Abstract
Liquid metal fast reactor using sodium as a coolant typically utilize a tightly packed triangular lattice of fuel pins enclosed in a hexagonal duct. During the reactor operation, partial or total flow blockage of coolant channels, may occur at different spatial locations within the fuel assembly, due to potential isolated or combined causes, including collection and accumulation of debris, and cladding deformation. Previous studies have shown that the flow characteristics within the wire-wrapped fuel assembly, i.e., including the interior and exterior subchannels, are very complicated and strongly influenced the flow and heat transfer phenomena between the coolant fluid and fuel rods. It is important to understand and characterize the effects of channel blockage to the flow mixing characteristics in the exterior subchannels (or bypass channels) of the wire-wrapped fuel bundle. Texas A&M University has conducted isothermal flow experiments in a wire-wrapped 61-pin hexagonal fuel bundle to support the research on advanced nuclear fuel development sponsored by the US Department of Energy (DOE). The experimental facility employs matched-index-of-refraction (MIR) techniques and laser diagnostic velocity measurement techniques. In this article, we present the time-resolved particle image velocimetry (TR-PIV) measurements to characterize turbulent flow characteristics in the exterior subchannels of the wire-wrapped fuel bundle, under the presence of a localized total blockage of one of the exterior subchannels. From the obtained TR-PIV veloc- ity fields, turbulent flow characteristics including mean velocity, root-mean-square fluctuating velocity, and Reynold stress, are computed and presented. In addition, spectral analysis to the turbulent velocity fields is performed to investigate the characteristic flow frequencies associated to different flow conditions with the presence of the blockage. Finally, proper orthogonal decomposition (POD) analysis is performed to the velocity snapshots to reveal the dominant flow structures that play important roles in the flow dynamics and heat transfers of the fuel bundle.
| Original language | English |
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| Title of host publication | Student Paper Competition; Thermal-Hydraulics; Verification and Validation |
| Publisher | American Society of Mechanical Engineers (ASME) |
| ISBN (Print) | 9784888982566 |
| State | Published - 2020 |
| Externally published | Yes |
| Event | 2020 International Conference on Nuclear Engineering, ICONE 2020, collocated with the ASME 2020 Power Conference - Virtual, Online Duration: Apr 4 2020 → Apr 5 2020 |
Publication series
| Name | International Conference on Nuclear Engineering, Proceedings, ICONE |
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| Volume | 3 |
Conference
| Conference | 2020 International Conference on Nuclear Engineering, ICONE 2020, collocated with the ASME 2020 Power Conference |
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| City | Virtual, Online |
| Period | 04/4/20 → 04/5/20 |
Funding
Texas A&M University has conducted isothermal flow experiments within of a wire-wrapped 61-pin hexagonal fuel bundle to support the research on advanced nuclear reactors, within the framework of sponsored US Department of Energy (DOE) projects. The experimental facility has been constructed to allow the application of advanced laser-based flow measurement techniques, such as time-resolved particle image velocimetry (TR-PIV) and stereoscopic PIV (TR-SPIV), combined with the matched-index-of-refraction (MIR). The results of these experimental activities will be a high-fidelity experimental database of flow field measurements that will be suitable for validating CFD codes [5, 6]. [6–9] have shown through previous studies that the flow characteristics within the wire-wrapped fuel assembly are very complicated and strongly influence the flow and heat transfer phenomena between the coolant and fuel rods. The characterization and understanding of channel blockage flow mixing effects are of particularly of interest inside of the interior subchannels of the wire wrapped fuel bundle. Recently, [10, 11] discussed the flow mixing characteristics in two interior subchannels located near the core of the bundle, one without and one with the presence of a blockage. The authors showed that in the blocked sub-channel, a large recirculation flow region in the vicinity of the blockage was created by the interaction between inflows from neighboring subchannels. The vortex shedding frequency indicated by the Strouhal number was found to be St=0.16 for the two Reynolds numbers investigated. This work was performed for the Department of Energy under contract DE-NE000832. The authors gratefully acknowledge Lance White and Blaze Boyed (Texas A&M) for their support with the experimental measurements.