ML043070192

Annual Steam Generator Inservice Inspection Summary Report Response to Request for Additional Information

ML043070192
Person / Time
Site:	Surry
Issue date:	11/01/2004
From:	Hartz L Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
04-574
Download: ML043070192 (12)

Text

VIRGINIA ELECTRIC A N D POWER COMPANY RICHMOND, VIRGINIA 23261 November 1, 2004 United Stated Nuclear Regulatory Commission Serial No.: 04-574 Attention: Document Control Desk NL&OS/GDM RO Washington D.C. 20555 Docket Nos.: 50-280, 281 License Nos.: DPR-32, 37 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 2003 ANNUAL STEAM GENERATOR INSERVICE INSPECTION

SUMMARY

REPORT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION Virginia Electric and Power Company (Dominion) submitted the 2003 Annual Steam Generator lnservice Inspection Summary Report for Surry Power Station in a letter dated February 23, 2004 (Serial No.03-622). The report included the inspection results for the Surry Unit 1 and Unit 2 steam generator inspections conducted during the Spring 2003 and Fall 2003 refueling outages, respectively. In a letter dated September 3, 2004, the NRC informed Dominion that additional information was necessary to complete their evaluation of our submittal and included four questions in the enclosure to the letter for Dominion's response. We have reviewed these questions and provided our response in the enclosure.

If you have any questions or require additional information, please contact Mr. Gary D.

Miller at (804) 273-2771.

Very truly yours, L. N. Hartz '1 L

Vice President - Nuclear Engineering Commitments made in this letter: None Enclosure

cc: U. S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. S. R. Monarque U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8H12 Rockville, MD 20852 Mr. N. P. Garrett NRC Senior Resident Inspector Surry Power Station Mr. R. A. Smith Authorized Nuclear Inspector Surry Power Station

Enclosure Response to NRC Reauest for Additional Information Surrv 2003 Annual Steam Generator Report

1. The Plugging/Repair Record table on page 3 of Attachment 1 to your submittal dated February 23, 2004, indicates that 7 tubes are plugged in the B steam generator of Unit 1. A historical review of the 2000 and 2001 inservice inspection summary reports indicates that 14 tubes were plugged in the B steam generator prior to the 2003 inspection. Please verify the total number of tubes plugged in Unit 1, Steam Generator B following the 2003 steam generator tube inspections.

Response

The NRC observation is correct. Only the tube plugging data for the outage was included. The cumulative plugging for the B steam generator should be 21 tubes.

A revised Attachment 1 tabulation is included for your use.

2. The February 23, 2004, submittal indicates that the steam generators at both units have experienced denting in peripheral tubes near the gh and f htube support plates. Please discuss whether new dents were identified during your 2003 inspections and whether existing dents have grown. If existing dents are increasing in magnitude, please discuss how this condition (i.e., increased stresses and associated increase in the propensity for stress corrosion cracking) was addressed in your operational assessment,

Response

This issue has been previously addressed in the Steam Generator Annual Reports for the 2001 inspections and 2002 inspections. For the sake of background information, please refer to those reports and the related follow-up responses to requests for additional information.

For the 2003 inspections on Units 1 and 2, attention continued to be given to these signals in our DNT monitoring program. For the respective routine inspections on the B steam generator on each unit, the reporting threshold was lowered to 2.0 volts with history resolution required as defined in the 2003 Annual Report.

Included in this population of tubes subject to tracking are obviously the referenced signals at the tube support plate (TSP) locations. As observed in other generators, the voltage levels continue to be low relative to a level that would cause any concern of significant stresses induced on the tubes. This is supported by the fact that standard size (i.e. 0.720) bobbin and rotating probes continue to pass at these locations. Even though some of these locations do not meet the signal change criteria that require a rotating coil examination, these locations or a sample thereof are included in the 20% DNT sampling program. Confirming with rotating probe Page 1 of 4

examinations that these locations are non-degraded forms the basis for acceptance going forward in the operational assessment. It should be noted that no corrosion cracking degradation has been identified to date at these or other locations in the generators on either of the Surry units.

With regard to new incidences and growth of existing signals, the following provides relevant information on DNT signals at these locations.

Unit Located @ 7 9.01 V and RC tested I 2B 153 6 432 1 11.45 V and RC tested Note: 1. Not indicated in the data as being required due to signal change, hence not exhibiting growth.

2. Some of the signals exceeded the signal change criteria and were by analysis guideline requirement included in the special Interest examination population. Specific growth evaluations have not been typically conducted nor have they been deemed necessary based on observed voltage levels and continued resolution by sample rotating coil examinations.

The monitoring of this category of signals will be continued. Ensuing inspections provide the opportunity to develop data using similar analysis and resolution criteria. This will provide additional data relative to further understanding this possible phenomenon or determining if any ongoing additional monitoring is necessary. As previously noted, no degradation has been observed at these locations based on rotating probe sample inspections.

3. The indications identified at the top of the tubesheet for hot leg locations R22C82 and R23C82 were attributed to interaction with a foreign object that is believed to no longer be in the area. These indications were identified during an inspection of the critical areaof the hot leg top of tubesheet. Please discuss the nature of this critical area (i.e., the low velocity region in the middle of the tube bundle). It was assumed that the object was no longer in this area. Please discuss the basis for this conclusion. Specifically address whether a visual inspection was performed in this critical area and the possibility that the part was not in contact with the tube during the eddy current inspections (or does not conduct eddy currents). Please discuss how other forms of degradation, such as intergranular attack and closely spaced pits, were ruled out as possible causes of the indications.

Page 2 of 4

Response

With regard to the question of critical area, the hot leg side top-of-tubesheet rotating coil inspections are typically focused in the area in the center of the bundle coincident with the low velocity region below the baffle plate. This is the area of the bundle where the largest accumulation of sludge and particulate fallout occurs as the bundle flow is directed upward through the baffle hole opening. Although no corrosion related degradation has been observed to date, this condition presents the potential for sludge and scale pockets and hence increased potential for secondary side tube corrosion. Therefore, the majority of any routine sample set is driven by the observed conditions through mapping the extents of sludge and scale distribution across the tubesheet from prior eddy current and visual inspections.

This area is typically bounded by R1 C27 to C67 and Row 30 C37 to C57. This is somewhat larger than the baffle hole opening to account for previous sludge area observations. Remaining tubes in the sample set outside the critical area include peripheral area tubes, tubes in the blowdown pipe lane, and others randomly selected in the inner bundle. It should be noted that a 100% bobbin inspection was also conducted on the subject generator.

Two (2) locations (R22C82 @ TSH + 0.31 and R23C82 @ TSH + 0.06) were identified with volumetric indications. It was determined with a high level of confidence that both indications did not have morphology representative of closely spaced pits or intergranular attack (IGA). This determination was based on the rotating coil signal attributes (length and width), data from previous indications with the similar responses, and past Surry operating experience. Additionally, the signals were in adjacent tubes consistent with a foreign object wear-type indication. Pitting and cracking type indications have a distinct signal not represented in these tubes.

Pitting has not been observed on this generator in other locations and specifically would not be expected at these locations, since they are in an area outside the sludge region. Commensurately, corrosion degradation (i.e. OD/IGA) would not be expected outside the sludge zone area. History reviews also confirm the presence of small foreign objects in this general area of the generator during past tubesheet lancing and visual inspections. Objects of concern were retrieved and removed from the generator.

Bounding inspections were conducted in the area using the plus point coil probe to determine if additional damage or foreign objects were present. The increased inspection identified no other indications of wear degradation or conductive loose parts. No visual examination was deemed necessary since as a part of a planned one-time expanded hot leg top-of-tubesheet rotating probe inspection program 71Yo of the tubes across the tubesheet were inspected. This was intended to capture tubes not previously subjected to a rotating coil examination. Based on:

1) boxing in the tubes in the area of the observed wear, 2) inspection of an expanded population of tubes, 3) the thoroughness of the examinations performed, and 4) no observed corrosion degradation, evidence of objects or other damage, adequate assurance of tube integrity is maintained.

Page 3 of 4

4. A search of our document management system indicates that the NRC staff does not have a 15-dayp1ugging report on file for the 2003 Unit 2 steam generator tube inspection. Please provide another copy of this report.

Response

A copy of the 2003 Surry Unit 2 steam generator tube plugging report is provided in Attachment 2.

Page 4 of 4

Attachment 1 Virqinia Electric and Power Companv (Dominion)

Annual Steam Generator Report

/Rev. 1 10/04)

Dominion Surry Power Station Unit 1

Station Unit Outage Date Generator Date of Report Examined Surry 1 April, 2003 I B I C October 20, 2003 SG TSP TSP Matl # TSP Baffle Mat7 AVB Mat7 # AVB Model Type.

51F Quatrefoil Type 405 7 Type 405 Chrome 2 ss ss Plated IN-600

1. Tubes Tube Dia. Tube Matl Tube Tube Tks Expansion Heat X-fer Area Pitch 3342 0.875 Alloy 600TT 1.281 0.050 Full Hydraulic 51,500 sq. ft.

Method B Bobbin 3328 3328 Bobbin TSH-TSC B Row 1 U-Bend RC 90 90 +U-Bend Point 7H - 7C SG NDE Ro Column Indication Location Active Measured Method W Code YedNo Wall Penetration B Bobbin 35 17 Percent AV2 No 12%

35 17 Percent AV3 No 17%

B Bobbin 35 18 Percent AV2 No 13%

B Bobbin 38 21 Percent AV1 No 13%

I I I 34 I 58 I Percent I AV3 I No I 17% I 34 58 Percent AV4 No 10%

B Bobbin 26 61 Percent AV3 No 13%

Page 1 of 2

Indications of ImDerfections Detected NDE 1 Ro I Column I Indication 1 Location 1 9 VOL (Wear) TSC + 15.81 No 15%

C +Point RC 1 28 VOL (Wear) TSH + 15.92 No 30%

1 28 VOL (Wear) TSC + 16.44 No 21%

C +Point RC 1 67 VOL (Wear) TSH + 16.72 No 26%

1 67 VOL (Wear) TSC + 15.96 No 35%

C +Point RC 1 86 VOL (Wear) TSH + 16.91 No 34%

Tube Pluaainq sG_ Reason/Mechanism Tubes Plugged B Sludge Lance Monorail Wear 4 (VOL)

B Dent (DNT) 2 B Permeability Variation (PVN) 1 C Sludge Lance Monorail Wear 4 (VOL)

Total Tubes Plugged I (SGB-7) (SGC-4)

I 1 I

~

SG Row Column ReasonIMechanism Repair Method NA I NA I NA NA NA Note 1: As described in the safety evaluation and plant LOCA analyses, steam generators are restricted to an equivalent plugging limit of 15% average and 15% in any one steam generator with no greater than a 5%

differential between any two steam generators expressed in number of tubes per generator.

Page 2 of 2

Attachment 2 Letter from Virqinia Electric and Power Companv to USNRC dated October 23.2003 Steam Generator Tube Inspection Report Dominion Surry Power Station Unit 2

Dominion Resources Services, Inc.

1)oiiiinion Koulcwrd. (;lcn Allcn. VA 23MiO October 23, 2003 Director of Nuclear Reactor Regulation Serial No.: 03-538 United States Nuclear Regulatory Commission NL&OS/mm Fa3 Washington, DC 20555-0001 Docket No.: 50-281 License No.: DPR-37 VIRGINIA ELECTRICAND POWER COMPANY (DOMINION)

SURRY POWER STATION UNIT 2 STEAM GENERATOR TUBE INSPECTION REPORT Planned inservice inspection of the Surry Unit 2 "B" steam generator was completed during the Fall 2003 Refueling Outage. In accordance with Surry Power Station Technical Specification 4.19.F.a, this letter provides notification of the number of steam generator tubes that were plugged during the outage.

Steam Generator "B" The following three (3) tubes were plugged in "B" steam generator as a result of this inspection:

Maximum Measured Through-Wall Location Plugging Attribute Penetration Comments Row 21 Column 10 Wear caused by 20% Preventatively foreign object Row 22 Column 10 Wear caused by foreign object Row 22 Column 11 Wear caused by foreign object

No new commitments are being made as a result of this letter. If YOU have any questions concerning these results, please contact Mr. Gary Miller at (804) 273-2771.

Very truly yours,

- 7-C. L. Funderburk , Director Nuclear Licensing and Operations Support Dominion Resources Services, Inc.

for Virginia Electric and Power Company cc: U. S.Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, GA 30303-8931 Mr. G. J. McCoy NRC Senior Resident Inspector Surry Power Station Mr. C. Gratton NRC Senior Project Manager U. S.Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8G9 Rockville, MD 20852 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555