Stratified Flows in Advanced LWR Passive Safety Systems

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Advanced Reactor Passive Emergency Core Cooling
System Stratified Flow Experiments
R. Schultz Idaho National Lab Idaho Falls, ID, USA
H. Kadakia B. Williams Idaho State
University Pocatello, ID, USA
J. C. P. Liou University of Idaho Moscow, ID, USA
IAEAs Second RCM on Natural Circulation 29 Aug
2 Sept, 2005 Corvallis, OR, USA
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A NEER Project

• Develop educational materials for nuclear
  engineering curricula that provide the basis for
  teaching students the principles that govern
  stratified flow
• Provide validation data that can be used as the
  basis for measuring whether existing software
  tools are adequate for calculating free-surface
  stratified flow

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Phenomena of Interest

• Steam over subcooled water has potential for
  condensation-induced water hammer (CIWH)
• Large thermal gradients also potential problem
• However, steam over subcooled water covered by
  saturated water may reduce CIWH induced loadings
  and CIWH

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Collaboration between UI and ISU

• Build portable visual instructional demonstration
  units for various stratified flow scenarios
• Using visual and inexpensive experiments to
  explore test parameters and experimental designs
  for rigorous (expensive) condensing experiments
• Obtain credible data to support analytical models
  that govern stratified flow in pipes
• Using developed models, investigate practical
  ways to eliminate CIWH in passive safety systems

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Portable Demo Unit (UI)
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Wedge and Surge Video
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Analysis
h1, ?1
a0
R
a
Q
h2, ?2
x
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Profile of the Interface
a0 a or a0 at x 0
a0 can be held constant during integration
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Critical Flow/Densimetric Froude Number
Intrusion of lighter fluid is prevented if the
densimetric Froude number is unity
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Experimental results
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Theory-Data Comparison
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Wedge Length vs Densimetric Froude Number
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Summary of UI Work

• Stratified flow is relevant to passive cooling
• A lighter (warmer) liquid can intrude into the
  cold leg forming a wedge over a heavier (colder)
  liquid
• The two-layer stratified flow is analyzed using
  momentum conservation principle
• Theory matches experimental observations
• The extent of intrusion and layer thickness can
  be reliably predicted

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Condensing Test Loop (ISU)

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Condensing Test Loop - 2
Test Section Supply
Receiver
Heat Exchanger
Cold Water Pump
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Condensing Test Loop - 3
Hot Side Pressurizer
65 kW Heater (insulated)
Insulated Piping (Hot Loop)
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Horizontal Transparent Test Section
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Horizontal Transparent Test Section - 2
Glass Pipe Sections

• Note We have 4 different lengths of glass pipe
  sections
• Range in length from 15 cm to 40 cm
• Can arrange with 4 instrument washers to create a
  variety of configurations

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Instrumentation

• Over 100 channels
• Two sampling frequencies
• High frequency for dynamic pressure transducers
• Will be using Particle Tracking Velocimeter (PTV)
• Will calibrate PTV with flow loop
• High-speed camera footage available

• What we can measure in test section
• Variable, radial T/C probe
• Fixed T/C rake
• ?T around pipe
• Differential dynamic pressures
• Liquid level
• Subcooled water velocity
• Can we measure?
• Steam velocity
• Saturated layer velocity

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Remaining Tasks

• System fabrication completed by mid September
  2005
• Component/system check-out test completed by mid
  October 2005
• Then test and take data!
• Enlarge existing CIWH data base
• Validation of computer codes