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Journal Articles

Visualization of the boron distribution in core material melting and relocation specimen by neutron energy resolving method

Abe, Yuta; Tsuchikawa, Yusuke; Kai, Tetsuya; Matsumoto, Yoshihiro*; Parker, J. D.*; Shinohara, Takenao; Oishi, Yuji*; Kamiyama, Takashi*; Nagae, Yuji; Sato, Ikken

JPS Conference Proceedings (Internet), 33, p.011075_1 - 011075_6, 2021/03

Journal Articles

Investigation of high-temperature chemical interaction of calcium silicate insulation and cesium hydroxide

Rizaal, M.; Nakajima, Kunihisa; Saito, Takumi*; Osaka, Masahiko; Okamoto, Koji*

Journal of Nuclear Science and Technology, 57(9), p.1062 - 1073, 2020/09

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

The interaction of cesium hydroxide and a calcium silicate insulation material was experimentally investigated at high temperature conditions. A thermogravimetry equipped with differential thermal analysis was used to analyze thermal events in the samples of mixed calcium silicate and cesium hydroxide under Ar-5%H$$_{2}$$ and Ar-4%H$$_{2}$$-20%H$$_{2}$$0 with maximum temperature of 1100$$^{circ}$$C. Prior being mixed with cesium hydroxide, a part of calcium silicate was pretreated at high temperature to evaluate the effect of possible structural changes of this material due to a preceding thermal history and also the sake of thermodynamic evaluation to those available ones. Based upon the initial condition (preliminary heat treatment) of calcium silicate, it was found that if the original material consisted of xonotlite (Ca$$_{6}$$Si$$_{6}$$0$$_{17}$$(0H)$$_{2}$$), the endothermic reaction with cesium hydroxide occurred over the temperature range 575-730$$^{circ}$$C meanwhile if the crystal phase of original material was changed to wollastonite (CaSi0$$_{3}$$), the interaction occurred over temperature range 700-1100$$^{circ}$$C. Furthermore, the X-ray diffraction analyses have indicated on both type of pretreated calsils that regardless of Ar-5%H$$_{2}$$ and Ar-4%H$$_{2}$$-20%H$$_{2}$$0 atmosphere, cesium aluminum silicate, CsAlSi0$$_{4}$$ was formed with aluminum in the samples as an impurity or adduct.

Journal Articles

Development of three-dimensional distribution visualization technology for boron using energy resolved neutron-imaging system (RADEN)

Abe, Yuta; Tsuchikawa, Yusuke; Kai, Tetsuya; Matsumoto, Yoshihiro*; Parker, J. D.*; Shinohara, Takenao; Oishi, Yuji*; Kamiyama, Takashi*; Nagae, Yuji; Sato, Ikken

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08

Journal Articles

Development of experimental technology for simulated fuel-assembly heating to address core-material-relocation behavior during severe accident

Abe, Yuta; Yamashita, Takuya; Sato, Ikken; Nakagiri, Toshio; Ishimi, Akihiro

Journal of Nuclear Engineering and Radiation Science, 6(2), p.021113_1 - 021113_9, 2020/04

Journal Articles

3D X Ray micro-tomography as a tool to formulate metakaolin-based geopolymer-oil emulsions

Lambertin, D.*; Davy, C. A.*; Hauss, G.*; Planel, B.*; Marchand, B.*; Cantarel, V.

Proceedings of 1st International Conference on Innovation in Low-Carbon Cement and Concrete Technology (ILCCC 2019) (USB Flash Drive), 4 Pages, 2019/06

Composite materials made of geopolymer (GP) cement and organic liquids are useful to synthetize porosity-controlled media, for the management of radioactive organic liquid waste, or as phase change materials (PCM). Indeed, GP cements are able to integrate huge amounts of organic oils by direct emulsion in the fresh paste. The emulsion (GEOIL) remains stable during GP hardening. In this contribution, by using 3D X Ray micro Computed Tomography (micro CT) with a voxel size of 1 micron$$^{3}$$, we investigate the effect of formulation parameters (oil proportion, Si/Al molar ratio, surfactant) on the 3D oil droplet structure of GEOIL pastes. Samples are emulsified in the fresh state, and imaged in the hardened state. Porosity, oil droplet size distribution and mean distance between droplets are all determined quantitatively. It is observed that the presence of surfactant provides significantly smaller oil droplets. The increase in Si/Al ratio also decreases the oil droplet sizes, but to a lesser extent.

Journal Articles

Observation of simulated fuel debris using synchrotron radiation

Yoneda, Yasuhiro; Harada, Makoto; Takano, Masahide

Transactions of the Materials Research Society of Japan, 44(2), p.61 - 64, 2019/04

We performed three-dimensional observation of simulated fuel debris using Synchrotron Computed Tomography (CT). CT was used to make the inside of fuel debris clear. The CT observation provides that a clear contrast in the zirconia rich part and concrete rich part. Zirconia heavier than concrete moved to the lower part when crystals precipitate and aggregates near the bottom surface. As a result, phase separation occurs. The phase separation is caused by the difference in the composition ratio of zirconia, and can also be observed difference in crystal growth mode by composition ratio.

Journal Articles

3D-microstructure analysis of compacted Na- and Cs-montmorillonites with nanofocus X-ray computed tomography and correlation with macroscopic transport properties

Takahashi, Hiroaki*; Tachi, Yukio

Applied Clay Science, 168, p.211 - 222, 2019/02

 Times Cited Count:8 Percentile:70.54(Chemistry, Physical)

Microstructural and mass transport properties of compacted Na- and Cs-montmorillonites with different swelling properties were investigated by combining 3D microstructure analysis using nanofocus X-ray CT and diffusion measurement of HDO. The X-ray CT observations indicated that macropores in the dry state of compacted Na-montmorillonite are filled with gel phases, and the grain sizes of clay particles shifted toward smaller values through the saturation and swelling processes. By contrast, no gel phase and no decrease in the grain and pore volumes were observed for saturated Cs-montmorillonite. The geometrical factors of the macropores including tortuosity and geometric constrictivity of saturated Cs-montmorillonite determined by the X-ray CT was consistent with the corresponding values derived in the HDO diffusion test. In the case of Na-montmorillonite, the larger differences between the geometric factors evaluated by the X-ray CT and the diffusion tests can be explained by the electrostatic constrictivity factor and the additional geometrical factors in gel phase and interlayer that are smaller than the detection limit of the X-ray CT.

Journal Articles

Evolution of the excavation damaged zone around a modelled disposal pit; Case study at the Horonobe Underground Research Laboratory, Japan

Aoyagi, Kazuhei; Miyara, Nobukatsu; Ishii, Eiichi; Nakayama, Masashi; Kimura, Shun

Proceedings of 13th SEGJ International Symposium (USB Flash Drive), 5 Pages, 2018/11

The construction of underground facilities induces fractures in the rock mass around the underground voids due to the resultant stress redistribution. This has particular implications for high-level radioactive waste (HLW) disposal projects, where fracture development creates an excavation damaged zone (EDZ) that increases the hydraulic conductivity of the surrounding rock mass and can provide a pathway for the migration of radionuclides from the storage facilities. It is therefore important to understand the long-term evolution of the EDZ and perform a comprehensive HLW disposal risk assessment. An in situ engineered barrier system experiment was conducted in the 350 m gallery at the Horonobe Underground Research Laboratory, Japan, to observe the near-field coupled thermo-hydro-mechanical-chemical (THMC) process in situ and validate coupled THMC models. Here we investigate the evolution of the EDZ around the gallery and model a test pit that was excavated below the floor of the gallery using a series of seismic tomography surveys. There was a significant decrease in the seismic velocity field around the test pit due to its excavation, which became slightly more pronounced over time after the excavation. These seismic results, coupled with hydraulic tests and pore pressure measurements around the pit, indicate that fracture development and the decrease in saturation around the test pit resulted in a decrease in the seismic velocity field after the excavation of the test pit. Furthermore, the increase in saturation around the test pit is a key reason for the increase in the seismic velocity field after the heater test.

Journal Articles

Development of experimental technology for simulated fuel-assembly heating to address core-material-relocation behavior during severe accident

Abe, Yuta; Yamashita, Takuya; Sato, Ikken; Nakagiri, Toshio; Ishimi, Akihiro; Nagae, Yuji

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 9 Pages, 2018/07

Journal Articles

Development of non-transfer type plasma heating technology to address CMR behavior during severe accident with BWR design conditions

Abe, Yuta; Sato, Ikken; Nakagiri, Toshio; Ishimi, Akihiro; Nagae, Yuji

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04

Journal Articles

Development of residual thermal stress-relieving structure of CFC monoblock target for JT-60SA divertor

Tsuru, Daigo; Sakurai, Shinji; Nakamura, Shigetoshi; Ozaki, Hidetsugu; Seki, Yohji; Yokoyama, Kenji; Suzuki, Satoshi

Fusion Engineering and Design, 98-99, p.1403 - 1406, 2015/10

 Times Cited Count:3 Percentile:32.14(Nuclear Science & Technology)

Journal Articles

A Code MOGRA for predicting the migration of ground additions and its application

Amano, Hikaru

Shigen Kankyo Taisaku, 41(12), p.89 - 96, 2005/10

no abstracts in English

JAEA Reports

Rod displacement measurements by X-ray CT and its impact on thermal-hydraulics in tight-lattice rod bundle (Joint research)

Mitsutake, Toru*; Katsuyama, Kozo*; Misawa, Takeharu; Nagamine, Tsuyoshi*; Kureta, Masatoshi*; Matsumoto, Shinichiro*; Akimoto, Hajime

JAERI-Tech 2005-034, 55 Pages, 2005/06

JAERI-Tech-2005-034.pdf:7.76MB

In tight-lattice bundles with about 1mm gap between rods, a rod displacement might affect thermal-hydraulic characteristics. The inside-structure observation of the simulated seven-rod bundle of RMWR was made with the high-energy X-ray CT of JNC. The CT view assured that the rod position was almost the same as expected by design. In the heat transfer experiments, all thermocouples on the center rod showed almost simultaneous BT-induced temperature increase and on the same axial heights showed quite similar time-variation behaviors in the vapor cooling heat transfer regime. It showed that the effect of the geometrical asymmetry was small on the BT characteristics. The calculated critical power by subchannel analysis with the input of the CT measured rod position was smaller by about 5% than that with the designed rod position. It concluded that the error in the calculated critical power was attributable not to the asymmetry in the rod position, but to the models in the subchannel analysis code.

Journal Articles

Electrochemical behaviors of PuN and (U, Pu)N in LiCl-KCl eutectic melts

Shirai, Osamu; Kato, Tetsuya*; Iwai, Takashi; Arai, Yasuo; Yamashita, Toshiyuki

Journal of Physics and Chemistry of Solids, 66(2-4), p.456 - 460, 2005/02

 Times Cited Count:8 Percentile:38.49(Chemistry, Multidisciplinary)

Electrochemical behaviors of PuN and (U, Pu)N in the LiCl-KCl eutectic melt containing UCl$$_{3}$$ and PuCl$$_{3}$$ at 773 K were investigated by cyclic voltammetry. The electrochemical dissolution of PuN and (U, Pu)N began nearly at -1.0 V vs. the Ag/AgCl reference electrode. The rest potentials of PuN and (U, Pu)N were observed at about 0.15 V more negative potential than that of UN since the equilibrium potential of UN is about 0.15 V more positive than that of PuN. In the cyclic voltammogram measured by using (U, Pu)N as the working electrode, a steep rise of the positive current was observed at more positive potential than -0.4 V in analogy with the cyclic voltammogram measured by using UN as the working electrode. In addition, there were two anodic current waves in the voltammogram with (U, Pu)N, though the wave form was not clear. This indicates that UN and PuN would be dissolved independently irrespective of formation of the solid solution, (U, Pu)N.

Journal Articles

Multiplexing thermography for International Thermonuclear Experimental Reactor divertor targets

Itami, Kiyoshi; Sugie, Tatsuo; Vayakis, G.*; Walker, C.*

Review of Scientific Instruments, 75(10), p.4124 - 4128, 2004/10

 Times Cited Count:9 Percentile:47.59(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Interfacial properties of a direct bonded Nd-doped YVO$$_{4}$$ and YVO$$_{4}$$ single crystal

Sugiyama, Akira; Nara, Yasunaga; Wada, Kengo*; Fukuyama, Hiroyasu

Journal of Materials Science; Materials in Electronics, 15(9), p.607 - 612, 2004/09

Laser crystal bonding of a neodymium-doped yttrium orthovanadate (Nd: YVO$$_{4}$$) and a non-doped yttrium orthovanadate (YVO$$_{4}$$) crystal as a cold finger has been demonstrated. Instead of a traditional chemical treatment, a newly developed dry etching process was applied to the preparation for contact of mechanically polished surfaces. In the subsequent heat treatment process, stable heating at 873 K was required to prevent precipitation at the bonded interface. The bonded interface of 3 mm $$times$$ 3 mm was investigated by optical scattering and wavefront distortion measurements. The scattering density around the bonded interface was less than 4.6$$times$$10$$^{6}$$ /cm$$^{3}$$ and the wavefront distortion caused by the bonded region was assumed to be around 0.04-wave at 633 nm. Additional magnified inspection showed that atoms in the bonded region were well arranged with the same regularity as the bulk crystal. The diffusion coefficient of Nd$$^{3+}$$ ions in the YVO$$_{4}$$ crystal was estimated at 2.3$$times$$10$$^{-23}$$ m$$^{2}$$/sec at 873 K.

Journal Articles

Preliminary examination of a CCD camera with a scintillator coated fiber optic plate for neutron imaging

Matsubayashi, Masahito; Soyama, Kazuhiko

Nuclear Instruments and Methods in Physics Research A, 529(1-3), p.384 - 388, 2004/08

 Times Cited Count:6 Percentile:42.52(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Reproducibility of thermal neutron flux distribution on patient's brain surface with a realistic phantom

Yamamoto, Kazuyoshi; Kumada, Hiroaki; Yamamoto, Tetsuya*; Matsumura, Akira*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(2), p.193 - 199, 2004/06

To investigate the possibility of experimental approach for dose evaluation using a realistic phantom that faithfully reproduced the shape of a head, this research considered the manufacture of a patient's realistic phantom and the reappearance of actual medical irradiation conditions. We selected the rapid prototyping technology to produce the realistic phantom from the Computed Tomography (CT) imaging. This phantom was irradiated under the same clinical irradiation condition of this patient, and the thermal neutron distribution on the brain surface was measured in detail. Several subjects on material and data conversion in the production of realistic phantom were mentioned. As a result of reproducing medical irradiation using the realistic phantom, the maximum thermal neutron flux became a value about 22% lower than the surface of the actual brain. If the problems pointed out in this paper are solved, it may also be expected that it would become possible to check computational dosimetry system.

Journal Articles

Electrode reaction of the Np$$^{3+}$$/Np couple at liquid Cd and Bi electrodes in LiCl-KCl eutectic melts

Shirai, Osamu; Uozumi, Koichi*; Iwai, Takashi; Arai, Yasuo

Journal of Applied Electrochemistry, 34(3), p.323 - 330, 2004/03

 Times Cited Count:26 Percentile:52.18(Electrochemistry)

The electrode reactions of the Np$$^{3+}$$/Np couple at liquid Cd and Bi electrodes were investigated by cyclic voltammetry at 723, 773 and 823 K in LiCl-KCl eutectic melt. It was found that the diffusion of Np$$^{3+}$$ in the salt phase was a rate-determining step in the cathodic reaction when the concentration of NpCl$$_{3}$$ was less than about 1 wt.% and the liquid Cd or Bi phase was not saturated with Np. The redox potentials of the Np$$^{3+}$$/Np couple at liquid Cd electrode at 723, 773 and 823 K were observed more positively than those at Mo electrode by 0.158, 0.140 and 0.126 V, respectively. The potential shift would result from a lowering of activity of Np in Cd phase according to the alloy formation of NpCd$$_{11}$$ at 723 K and NpCd$$_{6}$$ at 773 and 823 K. The redox potentials of the Np$$^{3+}$$/Np couple at liquid Bi electrode at 723, 773 and 823 K were more positive than those at Mo electrode by 0.427, 0.419 and 0.410 V, respectively, which would be attributable to a lowering of activity of Np in Bi phase according to the formation of NpBi$$_{2}$$.

Journal Articles

Development of a code MOGRA for predicting the migration of ground additions and its application to various land utilization areas

Amano, Hikaru; Takahashi, Tomoyuki*; Uchida, Shigeo*; Matsuoka, Shungo*; Ikeda, Hiroshi*; Hayashi, Hiroko*; Kurosawa, Naohiro*

Journal of Nuclear Science and Technology, 40(11), p.975 - 979, 2003/11

 Times Cited Count:2 Percentile:19.75(Nuclear Science & Technology)

MOGRA is a migration prediction code for toxic ground additions including radioactive materials in a terrestrial environment. MOGRA consists of computational codes that are applicable to various evaluation target systems, and can be used on personal computers. The computational code has the dynamic compartment analysis block, GUI for computation parameter settings and results displays, data bases. The compartments are obtained by classifying various natural environments into groups that exhibit similar properties. A hypothetical combination of land usage was supposed to check the function of MOGRA. The land usage was consisted from cultivated lands, forests, uncultivated lands, urban area, river, and lake. Each land usage has its own inside model which is basic module. Also supposed was homogeneous contamination of the surface land from atmospheric deposition of $$^{137}$$Cs (1.0 Bq/m$$^{2}$$). The system analyzed the dynamic changes of $$^{137}$$Cs concentrations in each compartment, fluxes from one compartment to another compartment.

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