United States Nuclear Regulatory Commission - Protecting People and the Environment

RBHT Reflood Heat Transfer Experiments Data and Analysis (NUREG/CR-6980)

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Publication Information

Manuscript Completed: January 2011
Date Published:
April 2012

Prepared by:
L. E. Hochreiter
Fan-Bill Cheung
T. F. Lin
J. P. Spring
S. Ergun
A. Sridharan
A. Ireland
E. R. Rosal (Applied Research Laboratory)

The Pennsylvania State University
University Park, PA 16802

K. Tien, NRC Project Manager

NRC Job Code N6154

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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A total of 25 valid bottom reflood heat transfer experiments have been performed in the Pennsylvania State University/U.S. Nuclear Regulatory Commission Rod Bundle Heat Transfer (RBHT) Test Facility to examine the effects of both dispersed flow film boiling and inverted annular film boiling in rod bundle geometry. The RBHT Test Facility had a full length, 3.66 m (12 ft), 7x7 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 had a top skewed power shape with a peak to average power of 1.5 at the 2.77 m (9.08 ft) elevation. The ranges of conditions for the experiments were pressures from 138 to 414 kPa (20 to 60 psia), flooding rates from 0.0254 to 0.1524 m/s (1 to 6 in/s), and initial peak clad temperatures from 1033 to 1144 degrees K (1400 to 1600 degrees F), inlet subcooling from 11 to 83 degrees K (20 to 150 degrees F), and peak powers of 1.32 to 2.31 kW/m (0.4 to 0.7 kW/ft). The experiments were performed using a constant power rather than simulating the reactor decay power. The use of a constant bundle power extended the reflood transient several hundred seconds and resulted in quasi-steady film boiling over the majority of the bundle length. There were approximately 500 channels of transient data recorded for each test including the bundle power, heater rod temperatures, upper plenum pressure, inlet flow rate, inlet water subcooling, superheated vapor temperatures in the bundle, spacer grid temperatures, liquid carryover of the bundle, and the detailed axial bundle pressure drop. Transient mass balances were typically within five percent for the low flooding rate experiments, and larger for the higher flooding rate experiments. The experimental data has been qualified and submitted to the U.S. Nuclear Regulatory Commission data bank for analysis and computer code validation.

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