United States Nuclear Regulatory Commission - Protecting People and the Environment

Rod Bundle Heat Transfer Facility Steam Cooling with Droplet Injection Experiments Data Report (NUREG/CR-7192, Volume 2)

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Publication Information

Manuscript Completed: October 2014
Date Published: May 2015

Prepared by:
L.E. Hochreiter, F.B. Cheung, T.F. Lin, D.J. Miller, B.R. Lowery

The Pennsylvania State University
University Park, PA 16802

Prepared for:
Division of Systems Analysis
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

K. Tien, Project Manager

NRC Job Code N6154

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Abstract

As part of the Nuclear Regulatory Commission safety analysis computer code development efforts, the Rod Bundle Heat Transfer (RBHT) test facility has been designed and constructed at The Pennsylvania State University. The test series described in this report is the steam cooling tests with droplet injection. A total of 85 steady-state steam cooling experiments with prescribed droplet injection was performed in the RBHT. The purpose of the experiments was to examine steady-state dispersed flow film boiling in prototypical rod bundle geometry for computer code model development and validation.

The Rod Bundle Heat Transfer facility is a full length, 3.66 m (12 ft.), 7 by 7 rod array with typical Pressurized Water Reactor rod diameters of 9.49 mm (0.374 in.) and a rod pitch of 12.59 mm (0.496 in.). The heater rods have a top skewed power shape with a peak to average power of 1.5 at the 2.74 m (9 ft.) elevation. The RBHT facility has been designed using prototypical mixing vane spacer grids.

The bundle inlet steam Reynolds number ranged from 2000 to 15,000 with most of the experiments at the lower Reynolds number range. The droplets were injected upward in the center of the sub-channels at the 1.295 m (51 in.) elevation using two or four injection tubes. The injection tubes used a single row, linear hole pattern of four holes per sub-channel and four sub-channels per tube in the center of the bundle. One additional hole was located at the center of the rod gap location to minimize the chance of local boiling in the injection tube. The hole sizes used were 0.381 mm (0.015 in.) and 0.254 mm (0.01 in.). The injection tubes were bench tested before the bundle tests to optimize the performance of the liquid jets such that the injected droplets would flow upwards in the center of the sub-channel. The droplet sizes issuing from the holes were also measured. The selected hole sizes would produce drops that were typical of the drop sizes observed in the RBHT and FLECHT-SEASET reflood experiments.

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