Study on uncertainty evaluation methodology for decay heat removal experiment in sodium experimental facility

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

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 9 Pages, 2023/05

A numerical analysis method has been developed to evaluate thermal-hydraulic behaviors in a reactor vessel under the operation of a NC-DHRS at the Japan Atomic Energy Agency. During the validation of the evaluation method, in addition to uncertainties due to the numerical solution and input parameters in simulations, it is important to quantify uncertainties due to the experimental data. From this perspective, JAEA has been developing an experimental database and uncertainty evaluation methods for sodium experiments during operation of the NC-DHRS. In this study, the authors have proposed an uncertainty evaluation approach during relative calibrations of thermocouples in sodium experiments. The proposed approach was applied to experimental data obtained in a sodium NC-DHRS experiment conducted at PLANDTL-2. As a result, uncertainties of the experimental data were successfully evaluated and the applicability of the method to temperature measurement in sodium experiments was confirmed.

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

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 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.

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

https://doi.org/10.1371/journal.pone.0070291

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 (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.

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

https://doi.org/10.14723/tmrsj.34.391

Carboxymethyl cellulose (CMC) with different molar mass was prepared by acid hydrolysis at 121C. 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.

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

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2008-055.pdf

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 -irradiation. The effect of KM molar mass on characteristics of CMC-KM mixture is examined using tensile test fixture.

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

https://doi.org/10.1016/j.radonc.2008.08.006

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

https://doi.org/10.2187/bss.22.54

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

https://doi.org/10.1016/j.mrfmmm.2007.07.002

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/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 -rays or energetic carbon ions (108 keV/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 -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.

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

https://doi.org/10.1292/jvms.69.605

no abstracts in English