ML093221014
| ML093221014 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 11/06/2009 |
| From: | - No Known Affiliation |
| To: | Division of License Renewal |
| References | |
| Download: ML093221014 (41) | |
Text
PrairieIslandNPEm Resource From: Eckholt, Gene F. [Gene.Eckholt@xenuclear.com]
Sent: Friday, November 06, 2009 10:15 AM To: Plasse, Richard
Subject:
Draft Prairie Island ACRS Full Committee Presentation Attachments: 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 1
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:
Prairie Island Nuclear Generating Plant ACRS License Renewal Meeting December 3, 2009 1
Introductions
z Mark Schimmel - Site Vice President z Gene Eckholt - License Renewal Project Manager z Steve Skoyen - Engineering Programs Manager z License Renewal Project Team and Subject Matter Experts 2
Agenda z Introductions z Background z ACRS LR Subcommittee Follow-Up Items z Refueling Cavity Leakage z Underground Medium Voltage Cables z Condensate Storage Tank Examinations z Questions 3
=
Background===
z Plant Owner and Operator z Northern States Power Company - Minnesota z Subsidiary of Xcel Energy z Location z SE of Minneapolis-Saint Paul, MN z On Mississippi River 4
=
Background===
z Construction Permits Issued - June 1968 z Operating Licenses Issued z Unit 1 - August 1973 z Unit 2 - October 1974 z LRA Submitted - April 2008 5
=
Background===
z Two 2 - Loop PWR Units z 1650 MWt z 575 MWe (Gross) per Unit z Westinghouse - NSSS z Pioneer Service & Engineering -
Architect/Engineer z Once-Through Cooling Supplemented with Four Forced Draft Cooling Towers (Seasonal) z Ultimate Heat Sink is Mississippi River via Cooling Water System 6
=
Background===
Containment Design z Steel Containment Vessel z 1-1/2 inch Thick Bottom Head, 1-1/2 inch Thick Shell, 3/4 inch Thick Top Head z 3-1/2 inch Thick at ECCS Sump (Sump B) Penetrations z SA-516-70 Low Temperature Carbon Steel z Provides Primary Containment z Lower Head Encased in Concrete z 5 foot Annular Gap Between Containment Vessel and Limited Leakage Reinforced Concrete Shield Building Containment Elevation 7
ACRS LR Subcommittee Follow-Up Items z Refueling Cavity Leakage z Underground Medium Voltage Cables z Condensate Storage Tank Examinations 8
Refueling Cavity Leakage
Background
z Intermittent Refueling Cavity Leakage Indications in Both Units Since Late 1980s z Leak Rate of 1-2 Gallons per Hour z Seen in ECCS Sump and Regenerative Heat Exchanger Room z Sealing Methods Have Stopped Leakage, but not Consistently 9
Refueling Cavity Leakage Leakage Seen in Path ECCS Sump and in Regenerative HX Room (below cavity)
Cavity Photo from NW Cavity Photo Overhead Containment Elevation
Refueling Cavity Leakage Leak Locations z Root Cause Evaluation was Completed in April of 2009 z Sources of Leakage were Determined to be Embedment Plates for Reactor Vessel Internals Stands and Rod Control Cluster Assembly (RCCA) Change Fixture 11
Refueling Cavity Leakage Leak Locations Typical Reactor Vessel Internals Stand Support Typical RCCA Change Fixture Support 12
Refueling Cavity Leakage Repair Method Replace existing nuts with fabricated blind nuts seal New seal weld between welded to baseplate. baseplate and embedment plate.
Existing 1/4" thk stainless steel cavity liner Existing cavity liner Side View fillet weld to Existing seal weld to embedment plate embedment plate not accessible. Failure of weld would result in leak.
13
Refueling Cavity Leakage Fall 2009 Unit 1 Repairs z Reactor Vessel Internals Stands and RCCA Change Fixture Embedment Plates Repaired z Existing Nuts Removed z Replaced with Blind Nuts z Blind Nuts Seal Welded to Baseplate z Seal Weld Applied Between Baseplate and Embedment Plate z Welds Examined by NDE 14
Refueling Cavity Leakage Fall 2009 Unit 1 Repairs 15
Refueling Cavity Leakage Fall 2009 Unit 1 Repair Results z Embedment Plate Repairs Eliminated that Leakage Source z ECCS Sump z No Evidence of Leakage z Minor Leakage from Regenerative Heat Exchanger Room Ceiling z Appeared After Cavity Flooded 14 Days z Estimated to be 0.05 Gallons per Hour z No Evidence Leakage is Reaching Containment Vessel 16
Refueling Cavity Leakage Fall 2009 Unit 1 Testing and Evaluation z Vacuum Box Testing of Reactor Cavity Liner Plate Seam Welds - No Leakage Identified z NDE of Fuel Transfer Tube Welds - No Indications z Evaluation of Other Possible Leakage Sources z NDE of Liner to Embedment Plate Fillet Welds z One Porosity Indication z Will be Repaired During Next Unit 1 Refueling Outage z RCCA Guide Box Embedment Plates 17
Refueling Cavity Leakage 2010 Unit 2 Corrective Actions z Repair of Reactor Vessel Internals Stands and RCCA Change Fixture Embedment Plates z Repair of RCCA Guide Box Embedment Plates z NDE of Fuel Transfer Tube Welds z Vacuum Box Testing of Reactor Cavity Liner Plate Seam Welds z NDE of Liner to Embedment Plate Fillet Welds z Other Repairs and Testing Resulting From Evaluation of 2009 Unit 1 Leakage 18
Refueling Cavity Leakage 2011 Unit 1 Corrective Actions z Repair of RCCA Guide Box Embedment Plates z Repair of Liner to Embedment Plate Fillet Weld Porosity Indication z Other Repairs and Testing Resulting From Evaluation of 2009 Unit 1 and 2010 Unit 2 Repair Results 19
Refueling Cavity Leakage Monitoring & Assessment z Ultrasonic and Visual Examinations of Containment Vessel z Unit 1 and 2 ECCS Sumps (Prior to 2009) z Grout Removed z Wall Thickness Measurements at or Above Nominal z No Corrosion Identified.
Sump Section z Unit 1 ECCS Sump (Fall 2009) z Grout Removed z Wall Thickness Measurements at or Above Nominal z No Corrosion of Rebar or Containment Vessel Annulus Photo z No Wet Areas or Leakage Containment Elevation 20
Refueling Cavity Leakage Monitoring & Assessment Unit 1 ECCS Sump Fall 2009 21
Refueling Cavity Leakage Monitoring & Assessment z Ultrasonic and Visual Examinations of Containment Vessel (contd) z Unit 2 Annulus (2008) z 144 Wall Thickness Measurements z All Measurements at or Above Nominal z Unit 1 Annulus (2009) z 80 Wall Thickness Measurements z 79 Locations at or Above Nominal z One Location Below Nominal 1.5" thickness at 1.492" 22
Refueling Cavity Leakage Monitoring & Assessment - Commitments z Removal of Concrete from Sump Below Reactor Vessel to Expose Containment Vessel z Next Outages Following Refueling Cavity Repairs z Inspect (VT and UT) Containment Vessel z Petrographic Examination of Removed Concrete z Evacuate any Water Observed Containment Elevation 23
Refueling Cavity Leakage Monitoring & Assessment - Commitments z Removal of Concrete Sample Wetted by Borated Water Leakage from Refueling Cavity z Concrete will be Tested For Compression Strength and will Undergo Petrographic Examination z Monitor Areas Previously Exhibiting Leakage for Next Two Outages After Repairs to Confirm That Leakage has not Recurred 24
Refueling Cavity Leakage Long Term Aging Management z Continue to Manage Aging of the Containment Structures and Vessel Using the Structures Monitoring Program and ASME Section XI, Subsection IWE Program z Utilize Corrective Action Program for Evaluation and Correction of New Issues 25
Refueling Cavity Leakage Evaluation of Potential Degradation z Evaluations have been performed for potential degradation of Steel Containment Vessel, Concrete and Rebar z Evaluations Concluded:
z Containment Vessel Corrosion Behind Concrete in Areas Wetted by Refueling Cavity Leakage is Expected to be Minor z No Significant Effect on Reinforced Concrete That Has Been Wetted by Refueling Cavity Leakage 26
Underground Medium Voltage Cables Manhole Inspection z ACRS LR Subcommittee Questioned Adequacy of Two Year Manhole Inspection Frequency z Inspection Frequency is Based on Actual Plant Experience, but not to Exceed Every Two Years z Consistent with GALL XI.E3 z One Manhole in Scope of License Renewal z Multiple Inspections Since September of 2007 Have Shown no Signs of Water Intrusion or Accumulation 27
Underground Medium Voltage Cables Manhole Inspection z Design Precludes Water Accumulation z Floor of Gravel and Sand z Approximately Ten Feet Above Water Table z Grade Around Manhole Precludes Significant Rain Water Intrusion z Based on Manhole Design and Actual Plant Experience, Two Year Inspection Frequency is Considered Sufficient 28
Underground Medium Voltage Cables Impact of Freeze/Thaw Conditions z Prairie Island Operating Experience was Reviewed for Evidence of Accelerated Cable Insulation Aging Related to Freeze/Thaw Conditions z The Following Organizations were also Contacted:
z Monticello Nuclear Generating Plant z Xcel Energy Distribution z EPRI z NEI License Renewal Electrical Working Group z Accelerated Cable Insulation Aging Related to Freeze/Thaw Conditions has not Been Identified as an Issue 29
Condensate Storage Tank Examinations z Aboveground Steel Tanks Program Included UT Inspection of the Bottom of 1 of the 3 Condensate Storage Tanks Prior to PEO z ACRS LR Subcommittee Felt That Inspection of Only 1 Tank to Assure Acceptability of all 3 Tanks was not Adequately Supported z LRA 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 30
Questions?
31
Supporting Slides 32
33 Refueling Cavity Leakage Path z Path to ECCS Sump z Under Refueling Cavity Liner Through Construction Joint Between Floor of Transfer Pit and Wall Behind Fuel Transfer Tube to Inner Wall of Containment Vessel z Travels Down and Horizontally, Between Containment Vessel and Concrete, to Low Point of Containment Vessel Bottom Head z Seeps Through Grout in ECCS Sump z Path to Regenerative Heat Exchanger Room z Once Under Liner, Follows Cracks in the Concrete, Seeping Through the Ceiling and Walls of the Regenerative HX Room ECCS Sump 34
Origin Regen HX ECCS Sump C Sump Room Fuel Transfer Tube Leak Paths ECCS Sump 35
ECCS Sump Showing Grout To 33 To 34 (Cont. 3D) Insp. 36
Plant Electrical Distribution 345kV Transmission 161kV 345kV 13.8kV (#10)
System 2R Plant 1CT Intake System Screen 34.5kV House Switchyard Fence 2RY 2RX 1R 13.8kV X Y Non-Safety Related Buses CT11 CT12 Cooling Tower 4kV Safety Related 4kV Unit 2 Unit 1 Cooling Tower Substation PINGP CLB Scope Expanded LR Scope per Proposed ISG 2008-01 38
Switchyard Scoping Boundary Spring Red Blue Red Byron Rock Lake Rock Creek
- 10 2 1 Bus 2 345kV 161kV 13.8kV Bus 1 Transmission System Plant System 1R CT12 Intake Training 2R Gen Gen 1CT Screen (U2) (U2) (U1) (U1)
(U1) (U2) House Center PINGP CLB Scope Expanded LR Scope per Proposed ISG 2008-01 Distribution 39