NL-10-0752, Fifteenth Maintenance/Refueling Outage Steam Generator Tube Inspection Report

Fifteenth Maintenance/Refueling Outage Steam Generator Tube Inspection Report

ML101040084
Person / Time
Site:	Vogtle
Issue date:	04/13/2010
From:	Ajluni M Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-10-0752
Download: ML101040084 (13)

Text

Southern Nuclear Operaling Company, Inc SOUTHERN'\'

April 13, 2010 COMPANY Docket Nos.: 50-424 U. S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, D. C. 20555-0001 Vogtle Electric Generating Plant - Unit 1 Fifteenth Maintenance/Refueling Outage Steam Generator Tube Inspection Report Ladies and Gentlemen:

In accordance with the requirements of Vogtle Electric Generating Plant Technical Specification 5.6.10, Southern Nuclear Operating Company submits this report of the steam generator tube inspections performed during the Unit 1 Fifteenth maintenance/refueling outage (1 R15). Entry into Mode 4 occurred on October 15, 2009.

This letter contains no NRC commitments. If you have any questions, please contact Jack Stringfellow at (205)992-7037.

Respectfully submitted, M. J. Ajluni Manager - Nuclear Licensing MJAlTAHllac

Enclosure:

1R 15 Steam Generator Tube Inspection Report

U. S. Nuclear Regulatory Commission Log: NL-10-0752 Page 2 cc: Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. T. E. Tynan, Vice President - Vogtle Ms. P. M. Marino, Vice President Engineering RType: CVC7000 U. S. Nuclear Regulatory Commission Mr. L. A Reyes, Regional Administrator Mr. R. E. Martin, NRR Project Manager - Vogtle Mr. M. Cain, Senior Resident Inspector - Vogtle Mr. P. Boyle, NRC Project Manager

Vogtle Electric Generating Plant - Unit 1 Fifteenth Maintenance/Refueling Outage Steam Generator Tube Inspection Report Enclosure 1R15 Steam Generator Tube Inspection Report

Enclosure Vogtle Electric Generating Plant - Unit 1 1R15 Steam Generator Tube Inspection Report 1 R15 STEAM GENERATOR TUBE INSPECTION REPORT Introduction The 1R15 outage was conducted after cumulative service equivalent to - 19.8 EFPY (effective full power years); the Cycle 15 power generation was -1.4 EFPY. Analyses based on conservative assumptions used in the Condition Monitoring and Operational Assessments demonstrated that there were no tubes that exceeded the Reg. Guide 1.121 and NEI-97-06 Revision 2 criteria for tube integrity during Cycle 15. During shutdown, primary-to-secondary leakage below the Vogtle Technical Specification limit was detected and evaluated. One tube, (SG3 R1 C20) was subjected to in situ pressure testing based on an apparent axial primary water stress corrosion cracking (PWSCC) indication near the tangent point of the U-bend, but no leakage was seen at Normal Operating differential pressure. A small amount of leakage was observed at Main Steam Line Break differential pressure and above, but all Condition Monitoring criteria were satisfied. The eddy current inspections and in situ testing were performed by the Steam Generator Maintenance Services Group of the Westinghouse Nuclear Services Division. Secondary data analysis was performed by NDE Technology under direct contract with Southern Nuclear.

1R15 Scope The scope for 1R 15 involved the scheduled inspections listed below. The inspection program addressed the known degradation mechanisms observed in Vogtle Unit 1 in prior inspections, as well as those regarded as potential degradation mechanisms.

• 100% Bobbin examination of tubes in SGs 2 and 3, full length except for Rows 1 and 2, which are inspected from tube end to TSP#7 from both HL and CL.

• +Point (mid-range) examination of 50% small radius U-bends (Row 1 and Row 2) in all SGs

• +Point (mid-range) examination of Special Interest, HL and CL, of bobbin possible flaw locations including U-bends. Tubes indicating Seabrook-type U-bend offset behavior, with DSls (TSP indications) that are not confirmed, will nonetheless be preventively plugged.

• +Point (mid-range) examination 100% at HL TTS, +/- 3" in all SGs and 25% CL in SG2 and SG3. Upon approval of the one-cycle of H* criteria for Cycle 16, 35% at HL TIS +/-

3"/-14" captured the required BLG/OXP locations down to the H* depth of 13.1". The remaining 65% of the HL population was inspected TIS +/- 3, while the CL TIS inspections were unaffected.

BLG = differential mix diameter discontinuity signal within the tubesheet of 18 volts or greater as measured by bobbin coil probe; OXP =a tube diameter deviation within the tubesheet of 1.5 mils or greater as measured by bobbin coil profile analysis.

• Bobbin full length examination of the region in SG4 adjacent to tubes affected by the tube pull event. The scope of this testing was bobbin probe examination of a two tube box around the stabilized tubes surrounding the tube pull location at R11 C62 and for columns 61, 62, and 63 rows 14 through 25.

• +Point examination of 100% of dents and dings ~2 volts in HL straight length 'free span of SG2 and SG3.

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Enclosure Vogtle Electric Generating Plant - Unit 1 1R15 Steam Generator Tube Inspection Report

• +Point examination of 100% of dents and dings ~2 volts in U-Bends of SG1 and SG4.

• Visual inspection of tube plugs in all 4 SGs.

As a result of the axial indication found during the base scope inspection at R1C20 in SG3, the scope was expanded from 50% to 100% of U-Bend RPC in all SGs, and to 20% of Row 3 U Bends in SG3. All previous data was reviewed for a similar indication.

Damage Mechanisms Found and NDE Techniques Utilized The following damage mechanisms were discovered in the Vogtle Unit 1 SGs during 1R15:

• Outside diameter stress corrosion cracking (OOSCC) at the top of the tube sheet was found in 20 tubes among the 4 SGs. The +Point probe was used to inspect 100% of the top of the tube sheet in all four SGs.

• A single axial PWSCC indication was found above the HL tangent point in SG3 (R1 C20).

The +Point probe was used for the small radius U-bend inspection.

• Antivibration bar (AVB) wear was found in SG 2 and SG3. AVB wear is identified during the bobbin inspection.

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Enclosure Vogtle Electric Generating Plant - Unit 1 1R15 Steam Generator Tube Inspection Report Service Induced Indication Descriptions ODSCC Outside diameter stress corrosion cracking identified in Vogtle 1R15 is provided in the following table:

VogtIe 1 ODSCC Ind'Icatlons f or 1R15 SG Row Col Volts Ind Max, Depth Circumferential Degraded Area

(%) Extent (deg) (%)

1 1 2 113 0.07 MCI 93.0 67.0 11.40 I

1 3 108 0.13 MCI 85.0 73.0 8.10 1 5 110 0.10 SCI;! 68.", 73.0 2.20 1 7 106 13.00 SCI 97.0 73.0 3.20 1 7 106 0.13 SCI 74.0 73.0 3.00 1 7 117 0.11 SCI 42.0 67.0 2.10 1 8 115 0.09 SCI 44.0 67.0 2.00 1 8 115 0.09 SCI 32.0 67.0 1.10 1 10 104 0.16 SCI 72.0 67.0 3.20 1 10 112 0.07 MCI 90.0 73.0 19.30 1 12 120 0.14 SCI 53.0 69.0 3.10 1 15 115 0.09 SCI 40.0 67.0 2.10 2 13 62 0.31 SCI 98.0 13.0 3.90 2 I ;.::;.:: 103 0.10 SCI 73.0 73.0 3.30 3 2 109 0.11 MCI 52.0 79.0 5.40 3 3 106 0.11 SCI 76.0 81.0 2.60 3 6 114 0.25 SCI 81.0 79.0 4.30 3 7 113 0.12 SCI 88.0 81.0 2.60 4 3 105 0.10 SCI 80.0 73.0 5.40 4 4 113 0.06 SCI 10.0 77.0 <

4 4 117 0.09 SCI 34.0 77.0 2.10 4 4 122 0.13 SCI 84.0 79.0 3.80

..

The inspection result was classified as an indication type In accordance with a convention of 3-letter codes used for grouping and tracking various types of indications.

2 SCI Single circumferential indication 3

MCI Multiple circumferential indication The circumferential OOSCC flaws were located at the bottom of the hydraulic expansion transition at the top of the tube sheet.

PWSCC Primary water stress corrosion cracking identified in Vogtle 1R 15 is provided in the following table:

Vone I 1 Ax:laI PWSCC I n SrnaII Rad'I US U- Bend f or 1R15 SG Row Col Volts Ind Max. Depth Axial Length

(%) (inches) 3 1 20 3.09 SAl 100.0 0.54

1. SAl - Single aXial indication Page 3 of 10

Enclosure Vogtle Electric Generating Plant - Unit 1 1R15 Steam Generator Tube Inspection Report Loose parts wear Loose parts wear indications re-confirmed in Vogtle 1 R15, are provided in the following table:

Vogtle 1 Loose Parts Wear Indications for 1R15 SG Row Col Volts %TWD Locn I 1 39 100 0.70 13.0 TSH 1 41 100 2.05 31.0 TSH 41 100 0.85 16.u I ISH 1 41 101 1.46 24.0 TSH 1 41 102 1.27 22.0 TSH 1 41 103 1.36 23.0 TSH 2 1 70 0.28 6.0 TSC'"

2 1 70 0.40 8.0 TSC 2 1 70 0.18 4.0 TSC 2 1 78 0.04 4.0 TSC 2 1 78 0.09 8.0 TSC 2 1 82 0.05 5.0 TSC I

2 1 91 0.17 15.0 BPCJ

• 4 2 6 1 0.07 7.0 1C 2 16 6 0.10 12.0 BPC K

16 7 0.33 29.0 BPC 30 111 1.96 BPH"

• 4 40 106 0.27 16.0 AV5° 1 TSH - Tubesheet region on HL side.

2 TSC - Tubesheet region on CL side 3 BPC - Flow distribution baffle plate on CL side 4 1C - Row 1 CL side 5 BPH - Flow distribution baffle plate (FDB) on HL side 6 AV - Antivibration Bar Page 4 of 10

Enclosure Vogtle Electric Generating Plant - Unit 1 1R15 Steam Generator Tube Inspection Report AVB Wear AVB wear continued to be identified in Vogtle 1R15 in SG2 and SG3. AVB wear identified is provided in the tables below:

VogltI e 1R15. SG2AVBWear Ind"Icaf Ions

.

Row Col Location 1 1R15% Row Col Location 1R15 %

26 49 AV2 11.0 43 88 AV3 17.0 26 114 AV1 9.0 43 88  ! AV5 16.0 27 115 AV6 10.0 43 91 AV2 28.0

~

AV6 10.0 43 91 AV3 17.0 12 AV1 10.0 43 91 AV4 11.0 32 12 AV3 18.0 43 91 AV5 30.0 34 106 AV3 16.0 43 93 AV2 12.0 34 108 AV4 14.0 43 93 AV3 21.0 !

35 13 AV3 9.0 43 93 AV4 22.0 35 35 13 13 AV4 AV5 11.0 11.0 f-H} 93 94 AV5 AV2 12.0 13.0 35 13 AV6 9.0 43 94 AV3 13.0 35 14 AV5 11.0 43 95 AV4 15.0 35 17 AV3 10.0 43 96 AV5 13.0 35 25 AV3 9.0 43 98 AV3 15.0 !

35 32 AV4 11.0 43 98 AV4 30.0 35 35 35 83 83 83 AV3 AV5 AV6 12.0 15.0 13.0

-¥a 43 98 98 101 AV5 AV6 AV4 43.0 10.0 19.0

,

35 100 AV5 10.0 46 49 AV3 25.0 ,

35 104 AV3 11.0 46 49 AV4 16.0 35 105 AV5 12.0 46 50 AV1 21.0 36 13 AV3 7.0 46 50 AV2 33.0 36 37 38 108 97 15 AV6 AV3 AV6 9.0 11.0 9.0 H 46 50 50 50 AV3 AV4 AV5 33.0 29.0 26.0 38 89 AV2 10.0 46 50 AV6  ! 13.0 38 89 AV4 12.0 46 53 AV5  ! 8.0 38 89 AV5 16.0 46 58 AV2 17.0 38 106 AV5 24.0 46 58 12.0 38 108 AV3 10.0 46 58 AV5 13.0 38 108 AV4 13.0 48 97 AV1 10.0 39 38 AV2 17.0 48 97 AV2 16.0

~~

3 AV5 19.0 48 97 I 34.0 39 105 AV5 17.0 48 98 11.0 40 37 AV4 14.0 48 98 AV4 17.0 40 41 AV3 12.0 48 98 AV5 18.0 40 41 AV4 11.0 48 98 AV6 24.0 40 93 AV2 15.0 49 89 AV3 11.0 40 93 AV5 20.0 49 89 AV4 20.0 40 98 AV5 18.0 49 89 AV5 25.0 1 AV# - Location of AVB intersection with the tube (there are up to 6)

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Enclosure Vogtle Electric Generating Plant - Unit 1 1R15 Steam Generator Tube Inspection Report Vogtle 1 R15: SG2 AVB Wear Indications (continued)

~w Col 33 Location AV4 1R15 %

25.0 Row 50 Col 83 Location AV2 1R15 %

11.0 !

41 33 AV5 22.0 50 84 AV2 12.0 41 42 AV2 17.0 50 84 AV3 29.0 I 41 42 AV3 13.0 50 84 AV4 21.0 41 42 AV4 32.0 50 84 AV5 11.0 41 42 AV5 37.0 50 89 AV2 16.0 41 102 AV3 20.0 50 89 AV3 15.0 41 102 AV5 35.0 50 89 AV4 28.0 42 76 AV1 9.0 50 92 AV2 15.0 42 76 AV2 31.0 50 92 AV3 17.0 42 76 AV3 19.0 51 81 AV2 12.0 42 76 AV4 21.0 51 81 AV4 13.0 42 76 AV5 38.0 52 91 AV2 17.0 I 42 76 AV6 21.0 52 91 AV5 12.0 42 86 AV3 12.0 53 61 AV5 11.0 42 92 AV4 17.0 53 79 AV2 17.0 42 92 AV5 13.0 53 79 AV3 22.0 42 94 AV3 18.0 53 83 AV2 31.0 42 94 AV4 25.0 53 83 AV3 28.0 42 94 AV5 15.0 54 84 AV2 10.0 42 96 AV3 13.0 54 84 AV3 21.0 42 96 AV4 18.0 54 84 AV4 21.0 I 42 96 AV5 17.0 54 84 AV5 24.0 42 97 AV2 12.0 54 85 AV2 21.0 42 97 AV3 16.0 54 85 AV3 37.0 42 97 AV4 25.0 54 85 AV4 32.0 42 100 AV3 18.0 I 54 85 AV5 46.0 42 100 AV4 21.0 54 85 AV6 13.0 43 68 AV3 14.0 55 59 AV3 14.0 43 68 AV5 14.0 55 59 AV3 12.0 43 87 AV2 14.0 55 59 AV5 11.0 43 87 AV3 16.0 55 83 AV5 16.0 43 87 AV4 9.0 55 84 AV5 19.0 43 87 AV5 19.0 57 72 AV1 12.0 43 88 AV2 10.0 57 79 AV5 16.0 1 AV# - Location of AVB intersection with the tube (there are up to 6)

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Enclosure Vogtle Electric Generating Plant - Unit 1 1 R15 Steam Generator Tube Inspection Report

.

Vogt Ie 1R15. SG3AVBWear Ind"Icatlons Row Col Location 1R15 % I Row Col Location 1R15%

28 8 AV6 23 42 28 AV2 10 28 8 AV1 14 42 28 AV4 10 32 52 AV1 13 42 29 AV4 20 35 16 AV3 11 42 35 AV4 19 36 13 AV5 12 42 43 AV2 19 36 34 AV5 15 42 43 AV5 19 36 I 34 AV2 12 42 43 AV6 14 I 36 44 AV5 12 42 50 AV4 38 36 44 AV2 10 42 50 AV2 31

~107 AV1 13 42 50 AV3 18 3 107 AV5 12 42 50 AV1 8 37 108 AV6 13 42 58 AV3 18 38 34 AV5 13 42 58 AV2 10 38 35 AV5 12 42 63 AV4 16 38 69 AV3 9 42 66 AV4 18 38 AV3 17 R2 66 AV3 13 38 106 AV6 12

-~~

38 106 AV5 15 38 107 AV4 AV4 12 39 17 AV3 25 22 V5 12 39 17 AV6 25 40 AV3 16 I 39 39 39 17 17 20 AV4 AV2 AV4 21 11 11 45 45 45

~

40 40

~1$15 A

AV6 15 9

39 26 AV2 20 45 46 AV3 28 39 39 39 35 35 35 AV3 AV4 AV5 24

~45 45 45 46 46 AV2 AV4 AV5 i=20 27 13 39 48 AV4 45 46 AV1 10 39 51 AV3 9 45 48 AV3 26 39 m=AV4 9 45 48 AV2 17 39 39 39 66 66 AV3 AV3 AV5 16=t 17 17 45 45 45 48

• f---AV3 AV5 AV2 15 24 20 39 66 AV4 14 45 61 AV5 22 39 67 I AV3 12 45B,1 AV4 I 19 39 67 I AV4 10 45 2 AV3 I 35 39 102 AV2 16 45 62 AV4 35

,

39 102 AV5 13 45 63 AV3 33 39 104 AV5 25 45 64 63 AV4 20 39 40 40 104 19 19 AV4 AV5 AV4 AV6 10 16 14 13

+/-E45 67 67 AV3 AV4 AV3 AV5 14 18 17 12 40 19 I 45 69 40 30 AV5 22 45 69 AV2 10 AV# - Location of AVB intersection with the tube (there are up to 6)

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Enclosure Vogtle Electric Generating Plant - Unit 1 1R15 Steam Generator Tube Inspection Report Vogtle 1R15: SG3 AVB Wear Indications (continued)

Row Col Location 1R15 % Row Col Location 1R15%

40 35 AV4 15 45 77 AV2 13 40 97 AV3 17 45 77 AV4 11 40 97 AV4 14 45 82 AV3 14 40 98 AV2 15 45 82 AV4 13 40 40 40 40 100 100 101 101 AV5 AV2 AV2 AV5 14 13 13 13

+/-ill 46 25 25 26 35 AV5 AV4 AV5 AV4 19 15 14 17 40 102 AV2 18 47 38 AV4 25 40 102 AV6 14 47 45 AV4 18 40 104 AV4 22 47 45 AV2 15 I 40 105 AV6 16 47 95 AV6 11 41 19 AV5 20 47 96 AV4 41 19 AV4 15 49 92 AV5 13 41 14 49 96 AV6 21 41 20 AV4 12 49 AV4 15 41 20 AV5 12 49 96 AV5 15 41 21 AV5 14 50 86 AV2 15 41 21 AV4 10 50 86 AV5 13

~

• 41 102 AV3 34 51 55 AV4 41 102 AV4 24 51 82 AV4 41 102 AV2 15 51 82 AV5 24 41 102 AV6 12 51 82 AV3 13 42 21 AV5 20 51 92 AV6 15 I 42 21 AV4 16 53 84 AV4 32 42 21 AV3 15 53 84 AV3 22 42 21 AV2 12 53 84 AV5 15 42 23 AV4 13 AV1 13 42 26 AV5 13 54 AV6 12 42 26 AV4 11 58 AV6 13 42 27 AV5 31 59 61 AV4 13 42 27 AV4 15 59 68 AV6 14 1 AV# - Location of AVB intersection with the tube (there are up to 6)

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Enclosure Vogtle Electric Generating Plant - Unit 1 1R15 Steam Generator Tube Inspection Report Number of Tubes Plugged Table 1 presents a summary list of all SG tubes plugged in Vogtle 1R15 and the related degradation mechanism.

Table 1: 1R15 Plugged TubesJ25)

SG Row Col Ind Degradation Mechanism 1 2 113 MCI OOSCC 1 3 108 MCI OOSCC 1 5 110 SCI OOSCC I 1 7 106 SCI OOSCC  !

I 1 7 117 SCI OOSCC 1 8 115 SCI OOSCC 1 10 104 SCI OOSCC 1 10 112 MCI OOSCC 1 12 120 SCI OOSCC 1 15 115 SCI OOSCC 1 7 35 PVN Administrative

• 1 44 60 RRT Administrative 2 13 62 SCI OOSCC 2 22 103 SCI OOSCC 2 43 98 PCT AVB Wear.

2 54 85 PCT AVB Wear 3 1 20 SAl PWSCC 3 2 109 MCI OOSCC 3 3 106 SCI OOSCC 3 6 114 SCI OOSCC 3 7 113 SCI OOSCC 105 SCI OOSCC 113 SCI OOSCC 117 SCI OOSCC 4 4 122 SCI OOSCC Total plugging in the SGs after 1R15 is as follows:

SG1 - 27 tubes for a total of 0.48% tubes plugged SG2 - 19 tubes for a total of 0.34% tubes plugged SG3 - 33 tubes for a total of 0.59% tubes plugged SG4 - 67 tubes for a total of 1.19% tubes plugged Page 9 of 10

Enclosure Vogtle Electric Generating Plant - Unit 1 1R15 Steam Generator Tube Inspection Report In Situ Testing Non-destructive evaluation (NDE) data determined the axial indication in SG3 R1C20 exceeded 80% depth over 0.28 inches in one segment and over 0.16 in a second segment. Its maximum

+Point amplitude was 3.09 volts in the longer of the 2 segments, which exceeds the threshold voltage for leakage in the EPRI Steam generator In Situ Pressure Test Guidelines, Revision 3.

The total length of the indication exceeded the proof of pressure testing criteria of 0.4 inches set forth in the 1R 15 Degradation Assessment.

No detectable leakage was observed at LlP NO (L'lP = 1323 psi) adjusted for temperature and gage uncertainty (actual test pressure 1700 psig). At MSLB conditions (L'lP= 2650 psi), adjusted to exceed 3046 psi to an actual test pressure 3200 psig, the observed leakage was 77.2 ml over 10 minutes, equivalent to 0.002 gpm. The results of the in situ test indicate that a short length of the crack is through-wall; the flaw is interrupted by part through-wall ligaments which increase the apparent strength of the tube. Since the leakage at MSLB pressure did not exceed 1gpm (0.25 gpm per worst case SG), and the tube did not burst at 3LlPNO , the condition monitoring requirements have been satisfied.

Condition Monitoring Conclusions No indications were found to exceed the condition monitoring limits specified in the Degradation Assessment.

No indications of axial ODSCC were reported. No new axial ODSCC indications have been found since 1R13. The absence of reportable axial ODSCC for cycle 15 presents no condition monitoring concern.

Tube pull analyses confirmed circumferential ODSCC at the top of tubesheet. Twenty tubes were identified as circumferential ODSCC across all SGs. None of these tubes passed the screening for in situ testing. The largest amplitude (SG2 R13C62) was determined to have 0.31 volts. The largest circumferential extent (SG1 R10C112) maintained a crack depth of 19.3%; far below the condition monitoring limit of 55.0%.

Primary-to-secondary leakage was not detected during the cycle. During cool down, a small amount of leakage was detected, but was not measurable. SG3 R1 C20 axial PWSCC was suspected to be responsible for the leakage and was subjected to in situ testing after exceeding length limits and +Point amplitudes. The results of the in situ testing revealed no leakage at LlPNO and very low leak rates at both MSLB and 3LlP NO conditions adjusted, which satisfied the condition monitoring criteria.

None of the AVB wear indications in either SG2 or SG3, adjusted for the sizing model and the 95% probability measurement error associated with the measurement technique, exceed the Condition Monitoring limits as given in the 1R15 Degradation Assessment.

Given the absence of operating leakage during Cycle 15, it is concluded that there was no leakage from plugs. This is consistent with the video inspection of the tube plugs in all 4 SGs which produced no exceptions to expected conditions.

Evaluation of the indications found in the 1R15 inspections confirms that the tube integrity structural and leakage performance criteria condition monitoring requirements as specified in I\IEI-97-06 Revision 2 are satisfied.

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