ML11124A009
| ML11124A009 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 04/25/2011 |
| From: | Gerald Bichof Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 11-185 | |
| Download: ML11124A009 (6) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 April 25, 2011 U.S. Nuclear Regulatory Commission Serial No.11-185 Attention: Document Control Desk SPS-LIC/CGL RO Washington, D.C. 20555-0001 Docket No. 50-281 License No. DPR-37 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)
SURRY POWER STATION UNIT 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION UNIT 2 2009 STEAM GENERATOR TUBE INSPECTION REPORT By a letter dated May 24, 2010 (Serial No. 10-220/ADAMS ML101530533), Virginia Electric and Power Company (Dominion) submitted information summarizing the results of steam generator tube inspections performed at Surry Unit 2 during the Fall 2009 refueling outage. A March 29, 2011 letter from the NRC indicates that the NRC staff has reviewed the information provided in our May 24, 2010 letter and has determined that additional information is required to complete their review. The NRC's questions and Dominion's responses are provided in the attachment.
If you have further questions or require additional information, please contact Ms. Candee G. Lovett at (757) 365-2178.
Sincerely, Gerald T. Bischof Site Vice President Surry Power Station Commitments made in this letter: None Attachment - Response to NRC Request for Additional Information Regarding the Unit 2 Fall 2009 Refueling Outage Steam Generator Tube Inspections 41cc'
Serial No.11-185 Docket No. 50-281 RAI Response - Surry Unit 2 2009 SG Tube Inspection Report Page 2 of 2 cc: U.S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Avenue NE Suite 1200 Atlanta, Georgia 30303-1257 Ms, K. R. Cotton NRC Project Manager - Surry U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G9A 11555 Rockville Pike Rockville, Maryland 20852 Mr. J. S. Wiebe NRC Project Manager- North Anna U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G9A 11555 Rockville Pike Rockville, Maryland 20852 NRC Senior Resident Inspector Surry Power Station Mr. R. A. Smith Authorized Nuclear Inspector Surry Power Station
Serial No.11-185 Docket No. 50-281 ATTACHMENT RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING UNIT 2 2009 REFUELING OUTAGE STEAM GENERATOR TUBE INSPECTION REPORT VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)
SURRY POWER STATION UNIT 2
Serial No.11-185 Docket No. 50-281 Attachment By a letter dated May 24, 2010 (Serial No. 10-220/ADAMS ML101530533), Virginia Electric and Power Company (Dominion) submitted information summarizing the results of steam generator (SG) tube inspections performed at Surry Unit 2 during the Fall 2009 refueling outage. A March 29, 2011 letter from the NRC indicates that the NRC staff has reviewed the information provided in our May 24, 2010 letter and has determined that additional information is required to complete their review. The NRC's questions and Dominion's responses are provided below.
NRC Question 1: Please clarify the difference between an overexpansion and overroll.
Dominion Response: Overexpansion (OXP) is an area of the tube that is hydraulically expanded more than 0.02 inches greater than the diameter of the unexpanded portion of the tube. On overroll is an area of the tube that is hydraulically expanded more than 0.25 inches above the top of the tubesheet.
NRC Question 2: With respect to tubes that may have potentially elevated residual stresses as a result of fabrication, please clarify the number of high row tubes (i.e., tubes in rows where the U-bends were not stress relieved following bending) in SG A that have this condition (either Tier 1 or Tier 2 tubes). It is the NRC staff's understanding that none of the low row tubes (i.e., tubes in rows where the U-bends were stress relieved) in either SGs A, B, or C have potentially elevated residual stresses (i.e., no eddy current offset) as a result of fabrication and that there are 2 high row tubes in SG B and 14 high row tubes in SG C that have potentially elevated residual stresses (i.e., 2 sigma tubes). Please confirm the NRC staffs understanding.
Dominion Response: The staffs understanding is correct. There are no low row tubes (i.e., tubes with stress relieved U-bends) in the Unit 2 SGs that have indications of potentially elevated residual stress. The number of high row tubes identified as having potentially elevated residual stress is provided for each SG in the table below.
Number of Tubes with Potentially Elevated Residual Stress:
SG A SG B SG C "Tier 1" 0 2 14 "Tier 2" 173 189 134 Page 1 of 3
Serial No.11-185 Docket No. 50-281 Attachment NRC Question 3: Please discuss the results of the secondary side inspections (other than foreign object search and retrieval) in SG C. Please discuss how the 2009 inspection results compare to the inspection results obtained in 2008 for this SG.
Dominion Response: In addition to the foreign object search and retrieval (FOSAR) inspections performed in all three SGs, a visual examination of the SG C upper internals was performed during the 2009 outage. All components examined in the steam drum (upper two decks, primary and secondary separators, swirl vanes, drain pipes, deck attachment welds, ladders, etc.) and upper tube bundle regions were found to be sound with no evidence of erosion or corrosion. Selected J-nozzle/feedring interfaces in SG C were internally examined. Only minor flow accelerated corrosion (FAC) related material reduction was observed.
Prior to this inspection the most recent examination of SG C upper internals was performed in 2005. During the 2005 examination, an anomalous condition was identified as localized through-wall FAC degradation on a capped-off, unused J-nozzle stub. This degradation was weld repaired during the 2005 outage, was reexamined during the 2009 outage, and was found to be in good condition. Inspection of the steam drum area was performed to determine the general condition of the primary and secondary moisture separators, support brackets, deck plates and other accessible parts, as well as to check for evidence of sludge or scale build-up, of FAC, or of other damage. No structural anomalies were noted.
NRC Question 4: During a prior outage, corrosion degradation was observed in the channel head area and in an unplugged tube (which was subsequently replugged) in SG A. Please discuss whether these areas were inspected/monitored during the 2009 outage. If so, please discuss the results.
Dominion Response: The conditions referred to in this question were identified in the SG A hot leg during the Fall 2006 refueling outage. The Fall 2009 primary side inspection scope included a visual examination of hot and cold leg channel heads and all previously installed plugs. No change was identified in the subject channel head degradation, and no anomalous conditions associated with any of the plugs were identified.
Page 2 of 3
Serial No.11-185 Docket No. 50-281 Attachment NRC Question 5: Based on a review of Tables 9 and 10, it appears that some tubes with no degradation were plugged since they had foreign objects present.
Please identify these tubes (i.e., tubes with loose part indications and no associated wear that were plugged) and the tubes that were plugged because they were not expanded in the tubesheet (NTE tubes).
Dominion Response: The table below identifies tubes that were plugged (and stabilized) due to the presence or the suspected presence of a foreign object, but without associated degradation.
Tubes with Loose Part Indications and no Associated Wear - Plugged:
SG Row Column Comment A 45 47 Preventive - No ECT Indication A 45 48 Preventive - No ECT Indication C 33 39 Preventive - No ECT Indication C 35 38 Preventive - No ECT Indication The table below identifies tubes that were plugged due to the NTE condition.
Tubes with NTE Condition - Plugged:
SG Row Column B 35 41 B 32 65 B 9 89 B 16 89 C 21 22 C 2 28 C 2 30 C 23 40 C 20 57 C 35 75 C 35 43 Page 3 of 3