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JAEA Reports

Calculation of the amount of leaching water from concrete-pit facilities under various facility design conditions

Nagao, Rina; Namekawa, Maki*; Totsuka, Masayoshi*; Nakata, Hisakazu; Sakai, Akihiro

JAEA-Technology 2021-009, 139 Pages, 2021/06

JAEA-Technology-2021-009.pdf:13.96MB

Japan Atomic Energy Agency is the implementing body of the near surface disposal of low-level radioactive waste (LLW) generated from research facilities and other facilities. Concrete-pit disposal are considered as a method of disposing of the LLW. Since the concrete-pits are placed at deeper position than the groundwater level, we need to consider that radionuclides might migrate with the flow of groundwater. Accordingly, in order to explain the safety of the concrete-pit disposal facility, it is necessary to investigate the flow of groundwater and the volumetric flow rate of leaching water from the facility. Therefore, in this report, sensitivity analysis of the volumetric flow rate of leaching water from concrete-pit was carried out by varying the permeability of cover-soil filled with in outside of the lateral sides of the bentonite mixed soil (BMS) and the conditions of the BMS on the upper part of the concrete-pits. As a result of the analysis, when the BMS is normal condition, the volumetric flow rate of leaching water from the concrete-pits is reduced by lowering permeability of the lateral cover-soil. However, in the case of occurring the deterioration of the function of BMS on the upper part of the concrete-pit, significant reduction of the volumetric flow rate of leaching water is not seen even if the permeability of the lateral cover-soil is lowered. Therefore, taking into consideration the possibility of the deterioration of the function of BMS on the upper part of the concrete-pit, it is necessary to consider that cover-soil with low permeability is equipped on the upper part of the BMS.

Journal Articles

Online coupling of two-phase flow solvent extraction microfluidics with inductively coupled plasma mass spectrometry

Do, V. K.; Yamamoto, Masahiko; Taguchi, Shigeo; Kuno, Takehiko; Surugaya, Naoki

Current Analytical Chemistry, 14(2), p.111 - 119, 2018/00

 Times Cited Count:3 Percentile:15.38(Chemistry, Analytical)

A direct coupling of two-phase flow solvent extraction microfluidics with ICP-MS for element-selective analysis is successfully established. Two-phase flow in microchannels of two combined glass chips for continuous extraction and back-extraction is stabilized through balancing the pressure by using an external coiled tube that functions as a flow resistor. The difference of fluid flow rate between microchannels and ICP-MS is adjusted by a proposed interface system including T-junction mixer and a switching valve. An online measurement of rhenium is successfully demonstrated. The calibration curve for Re is carried out in the range of 1 $$mu$$g/L to 20 $$mu$$g/L. The limit of detection is 0.2 $$mu$$g/L with a needed sample volume of one milliliter. Total time including extraction, back-extraction, and measurement is less than one hour. The development of the online coupling is a first step towards future applications to the selective measurement of highly radioactive elements.

Journal Articles

Development of evaluation method of liquid flow rate by self-priming phenomena in venturi scrubber

Horiguchi, Naoki; Yoshida, Hiroyuki; Kanagawa, Tetsuya*; Kaneko, Akiko*; Abe, Yutaka*

Proceedings of 9th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-9) (CD-ROM), 5 Pages, 2014/11

Journal Articles

Bispectral analysis applied to coherent floating potential fluctuations obtained in the edge plasmas on JFT-2M

Nagashima, Yoshihiko*; Ito, Kimitaka*; Ito, Sanae*; Fujisawa, Akihide*; Hoshino, Katsumichi; Takase, Yuichi*; Yagi, Masatoshi*; Ejiri, Akira*; Ida, Katsumi*; Shinohara, Koji; et al.

Plasma Physics and Controlled Fusion, 48(4), p.S1 - S15, 2006/04

 Times Cited Count:34 Percentile:75.48(Physics, Fluids & Plasmas)

This paper presents the results of bispectral analysis of floating potential fluctuations in the edge region of ohmically heated plasmas in the JFT-2M tokamak. Inside of the outermost magnetic surface,coherent modes were observed around the frequency of geodesic acoustic mode which is a kind of the zonal flow. The squared bicoherence shows significant nonlinear couplings between the coherent fluctuations and the background fluctuations (which are likely to contain drift wave turbulent fluctuations). The experimental results that the total bicoherence is proportional to the squared amplitude of the coherent fluctuation, and that the biphase of the coherent modes localizes around a constant value $$pi$$, are consistent with the theoretical prediction on the drift wave - zonal flow systems based on the Hasegawa-Mima model.

Journal Articles

Large-scale direct simulation of two-phase flow structure around a spacer in a tight-lattice nuclear fuel bundle

Takase, Kazuyuki; Yoshida, Hiroyuki; Ose, Yasuo*; Akimoto, Hajime

Computational Fluid Dynamics 2004, p.649 - 654, 2006/00

no abstracts in English

Journal Articles

Numerical predictions on a large-scale bubbly flow configuration in a minichannel

Takase, Kazuyuki; Yoshida, Hiroyuki; Akimoto, Hajime; Ose, Yasuo*; Aoki, Takayuki*

Nihon Kikai Gakkai 2005-Nendo Nenji Taikai Koen Rombunshu, Vol.7, p.17 - 18, 2005/09

no abstracts in English

Journal Articles

Numerical analysis of three-dimensional two-phase flow behavior in a fuel assembly

Takase, Kazuyuki; Yoshida, Hiroyuki; Ose, Yasuo*; Akimoto, Hajime

WIT Transactions on Engineering Sciences, Vol.50, p.183 - 192, 2005/00

no abstracts in English

Journal Articles

Investigation of water-vapor two-phase flow characteristics in a tight-lattice core by large scale numerical simulation, 1; Development of a direct analysis procedure on two-phase flow with an advanced interface tracking method

Yoshida, Hiroyuki; Nagayoshi, Takuji*; Ose, Yasuo*; Takase, Kazuyuki; Akimoto, Hajime

Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(3), p.233 - 241, 2004/09

When there are no experimental data such as the reduced-moderation water reactor (RMWR), therefore, it is very difficult to obtain highly precise predictions. The RMWR core adopts a hexagonal tight lattice arrangement with about 1 mm gap between adjacent fuel rods. In the core, there is no sufficient information about the effects of the gap spacing and grid spacer configuration on the flow characteristics. Thus, we start to develop a predictable technology for thermal-hydraulic performance of RMWR core using advanced numerical simulation technology. As part of this technology development, we are developing advanced interface tracking method to improve conservation of volume of fluid. In this paper, we describe a newly developed interface tracking method and examples of the numerical results. In the present results, the error of volume conservation in the bubbly flow is within 0.6%.

Journal Articles

Numerical simulation on large-scale bubbly flow behavior in a narrow duct

Takase, Kazuyuki; Yoshida, Hiroyuki; Tamai, Hidesada; Ose, Yasuo*

Nihon Kikai Gakkai 2004-Nendo Nenji Taikai Koen Rombunshu, Vol.2 (No.04-1), p.251 - 252, 2004/09

no abstracts in English

Journal Articles

Numerical analysis of a water-vapor two-phase film flow in a narrow coolant channel with a three-dimensional rectangular rib

Takase, Kazuyuki; Yoshida, Hiroyuki; Ose, Yasuo*; Tamai, Hidesada

JSME International Journal, Series B, 47(2), p.323 - 331, 2004/05

no abstracts in English

Journal Articles

Flow scheme and controllability of the HTTR hydrogen production system

Nishihara, Tetsuo; Shimizu, Akira; Inagaki, Yoshiyuki; Tanihira, Masanori*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 2(4), p.517 - 524, 2003/12

no abstracts in English

Journal Articles

Study on gas-liquid two-phase flow distribution in a tight-lattice rod bundle

Onuki, Akira; Shibata, Mitsuhiko; Tamai, Hidesada; Akimoto, Hajime; Yamauchi, Toyoaki*; Mizokami, Shinya*

Nihon Konsoryu Gakkai Nenkai Koenkai 2003 Koen Rombunshu, p.35 - 36, 2003/07

Analytical evaluation of maximum critical power by so-called subchannnel code is indispensable for design of reduced moderation water reactor. In this study, two-phase flow distribution in a tight-lattice rod bundle is investigated using 19-rod bundle experimental rig and subchannnel analysis code NASCA. The flow distribution was measured under so-called churn flow regime and the predictive capability of NASCA was assessed. NASCA can predict the flow distribution qualitatively depending on local pressure drop. Quantitative prediction is also reasonable for liquid phase but the gas phase distribution was underestimated. Void-drift model has a dominant contribution and we should improve the model for the tight-lattice rod bundle.

Journal Articles

Thermofluid analysis of free surface liquid divertor in tokamak fusion reactor

Kurihara, Ryoichi

Fusion Engineering and Design, 61-62, p.209 - 216, 2002/11

 Times Cited Count:4 Percentile:30.15(Nuclear Science & Technology)

To attain high fusion power density, the divertor must suffer high heat flux from the fusion plasma. It is very difficult to remove a high heat flux more than 20 MW/m$$^{2}$$ using the only solid divertor plate from the viewpoint of severe mechanical state such as thermal stress and crack growth. Therefore, a concept of liquid divertor is proposed to remove high heat flux by liquid films flowing on a solid wall. This paper mainly descries a preliminary thermofluid analysis of the free surface liquid flow, made of the FliBe molten salt, using the finite element analysis code ADINA-F. The heat flux of 25$$sim$$100 MW/m$$^{2}$$ was given on the free surface liquid of the flow. I explored a possibility of applying the secondary flow to enhance the heat transfer of the liquid flow suffering high heat flux. This analysis shows that the heat flux of 100 MW/m$$^{2}$$ can be removed by inducing the secondary flow in the free surface liquid FLiBe. And this paper shows that the liquid divertor using solid-liquid multi-phase flow makes possible large heat removal by utilizing the latent heat of fusion of solid phase.

JAEA Reports

Measurement of coolant flow in fuel elements at the JRR-4 silicide fuel core

Yamamoto, Kazuyoshi; Watanabe, Shukichi; Nagatomi, Hideki; Kaminaga, Masanori; Funayama, Yoshiro

JAERI-Tech 2002-034, 40 Pages, 2002/03

JAERI-Tech-2002-034.pdf:1.97MB

JRR-4, a swimming-pool type research reactor with a thermal power of 3.5MW, attained criticality in July 1998, after replacing its 90% enrichment fuel with a 20% enrichment fuel under the Reduced Enrichment Program. As a part of the program, safety analysis on thermo-hydraulics of the reactor core was conducted on cases including single channel blockage accident. With the conclusion that a certain margin on thermo-hydraulics was necessary, investigation and experiments were carried out with an aim to increase the core flow rate. To increase the core flow, it was carried out to reduce the bypass flow in the core and to increase the primary coolant flow rate from 7m$$^{3}$$/min to 8m$$^{3}$$/min. After flow measurements using a mock-up fuel element, flow velocity of the fuel channel was determined as 1.45m/s as opposed to the designed value of 1.44m/s, and the ratio of core flow to total flow was 0.88, exceeding the value 0.86 used for the safety analysis.This report describes the JRR-4 core flow increase plan as well as the results of the channel flow rate measurement

Journal Articles

Water flow experiments and analyses on the cross-flow type mercury target model with the flow guide plates

Haga, Katsuhiro; Terada, Atsuhiko*; Kaminaga, Masanori; Hino, Ryutaro

Nuclear Engineering and Design, 210(1-3), p.157 - 168, 2001/12

 Times Cited Count:3 Percentile:27.65(Nuclear Science & Technology)

The mercury target is used in the spallation neutron source driven by a high intensity proton accelerator. In this study the effectiveness of the cross-flow type mercury target structure was evaluated experimentally and analytically. Prior to the experiment, the mercury flow field and the temperature distribution in the target container were analyzed assuming the proton beam energy and power of 1.5GeV and 5MW. Then the average water flow velocity field in the target mock-up model, which was fabricated from plexiglass for a water experiment, was measured at room temperature using the PIV technique. Water flow analyses were also conducted. The experimental results showed that the cross-flow could be realized in most of the proton beam path area and the analytical result of the water flow velocity field showed good correspondence to the experimental result in the case of the Reynolds number of more than 4.83E5 at the model inlet. With these results, the effectiveness of the cross-flow type mercury target structure and the present analysis code system was demonstrated.

Journal Articles

Three-dimensional computations of two-phase flow behavior in a simulated fusion reactor under water ingress

Takase, Kazuyuki; Ose, Yasuo*; Akimoto, Hajime

Proceedings of the 1st International Symposium on Advanced Fluid Information (AFI-2001), p.227 - 232, 2001/10

no abstracts in English

Journal Articles

Study on oscillated flow around excited cylinder using built-in electromagnetic flowmeters

Kondo, Masaya; Anoda, Yoshinari

Emerging Technologies for Fluids, Structures and Fluid-Structure Interaction, 2001 (PVP-Vol.431), p.111 - 117, 2001/07

no abstracts in English

Journal Articles

Depressurization effects of vacuum vessel pressure supression systems in fusion reactors at multiple first wall pipe break events

Takase, Kazuyuki; Akimoto, Hajime

Applied Electromagnetics in Materials, p.177 - 178, 2001/00

no abstracts in English

JAEA Reports

Status and subjects of thermal-hydraulic analysis for next-generation LWRs

Subcommittee on Improvement of Reactor Thermal-Hydraulic Analysis Codes

JAERI-Review 2000-002, p.105 - 0, 2000/03

JAERI-Review-2000-002.pdf:6.24MB

no abstracts in English

Journal Articles

Effect of alternate-vortex on flow-induced in-line oscillation

; Anoda, Yoshinari

Nihon Kikai Gakkai Rombunshu, C, 65(639), p.4252 - 4259, 1999/11

no abstracts in English

70 (Records 1-20 displayed on this page)