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, 2007 Mr. Karl W. Singer Chief 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 FOR ADDITIONAL 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 Relief Requests (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, we request 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 Regulation Docket No. 50-327 and 50-328

Enclosure:

RAI cc: See next page

ML070880059 NRR-088 OFFICE LPL2-2/PM LPL2-2/LA APLA/BC CPNB/BC LPL2-2/BC NAME BMoroney RSola LMrowca TChan TBoyce memo dated by email DATE 3 /29 /07 3 /29/07 01/22/07 01 /23 /07 3/29 /07 REQUEST FOR ADDITIONAL INFORMATION RISK-INFORMED INSERVICE INSPECTION RELIEF REQUEST THIRD TEN-YEAR INSERVICE INSPECTION PROGRAM RELIEF REQUESTS TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOs. 50-327 AND 50-328

1. 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 Owners 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 PRA Peer 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 release frequencies (for both Units 1 and 2) from SQN PRA Revision 3.

2. Please update the following table, which was completed and provided by the Tennessee Valley 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.

System Number of Number of Number of Number of Segments with Segments with Segments with Segments with Any RRW $ Any RRW Any RRW All RRW < 1.005 1.005 Between 1.005 $1.005 but but Placed in and 1.001 Placed in LSS HSS

3. For the 72 pipe segments of SQN Units 1 and 2 that were moved from being in the category 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 an explanation 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 and has 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 with revised RRW $1.005 that were reclassified by the EP decision.

e. Describe how the risk impacts of external events, internal fire, and shutdown were considered and evaluated by the EP.

4. Has the uncertainty analysis as discussed on page 125 of the WCAP-14572 been re-performed? If so, please identify those systems/components for which the RRW increased to or above 1.005 and provide the results of the EPs 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 previous submittal 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 LSS segments 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 segment that 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, 3rd Interval RI-ISI, it appears that the total numbers of exam locations should be 27 and 8 for nondestructive examination

(NDE) and VT2 (not 25 and 10), respectively. Please correct these numbers or otherwise explain this apparent discrepancy.

d. Please explain how and why you have chosen two additional examinations of reactor 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 previous submittal 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 as HSS 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 segment that 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, 3rd Interval RI-ISI, it appears that the total numbers 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 of Reactor Coolant system to meet the change in risk criteria.

7. The newer versions of the American Society of Mechanical Engineers (ASME) Code have 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 ASME Class 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) of Alloy 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 at what 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 by footnote 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, since VT-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 that were required in the 2nd ISI interval and no longer required in the 3rd ISI interval.

Mr. Karl W. Singer SEQUOYAH NUCLEAR PLANT Tennessee Valley Authority cc:

Mr. Ashok S. Bhatnagar, Senior Vice President Mr. Randy Douet, Site Vice President Nuclear Operations Sequoyah Nuclear Plant Tennessee Valley Authority Tennessee Valley Authority 6A Lookout Place P.O. Box 2000 1101 Market Street Soddy Daisy, TN 37384-2000 Chattanooga, TN 37402-2801 Mr. Glenn W. Morris, Manager Mr. Preston D. Swafford, Senior Vice President Licensing and Industry Affairs Nuclear Support Sequoyah Nuclear Plant Tennessee Valley Authority Tennessee Valley Authority 6A Lookout Place P.O. Box 2000 1101 Market Street Soddy Daisy, TN 37384-2000 Chattanooga, TN 37402-2801 Mr. David A. Kulisek, Plant Manager Mr. Larry S. Bryant, Vice President Sequoyah Nuclear Plant Nuclear Engineering & Technical Services Tennessee Valley Authority Tennessee Valley Authority P.O. Box 2000 6A Lookout Place Soddy Daisy, TN 37384-2000 1101 Market Street Chattanooga, TN 37402-2801 Senior Resident Inspector Sequoyah Nuclear Plant General Counsel U.S. Nuclear Regulatory Commission Tennessee Valley Authority 2600 Igou Ferry Road 6A West Tower Soddy Daisy, TN 37379 400 West Summit Hill Drive Knoxville, TN 37902 Mr. Lawrence E. Nanney, Director Division of Radiological Health Mr. John C. Fornicola, Manager Dept. of Environment & Conservation Nuclear Assurance Third Floor, L and C Annex Tennessee Valley Authority 401 Church Street 6A Lookout Place Nashville, TN 37243-1532 1101 Market Street Chattanooga, TN 37402-2801 County Mayor Hamilton County Courthouse Ms. Beth A. Wetzel, Manager Chattanooga, TN 37402-2801 Corporate Nuclear Licensing and Industry Affairs Ms. Ann P. Harris Tennessee Valley Authority 341 Swing Loop Road 4X Blue Ridge Rockwood, TN 37854 1101 Market Street Chattanooga, TN 37402-2801 Mr. Robert H. Bryan, Jr., General Manager Licensing and Industry Affairs Tennessee Valley Authority 4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801