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DavisDavis--Besse Besse Nuclear Power StationNuclear Power Station
November 26, 2002November 26, 2002
1
Davis-Besse Nuclear Power Station
New Containment Emergency Sump Design
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DavisDavis--Besse Besse Nuclear Power StationNuclear Power Station
November 26, 2002November 26, 2002
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Opening Remarks . . . . . . . . . . ………………Gary Leidich
New Containment Emergency Sump ………... Jim Powers
Closing Comments………………………….. Gary Leidich
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DavisDavis--Besse Besse Nuclear Power StationNuclear Power Station
November 26, 2002November 26, 2002
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Gary Leidich,Executive Vice President - FENOC
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DavisDavis--Besse Besse Nuclear Power StationNuclear Power Station
November 26, 2002November 26, 2002
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•Present the new Containment Sump Design/Modification at Davis-Besse
• Obtain NRC comments on Davis-Besse approach
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DavisDavis--Besse Besse Nuclear Power StationNuclear Power Station
November 26, 2002November 26, 2002
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CEO of FirstEnergy has set the standard of returning
Davis-Besse back to service in a safe
and reliable manner
We must do the job right the first time and regain the
confidence of our customers, regulators, and investors in our
nuclear program
We are committed to meeting this challenge
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DavisDavis--Besse Besse Nuclear Power StationNuclear Power Station
November 26, 2002November 26, 2002
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Reactor Head Reactor Head Resolution Plan Resolution Plan
Bob SchrauderBob Schrauder
Program Compliance Program Compliance PlanPlan
Jim PowersJim Powers
Containment Health Containment Health Assurance PlanAssurance Plan
Randy FastRandy Fast
Restart Test PlanRestart Test PlanRandy FastRandy Fast
Management and Management and Human Performance Human Performance
Excellence PlanExcellence Plan
Lew MyersLew Myers
System Health System Health Assurance PlanAssurance Plan
Jim PowersJim Powers
Restart Action PlanRestart Action Plan
Lew Lew MyersMyers
Restart Overview PanelRestart Overview Panel
Return to Service PlanReturn to Service Plan
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November 26, 2002November 26, 2002
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• New Containment Emergency Sump Design is part of the Containment Health Assurance Building Blockfrom the Davis-Besse Return to Service Plan
• Restore operability as well as add margin to Containment Emergency Sump
• Containment Emergency Sump Intake Screen is on the Davis-Besse IMC 0350 Restart List
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DavisDavis--Besse Besse Nuclear Power StationNuclear Power Station
November 26, 2002November 26, 2002
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Jim PowersDirector - Nuclear Engineering
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• 10CFR50.46 (b)(5) and Appendix A to 10CFR50, Criterion 35 require long term emergency cooling
• Strainer protects Low Pressure Injection (LPI), High Pressure Injection (HPI) and Containment Spray(CS) systems from debris intrusion during a LOCA event
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• Nominally 14 ft. X 5 ft. X 2 ft. (L x W x H)• Approximately 50 sq. ft. available (vertical) surface area• 1/4” square screen openings, galvanized wire - 53.4%
open area• Vortex Suppression with existing grating qualified by
testing
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ELEV. 565
LC
TRASH RACK GATE
TRASHRACKGATE
ContainmentSump Area
ReactorVessel
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November 26, 2002November 26, 2002
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Increase Net Positive Suction Head (NPSH) margin for Emergency Core Cooling System under design
basis accident conditions
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• Conduct reviews of the design basis of the sump
• Identify debris sources (NEI 02-01 guidance):– Containment walkdowns,– Coating evaluations, and, – Foreign material evaluations
• Evaluate the transport of debris to the sump screen
• Develop corrective actions to reduce debris sources
• Develop plan to significantly increase sump intake surface area
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November 26, 2002November 26, 2002
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• Flow Rates– Low Pressure Injection (LPI) 4000 gpm per train– Containment Spray (CS) 1500 gpm per train– Total Strainer Design Flow 11,000 gpm
• Minimum Water Level– Small Break LOCA Elevation 566.76 ft. (1.76 ft. above floor)– Limiting Large Break LOCA Elevation 566.83 ft. (1.83 ft. above floor)
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• Net Positive Suction Head (NPSH) Margin(NPSH Margin = NPSH Available - NPSH Required)– Approximately 3 feet for LPI (before adding strainer/debris head loss)– Approximately 5 feet for CS (before adding strainer/debris head loss)
Note: No credit taken for containment over pressure above vapor pressure of water (Licensing Basis)
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• Increase NPSH available• Increase strainer surface area
– Lower approach velocity– Lower head loss
• Increase margin • Design based on conservative approach
for debris generation, transport and head loss
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• Available surface area ~ 1200 sq. ft. – Upper strainer ~ 400 sq. ft.– Lower Strainer ~ 800 sq. ft.
• Strainer and supporting structure made from stainless steel
• Strainer made from 10 gauge perforated plate with 3/16” diameter holes with 41% open area
• Strainer designed to ASME Section III, Subsection NF Code to withstand 5 psi differential pressure
• Vortex suppression designed to the guidance of RG 1.82, Rev.2
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Tunnel AccessSump Access
Lower StrainerTunnel Floor 537’ Elevation
Containment 565’ Elevation
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Containment Floor, 565’elev. “Upper Strainer”
“LowerStrainer”
Reactor Annulus
Incore Tunnel Stairs
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• New design facilitates two controlling pipe break scenarios
– Hot Leg break at top of OTSG (Case I)– Hot Leg break at RPV (Case II)
• Case I generates largest volume of debris– Both upper and lower strainer sections available
• Case II generates smaller volume of debris– Upper strainer section available– No credit taken for lower strainer due to potential
damage from pipe break blowdown
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• NEI 02-01, “Condition Assessment Guideline: Debris Sources Inside Containment”
– Conducted field walkdowns to collect plant specific data
• Methodology used:– BWROG Utility Resolution Guidance methodology
(plus NRC comments)– Conservative Zone of Influence (ZOI)– 100% destruction of fibrous insulation in ZOI– 42% destruction of Reflective Metal Insulation
(RMI) in ZOI• Unqualified Coatings
– Assumed 100% failure under Design Basis Accident
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• Pipe Breaks– Loss-of-Coolant-Accident (LOCA) locations
per NRC’s Standard Review Plan (MEB 3-1)– Pipe breaks on Reactor Coolant System
included– Critical pipe breaks
–Hot Leg break at top of OSTG (Case I)–Hot Leg break at RPV (Case II)
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Debris Type Case ICase II
Fiber 42 ft3 3ft3RMI Foils 67,700 ft2 11,900 ft2
Dust, Dirt, Concrete 475 lbs.Rust 159 lbs.
CoatingsInorganic Zinc 9620 ft2
(577 lbs.)Epoxy 9620 ft2 (481 lbs.)Alkyds 3500 ft2 (105 lbs.)
(Preliminary Results)
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Sample Davis-Besse Debris Transport Logic Tree (Per NUREG/CR-6369) (RMI Transport)
B r e a k T y p e a n d L o c a t i o n D e b r i s S i z e B l o w d o w n
T r a n s p o r t
C o n t a i n m e n t S p r a y W a s h d o w n
T r a n s p o r t
R e c i r c u l a t i o n P h a s eT r a n s p o r t F i n a l L o c a t i o n
U p p e r C o n t a i n m e n t
S m a l l C o n t a i n m e n t F l o o r
R e a c t o r A n n u l u s
L a r g e
L B L O C AR V N o z z l e
B r e a k
C o n t a i n m e n tF l o o r
R e a c t o r A n n u l u s
S e d i m e n t
C o n t a i n m e n tF l o o r
E C C S S u m p
S e d i m e n t
I n c o r e T u n n e l
E C C S S u m p
S e d i m e n t
I n c o r e T u n n e l
E C C S S u m p
S e d i m e n t
U p p e r C o n t a i n m e n t
U p p e r S t r a i n e r s
C o n t a i n m e n t F l o o r
L o w e r S t r a i n e r s
I n c o r e T u n n e l F l o o r
U p p e r S t r a i n e r s
C o n t a i n m e n t F l o o r
L o w e r S t r a i n e r s
I n c o r e T u n n e l F l o o r
U p p e r S t r a i n e r s
C o n t a i n m e n t F l o o r
R e s u s p e n d
S e d i m e n t
U p p e r S t r a i n e r s
A n n u l u s F l o o r
R e s u s p e n d
S e d i m e n t
L o w e r S t r a i n e r s
A n n u l u s F l o o r
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• All Significant flow paths modeled
• Interactions between access tunnels and containment floor
• Strainers incorporated• Models movement and
settling of debris• Computational cells
~ 2,000,000
CFD Modeling of Davis-Besse Incore Tunnel
Tunnel AccessSump Access
Lower Strainer
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• All significant flow obstructions modeled
• Interactions between containment floor and incore tunnel
• Emergency sump and strainers incorporated
• Movement and settling of debris is modeled
• Computational cells ~ 500,000
CFD Modeling of Davis-Besse Containment Floor
Tunnel AccessSump Access (Upper Strainer)
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• Red: Turbulence > RMI debris suspended
• Break on lower right• Flow: 11,000 gpm• Pool height: 2 feet• Elevation: +1.5 inches
above floor level
CFD Analysis of Davis-Besse Containment Floor
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• New strainer features greatly increased surface area
• Preliminary calculations indicate that Emergency Core Cooling System pumps will have NPSH margin under Design Basis Accident debris loading
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Gary Leidich,Executive Vice President - FENOC