Abstract
Liquid metal fast reactors typically utilize a tightly packed triangular lattice of fuel pins helically wrapped with a wire spacer and enclosed in a hexagonal duct. During reactor operation partial or total flow blockage of coolant channels may occur at different locations of the fuel assembly. Due to potential isolated or combined causes, these blockages may include collection and accumulation of debris, and cladding deformation. The complexity of the flow behavior and heat transfer phenomena within a wire-wrapped fuel assembly accompanied with the effects of channel blockage has motivated the research community around the world, initiating extensive experimental and numerical investigations. The 61-pin wire-wrapped experimental bundle at Texas A& M University, with its clear, fully accessible test section, has been designed, constructed, and operated to conduct high-resolution measurements of the flow characteristics at different locations within the bundle. High spatial and temporal resolution measurements of the velocity fields within vertical and horizontal planes at different locations in test bundle have been produced using advanced laser-based techniques. The pressure at different axial and azimuthal locations in the bundle has been measured within a wide Reynolds number range to investigate laminar, transitional, and turbulent flow regimes. In this article new high-resolution measurements of the velocity fields and turbulent characteristics within a totally blocked interior subchannel are presented. The time-resolved particle image velocimetry (TR-PIV) measurements have been performed within the interior subchannel of the wire wrapped fuel bundle, under the presence of a localized, total blockage of one of the subchannels near the center pin. From the obtained velocity fields the first and second-order flow statistics, such as mean velocity, root-mean-square fluctuating velocity, and Reynolds stress, are computed and presented. Spectral analysis was performed to the fluctuating velocity and the vortex shedding frequency was found at St=0.16. Finally, proper orthogonal decomposition (POD) analysis was applied to the instantaneous velocity fields to extract the coherent flow structures in the flow region downstream of the blockage. The experimental results produced not only provide a better understanding of the flow behaviors under a channel blockage, but also support the validation of commercial and advanced Computational Fluid Dynamics (CFD) codes with a unique set of experimental data.
| Original language | English |
|---|---|
| Article number | 110234 |
| Journal | Nuclear Engineering and Design |
| Volume | 353 |
| DOIs | |
| State | Published - Nov 2019 |
| Externally published | Yes |
Funding
Previous studies of Shams et al. (2015), Nguyen et al. (2017, 2018a), Goth et al. (2018a,b), and Brockmeyer et al. (2017) have shown 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. Characterization and understanding of the effects of channel blockage on flow mixing characteristics are of particular interest in the interior subchannels of the wire wrapped fuel bundle ( Nguyen et al., 2019 ). 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 development sponsored by the US Department of Energy (DOE). The experimental facility is built and employed matched-index-of-refraction (MIR) techniques and laser diagnostic velocity measurement techniques, such as time-resolved particle image/tracking velocimetry (TR-PIV/PTV) ( Nguyen et al., 2017, 2019; Goth et al., 2018b ) and stereoscopic PIV (TR-SPIV) ( Nguyen et al., 2018a ). The result of these experimental activities will be a high-fidelity experimental database of pressure ( Vaghetto et al., 0311 ) and flow field measurements that will be suitable for validating CFD codes Goth et al. (2018a) . This research is financially supported by the U.S. Department of Energy , NEUP project and under a contract DE-NE0008652 . The authors gratefully acknowledge Jake Pettyjohn, Jadyn Reis, and Blaze Boyed (Texas A&M) for their support with the experimental measurements.
| Funders | Funder number |
|---|---|
| US Department of Energy | |
| U.S. Department of Energy | |
| Nuclear Energy University Program | DE-NE0008652 |