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Journal Articles

A Study on self-terminating behavior of sodium-concrete reaction, 2

Kawaguchi, Munemichi; Miyahara, Shinya; Uno, Masayoshi*

Journal of Nuclear Science and Technology, 55(8), p.874 - 884, 2018/08

https://doi.org/10.1080/00223131.2018.1449677

Times Cited Count：4 Percentile：37.66(Nuclear Science & Technology)

As parts of severe accident studies in sodium-cooled fast reactor, experiments were performed to investigate the termination mechanism of sodium-concrete reaction (SCR). In the experiment, the reaction time was controlled to investigate the distribution change of sodium (Na) and the reaction products in the pool and around the reaction front. In the results, the Na around the reaction front decreased from the enough amount with the reaction time. The concentrations were 18-24 wt.% for Na, and 22-18 wt.% for Si after the termination. From the thermodynamics calculations, the stable materials around the reaction front comprised more than 90 wt.% solid products such as Na $_{2}$ SiO $_{3}$ , and no Na. Further, the distribution of Na and reaction products could be explained by a steady-state sedimentation-diffusion model. At the early stage of SCR, the reaction products were suspended as particles in the Na pool because of the high H $_{2}$ -generation rate. As the concrete ablation proceeds, they start settling down due to the decreased H $_{2}$ -generation rate, thereby allowing SCR termination. It was concluded that SCR termination was caused by the sediment of the reaction products and the lack of Na around the reaction front.

Journal Articles

Upgrade in catalytic activity of hydrophobic platinum catalysts by irradiation with electron beams

Iwai, Yasunori

Fusion Engineering and Design, 98-99, p.1796 - 1799, 2015/10

https://doi.org/10.1016/j.fusengdes.2015.03.024

Times Cited Count：5 Percentile：39.5(Nuclear Science & Technology)

Hydrophobic platinum catalysts have been widely applied in the field of nuclear fusion for the exchange reactions of hydrogen isotopes between hydrogen and vapor in the water detritiation system, and for the oxidation of tritium on the atmospheric detritiation system. Hydrophobic platinum catalysts are hardly susceptible to water mist and water vapor. Hydrophobic platinum catalysts are produced by supporting platinum directly on hydrophobic polymer beads. For the hydrophobic polymer, styrene - divinyl benzene (SDB) has been applied in Japan. It can be pointed out that the upgrade in catalytic activity of hydrophobic catalyst is expected to downsize the catalytic reactor based on a hard look at a large increase in flow rate in future. The upgrade in catalytic activity of two types of commercial Pt/SDB catalysts was found when they were irradiated with electron beams. After irradiation with electron beams, the catalytic activity was evaluated by means of overall reaction rate constant for the oxidation of tritium. The overall reaction rate constant increased as increase in dose. The constant showed the peak value in the dose between 500 to 1000 kGy. After the peak, the constant decreased as increase in dose. The overall reaction rate constant at the peak was 6 times larger than that evaluated with unirradiated. The mechanical strength of irradiated Pt/SDB kept sound until 1500 kGy. The irradiation is a promising method to the upgrading in catalytic activity of Pt/SDB catalyst.

Journal Articles

Analysis of sequential charged particle reaction experiments for fusion reactors

Yamauchi, Michinori*; Hori, Junichi*; Ochiai, Kentaro; Sato, Satoshi; Nishitani, Takeo; Kawasaki, Hiromitsu*

Fusion Engineering and Design, 81(8-14), p.1577 - 1582, 2006/02

https://doi.org/10.1016/j.fusengdes.2005.09.066

Times Cited Count：1 Percentile：9.91(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Time-dependence of differential G-values of OH radicals in water under Ne ion radiolysis

Taguchi, Mitsumasa; Kojima, Takuji

JAEA-Review 2005-001, TIARA Annual Report 2004, p.181 - 182, 2006/01

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2005-001-p0127-p0267.pdf

The yields of OH radicals in water containing phenol have been investigated for several ten MeV/n C ion and Ne ion having the same LET value, as a function of the residual ion energy at the specific depth in water. In this study, beside such energy dependence, the dependence of reaction time of OH radical yield was examined by changing the concentration of phenol as solute. The defferential G'-values of OH radicals, those G-values per kinetic energy of ions increase with specific energy of Ne ions. The G'-value just after irradiation(1.5ns) is relatively high but become lower with reaction time to be the value (2.7) obtained for $^{60}$ Co -rays. It suggests the diffusion behavior of OH radicals locally induced in water.

Journal Articles

Cross sections of charge transfer by slow doubly-charged carbon ions from various carbon containing molecules

Kusakabe, Toshio*; Shiota, Kenji*; Kubo, Hirotaka; Shirai, Toshizo*

Journal of Plasma and Fusion Research SERIES, Vol.7, p.237 - 239, 2006/00

no abstracts in English

Journal Articles

Measurement of energetic charged particles produced in fusion materials with 14 MeV neutron irradiation

Ochiai, Kentaro; Kondo, Keitaro; Murata, Isao*; Miyamaru, Hiroyuki*; Kubota, Naoyoshi; Takahashi, Akito*; Nishitani, Takeo

Fusion Engineering and Design, 75-79, p.859 - 863, 2005/11

https://doi.org/10.1016/j.fusengdes.2005.06.116

Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)

The Fusion Neutronics Source (FNS) of JAERI currently carries out the measurements of energetic charged particles emitted from fusion materials irradiated with a well-collimated 14 MeV neutron beam. At the beginning, the double differential cross section beryllium was measured. We have measured proton, triton and a particle emitted from a beryllium sample of 100 m in thickness.The a particle and triton were produced by $^{9}$ Be(n,) $^{6}$ He, $^{9}$ Be(n,2n)2 and $^{9}$ Be(n,t) $^{7}$ Li reactions respectively. Measured total reaction rates from the counts of a particles and tritons were 2.710 $^{-24}$ and 610 $^{-27}$ /atom/neutron, respectively, which were consistent with the calculated values from the nuclear data JENDL-3.2.

Journal Articles

Methods for tritium production rate measurement in design-oriented blanket experiments

Verzilov, Y. M.; Ochiai, Kentaro; Nishitani, Takeo

Fusion Science and Technology, 48(1), p.650 - 653, 2005/07

https://doi.org/10.13182/FST05-A1009

Times Cited Count：7 Percentile：44.75(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Intelligible seminor on fusion reactors, 1; Introduction to fusion reactors

Ueda, Yoshio*; Inoue, Takashi; Kurihara, Kenichi

Nihon Genshiryoku Gakkai-Shi, 46(12), p.845 - 852, 2004/12

http://ci.nii.ac.jp/naid/10013704970

no abstracts in English

JAEA Reports

Experimental study on sequential reactions in fusion reactor materials by D-T neutron irradiation

Hori, Junichi; Sato, Satoshi; Yamauchi, Michinori*; Ochiai, Kentaro; Nishitani, Takeo

JAERI-Research 2003-002, 50 Pages, 2003/03

JAERI-Research-2003-002.pdf:2.21MB

D-T neutron irradiation experiments have been performed with F82H and ODS ferritic steels and the effective cross sections for $^{56}$ Co productions in those materials via the sequential reactions were measured. The effective cross sections for F82H and ODS ferritic steels were about 1.5 times larger than that for iron. The distributions of effective cross sections were measured for 6 materials (iron, copper, vanadium, titanium, tungsten and lead) and F82H. The sequential reaction rates in the region close to hydrogen compound became over 20 times larger than that in material itself. In the case of F82H, the increase ratio was about 50. It was indicated that the activity for the sequential reaction product $^{56}$ Co will reach to 3-10 of that for primary neutron reaction product $^{54}$ Mn aound the surface of a cooling pipe in a fusion reactor. The effective cross sections were estimated by using (n,xp), (p,n) reaction cross sections, proton emission spectra, proton stopping power in the material. The estimated values were compared with experimental results.

Journal Articles

Radioactivity production around the surface of a cooling water pipe in a D-T fusion reactor by sequential charged particle reactions

Hori, Junichi; Maekawa, Fujio; Wada, Masayuki*; Ochiai, Kentaro; Yamauchi, Michinori*; Morimoto, Yuichi*; Terada, Yasuaki; Klix, A.; Nishitani, Takeo

Fusion Engineering and Design, 63-64, p.271 - 276, 2002/12

https://doi.org/10.1016/S0920-3796(02)00127-8

Times Cited Count：2 Percentile：16.76(Nuclear Science & Technology)

In order to the waste management method and the safety design of future D-T fusion reactor, it is important to consider the radioactivity productions via not only primary neutron reactions but also sequential charged particle reactions (SCPR). Especially, on the surface of a coolant channel many recoiled protons are generated by the neutron irradiation with coolant water, so it is apprehensive that the undesirable radioactive nuclide production yields via SCPR are enhanced. In this work, the laminated sample pieces of fusion material foils (V, Fe, W, Ti, Pb, Cu) were made and attached on a polyethylene board to simulate water flowing inside a coolant channel. They were irradiated with D-T neutrons. The effective radioactivity cross section and the depth distribution of the radioactivity production yields due to SCPR were obtained for each material. On the other hand, the estimated values were compared with the experimental ones.

Journal Articles