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7/27/2019 PDF-6.3 Safety Systems and Plant Tour
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1
A Look at Nuclear Scienceand Technology
Larry Foulke
Module 6.3
Safety Systems and Plant Tour
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Nuclear Engineering Program
PWR Control Rod
Spider
Image Source: See Note 1
Full-Length Control Rods (inyellow) Mounted to Drives abovew/ Electromagnets
Fuel rods (in red) contain UO2pellets inserted into a Zircaloy-4tube
Spring clip grids provide supportfor the fuel rods in the fuelassembly
Top and bottom nozzles of the fuelassembly control the coolant flowdistribution and serve as structuralelements
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Nuclear Engineering Program
SCRAM / TRIP Full-Length Control Rods Mounted to Drives
w/ Electromagnets
Loss-of-Current Full Insertion
PWR Protective System
Trip / Protective Signals High Flux
High Temperature
High Pressure
Manual
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Nuclear Engineering Program
PWR (W)
Plant
Protection
System
Image Source: See Note 1
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Nuclear Engineering Program
Trip Signals
Redundancy
Interlocks for Power Changes
Reliability
Avoid Spurious Trips
Two-Out-of-Four Logic Same / Different Parameter
Consistent w/ Need for Repair
Fail-Safe Design
PWR Protective System
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Nuclear Engineering Program
7/27/2019 PDF-6.3 Safety Systems and Plant Tour
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Engineered Safety Features (ESFs)
Image Source: See Note 3
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Engineered Safety Features
Reactor Trip (RT) - 1st function
Control rods
Electromagnets / gravity insertion
Protective system / redundant sensors
Boric acid w/ emergency coolant injection
Rods alone may not shut core down on reflood
Boric acid concentration compensates for rodfailure
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Engineered Safety Features
Emergency core cooling (ECC) - 2ndfunction
Break location
Multiple loops
Distributed insertion points
Redundant / diverse
High-pressure injection (HPI) Low-pressure injection (LPI)
Accumulator
On-site / off-site power supplies
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Nuclear Engineering Program
Engineered Safety Features
Post-accident heat removal (PAHR) - 3rdfunction Large break - Initially cool ECCS water
Small break Forced circulation
Single-phase natural circulation
Two-phase natural circulation (reflux)
Feed and bleed HPI/LPI water into core
Steam discharged through Pzr PORV / safeties
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Nuclear Engineering Program
Engineered Safety Features
Post-accident radioactivity removal(PARR) - 4th function
Charcoal adsorbers for fission products
High-efficiency particulate air (HEPA) Filters
Reactive coatings for passive removal ofhalides
Containment water sprays
wash reactive products from atmosphere
Additives for pH control
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Nuclear Engineering Program
Engineered Safety Features
Containment integrity (CI) - 5th function
Isolation valves on containment buildingpenetrations
Automatic on overpressure signal
Main steam line valve design for quick close
Containment building
Inner leak-tight steel liner
Reinforced concrete shell
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Nuclear Engineering Program
Engineered Safety Features
Image Source: See Note 4
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Nuclear Engineering Program
PWR Engineered Safety Features
Image Source: See Note 3
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Nuclear Engineering Program
Engineered Safety Features (ESFs)
Image Source: See Note 3
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Nuclear Engineering Program
Safety Design Principles
Multiple barriers
Defense-in-depth
Protection / safety functions
Redundancy
Diversity
Physical separation
Fail-safe principle
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Nuclear Engineering Program
Safety Design Principles
Redundancy
More than minimum number of components
Design to tolerate component failure
Diversity
Protects against common-mode failure
Control rods and boric acid injection
Aux feed pumps - both electric and steam driven
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Nuclear Engineering Program
Safety Design Principles
Physical separation
Protects against simultaneous loss
Distance / physical barriers
Combination redundant / diverse / separated
Example: emergency electric power supply
Diesel generators
Multiple ties to off-site electrical grid Storage battery systems
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Nuclear Engineering Program
Safety Design Principles
Fail-safe principle
Components / systems automatically into safestcondition w/ failure or power loss
Examples: PWR rods - electromagnetic and gravity
BWR rods - solenoid / gas pressure
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1. Reprinted with permission from Westinghouse. Course:The Westinghouse Pressurized Water Reactor NuclearPower Plant (The Masche Book).
2. Reprinted with permission from Nuclear Engineering
International UK. Source: World Nuclear IndustryHandbook 2013
3. Adapted with permission from the American NuclearSociety. Nuclear Engineering Theory and Technology ofCommercial Nuclear Powerby Ronald Allen Knief, 2nd
Edition. Copyright 2008 by the American Nuclear Society,La Grange Park, Illinois. Figure 14-1 (slides 7 and 15) and14-2 (slide 14).
4. Reprinted with permission from Nuclear Energy Institute.http://www.nei.org/corporatesite/media/filefolder/containm
ent wall construction.jpg
Image Source Notes
http://www.nei.org/corporatesite/media/filefolder/containment_wall_construction.jpghttp://www.nei.org/corporatesite/media/filefolder/containment_wall_construction.jpghttp://www.nei.org/corporatesite/media/filefolder/containment_wall_construction.jpghttp://www.nei.org/corporatesite/media/filefolder/containment_wall_construction.jpgRecommended