NL-13-2036, Sixteenth Maintenance / Refueling Outage Steam Generator Tube Inspection Report

Sixteenth Maintenance / Refueling Outage Steam Generator Tube Inspection Report

ML14170A021
Person / Time
Site:	Vogtle
Issue date:	09/26/2013
From:	Pierce C Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-13-2036
Download: ML14170A021 (11)

Text

Charles R.Pierce Southern Nuclear Regulatory Affairs.Director Operating Company, Inc.

40 Inverness Center Parkway Post Office Box 1295 Birmingham, Alabama 35201 Tel 205.992.7872 Fax 205.992.7601 SOUTHERN COMPANY September 26, 2013 Docket Nos.: 50-425 NL-13-2036 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Vogtle Electric Generating Plant - Unit 2 Sixteenth Maintenance / Refueling Outage Steam Generator Tube Inspection Reoort 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 2 sixteenth maintenance / refueling outage (2R16). Entry into Mode 4 occurred on March 31, 2013.

This letter contains no NRC commitments. If you have any questions, please contact Ken McElroy at (205) 992-7369.

Respectfully submitted, C. R. Pierce Regulatory Affairs Director CRP/RMJ/Iac

Enclosure:

2R16 Steam Generator Tube Inspection Report cc: Southern Nuclear Operatinq Company Mr. S. E. Kuczynski, Chairman, President & CEO Mr. 0. G. Bost, Executive Vice President & Chief Nuclear Officer Mr. T. E. Tynan, Vice President - Vogtle Mr. B. L. Ivey, Vice President - Regulatory Affairs Mr. B. J. Adams, Vice President - Fleet Operations RType: CVC7000 U. S. Nuclear Regulatory Commission Mr. V. M. McCree, Regional Administrator Mr. R, E. Martin, NRR Senior Project Manager - Vogtle Mr. L. M. Cain, Senior Resident Inspector - Vogtle A* (

Mr.uecAII &nRset

Vogtle Electric Generating Plant - Unit 2 Sixteenth Maintenance/ Refueling Outage Steam Generator Tube Inspection Report Enclosure 2R16 Steam Generator Tube Inspection Report

Enclosure to NL-13-2036 2R1 6 Steam Generator Tube Inspection Report Introduction The Vogtle 2R16 outage was conducted after cumulative steam generator (SG) service equivalent to approximately 21.3 effective full power years (EFPY); the Cycle 16 power generation was approximately 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 or NEI-97-06 Revision 3 criteria for tube integrity during Cycle 16. The eddy current inspections 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. One tube (R56C82) in SG 3 was plugged due to 41% through wall (TW) anti-vibration bar (AVB) wear that exceeded the Technical Specifications (TS) plugging criteria. One tube (R15C60) was stabilized and plugged in SG 2 due to a single circumferential outer diameter stress corrosion crack (ODSCC) signal at the hot leg top of tubesheet. Criteria for in-situ testing were not met for either tube. Permanent H* Alternate Repair Criteria was approved by the NRC for implementation. Therefore, tube end +Point inspections below top of tubesheet (TTS) -15.2 inches were omitted, and the TTS inspections ranged from TTS +3 inches to TTS -15.2 inches.

2R16 SG Primary Side Base Scope The scope for 2R16 involved the scheduled inspections listed below. The inspection program, required by Revision 7 of the EPRI PWR SG Examination Guidelines, addressed the known degradation mechanisms observed in Vogtle Unit 2 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 tube support plate (TSP) #7 from both hot leg (HL) and cold leg (CL).

• 100% +Point examination of Row 1 and Row 2 U-bends from the top TSP on the HL to the top TSP on the CL in SGs 2 and 3.

• +Point examination of Special Interest, HL and CL, of bobbin possible flaw locations including U-bends.

• 100% +Point examination at HL tubes in SGs 2 and 3 from TTS + 3 inches to the licensed Permanent Alternative Repair Criteria (ARC) depth for H* (tubesheet region on HL side (TSH) +3/-15.2 inches). This inspection captured the U-S BLG / OXP populations, as defined below, along with the required periodic sample specified in the regulatory approval of ARC.

- 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.

0 100% +Point examination of total dents and dings > 2 volts in SGs 2 and 3 HL straight lengths and U-bends.

0 100% Visual inspection of tube plugs in SGs 2 and 3.

= Visual inspection in SGs 2 and 3 of channel head primary side HL and CL in accordance with Westinghouse Letter NSAL 12-1, "Steam Generator Channel Head Degradation".

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Enclosure to NL-1 3-2036 2R16 Steam Generator Tube Inspection Report Inspection Expansion Based on the confirmation of a single indication of ODSCC at the HL tubesheet expansion transition in SG 2, an expansion of the eddy current program was conducted in SG l and 4 in accordance with the EPRI PWR SG Examination Guidelines. The following inspection scope listed below was conducted during 2R16 for SG 1 and SG 4:

• 20% +Point examination at HL tubes in SGs 1 and 4 from TTS +3 inches to the licensed Permanent ARC depth for H* (TSH +3/-15.2 inches).

• 100% Visual inspection of tube plugs in SGs 1 and 4.

. Visual inspection in SGs 1 and 4 of channel head primary side HL and CL in accordance with Westinghouse Letter NSAL 12-1, "Steam Generator Channel Head Degradation".

2R16 SG Secondary Side Activities TTS Sludge Lancing in all 4 SGs.

• Foreign Object Search and Retrieval (FOSAR) in all 4 SGs.

o Annulus and tubelane region including periphery tubes, o Possible loose parts (PLP) calls from eddy current tube inspections, and o Legacy items.

Damage Mechanisms Found and NDE Techniques Utilized Based on SG eddy current and visual inspection results, a new degradation mechanism to Unit 2 was identified. The existing degradation mechanisms in the Vogtle Unit 2 are:

• (New) ODSCC at the hot leg tubesheet expansion transitions. A single circumferential ODSCC indication was identified in SG 2.

o + Point and Ghent probe techniques were used to analyze the indication.

• Mechanical Wear due to Foreign Objects o +Point and bobbin techniques were used to evaluate the wear indications.

• Mechanical Wear at AVB Supports.

o Bobbin techniques were used to evaluate wear indications.

• Mechanical Wear and Wall loss from Secondary Side Cleaning Activities.

o Bobbin techniques were used to evaluate the wear indications.

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Enclosure to NL-13-2036 2R1 6 Steam Generator Tube Inspection Report Service Induced Indication Descriptions ForeignObject Wear Foreign objects have been reported as the cause for tube wear at Vogtle Unit 2 during prior inspections; therefore, wear due to foreign objects is classified as an existing degradation mechanism and has been addressed in the SG inspections during 2R16. For the tubesheet locations given in Table 1, all surrounding open tubes were examined for 3 inches above the top of the tubesheet as part of the HL TTS +Point program.

Tube location SG 1 R47C85 was visually inspected as part of the planned secondary side inspection in SG 1 during 2R16. No change in the tube wear indication is observed visually and no objects were noted in the adjacent areas between the 2R15 and 2R16 outage inspections.

This tube location, SG 1 R47C85, and surrounding area was +Point tested again in 2R1 6 as part of the eddy current expansion program. A newly reported 10% TW tube wear indication was observed on SG1 R47C84. A history review of tube SG 1 R47C84 found this indication was present during 2R1 5 with no apparent growth. The historical PLPs at tubes SG 1 R48C86 and R49C86 were also inspected during 2R16 with no foreign objects found. The visual inspection information combined with the evaluation of the 2R16 and historical eddy current

+Point data for these wear indications show there has been no growth and no foreign objects in the area.

There was one set of adjacent PLP indications in SG 2 at the top of the HL tubesheet at R31C49, R32C49, R32C50, and R33C50 observed during 2R16. These tubes were boxed in with +Point inspection and visual confirmation was performed after sludge lancing with no further indications of a foreign object. The historical PLP indication in SG 2 at RIC1 18 was visually inspected. A sludge rock was identified, added to the foreign object log, and evaluated.

No PLPs or tube wear indications were identified from the eddy current inspections in SG 3 during 2R16.

A historical tube wear indication is located in SG 4 at R12C57 just above the HL TTS. This indication was measured at 20% through-wall during 2R16 and 19% TW in 2R1 5. The TW measurement variation for this historical wear call is inside the uncertainty range for the applied

+Point sizing technique. No PLP indications were identified in SG 4 during the 2R16 inspection.

Based on the final inspection results, the observed indications did not exceed the condition monitoring limits and did not require in-situ proof of pressure and leakage testing to demonstrate tube integrity.

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Enclosure to NL-13-2036 2R16 Steam Generator Tube Inspection Report Table 1: Vogte 2 PLP/PCT for 2R16 SG Row Column Indication %TWD Location 1 49 86 PLP TSH+0.41 inch 1 48 86 PLP TSH +0.47 inch 1 48 86 PLP - TSH +0.21 inch 1 47 85 POT 9 TSH +0.07 inch 1 47 84 PCT 10 TSH +0.16 inch 2 1 118 PLP - TSH +0.09 inch 2 33 50 PLP - TSH +0.11 inch 2 32 50 PLP - TSH +0.59 inch 2 32 49 PLP - TSH +1.23 inches 2 32 49 PLP - TSH +0.83 inch 2 31 49 PLP - TSH +1.7 inches 4 12 57 PCT 20 TSH +0.4 inch

%TWD - Percent Through-wall Depth PLP - Possible Loose Part TSH - Tubesheet region on HL side PCT - Foreign Object Wear Mechanical Wear and Wall Loss from Secondary Side Cleaning Volumetric indications associated with secondary side cleaning activities have been reported in the Vogtle Unit 2 SGs during previous inspections. They have been reported to visually resemble tube oxide removal patterns. The only indication tested during 2R16, identified in Table 2, was SG 3 at R1C112 at TSC+18.15 inches. The TW measurement variation for this historical wear call is inside the uncertainty range for the applied +Point sizing technique; therefore, no apparent growth of this indication has occurred between the 2R14 and 2R16 inspections. Based on the inspection data, the indication did not exceed the condition monitoring limits and did not require in-situ proof of pressure and leakage testing to demonstrate tube integrity.

Table 2: Vogtle 2 Tube Wear and Wall Loss from Secondary Side Cleaning for 2R16 SG Row Column Volts Indication %TWD Location 3 1 112 0.26 PCT 24 TSC+18.15 TSC - Tubesheet region on CL side Anti-Vibration Bar (A VB) Wear AVB wear continued to be identified in Vogtle 2R16 in SG2 and SG3. AVB wear identified is provided in Table 3 (SG 2) and Table 4 (SG 3). All AVB locations have been examined in SG 2 and SG 3; only one wear location, SG 3 R56C82, exceed the technical specification plugging criteria of 40% TW. None of the indications exceeded the condition monitoring limits and therefore did not require in-situ pressure and leakage testing to demonstrate tube integrity.

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Enclosure to NL-1 3-2036 2R1 6 Steam Generator Tube Inspection Report Table 3: Vogtle 2R16 SG2 AVB Wear Indications Row Col Location' 2R16 % TWO Row Col Location1 2R16% TWO 12 121 AV6 10 39 44 AV3 15 28 115 AV1 13 39 44 AV5 10 28 115 AV6 17 39 44 AV6 5 29 10 AV5 10 39 52 AV4 14 30 10 AV5 10 39 88 AV4 13 34 12 AV3 6 39 107 AV2 9 36 14 AV4 6 40 48 AV4 22 36 16 AV5 11 40 48 AV5 13 36 16 AV6 12 40 52 AV3 22 36 106 AV3 9 40 52 AV5 14 36 106 AV4 13 .40 54 AV3 12 36 106 AV5 11 40 57 AV3 11 36 106 AV6 10 40 63 AV3 16 37 54 AV5 13 40 64 AV4 10 38 15 AV2 9 40 73 AV3 12 38 15 AV3 9 40 73 AV5 14 38 39 AV2 8 40 73 AV6 12 38 39 AV3 12 42 19 AV2 11 38 39 AV4 12 42 19 AV3 11 38 39 AV5 18 42 19 AV4 12 38 45 AV1 12 42 19 AV5 12 38 74 AV1 9 42 50 AV2 13 38 74 AV2 12 42 50 AV3 10 38 74 AV3 16 42 50 AV4 10 38 74 AV4 16 42 74 AV2 32 38 74 AV5 10 42 74 AV3 29 38 74 AV6 6 42 74 AV4 11 38 81 AV2 13 42 74 AV5 11 38 81 AV3 10 42 74 AV6 11 38 81 AV5 13 42 88 AV2 13 38 81 AV6 14 43 20 AV1 10 38 100 AV3 12 43 20 AV2 13 39 43 AV2 22 43 64 AV1 15 39 43 AV3 20 43 73 AV4 22 39 43 AV4 14 44 72 AV5 18 39 43 AV5 16 45 49 AV3 12 39 43 AV6 12 48 56 AV3 12 39 44 AV2 11 49 32 AV4 11 AV# - Location of AVB intersection with the tube (there are up to 6)

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Enclosure to NL- 13-2036 2R1 6 Steam Generator Tube Inspection Report ThbIA ~ (c~nntinuAd~~ VocitlA 2RIR ~2 AVA WARr Indir~ntinnR Row Col Location ' 2R16 % TWD Row Col Location' 2R16% TWD 49 66 AV2 16 51 91 AV4 15 49 66 AV3 15 51 91 AV5 26 49 74 AV3 24 .51 91 AV6 15 49 91 AV2 22 52 52 AV3 8 49 91 AV3 13 52 91 AV4 15 50 70 AV4 17 53 52 AV3 9 50 89 AV3 10 53 88 AV4 14 50 89 AV4 14 53 88 AV5 20 50 89 AV5 11 53 90 AV4 11 50 89 AV6 12 53 90 AV6 10 50 91 AV4 9 54 86 AV4 12 51 71 AV6 9 55 74 AV5 10 51 72 AV2 11 55 84 AV1 8 51 72 AV3 10 55 84 AV4 11 51 72 AV4 10 56 41 AV3 11 51 72 AV5 11 56 43 AV2 10 151 74 AV2 11 56 43 AV6 12 51 74 AV3 24 56 52 AV3 11 51 74 AV4 14 56 82 AV5 11 51 74 AV5 9 57 49 AV6 14 51 74 AV6 9 57 62 AV1 10 51 87 AV2 29 57 62 AV2 10 51 87 AV3 30 57 64 AV3 15 51 87 AV4 22 57 64 AV4 14 51 87 AV5 30 57 72 AVI 12 51 89 AV3 12 57 72 AV3 12 51 89 AV4 32 57 79 AV3 9 51 89 AV5 29 57 79 AV4 11 51 89 AV6 17 58 70 AV2 11 51 90 AV4 19 59 56 AV4 13 51 90 AV5 15 59 66 AV2 14 51 91 AV3 12 1 AV# - Location of AVB intersection with the tube (there are up to 6)

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Enclosure to NL-13-2036 2R16 Steam Generator Tube Inspection Report Table 4: Vogtle 2R16 SG3 AVB Wear Indications Row Col Location' 2R16 % TWD Row Col Location' 2R16% TWD 12 121 AVI 10 43 82 AV5 14

,30 112 AV5 12 44 23 AV3 11 32 12 AV2 13 44 64 AV4 6 32 12 AV5 21 44 68 AV3 6 34 13 AVI1 11 45 62 AV4 10 34 13 AV2 10 46 62 AV4 12 34 13 AV4 12 48 37 AV3 15 34 13 AV5 20 50 29 AV4 12 34 13 AV6 12 50 48 AV4 12 35 64 AV4 5 50 48 AV5 14 39 72 AV2 19 50 48 AV6 11 39 72 AV3 24 50 95 AV5 9 39 72 AV4 27 51 38 AV5 9 40 44 AV2 12 52 83 AV2 18 41 19 AV4 13 52 83 AV3 33 41 77 AV2 14 52 83 AV4 27 41 77 AV3 10 52 83 AV5 26 41 77 AV4 24 53 62 AV3 12 41 77 AV5 22 53 62 AV5 6 41 82 AV2 11 54 38 AV5 14 41 82 AV3 10 54 62 AV2 5 41 82 AV4 9 56 82 AV2 27 42 20 AV3 15 56 82 AV3 41 42 20 AV4 13 56 82 AV4 22 42 53 AV2 11 57 48 AV4 15 42 53 AV4 8 57 48 AV5 14 42 64 AVI 6 57 48 AV6 16 42 64 AV2 24 57 49 AV4 8 42 64 AV3 20 57 62 AV4 13 42 64 AV4 33 57 78 AV2 10 42 64 AV5 21 58 49 AVi 14 43 62 AV4 8 58 49 AV5 14 43 82 AV2 10 _58 49 AV6 10

'AV# - Location of AVB intersection with the tube (there are up to 6)

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Enclosure to NL-13-2036 2R16 Steam Generator Tube Inspection Report ODSCC A single circumferential ODSCC indication was found at the top of tubesheet hot leg expansion transition in SG2 R15C60. Criteria for in-situ proof testing and leak testing were not met; therefore, in-situ testing was not required to be performed to demonstrate tube integrity. The tube was stabilized and plugged based on detection of circumferential ODSCC.

Table 5: Voc te Single Circumferential ODSCC for 2R16 SG Row Column Indication Crack Max. Stabilized?

Angle Depth (%)

(degrees) 2 15 60 SO0 47 33% Yes SCI - Single circumferential indication Number of Tubes Plugged Table 6 presents a summary list of all SG tubes plugged in 2R16 and the related degradation mechanism.

Table 6: 2R16 Plugged Tubes

=SG Row Column Indication Degradation Mechanism 2 15 60 SCI ODSCC 3 56 82 PCT AVB Wear Total plugging in the SGs after 2R16 is as follows:

SG 1- 6 tubes for a total of 0,11% tubes plugged SG 2- 15 tubes for a total of 0.27% tubes plugged SG 3- 5 tubes for a total of 0.09% tubes plugged SG 4- 22 tubes for a total of 0.39% tubes plugged Total tubes plugged for all Unit 2 SGs: 48, 0.21%

Tube Axial Displacement (Slippage) Monitoring Bobbin data collected from SG2 and SG3 has been screened for large amplitude tubesheet indications of greater than 50 volts with a phase angle between 25 and 50 degree, indicative of a severed tube. No tube severance indications were reported; therefore, no tube slippage was identified. There was no SG primary to secondary leakage present during Cycle 16. The calculated accident induced leakage rate is zero; therefore, the performance criteria for Cycle 16 with respect to the H* permanent alternate repair criteria have been satisfied.

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Enclosure to NL- 13-2036 2R1 6 Steam Generator Tube Inspection Report Condition Monitoring Conclusions Based on the final Vogtle 2R1 6 inspection data, no tubes exhibited degradation that required in-situ pressure testing to demonstrate structural and leakage integrity. There was no reported primary-to-secondary leakage prior to the end of the SG inspection interval. No secondary side tube degradation attributable to foreign objects in excess of the Vogtle Unit 2 Condition Monitoring limits has been identified from the FOSAR and visual inspections. The Condition Monitoring limits and correspondingly the SG Performance Criteria for operating leakage and structural integrity were satisfied for the preceding Vogtle Unit 2 SG operating interval. No operational leakage was reported during the previous cycle; therefore, the calculated accident induced leakage rate is zero.

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