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Research Papers

Benchmark Experiments for Steady-State Natural Convection in Fuel Rod Bundles

[+] Author and Article Information
Kyle L. Jones

Department of Mechanical and
Aerospace Engineering,
Utah State University,
Logan, UT 84322
e-mail: kyle.jones@aggiemail.usu.edu

Barton L. Smith

Professor
Fellow ASME
Department of Mechanical and
Aerospace Engineering,
Utah State University,
Logan, UT 84322
e-mail: barton.smith@usu.edu

Manuscript received May 26, 2016; final manuscript received February 28, 2017; published online May 22, 2017. Assoc. Editor: Kevin Dowding.

J. Verif. Valid. Uncert 2(2), 021001 (May 22, 2017) (13 pages) Paper No: VVUQ-16-1015; doi: 10.1115/1.4036496 History: Received May 26, 2016; Revised February 28, 2017

Natural convection is a phenomenon in which fluid flow surrounding a body is induced by a change in density due to the temperature difference between the body and fluid. After removal from the pressurized water reactor (PWR), decay heat is removed from nuclear fuel bundles by natural convection in spent fuel pools for up to several years. Once the fuel bundles have cooled sufficiently, they are removed from fuel pools and placed in dry storage casks for long-term disposal. Little is known about the convective effects that occur inside the rod bundles under dry-storage conditions. Simulations may provide further insight into spent-fuel dry storage, but the models used must be evaluated to determine their accuracy using validation methods. The present study investigates natural convection in a 2 × 2 fuel rod model in order to provide validation data. The four heated aluminum rods are suspended in an open-circuit wind tunnel. Boundary conditions (BCs) have been measured and uncertainties calculated to provide necessary quantities to successfully conduct a validation exercise. System response quantities (SRQs) have been measured for comparing the simulation output to the experiment. Stereoscopic particle image velocimetry (SPIV) was used to nonintrusively measure three-component velocity fields. Two constant-heat-flux rod surface conditions are presented, 400 W/m2 and 700 W/m2, resulting in Rayleigh numbers of 4.5 × 109 and 5.5 × 109 and Reynolds numbers of 3450 and 4600, respectively. Uncertainty for all the measured variables is reported.

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References

Figures

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Fig. 1

The validation hierarchy and their descriptions as presented in Ref. [3]

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Fig. 2

Spectrum of difficulty to measure or acquire an arbitrary SRQ, y(x), adapted from Ref. [5]

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Fig. 3

A schematic of the wind tunnel showing the major components used in this study

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Fig. 4

Surface treatment of the leading edge of the fuel rod assembly. Dark surfaces represent polished aluminum, and light surfaces represent nickel plating.

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Fig. 5

Surface treatment of the trailing edge of the fuel rod assembly. Dark surfaces represent polished aluminum, and light surfaces represent nickel plating.

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Fig. 6

Inlet view of the test section with several important features labeled. The “border” is the frame used to maintain the grid spacer shape. It is embedded in the test section walls such that the walls themselves are smooth.

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Fig. 7

Locations in the xy-directions of the PIV fields of view for SRQ data acquisition. The coordinate system is shown fordirectional reference only and does not correspond to theactual location of the origin. The fields of view on the x =−0.060 m plane are centered at y = 0.152 m and y = 0.197 m. The field of view on the x = 0 plane is centered at y = 0.152 m.

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Fig. 8

A photograph of the PIV setup used to acquire inlet velocity profiles. The laser is fired in a horizontal sheet from the bottom left corner of the image.

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Fig. 9

A photograph of the PIV setup used to acquire SRQ velocity measurements. The camera lenses are shown in the upper right and lower right corners with the cameras out of frame. The laser is fired in a vertical sheet from the left of the image.

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Fig. 10

Contour plot of the test section time-averaged inflow measurement for the Natural400 case. The first contour level begins at 0 m/s, and the increment is 0.0125 m/s. The arrow indicates increasing contour levels, and the dashed line represents the location of the line profile in Fig. 12.

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Fig. 11

Inlet velocity profile at the test section centerline (x = 0 m) for the Natural400 case. The location of the profile is shown as a dashed line in Fig. 11. The velocity used for calculating turbulence intensity was w¯bulk=0.2083 m/s.

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Fig. 12

Contour plot of the test section time-averaged inflow measurement for the Natural700 case. The first contour level begins at 0 m/s, and the increment is 0.0175 m/s. The arrow indicates increasing contour levels, and the dashed line represents the location of the line profile in Fig. 14.

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Fig. 13

Inlet velocity profile at the test section centerline (x = 0 m) for the Natural700 case. The location of the profile is shown as a dashed line in Fig. 13. The velocity used for calculating turbulence intensity was w¯bulk=0.2748 m/s.

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Fig. 14

Locations in the yz-plane of the PIV viewing windows for SRQ data acquisition. The fields of view on the x =−0.060 m plane arecentered at y = 0.152 m and y = 0.197 m. The fields of view on the x = 0 m plane are aligned in the y- and z-directions with the fields of view at y = 0.152 m.

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Fig. 22

Velocity profile along y-direction for x = −0.06 m at four z-positions indicated on each plot for the Natural700 case. The relative locations of the swirl elements in the y-position (not to scale in z) are shown in the background of each figure. Uncertainties are found in the corresponding data files for download.

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Fig. 21

Velocity profile along y-direction for x = 0 m at four z-positions indicated on each plot for the Natural700 case. Uncertainties are found in the corresponding data files for download.

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Fig. 20

Outlet fluid temperatures at z = 2 m for the Natural700 case. The contour scale begins at θ = 0 and has an increment of 0.008. The arrow indicates the direction of increasing temperature. The TCs were arranged in a 4 × 4 sq grid and were evenly spaced across the test section outlet (61 mm apart in the x and y directions). TC uncertainty in terms of θ was approximately ±0.0047.

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Fig. 19

Outlet fluid temperatures at z = 2 m for the Natural400 case. The contour scale begins at θ = 0 and has an increment of 0.008. The arrow indicates the direction of increasing temperature. The TCs were arranged in a 4 × 4 sq grid and were evenly spaced across the test section outlet (61 mm apart in the x- and y-directions). TC uncertainty in terms of θ was approximately ±0.0046.

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Fig. 18

Wall temperatures in the streamwise direction for the Natural700 case

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Fig. 17

Wall temperatures in the streamwise direction for the Natural400 case

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Fig. 16

Rod temperatures in the streamwise direction for the Natural700 case

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Fig. 15

Rod temperatures in the streamwise direction for the Natural400 case

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