Basic study on flow separation phenomenon at the elbow in a large-diameter pipe; Research report in FY2007

Iwamoto, Yukiharu*; Sogo, Motosuke*; Aizawa, Kosuke; Nakanishi, Shigeyuki*; Yamano, Hidemasa

JAEA-Research 2010-009, 58 Pages, 2010/06

JAEA-Research-2010-009.pdf:31.02MB

Experimental studies of the 1/10-scale model of a hot leg piping and their numerical analyses were carried out in order to guarantee the designing of the sodium-cooled fast breeder reactor. The structure of the flow fluctuation was clarified by means of pressure measurements, laser doppler velocimetry (LDV) and flow visualization. LDV measurements were examined for Reynolds number of 50000. FFT analyses of axial velocities indicate that two kinds of flow fluctuations exist in the present elbow. One is the fluctuation with approximate Strouhal number of 1.0 (3.2 Hz) occurring in a shear flow region. The other is with approximate Strouhal number of 0.5 (1.6 Hz) occurring in the separated and its downstream regions. These fluctuations were also observed by flow visualization. The analyses showed that the stream regime was in good agreement with visualization test results.

Basic study on flow separation phenomenon in cooling system piping in fast reactors; Clarification of complex flow structure in a multi-elbow in a high Reynolds number regime (Joint research report in FY2007)

Yuki, Kazuhisa*; Hashizume, Hidetoshi*; Nakanishi, Shigeyuki*; Aizawa, Kosuke; Yamano, Hidemasa

JAEA-Research 2009-017, 55 Pages, 2009/08

JAEA-Research-2009-017.pdf:16.5MB

At Tohoku University, 1/15 scale and 1/7 scale flow tests are being performed in order to clarify an unsteady flow structure in the cold leg piping and to investigate the scale effect. In FY2007, the 1/15 scale test was carried out using a double elbow geometry. It was confirmed that there existed a separation along the inner wall of the 1st elbow and a large swirling flow in the 2nd elbow. Furthermore, the unsteady flow formed in and/or behind the separation region was transported downstream and flows into the center area of the 2nd elbow. At JAEA, a numerical analytical evaluation method is being developed to evaluate the feasibility of the reactor design. In FY2007, numerical analyses for the 1/15 scale test were performed using the commercial thermal-hydraulics code FLUENT. The analyses showed that the trend of calculated velocity distributions was in good agreement with the visualization test results.

Study on flow-induced-vibration evaluation of large-diameter pipings in a sodium-cooled fast reactor, 1; Sensitivity analysis of turbulent flow models for unsteady short-elbow pipe flow

Aizawa, Kosuke; Nakanishi, Shigeyuki; Yamano, Hidemasa; Kotake, Shoji; Hayakawa, Satoshi*; Watanabe, Osamu*; Fujimata, Kazuhiro*

Proceedings of 6th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-6) (USB Flash Drive), 7 Pages, 2008/11

To evaluate the flow-induced vibration in the actual-sized pipings of JSFR, computer simulation is necessary. In this study, as the first step, sensitivity analysis of turbulence flow models for unsteady short-elbow pipe flow has been carried out with the STAR-CD thermal-hydraulic simulation code. Through the sensibility analysis, the objective of this study is to propose the best analysis models which can reproduce the unsteady characteristics obtained in the 1/3-scale test results with 9.2 m/s of main flow. In this study, to take into account anisotropic characteristics of turbulence, two turbulent flow models were used: large eddy simulation (LES) and Reynolds stress model (RSM). The both validated simulations have reproduced flow separation region and periodic vortex shedding. The simulation results with both models were compared with power spectrum densities of pressure fluctuations which were used in the pipe vibration evaluation. Only the RSM simulation with the best combination has reproduced the pressure-fluctuation power spectrum densities, which were characterized by a peak frequency of 10 Hz in the 1/3 test with 9.2 m/s.

A Modular metal-fuel fast reactor with one-loop main cooling system

Chikazawa, Yoshitaka; Okano, Yasushi; Konomura, Mamoru; Sato, Koji; Sawa, Naoki*; Sumita, Hiroyuki*; Nakanishi, Shigeyuki*; Ando, Masato*

Nuclear Technology, 159(3), p.267 - 278, 2007/09

https://doi.org/10.13182/NT07-A3875

A diversified or modular power source is attractive since it requires a low construction cost per unit and can be demonstrated in small scale experimental facilities. In this study, a new metal fuel sodium cooled reactor with 300MW electric has been developed enhancing cost reduction. And economical potential at demonstration stage with first of a kind (FOAK) is emphasized. A minimum configuration with a compact reactor vessel, a one-loop main cooling system and a simple fuel handling system is adopted enhancing cost reduction. For safety evaluation, reliability of the one-loop main cooling system has been shown by pipe-break transient analyses. Besides, construction cost of a demonstration plant with a first reactor and a small reprocessing and fuel fabrication facility is also evaluated. A major feature of the present concept is that the demonstration reactor and facilities can be directly appropriated for first commercial modules and the power plant can easily increase its capacity adding reactor and electrorefiner modules. A fast reactor cycle commercialization scenario using the present concept is thought to give low R&D or investment risk and high cost performance since the total demonstration plant cost is relatively small and the facilities are directly appropriated to commercial use.

Reaction analysis of MOX co-deposition in oxide electrowinning process

Sato, Fuminori; Mizuguchi, Koji; Nakanishi, Shigeyuki; Myochin, Munetaka

Nihon Genshiryoku Gakkai Wabun Rombunshi, 5(4), p.268 - 281, 2006/12

https://doi.org/10.3327/taesj2002.5.268

MOX co-deposition process, which is one of the main parts of oxide electrowinning process, was studied by both sides of examination and analysis. Parameter tests using U and Pu were performed as basic examination, and fundamental data of the process such as polarization property of molten salt including U and Pu, current efficiency of electrolysis and PuO concentration in recovered deposit, etc. were acquired. In addition, to analyze the process behavior, especially polarization property at electrolysis, a reaction model considering Pu, Pu, UO, UO, PuO and PuOin molten NaCl-2CsCl salt was developed. The validity of this model was confirmed by comparison of the experimental and analytical results. Using this model behavior of chemical species in the process was studied and control factors of MOX co-deposition process were discussed.