https://orcid.org/0000-0002-7133-0010
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Abstract
High-resolution two-phase flow data in the rod bundle are important in the development and validation of high-fidelity models for computational fluid dynamics and subchannel codes, in particular, those pertaining to light water reactor cooling systems. The Michigan Adiabatic Rod Bundle Flow Experiment (MARBLE) has been constructed as a modular assembly of an 8 × 8 lattice rod bundle to simulate scaled pressurized water reactor and boiling water reactor subchannel assemblies. To establish a high-spatial resolution database of the void fraction in the reactor fuel assembly geometries, tomographic measurements were performed with the High-Resolution Gamma-ray Tomography System, which was designed and built in house; the detector system has a spatial resolution of less than 1.0 mm using 240 LYSO (Lu1.8Y0.2SiO5) scintillators with a fan-beam array. In the present study, the local void fraction was measured with the MARBLE facility under various air-water flow conditions (jg = 0.04 to 0.85 m/s and jl = 0.12 to 0.77 m/s) covering from bubbly to cap-turbulent flows. The local void fraction was also successfully measured under nonuniform and asymmetric air bubble distribution conditions with an investigation of the effect of spacer grids and mixing vanes on void drift across subchannels.
Nomenclature
| Dh | = | = hydraulic equivalent diameter |
| j | = | = superficial velocity (m/s) |
| N | = | = counts with the object present |
| N0 | = | = counts of flat field calibration |
| n | = | = number of measurement iterations |
| P | = | = pixel pitch (mm/pixel) |
| p | = | = attenuation value in the sinogram |
| r | = | = detector location in the angular projection data |
| x | = | = x-coordinates in the constructed CT image |
| y | = | = y-coordinates in the constructed CT image |
Greek
| α | = | = void fraction (%) |
| θ | = | = detector angle in the angular projection data (deg) |
| μ | = | = linear attenuation coefficient (1/cm) |
Subscripts
| avg | = | = area-weighted average |
| g | = | = gas phase |
| l | = | = liquid phase |
| tp | = | = two-phase flow |
Acknowledgments
This paper was prepared as an account of work sponsored by an agency of the U.S. government. Neither the U.S. government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third party’s use, or the results of such use, of any information, apparatus, product, or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights. The views expressed in this paper are not necessarily those of the U.S. Nuclear Regulatory Commission.
Disclosure Statement
No potential conflict of interest was reported by the authors.