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
1 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
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:
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1 Prairie Island Nuclear Generating Plant ACRS License Renewal Meeting December 3, 2009
2
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
3 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
4 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
5 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
6 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
7 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
8 ACRS LR Subcommittee Follow-Up Items z Refueling Cavity Leakage z Underground Medium Voltage Cables z Condensate Storage Tank Examinations
9 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
Refueling Cavity Leakage Path Cavity Photo Overhead Cavity Photo from NW Leakage Seen in ECCS Sump and in Regenerative HX Room (below cavity)
Containment Elevation
11 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
12 Refueling Cavity Leakage Leak Locations Typical Reactor Vessel Internals Stand Support Typical RCCA Change Fixture Support
13 Refueling Cavity Leakage Repair Method Existing 1/4" thk stainless steel cavity liner New seal weld between baseplate and embedment plate.
Existing cavity liner fillet weld to embedment plate Existing 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
14 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
15 Refueling Cavity Leakage Fall 2009 Unit 1 Repairs
16 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
17 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
18 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
19 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
20 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.
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 z No Wet Areas or Leakage Sump Section Annulus Photo Containment Elevation
21 Refueling Cavity Leakage Monitoring & Assessment Unit 1 ECCS Sump Fall 2009
22 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"
23 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
24 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
25 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
26 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
27 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
28 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
29 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
30 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
31 Questions?
32 Supporting Slides
33
34 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
35 Origin ECCS Sump Sump C Fuel Transfer Tube Regen HX Room Leak Paths ECCS Sump
36 ECCS Sump Showing Grout To 33 (Cont. 3D)
To 34 Insp.
38 Plant Electrical Distribution X
1R CT12 2R 1CT 161kV 13.8kV (#10) 345kV Transmission System Plant System Cooling Tower CT11 2RX 2RY Intake Screen House Unit 2 Unit 1 Cooling Tower Substation Switchyard Fence Y
345kV 13.8kV Non-Safety Related Buses 4kV Safety Related 4kV 34.5kV PINGP CLB Scope Expanded LR Scope per Proposed ISG 2008-01
39 Switchyard Scoping Boundary 1R (U1)
CT12 (U2)
Intake Screen House Training Center 2R (U2)
Gen (U1) 1CT (U1)
Spring Creek Byron Red Rock 1
Gen (U2)
Blue Lake Red Rock 2
161kV 13.8kV 345kV Bus 1 Bus 2