_10, 2013/07

 Times Cited Count:7 Percentile:39.02(Multidisciplinary Sciences)

Clonogenicity gives important information about the cellular reproductive potential following ionizing irradiation. We firstly plotted the experimentally determined colony size distribution of abortive colonies in irradiated normal human fibroblasts, and found the linear relationship on the log-log plot. By applying the simple model of branching processes to the linear relationship, we found the persistent reproductive cell death (RCD) over several generations following irradiation. To verify the estimated probability of RCD, abortive colony size distribution ($$leq$$15 cells/colony) and the surviving fraction were simulated by the Monte Carlo computational approach. Radiation-induced RCD (i.e. excess probability) lasted over 16 generations and mainly consisted of two components in the early and late phases. We found that short-term RCD is critical to the abortive colony size distribution, and long-lasting RDC is important for the dose response of the surviving fraction.

Journal Articles

Effect of KM molar mass on CMC-KM-Acid gel

Kasahara, Takamitsu*; Takigami, Machiko*; Nagasawa, Naotsugu; Takigami, Shoji*

Transactions of the Materials Research Society of Japan, 34(3), p.395 - 398, 2009/09

no abstracts in English

Journal Articles

Effects of CMC molar mass on mechanical properties of CMC-acid gel

Takigami, Machiko*; Hiroki, Akihiro; Nagasawa, Naotsugu; Kasahara, Takamitsu*; Takigami, Shoji*; Tamada, Masao

Transactions of the Materials Research Society of Japan, 34(3), p.391 - 394, 2009/09

Carboxymethyl cellulose (CMC) with different molar mass was prepared by acid hydrolysis at 121$$^{circ}$$C. CMC thus prepared was mixed with citric acid aqueous solution to form CMC-acid gel. By replacing sodium existing as counter ion in carboxymethyl group with hydrogen, CMC molecules coagulate and hydrogen bonds are formed among CMC molecules. The CMC-acid gel prepared in that way was subjected to evaluation of gel fraction, water absorption and mechanical properties. Gel fraction was higher in CMC with higher molar mass than that in CMC with lower molar mass at short incubation time. However, there was no difference in gel fraction attributable to molar mass of CMC after long time incubation. CMC with higher molar mass crosslinked more easily than CMC with lower molar mass. The gel made of CMC with lower molar mass was softer and absorbed more amount of water than that with higher molar mass. All the results were elucidated by number of hydrogen bonds in CMC molecule. The gel made of higher molar mass CMC becomes stiff and brittle after long time incubation, however, the gel made of lower molar mass CMC keeps softness and strength longer.

Journal Articles

Preparation and characterization of CMC-Konjac mannan mixture gel

Kasahara, Takamitsu*; Takigami, Machiko*; Nagasawa, Naotsugu; Prawitwong, P.*; Takigami, Shoji*

Transactions of the Materials Research Society of Japan, 33(4), p.927 - 930, 2008/12

Carboxymethyl cellulose (CMC) forms a gel when mixed with acid as a result of replacement of sodium in carboxymethyl group with hydrogen; hydrogen bonds are formed among CMC molecules. CMC gel gets new property by mixing with other materials. Konjac mannan (KM) is a water soluble glucomannan with high molar mass and has high viscosity in low concentration aqueous solution. CMC gel is expected to have more elasticity by mixing with KM. Novel CMC-KM mixture gel is made by two processes; (1) mixing CMC with KM solution, (2) immersion of CMC-KM mixture in hydrochloric acid aqueous solution. Interaction of CMC and KM was studied by using KM with different molar mass. Molar mass of KM easily decreases by $$gamma$$-irradiation. The effect of KM molar mass on characteristics of CMC-KM mixture is examined using tensile test fixture.

Journal Articles

Preparation and characterization of CMC-konjac mannan mixture gel

Kasahara, Takamitsu*; Takigami, Machiko*; Nagasawa, Naotsugu; Prawitwong, P.*; Tamada, Masao; Takigami, Shoji*

JAEA-Review 2008-055, JAEA Takasaki Annual Report 2007, P. 45, 2008/11

Carboxymethyl cellulose (CMC) forms a gel when mixed with acid as a result of replacement of sodium in carboxymethyl group with hydrogen; hydrogen bonds are formed among CMC molecules. CMC gel gets new property by mixing with other materials. Konjac mannan (KM) is a water soluble glucomannan with high molar mass and has high viscosity in low concentration aqueous solution. CMC gel is expected to have more elasticity by mixing with KM. Novel CMC-KM mixture gel is made by two processes; (1) mixing CMC with KM solution, (2) immersion of CMC-KM mixture in hydrochloric acid aqueous solution. Interaction of CMC and KM was studied by using KM with different molar mass. Molar mass of KM easily decreases by $$gamma$$-irradiation. The effect of KM molar mass on characteristics of CMC-KM mixture is examined using tensile test fixture.

Journal Articles

Energetic heavy ions overcome tumor radioresistance caused by overexpression of Bcl-2

Hamada, Nobuyuki*; Hara, Takamitsu*; Omura, Motoko*; Funayama, Tomoo; Sakashita, Tetsuya; Sora, Sakura; Yokota, Yuichiro; Nakano, Takashi*; Kobayashi, Yasuhiko

Radiotherapy and Oncology, 89(2), p.231 - 236, 2008/11

 Times Cited Count:22 Percentile:59.19(Oncology)

Journal Articles

The Small-molecule Bcl-2 inhibitor HA14-1 sensitizes cervical cancer cells, but not normal fibroblasts, to heavy-ion radiation

Hamada, Nobuyuki*; Kataoka, Keiko*; Sora, Sakura*; Hara, Takamitsu*; Omura, Motoko*; Funayama, Tomoo; Sakashita, Tetsuya; Nakano, Takashi*; Kobayashi, Yasuhiko

Radiotherapy and Oncology, 89(2), p.227 - 230, 2008/11

 Times Cited Count:8 Percentile:31.07(Oncology)

Journal Articles

Heavy-ion microbeam irradiation induces bystander killing of human cells

Hamada, Nobuyuki*; Hara, Takamitsu*; Omura, Motoko*; Ni, M.*; Funayama, Tomoo; Sakashita, Tetsuya; Sora, Sakura*; Nakano, Takashi*; Kobayashi, Yasuhiko

Uchu Seibutsu Kagaku, 22(2), p.46 - 53, 2008/10

Journal Articles

Exposure of normal human fibroblasts to heavy-ion radiation promotes their morphological differentiation

Sora, Sakura*; Hamada, Nobuyuki*; Hara, Takamitsu*; Funayama, Tomoo; Sakashita, Tetsuya; Yokota, Yuichiro; Nakano, Takashi*; Kobayashi, Yasuhiko

Uchu Seibutsu Kagaku, 22(2), p.54 - 58, 2008/10

Journal Articles

The Survival of heavy ion-irradiated Bcl-2 overexpressing radioresistant tumor cells and their progeny

Hamada, Nobuyuki*; Hara, Takamitsu*; Omura, Motoko*; Funayama, Tomoo; Sakashita, Tetsuya; Sora, Sakura*; Nakano, Takashi*; Kobayashi, Yasuhiko

Cancer Letters, 268(1), p.76 - 81, 2008/09

 Times Cited Count:10 Percentile:25.1(Oncology)

Journal Articles

Energetic heavy ions accelerate differentiation in the descendants of irradiated normal human diploid fibroblasts

Hamada, Nobuyuki*; Hara, Takamitsu*; Funayama, Tomoo; Sakashita, Tetsuya; Kobayashi, Yasuhiko

Mutation Research; Fundamental and Molecular Mechanisms of Mutagenesis, 637(1-2), p.190 - 196, 2008/01

 Times Cited Count:22 Percentile:53.36(Biotechnology & Applied Microbiology)

Dependence of ionizing radiation-induced genomic instability on the linear energy transfer (LET) of the radiation is incompletely characterized; however, our previous work has shown that delayed reductions in clonogenicity can be most pronounced at LET of 108 keV/$$mu$$m. To gain insight into potential cellular mechanisms involved in LET-dependent delayed loss of clonogenicity, we investigated morphological changes in colonies arising from normal human diploid fibroblasts exposed to $$gamma$$-rays or energetic carbon ions (108 keV/$$mu$$m). Exposure of confluent cultures to carbon ions was 4-fold more effective at inactivating cellular clonogenic potential and produced more abortive colonies containing reduced number of cells per colony than $$gamma$$-rays. Second, colonies were assessed for clonal morphotypic heterogeneity. The yield of differentiated cells was elevated in a dose- and LET-dependent fashion in clonogenic colonies, whereas differentiated cells predominated to a comparable extent irrespective of radiation type or dose in abortive colonies.

Journal Articles

Preparation and properties of CMC gel

Takigami, Machiko*; Amada, Haruyo*; Nagasawa, Naotsugu; Yagi, Toshiaki; Kasahara, Takamitsu*; Takigami, Shoji*; Tamada, Masao

Transactions of the Materials Research Society of Japan, 32(3), p.713 - 716, 2007/09

Carboxymethylcellulose (CMC) gel was formed by addition of acid to CMC (CMC-acid gel). Gel fraction (weight of insoluble part/initial CMC weight) was calculated after removing uncrosslinked CMC by immersing the CMC-acid gel in water. It increased with acid concentration. Mechanism of CMC-acid gel formation was elucidated by aggregation of CMC molecules as the result of replacement of sodium in carboxyl group with hydrogen. Gels could be prepared by three different procedures; (1) mixing CMC and acid, (2) immersion of CMC or $$gamma$$-irradiated CMC pastes in acid, and (3) $$gamma$$-irradiation of CMC-acid gel. Gels with different elasticity and hardness were prepared changing degree of substitution of CMC, molar mass of CMC, species of acid, concentrations of acid and CMC, and application of $$gamma$$-irradiation.

Journal Articles

Vulnerability of feline T-lymphocytes to charged particles

Kakizaki, Takehiko; Hamada, Nobuyuki*; Sakashita, Tetsuya; Wada, Seiichi*; Hara, Takamitsu*; Funayama, Tomoo; Hodatsu, Tsutomu*; Natsuhori, Masahiro*; Sano, Tadashi*; Kobayashi, Yasuhiko; et al.

Journal of Veterinary Medical Science, 69(6), p.605 - 609, 2007/06

 Times Cited Count:1 Percentile:14.38(Veterinary Sciences)

no abstracts in English

Journal Articles

Intercellular and intracellular signaling pathways mediating ionizing radiation-induced bystander effects

Hamada, Nobuyuki*; Matsumoto, Hideki*; Hara, Takamitsu*; Kobayashi, Yasuhiko

Journal of Radiation Research, 48(2), p.87 - 95, 2007/03

 Times Cited Count:171 Percentile:95.29(Biology)

Experimental evidence has accumulated demonstrating that biological effects of ionizing radiation arise in non-irradiated bystander cells that have received signals from near or distant irradiated cells. This phenomenon has been termed the radiation-induced bystander effect and challenges the long-held tenet that cell nucleus is the quintessential target for radiation damage. Bystander effects encompass a range of endpoints, such as genetic and epigenetic alterations, changes in gene expression, signal transduction pathway activation, and late-arising effects in their descendants. Proposed mechanisms involve gap junctional cell-to-cell communication, transmissible soluble factors, oxidative stress, lipid rafts, and calcium fluxes. In this article, we review proposed mechanisms underpinning the bystander effect and also briefly discuss the potential benefit of bystander effects in cancer radiotherapy.

Journal Articles

Bystander effect studies using heavy-ion microbeam

Kobayashi, Yasuhiko; Funayama, Tomoo; Sakashita, Tetsuya; Furusawa, Yoshiya*; Wada, Seiichi*; Yokota, Yuichiro; Kakizaki, Takehiko; Hamada, Nobuyuki*; Hara, Takamitsu*; Fukamoto, Kana; et al.

JAEA-Conf 2007-002, p.28 - 35, 2007/02

no abstracts in English

61 (Records 1-20 displayed on this page)