ML070880059

Request for Additional Information, Regarding Risk-Informed Inservice Inspection Program Relief Requests

ML070880059
Person / Time
Site:	Sequoyah
Issue date:	03/29/2007
From:	Moroney B NRC/NRR/ADRO/DORL/LPLII-2
To:	Singer K Tennessee Valley Authority
Moroney B, NRR/DORL, 415-3974
References
TAC MD1452, TAC MD1453, TAC MD1454, TAC MD1455
Download: ML070880059 (7)

Text

March 29, 2007Mr. Karl W. SingerChief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801

SUBJECT:

SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 - REQUEST FORADDITIONAL INFORMATION REGARDING RISK-INFORMED INSERVICE INSPECTION PROGRAM RELIEF REQUESTS (TAC NOS. MD1452, MD1453, MD1454 AND MD1455)

Dear Mr. Singer:

By letter dated April 21, 2006, the Tennessee Valley Authority (TVA) submitted ReliefRequests (RRs) 1-RI-ISI-1 and 2-RI-ISI-1 for the Risk-Informed Inservice Inspection program at Sequoyah Nuclear Plant (SQN), Units 1 and 2, to reflect Revision 3 to the SQN Probabilistic Risk Assessment. The submittal also included RRs 1-RI-ISI-2 and 2-RI-ISI-2, which proposed visual testing in lieu of volumetric examination of certain high safety significant weld segments. In order for the staff to complete its review of the information provided by the licensee, werequest that TVA provide responses to the enclosed request for additional information (RAI).

Based on discussions with your staff, we understand that you plan to respond to the enclosed RAI by April 15, 2007. If you have any questions about this material, please contact me at (301) 415-3974.Sincerely,/RA/Brendan T. Moroney, Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor RegulationDocket No. 50-327 and 50-328

Enclosure:

RAI cc: See next page

ML070880059NRR-088OFFICELPL2-2/PMLPL2-2/LAAPLA/BCCPNB/BCLPL2-2/BCNAMEBMoroneyRSolaLMrowca memo datedTChanby emailTBoyceDATE 3 /29 /07 3 /29/07 01/22/07 01 /23 /07 3/29 /07 REQUEST FOR ADDITIONAL INFORMATIONRISK-INFORMED INSERVICE INSPECTION RELIEF REQUESTTHIRD TEN-YEAR INSERVICE INSPECTION PROGRAM RELIEF REQUESTSTENNESSEE VALLEY AUTHORITYSEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2DOCKET NOs. 50-327 AND 50-3281.Noting that the Sequoyah Nuclear Plant (SQN) Probabilistic Risk Assessment (PRA)Revision 1 model was used in support of the original risk-informed inservice inspection program (RI-ISI) relief in March 2001; the SQN PRA Revision 2 model underwent the Westinghouse Owner's Group (WOG) PRA Peer Review Certification process; and the SQN PRA Revision 3 is being used for this recent RI-ISI relief request. As stated in the Regulatory Guide 1.178: "A description of the staff and industry reviews performed on the PRA. Limitations, weakness, or improvements identified by the reviewers that could change the results of the PRA should be discussed. The resolution of the review comments, or an explanation of the insensitivity of the analysis should be provided."

However, in the current relief request, there is no discussion of PRA updates. Hence, to establish confidence that the quality of the SQN PRA Revision 3 is sufficient to support this RI-ISI relief, please answer the following questions and/or provide the information requested below.a.Confirm the dates of SQN Revision 3 PRA models for both Units 1 and 2.

b.Were all of the Level A and B Facts & Observations (F&Os) from the WOG PRAPeer Review Certification resolved and/or incorporated into the PRA model(s) used for this application (i.e., Units 1 and 2 SQN PRA Revision 3)? If not, identify and state why the unincorporated F&Os are not expected to have an impact on the RI-ISI program.c.Provide the baseline core damage frequencies and large early releasefrequencies (for both Units 1 and 2) from SQN PRA Revision 3.2.Please update the following table, which was completed and provided by the TennesseeValley Authority in a response (dated August 31, 2001) to the U.S. Nuclear Regulatory Commission request for additional information (RAI) on the original RI-ISI program (dated July 13, 2001), with the SQN PRA Revision 3 results.SystemNumber ofSegments withAny RRW 1.005Number ofSegments with Any RRW Between 1.005 and 1.001Number ofSegments with Any RRW1.005 butPlaced in LSSNumber ofSegments with All RRW < 1.005 but Placed in

HSS 3.For the 72 pipe segments of SQN Units 1 and 2 that were moved from being in thecategory of high safety significant (HSS) to low safety significant (LSS) and the 31 LSS segments of Units 1 and 2 that were increased to HSS category:a.Please identify pipe segments that moved from HSS to LSS and provide anexplanation why each segments' safety significance changed. Please summarize the changes that caused other pipe segments to move from LSS to

HSS.b.For the multiple pipe diameter (MPD) segments, have their failure probability(FP) changes been revised as a result of using WCAP-14572 Supplement 2? If so, describe how you implemented Supplement 2 methodology.c.How were the number of examinations for these MDP segments determined andhas the number or the location of these examinations been revised as a result of using WCAP-14572 Supplement 2?d.Identify and provide expert panel (EP) justification for those pipe segments withrevised RRW 1.005 that were reclassified by the EP decision.e.Describe how the risk impacts of external events, internal fire, and shutdownwere considered and evaluated by the EP.4.Has the uncertainty analysis as discussed on page 125 of the WCAP-14572 beenre-performed? If so, please identify those systems/components for which the RRW increased to or above 1.005 and provide the results of the EP's evaluation of these segments. If not, provide a description and justification of how your process considered uncertainty and why the deviation is acceptable? 5.For Unit 1, based on a comparison between Table 5-1 on page E-19 of the previoussubmittal and Table 1 on page E1-5 of the current submittal, the following information and/or explanations are requested.a.Page E1-2 of the current submittal, last paragraph indicates that 16 LSSsegments were reclassified as HSS and 36 HSS segments were reclassified as LSS segments for Unit 1. However, staff review of the above tables seems to indicate that only 12 LSS segments were reclassified as HSS and 30 HSS segments were reclassified as LSS segments. Please explain the difference in these numbers.b.Was there a reduction in the number of inspection locations in any pipe segmentthat was and remains a HSS segment? If so, how great was the reduction an why was the reduction taken.c.On page E1-7, Code Category C-F-1, 3 rd Interval RI-ISI, it appears that the totalnumbers of exam locations should be 27 and 8 for nondestructive examination (NDE) and VT2 (not 25 and 10), respectively. Please correct these numbers orotherwise explain this apparent discrepancy.d.Please explain how and why you have chosen two additional examinations ofreactor coolant system to meet the change in risk criteria.6.For Unit 2, based on a comparison between Table 5-2 on page E-21 of the previoussubmittal and Table 2 on page E1-8 of the current submittal, the following information and/or explanations are requested.a.Page E1-2, last paragraph indicates that 15 LSS segments were reclassified asHSS and 36 HSS segments were reclassified as LSS segments for Unit 2.

However, staff review of the above tables seems to indicate that Table 5-2 shows only 10 LSS segments that were reclassified as HSS and 31 HSS segments that were reclassified as LSS segments. Please explain the difference in these numbers.b.Was there a reduction in the number of inspection locations in any pipe segmentthat was and remains a HSS segment? If so, how great was the reduction an why was the reduction taken.c.On page E1-10, Code Category C-F-1, 3 rd Interval RI-ISI, it appears that the totalnumbers of exam locations are 24 and 8 for NDE and VT2 (not 22 and 10),

respectively. Please correct these numbers or otherwise explain this apparent discrepancy.d.Please explain how and why you have chosen one additional examination ofReactor Coolant system to meet the change in risk criteria.7.The newer versions of the American Society of Mechanical Engineers (ASME) Codehave reduced the exempted portions of auxiliary feedwater piping from NPS 4 to NPS 11/2. This reduction in exempted piping has caused other licensees to add ASMEClass 2 and/or Class 3 Auxiliary Feedwater piping to the scope of their RI-ISI programs, and to implement the (EPRI or) WCAP-14572 methodology to classify, risk-rank, and to select, as necessary, additional locations for the next ISI interval. Please describe how you treated this issue.8.Based on industry experience with primary water stress corrosion cracking (PWSCC) ofAlloy 600 and associated weld material Alloy 82/182 the staff finds that these welds should be inspected at a minimum in accordance with ASME Code Section XI requirements until such time that industry has gathered sufficient data to justify incorporating these items into the RI-ISI program.Please describe what examinations (e.g., UT-Appendix VIII) will be performed and atwhat frequency for each dissimilar metal welds containing either Alloy 600 or its associated weld metal in Class 1 and 2 components for each unit.9.In Enclosure 1, Tables 1 and 2 of the April 21, 2006, submittal, what is meant byfootnote "c. Augmented programs for erosion-corrosion (including MIC) continue?" How will the NDE examinations for these elements be performed (Appendix VIII,thickness measurements or other)?10.In Enclosure 1, Tables 1 and 2, please describe what is meant by footnotes o and p.

11.Provide justification on how adding VT-2 examinations will maintain risk neutrality, sinceVT-2 examinations are already required (footnote a).12. For footnotes a, b, d, e, g, and l, what is the frequency of the VT-2 visual examinations?

13.For each NDE examination list what type of NDE examination will be performed(e.g., UT-Appendix VIII, UT-Thickness, surface examination).14.Discuss the changes to the feedwater system that eliminated the examinations thatwere required in the 2 nd ISI interval and no longer required in the 3 rd ISI interval.

Mr. Karl W. SingerSEQUOYAH NUCLEAR PLANTTennessee Valley Authority cc: Mr. Ashok S. Bhatnagar, Senior Vice President Nuclear Operations Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Preston D. Swafford, Senior Vice PresidentNuclear Support Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801Mr. Larry S. Bryant, Vice PresidentNuclear Engineering & Technical Services Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801General CounselTennessee Valley Authority 6A West Tower 400 West Summit Hill Drive Knoxville, TN 37902Mr. John C. Fornicola, ManagerNuclear Assurance Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801Ms. Beth A. Wetzel, ManagerCorporate Nuclear Licensing and Industry Affairs Tennessee Valley Authority 4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801Mr. Robert H. Bryan, Jr., General ManagerLicensing and Industry Affairs Tennessee Valley Authority 4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801Mr. Randy Douet, Site Vice PresidentSequoyah Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Soddy Daisy, TN 37384-2000Mr. Glenn W. Morris, ManagerLicensing and Industry Affairs Sequoyah Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Soddy Daisy, TN 37384-2000Mr. David A. Kulisek, Plant ManagerSequoyah Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Soddy Daisy, TN 37384-2000Senior Resident InspectorSequoyah Nuclear Plant U.S. Nuclear Regulatory Commission 2600 Igou Ferry Road Soddy Daisy, TN 37379Mr. Lawrence E. Nanney, DirectorDivision of Radiological Health Dept. of Environment & Conservation Third Floor, L and C Annex 401 Church Street Nashville, TN 37243-1532County MayorHamilton County Courthouse Chattanooga, TN 37402-2801Ms. Ann P. Harris341 Swing Loop Road Rockwood, TN 37854