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PrairieIslandNPEm Resource

From: Eckholt, Gene F. [Gene.Eckholt@xenuclear.com]Sent: Friday, November 06, 2009 10:15 AMTo: Plasse, RichardSubject: Draft Prairie Island ACRS Full Committee PresentationAttachments: ACRS Full Committee Presentation - NRC Draft 11-6-09.pdf

Rick Here is a preliminary version of our presentation to the full ACRS. This document is still subject to change and refinement as we go through our dry run process. Let me know if you have any questions. Gene Eckholt Project Manager License Renewal Project Prairie Island Nuclear Generating Plant Phone: 651-388-1121 ext. 4137

Hearing Identifier: Prairie_Island_NonPublic Email Number: 1105 Mail Envelope Properties (71AC1869DEB82E47AAC75C450F60546A0BEAD6A322) Subject: Draft Prairie Island ACRS Full Committee Presentation Sent Date: 11/6/2009 10:14:57 AM Received Date: 11/6/2009 10:18:38 AM From: Eckholt, Gene F. Created By: Gene.Eckholt@xenuclear.com Recipients: "Plasse, Richard" <Richard.Plasse@nrc.gov> Tracking Status: None Post Office: enex04 Files Size Date & Time MESSAGE 352 11/6/2009 10:18:38 AM ACRS Full Committee Presentation - NRC Draft 11-6-09.pdf 1045347 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date: Recipients Received:

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Prairie Island Nuclear Generating PlantACRS License Renewal Meeting

December 3, 2009

2

Introductions

Mark Schimmel – Site Vice PresidentGene Eckholt – License Renewal Project ManagerSteve Skoyen – Engineering Programs ManagerLicense Renewal Project Team and Subject Matter Experts

3

Agenda

IntroductionsBackgroundACRS LR Subcommittee Follow-Up Items

Refueling Cavity LeakageUnderground Medium Voltage CablesCondensate Storage Tank Examinations

Questions

4

Background

Plant Owner and OperatorNorthern States Power Company – MinnesotaSubsidiary of Xcel Energy

LocationSE of Minneapolis-Saint Paul, MNOn Mississippi River

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Background

Construction Permits Issued - June 1968Operating Licenses Issued

Unit 1 - August 1973Unit 2 - October 1974

LRA Submitted – April 2008

6

Background

Two 2 - Loop PWR Units1650 MWt575 MWe (Gross) per Unit

Westinghouse - NSSS Pioneer Service & Engineering -Architect/EngineerOnce-Through Cooling Supplemented with Four Forced Draft Cooling Towers (Seasonal)Ultimate Heat Sink is Mississippi River via Cooling Water System

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Background

Containment DesignSteel Containment Vessel

1-1/2 inch Thick Bottom Head, 1-1/2 inch Thick Shell, 3/4 inch Thick Top Head3-1/2 inch Thick at ECCS Sump (Sump B) PenetrationsSA-516-70 Low Temperature Carbon Steel

Provides Primary Containment Lower Head Encased in Concrete5 foot Annular Gap Between Containment Vessel and Limited Leakage Reinforced Concrete Shield Building

ContainmentElevation

8

ACRS LR Subcommittee Follow-Up Items

Refueling Cavity Leakage

Underground Medium Voltage CablesCondensate Storage Tank Examinations

9

Refueling Cavity LeakageBackground

Intermittent Refueling Cavity Leakage Indications in Both Units Since Late 1980s Leak Rate of 1-2 Gallons per HourSeen in ECCS Sump and Regenerative Heat Exchanger RoomSealing Methods Have Stopped Leakage, but not Consistently

Refueling Cavity Leakage Path

Cavity Photo Overhead

Cavity Photo from NW

Leakage Seen in ECCS Sump and in Regenerative HX Room (below cavity)

ContainmentElevation

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Refueling Cavity LeakageLeak Locations

Root Cause Evaluation was Completed in April of 2009Sources of Leakage were Determined to be Embedment Plates for Reactor Vessel Internals Stands and Rod Control Cluster Assembly (RCCA) Change Fixture

12

Refueling Cavity LeakageLeak Locations

Typical Reactor Vessel Internals Stand Support Typical RCCA Change Fixture Support

13

Refueling Cavity LeakageRepair Method

Existing 1/4" thk stainless steel cavity liner

New seal weld between baseplate and embedment plate.

Existing cavity liner fillet weld to embedment plateExisting seal weld to

embedment plate not accessible. Failure of weld would result in leak.

Replace existing nuts with fabricated blind nuts seal welded to baseplate.

Side View

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Refueling Cavity LeakageFall 2009 Unit 1 Repairs

Reactor Vessel Internals Stands and RCCA Change Fixture Embedment Plates Repaired

Existing Nuts RemovedReplaced with Blind Nuts Blind Nuts Seal Welded to BaseplateSeal Weld Applied Between Baseplate and Embedment PlateWelds Examined by NDE

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Refueling Cavity LeakageFall 2009 Unit 1 Repairs

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Refueling Cavity LeakageFall 2009 Unit 1 Repair Results

Embedment Plate Repairs Eliminated that Leakage SourceECCS Sump

No Evidence of LeakageMinor Leakage from Regenerative Heat Exchanger Room Ceiling

Appeared After Cavity Flooded 14 DaysEstimated to be 0.05 Gallons per Hour

No Evidence Leakage is Reaching Containment Vessel

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Refueling Cavity LeakageFall 2009 Unit 1 Testing and Evaluation

Vacuum Box Testing of Reactor Cavity Liner Plate Seam Welds - No Leakage IdentifiedNDE of Fuel Transfer Tube Welds – No IndicationsEvaluation of Other Possible Leakage Sources

NDE of Liner to Embedment Plate Fillet WeldsOne Porosity IndicationWill be Repaired During Next Unit 1 Refueling Outage

RCCA Guide Box Embedment Plates

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Refueling Cavity Leakage2010 Unit 2 Corrective Actions

Repair of Reactor Vessel Internals Stands and RCCA Change Fixture Embedment PlatesRepair of RCCA Guide Box Embedment PlatesNDE of Fuel Transfer Tube WeldsVacuum Box Testing of Reactor Cavity Liner Plate Seam WeldsNDE of Liner to Embedment Plate Fillet Welds Other Repairs and Testing Resulting From Evaluation of 2009 Unit 1 Leakage

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Refueling Cavity Leakage2011 Unit 1 Corrective Actions

Repair of RCCA Guide Box Embedment PlatesRepair of Liner to Embedment Plate Fillet Weld Porosity Indication Other Repairs and Testing Resulting From Evaluation of 2009 Unit 1 and 2010 Unit 2 Repair Results

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Refueling Cavity LeakageMonitoring & Assessment

Ultrasonic and Visual Examinations of Containment Vessel

Unit 1 and 2 ECCS Sumps (Prior to 2009)Grout RemovedWall Thickness Measurements at or Above NominalNo Corrosion Identified.

Unit 1 ECCS Sump (Fall 2009)Grout RemovedWall Thickness Measurements at or Above NominalNo Corrosion of Rebar or Containment VesselNo Wet Areas or Leakage

Sump Section

Annulus Photo

ContainmentElevation

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Refueling Cavity LeakageMonitoring & Assessment

Unit 1 ECCS Sump Fall 2009

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Refueling Cavity LeakageMonitoring & Assessment

Ultrasonic and Visual Examinations of Containment Vessel (cont’d)

Unit 2 Annulus (2008)144 Wall Thickness MeasurementsAll Measurements at or Above Nominal

Unit 1 Annulus (2009)80 Wall Thickness Measurements 79 Locations at or Above NominalOne Location Below Nominal 1.5" thickness at 1.492"

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Refueling Cavity LeakageMonitoring & Assessment – Commitments

Removal of Concrete from Sump Below Reactor Vessel to Expose Containment Vessel

Next Outages Following Refueling Cavity RepairsInspect (VT and UT) Containment Vessel Petrographic Examination of Removed Concrete Evacuate any Water Observed

ContainmentElevation

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Refueling Cavity LeakageMonitoring & Assessment – Commitments

Removal of Concrete Sample Wetted by Borated Water Leakage from Refueling Cavity

Concrete will be Tested For Compression Strength and will Undergo Petrographic Examination

Monitor Areas Previously Exhibiting Leakage for Next Two Outages After Repairs to Confirm That Leakage has not Recurred

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Refueling Cavity LeakageLong Term Aging Management

Continue to Manage Aging of the Containment Structures and Vessel Using the Structures Monitoring Program and ASME Section XI, Subsection IWE Program Utilize Corrective Action Program for Evaluation and Correction of New Issues

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Refueling Cavity LeakageEvaluation of Potential Degradation

Evaluations have been performed for potential degradation of Steel Containment Vessel, Concrete and RebarEvaluations Concluded:

Containment Vessel Corrosion Behind Concrete in Areas Wetted by Refueling Cavity Leakage is Expected to be MinorNo Significant Effect on Reinforced Concrete That Has Been Wetted by Refueling Cavity Leakage

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Underground Medium Voltage CablesManhole Inspection

ACRS LR Subcommittee Questioned Adequacy of Two Year Manhole Inspection FrequencyInspection Frequency is Based on Actual Plant Experience, but not to Exceed Every Two YearsConsistent with GALL XI.E3One Manhole in Scope of License RenewalMultiple Inspections Since September of 2007 Have Shown no Signs of Water Intrusion or Accumulation

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Underground Medium Voltage CablesManhole Inspection

Design Precludes Water AccumulationFloor of Gravel and SandApproximately Ten Feet Above Water TableGrade Around Manhole Precludes Significant Rain Water Intrusion

Based on Manhole Design and Actual Plant Experience, Two Year Inspection Frequency is Considered Sufficient

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Underground Medium Voltage CablesImpact of Freeze/Thaw Conditions

Prairie Island Operating Experience was Reviewed for Evidence of Accelerated Cable Insulation Aging Related to Freeze/Thaw ConditionsThe Following Organizations were also Contacted:

Monticello Nuclear Generating PlantXcel Energy DistributionEPRINEI License Renewal Electrical Working Group

Accelerated Cable Insulation Aging Related to Freeze/Thaw Conditions has not Been Identified as an Issue

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Condensate Storage Tank Examinations

Aboveground Steel Tanks Program Included UT Inspection of the Bottom of 1 of the 3 Condensate Storage Tanks Prior to PEOACRS LR Subcommittee Felt That Inspection of Only 1 Tank to Assure Acceptability of all 3 Tanks was not Adequately SupportedLRA Change Submitted on August 7, 2009 Which Revised the Aboveground Steel Tanks Program to Include UT Inspection of the Bottom of all 3 Condensate Storage Tanks Prior to PEO

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Questions?

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Supporting Slides

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Refueling Cavity LeakagePath

Path to ECCS SumpUnder Refueling Cavity Liner Through Construction Joint Between Floor of Transfer Pit and Wall Behind Fuel Transfer Tube to Inner Wall of Containment VesselTravels Down and Horizontally, Between Containment Vessel and Concrete, to Low Point of Containment Vessel Bottom HeadSeeps Through Grout in ECCS Sump

Path to Regenerative Heat Exchanger RoomOnce Under Liner, Follows Cracks in the Concrete, Seeping Through the Ceiling and Walls of the Regenerative HX Room

ECCS Sump

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Origin

ECCSSumpSump C

Fuel Transfer Tube

Regen HX Room

Leak Paths ECCS Sump

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ECCS Sump Showing Grout

To 33 (Cont. 3D)

To 34 Insp.

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Shield Building Annulus

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Plant Electrical Distribution

X

1R

CT12

2R 1CT

161kV 13.8kV (#10)345kV TransmissionSystem

PlantSystem

Cooling Tower

CT11

2RX2RY

IntakeScreenHouse

Unit 2 Unit 1 Cooling Tower Substation

Switchyard Fence

Y

345kV

13.8kV

Non-Safety Related Buses

4kVSafety

Related

4kV

34.5kV

PINGP CLB Scope Expanded LR Scope per Proposed ISG 2008-01

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Switchyard Scoping Boundary

1R(U1)

CT12(U2)

IntakeScreenHouse

TrainingCenter

2R(U2)

Gen(U1)

1CT(U1)

SpringCreek

ByronRedRock

1

Gen(U2)

BlueLake

RedRock

2

161kV 13.8kV

345kV

Bus 1

Bus 2

#10

TransmissionSystem

PlantSystem

PINGP CLB Scope Expanded LR Scope per Proposed ISG 2008-01

Distribution