pdf 5.5 energy removal from the core
TRANSCRIPT
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1
A Look at Nuclear Scienceand Technology
Larry Foulke
Module 5.5
Energy removal from the core
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Nuclear Engineering Program
Constraints
Least Favorable Local Temperatures &
Coolant Flows Must Be Accommodated Cant Control to Average Parameters
Must Assess Worst-Case Core Conditions
Normal Operation Potential Energy Removal Degradation
Transient & Accident Conditions
Reactor Energy Removal
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Thermal-Hydraulic Analysis
Consider Global Core Power Distributions
Fuel and Clad and Coolant Temperatures
Coolant & Moderator Feedbacks
Local Element Power Density
Fuel-Pin Temperature Distribution
Coolant Flow Conditions
Establish Operating Limits to Prevent Melting
Reactor Energy Removal
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Power Density Peak-to-Average
Power-Shaping (Peak-Reduction) Techniques Reflector
Enrichment Zoning Example: Two Different (Higher/Lower)
Homogeneous EnrichmentBatches
Multiple-Batch Fuel Management
Power Distribution
Fmax(
r
)=
Pmax(r)
P(r)=max(r)
(r)= unitless
,want
itclose
to
1.0
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Calvert Cliffs Assembly Inlet Temp: 560 K (~287 C)
Pressure: 15 Mpa (~2235 psi)
Flow Rate: 103.63 kg/s
50 axial segments of 7 cm
17,850 Thermal Regions
Four control rod locations
One instrument tube (center)
Image Source: See Note 1
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Axial Location (cm)
Temperature(
K)
Calvert Cliffs Assembly Axial Temperature Profile (Fuel & Coolant)
Fuel Centerline Temperature
Coolant Temperature
Average Fuel Temperature
Image Source: See Note 1
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AxialPosition(cm)
Tempera
ture(
K)
Calvert Cliffs Assembly Axial Fuel & Coolant Temperature Distributions
Image Source: See Note 1
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AxialPosition(cm)
Tempera
ture(
K)
Calvert Cliffs Assembly Axial Coolant Temperature Distributions
Image Source: See Note 1
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Coolant Temperature Rise Factor
Temperature Parameters
Heat Flux From Surrounding Pins
Coolant Heat Capacity Inlet Temperature
Pressure
FH
(r) =temperature rise in channel at r
temperature rise in core average channel
Peaking Factors
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Nuclear Engineering Program
Reflector Peaking EffectPmaxPmax
PavePave
Image Source: See Note 2
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Nuclear Engineering Program
Enrichment Zoning Effect
Same peak, but raised average
Image Source: See Note 2
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Nuclear Engineering Program
Fuel Pin Heat Transport
We have described the relative powerdistribution on a per fuel pin (or per channel)
basis in the core; now lets consider localheating within a single fuel pin.
Lets cover fuel pin heat transport in aqualitative way.
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Nuclear Engineering Program
Fuel Pin Temperatures depend upon:
Fission Source Distribution
Fuel Pin Heat Transport Properties
Coolant Heat Sink
Fuel Pin Geometry
Fuel Pellet
Gap
Cladding Tube
Coolant
Fuel Pin Heat Transport
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rFOrFcl= 0
rCI
rCO
Fuel Pin Radial Cross Section
Image Source: See Note 2
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Fuel Pin Heat Transport
Assume that fissions occur uniformly throughout thefuel region, therefore heat is produced uniformly in fuelregion.
Heat generated in the fuel must pass through all of thefuel element layers before it is absorbed in the coolant.
Fuel: Conduction (with uniform heat source)
Gap: Convection
Clad: Conduction
Coolant: Convection
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Nuclear Engineering Program
200
300
400
500
600
700
800
0.0 0.2 0.4 0.6 0.8
Temperature
,C
Fuel Pin Radial Distance, cm
Fuel
Gap
CladCoolant
PWR Fuel-Pin Temperature Profile
Image Source: See Note 3
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Nuclear Engineering Program
Nuclear Limits
We want to set operating limits so thatthe maximum centerline fuel temperature
at the hottest axial position of the hottestfuel rod remains below the fuel meltingtemperature.
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Departure from Nucleate Boiling (DNB)PWR BWR
Image Source: See Note 2
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Reactor Control
Maximum Hot-Spot
Normal Operation Anticipated Transients
Reactivity Control
Control Rods
Insertion Increases Peaking
Radial
Axial
Feedbacks
Design Considerations
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Axial
Flux w/
ControlRods
Image Source: See Note 2
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Radial Flux w/ Control Rods
Image Source: See Note 2
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1. Reprinted with permission from David Griesheimer, DF Gill, J WLane, DL Aumiller, An Integrated Thermal Hydraulic FeedbackMethod for Monte Carlo Reactor Calculations, Presented at theInternational Conference on the Physics of Reactors (PHYSOR
2010).2. Adapted and reprinted with permission from the American
Nuclear Society. Nuclear Engineering Theory and Technologyof Commercial Nuclear Powerby Ronald Allen Knief, 2ndEdition. Copyright 2008 by the American Nuclear Society, La
Grange Park, Illinois. Figure 7-1 (slide 10), 7-2 (slide 11), 7-3(slide 14), 7-7 (slide 18), 7-9 (slide 20), and 7-10 (slide 21).
3. Reprinted with permission from Ron Knief.
Image Source Notes