L-2019-175, Steam Generator Tube Inspection Report

Steam Generator Tube Inspection Report

ML19268B738
Person / Time
Site:	Turkey Point
Issue date:	09/25/2019
From:	Hess R Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2019-175
Download: ML19268B738 (9)

Text

September 25, 2019 L-2019-175 10 CFR 50.36 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-00001 Re: Turkey Point Unit 4 Docket No. 50-251 Steam Generator Tube Inspection Report The attached Turkey Point Unit 4 Cycle 31 Refueling Outage Steam Generator Tube Inspection Report is submitted in accordance with Turkey Point Technical Specification, 6.9.1.8 and within 180 days after the initial entry to MODE 4 following completion of the inspections performed in accordance with Technical Specification 6.8.4.j, Steam Generator (SG) Program.

Should there be any questions, please contact Mr. Robert Hess, Licensing Manager, at (305) 246-4112.

SGl\\~.)------~)

R~ ss Licensing Manager Turkey Point Nuclear Plant Attachments cc: Regional Administrator, Region II, USNRC.

Senior Resident Inspector, USNRC, Turkey Point Plant Florida Power & Light Company 9760 SW 344 St Homestead, FL 33035

L-2019-175 Page 1 of 8 Enclosure Turkey Point Unit 4 TP4-31 Steam Generator Tube Inspection Report

==

Introduction:==

The enclosed Steam Generator Tube Inspection Report for Turkey Point Unit 4 is submitted for the inspection of the SGs during refueling outage 31 (hereafter referred to as the TP4-31 inspection or outage), as required by Technical Specification section 6.9.1.8. Per the Turkey Point Unit 4 Technical Specification section 6.8.4.j.d.2.c, the 4th ISI period is 72 EFPM. The inspection in TP4-31 was performed in accordance with Technical Specification 6.8.4.j.d.2.c, and was the 2nd (and last) inspection of the SGs in the 4th ISI period. The TP4-30 outage was a SG inspection skip. At unit shutdown for the TP4-31 inspection, the SGs had operated for approximately 28.53 EFPY (342.4 EFPM) since installation, including 46.6 EFPM in the 4th ISI period. Since the last SG inspection (TP4-29), the SGs operated for approximately 1.40 EFPY (16.77 EFPM) and 1.34 EFPY (16.12 EFPM) during fuel cycles 29 and 30, respectively, leading up to the TP4-31 inspection. Initial entry into Mode 4 following completion of the TP4-31 inspection was made on April 6, 2019.

Turkey Point Unit 4 is a Westinghouse 3-loop PWR with Model 44F steam generators. The SGs are U-tube heat exchangers with tube bundles fabricated using thermally treated Alloy 600 tubing. Each SG contains 3,214 tubes arranged in 45 rows and 92 columns, in a square-pitch configuration. Nominal tube OD is 0.875" with a 0.050" nominal wall thickness. Each SG tube bundle is supported by one drilled-hole flow distribution baffle (FDB) and 6 quatrefoil, broached-hole tube support plates (TSPs) all fabricated from stainless steel. Two (2) sets of anti-vibration bars (AVBs) in the U-bends also provide tube bundle support.

The inspection of the SGs during the TP4-31 outage met the requirements of the Turkey Point Unit 4 Technical Specifications, EPRI SGMP: PWR Steam Generator Examination Guidelines Revision 8, and EPRI SGMP: Steam Generator Integrity Assessment Guidelines Revision 4.

Appendix A provides references to recent SG Tube Inspection Reports and acronyms used in this report.

Appendix B provides a list of indications reported in TP4-31.

A. Scope of Inspections Performed on each SG The inspection scope for TP4-31 met the requirements of Turkey Point Unit 4 Technical Specification 6.8.4.j. For all sample inspections, tube selection priority was given to the ones not inspected in TP4-29 to meet the sequential period requirements in Technical Specifications. Unless otherwise noted, the defined TP4-31 base inspection scope in all 3 SGs was:

Primary-side:

100% full-length bobbin probe examination of all active tubes except U-bends of Rows 1 and 2.

50% sample of tubes in the U-bends of Rows 1 & 2 using the +Point' probe.

Peripheral tubes (2 outermost tubes of each row) exposed to the annulus, and Rows 1 and 2 in the tube-free lane were inspected in the HL and CL using the array probe. The test extent was from the first broached TSP (designated 01H or 01C) to the tube-end (TEH or TEC).

50% sample of tubes in the HL tubesheet section from 01H to TEH using the array probe, including 50% of the BLG/OXP within the H* depth (TTS-18.11) of the tubesheet.

50% sample of Dings/Dents > 5V in the HL (freespan, TSPs), and the U-bend using the +Point' probe.

+Point' probe inspection of a) all high stress (minus 2-sigma) tubes within the HL tubesheet section (TSH+3 to TEH), and b) 75% of high stress tubes at HL tube support structures and top CL TSP.

+Point' or array probe exam of all tubes adjacent to (1-tube bounding of) current and previously-reported PLP indications and foreign objects reported during FOSAR in TP4-29.

Other special interest exams based on the results of bobbin coil exams including +Point' probe inspection of all I-codes from bobbin or array probe.

L-2019-175 Page 2 of 8 Enclosure 0F Visual inspection of all mechanical and welded plugs.

Channel head visual inspection, and bowl scan per Westinghouse NSAL 12-1 Rev 1, Steam Generator Channel Head Degradation, October 2017.

Inspection Expansion: No scope expansion was required based on the TP4-31 base exam scope.

Secondary-side:

Upper bundle flush and top-of-tubesheet (TTS) Sludge Lancing in all SGs.

TTS FOSAR performed in the annulus and tube-free lane of each SG. This included TTS in-bundle inspections in each SG.

Upper tube-bundle visual inspection in SG-B at the top TSP (06H/06C).

Upper steam drum visual inspection in SG-B. UT thickness measurements were also obtained at sample locations on the feedring T-box and all J-tubes.

B. Degradation Mechanisms Found The following degradation mechanisms were identified during the TP4-31 inspection:

Wear at anti-vibration bar (AVB) contact points.

Wear at horizontal tube support structures (FDBs, TSPs).

Foreign object wear at one location in SG-B at the TTS in the HL (reported as VOL).

No degradation was identified as a result of a corrosion damage mechanism.

L-2019-175 Page 3 of 8 Enclosure C. NDE Techniques utilized for each Degradation Mechanism Table 1a is the list of the EPRI ETSSs used for degradation detection during the TP4-31 ECT inspection.

Table 1a - NDE Detection Techniques for Degradation Mechanisms Detection Degradation ETSS used for Detection Location / Applicability probe Mechanism I96041.1 Rev 6 AVB locations 96004.1 Rev 13 Broached TSP locations I96042.1 Rev 4 Wear Drilled supports (FDB)

Foreign object wear (with/without 27091.2 Rev 2 part present) 96005.2 Rev 9 Pitting In the freespan and sludge pile Bobbin I-28411 Rev 4 At FDBs locations I-28412 Rev 4 In the freespan I-28413 Rev 5 I-28413 Rev 5 At broached TSPs 24013.1 Rev 2 At Dents/Dings 5V 10013.1 Rev 1 Axial ODSCC I-28424 Rev 4 At Dents/Dings > 5V I-28425 Rev 4 10411.1 Rev 0 All U-bends 10411.2 Rev 0 I28424 Rev 4 sludge pile/expansion transition 20511.1 Rev 8 Axial PWSCC At expansion transition

+Point I11524 Rev 0 Circ PWSCC 96511.1 Rev 16 Axial/Circ PWSCC In low row U-bends 96511.2 Rev 16 27901.1 Rev 1; 27902.1 Rev 2; 27903.1 Rev 1; 27904.1 Rev 2; 27905.1 Rev 2; 27906.1 Rev 1; 27907.1 Rev 2 Foreign object wear (with/without Wear 17901.1/ .3; 17902.1/ .3; part present) 17903.1/ .3; 17904.1/ .3; 17905.1/ .3; 17906.1/ .3 Array [All Rev 0]

20400.1 Rev 5 Axial/Circ ODSCC At expansion transition 20500.1 Rev 4 Circ PWSCC At expansion transitions / BLGs /

20501.1 Rev 4 Axial PWSCC OXPs Table 1b is the list of the EPRI ETSSs used for degradation sizing based on the degradation mechanisms reported during the TP4-31 ECT inspection.

Table 1b - NDE Sizing Techniques for Degradation Mechanisms Sizing Degradation ETSS used for Sizing Location / Applicability probe Mechanism Bobbin I96041.1 Rev 6 AVB locations 10908.4 Rev 1 96910.1 Rev 11 TSP and FDB locations 27905.1 Rev 2 Wear Just above or below TSP edges

+Point 27902.1 Rev 2 Foreign object wear at TSPs Foreign object wear (volumetric) 27901.1 Rev 1 at or slightly above TTS

L-2019-175 Page 4 of 8 Enclosure D. Location, orientation (if linear), and measured sizes (if available) of service induced indications For each SG, Attachment B provides the listing of service-induced indications identified during the TP4-31 inspection, including locations and measured sizes. Note:

For AVB wear, the indication depth as measured by the bobbin probe is provided.

For all other locations, the indication depth as measured by the +Point' probe is provided.

E. Number of tubes plugged during the inspection outage for each degradation mechanism Five (5) tubes were plugged based on the TP4-31 inspection; the tubes plugged for each degradation mechanism are summarized below in Table 2:

Table 2 - TP4-31 Tubes Plugged SG Tube Degradation Mechanism Notes R38C58 AVB wear Preventively plugged due to atypical AVB wear growth.

R28C34, Four (4) adjacent tubes reported dent signals (no B R28C35, No degradation reported wear) just above the TTS in the HL from a bounded R29C34, at dent locations legacy foreign object. The tubes were preventively R29C35 plugged and stabilized.

F. Number and percentage of tubes plugged to date, and the effective plugging percentage in each steam generator The number and percentage of SG tubes plugged to-date, and the effective plugging percentage in each SG are summarized in Table 3.

Table 3 - Tubes plugged to-date and effective plugging percentage SG-A SG-B SG-C Total Tubes Plugged 33 28 11 72 Percent Plugged 1.03% 0.87% 0.34% 0.75%

G. Results of Condition Monitoring, including the results of tube pulls and in-situ testing All indications found in TP4-31 satisfy the condition monitoring (CM) requirements of NEI 97-06 and Turkey Point Technical Specifications for structural and leakage integrity. No indication exceeded the structural limits. The tubes identified for plugging were screened against the in-situ test selection criteria contained in the EPRI SGMP Steam Generator In-Situ Pressure Test Guidelines, Rev 5, and provided for Turkey Point Unit 4 conditions. None of the tubes identified for plugging met the requirements for in-situ pressure testing, and no tube pulls were performed. The TP4-31 inspection results validate the projections and conclusions of the Operational Assessment of the previous inspection at TP4-29.

1. Wear at AVB locations has been the dominant mode of degradation for the Turkey Point Unit 4 SGs and accounts for the majority of the indications reported (Attachment B). One tube showed an atypical growth rate history having reported indication growths of 8% and 10% TW at two AVB locations over the last 2 cycles, and was preventively plugged. The maximum observed AVB wear indication in TP4-31 for all SGs was 32% TW and meets the CM requirements

L-2019-175 Page 5 of 8 Enclosure for burst and leakage integrity. The largest wear indications at TSP and FDB locations also fell well-below the CM limits.

2. A FO wear (volumetric) indication was reported in the HL at the TTS (tube R27C22) in SG-B.

Since a FO was not detected in the vicinity of this indication, it was likely removed during bundle flush and sludge lancing. The NDE depth of the FO wear indication was 31% TW and met the performance requirements when evaluated against the ISPT screening charts for CM.

3. No degradation was detected during the +Point inspection of high stress tubes, and the DNG/DNT sample inspection scope. During the array probe inspection of tubes in the tubesheet, no indication was detected at locations where BLGs/OXPs were located. No corrosion degradation mechanisms were observed during the TP4-31 inspection. All wear reported at broached TSP and FDB locations fell well below the CM limits; therefore, these indications met the acceptance criteria of NEI 97-06 structural performance criterion for burst and leak integrity.

4. Channelhead Components Visual Inspection:

Tube Plug Inspection: During the inspection of tube plugs in TP4-31, all installed plugs were confirmed to be in their correct location. In addition, all plugs were found to be dry; no dripping plugs were identified. No degradation or visible signs of leakage were noted on the plugs during the visual inspection.

Other Channelhead Inspections: Visual inspection of various channelhead components were performed to identify degradation per guidance in Westinghouse NSAL 12-1 Rev 1, Steam Generator Channel Head Degradation and LR-ISG-2016-01, Changes to Aging Management Guidance for Various Steam Generator Components. Areas inspected include the divider plate-to-channelhead weld, the weld at the top of the channelhead bowl drain tube, the channelhead-to-tubesheet girth weld seam region, the divider plate, and all cladded surfaces of the channelhead bowl and tubesheet. No degradation was found; the observed condition during the TP4-31 inspection is consistent with the manufacturing process.

5. Secondary-side Inspections and Maintenance:

A total of 116 lbs. of sludge was removed from the 3 SGs based on upper bundle flush and sludge lancing in TP4-31 (36, 31 and 49 lbs. in SGs A, B and C, respectively). The TTS locations of all legacy FOs were visually inspected, and 5 newly-identified objects were removed during TTS FOSAR. One newly-identified FO in SG-B (in the shape of a button-head bolt) could not be removed since it was fixed in place between 4 adjacent tubes. The object appears to have been in place since the SG was manufactured. ECT results also reported dent signals (but no degradation) on these tubes just above the TTS; these tubes were plugged and stabilized. The other FOs remaining in the SGs were mostly small sludge rocks, hard deposits and scale. An evaluation is in place for all irretrievable FOs that have the potential to cause tube damage. Upper tube-bundle visual inspection in SG-B at the top TSP reported no fouling/deposit material or abnormal conditions.

Upper Internals Inspection: Visual inspections performed in SG-B (for erosion/corrosion, mechanical damage, foreign material and unusual conditions) included the moisture separators, swirl vanes, feedring and J-nozzles. A light deposit material was noted on the surfaces of the steam drum. No fouling was observed in the flow holes of the moisture separators, and no erosion or corrosion was apparent on the separators or swirl vanes. A minimal amount of scouring was observed inside some of the J-tubes at the interface with the feedring; these have been noted previously and do not appear to have changed. The welds of all steam drum components were noted to be intact. Some wall-thinning (external) was noted based on UT thickness measurements taken on the feedring in SG-B in TP4-31. The condition appears to have been caused by impingement of feedwater as it discharges from the neighboring j-tube.

This was entered in the corrective action program and repairs were performed in TP4-31 to address this condition.

L-2019-175 Page 6 of 8 Enclosure H. Primary-to-secondary leakage rate observed in each SG during the previous cycle No primary-to-secondary leakage was observed during the previous 2 fuel cycles (Cycles 29 and 30).

I. Calculated accident induced leakage rate As described in the H* alternate repair criteria (ARC) for the Turkey Point Plant1, the accident induced leakage rate from the portion of the tubes below 18.11 inches from the TTS is calculated from any observed normal operating leakage that cannot be attributed to a source other than the tubesheet expansion region. For Turkey Point Unit 4, the maximum operational primary-to-secondary leakage rate from the portion of the tubes below 18.11 inches from the top of the tubesheet is determined by multiplying any normal operating leakage by a factor of 1.82 to determine the accident induced leakage rate. Since no operational primary-to-secondary leakage has been observed (per section H of this report), the calculated accident induced leakage rate is zero.

J. Results of monitoring for tube axial displacement (slippage)

A condition for licensing H* was to monitor for tube slippage within the tubesheet region. Monitoring for tube slippage was completed during the TP4-31 inspections. No tube slippage was reported.

1 Turkey Point Nuclear Generating Station Unit Nos. 3 and 4 - Issuance of Amendments Regarding Permanent Alternate Repair Criteria for Steam Generator Tubes (TAC NOS. ME8515 and ME8516); ADAMS Accession No. ML12292A342

L-2019-175 Page 7 of 8 Enclosure APPPENDIX A - Additional Information References to recent SG Tube Inspection Reports (SGTIR)

EOC # Outage ADAMS Accession No.

EOC-26 TP4-27 ML13277A358 EOC-27 TP4-28 Inspection skip (no SGTIR)

EOC-28 TP4-29 ML16298A391 EOC-29 TP4-30 Inspection skip (no SGTIR)

Abbreviations and Acronyms:

ARC Alternate Repair Criteria NEI Nuclear Energy Institute AVB Anti Vibration Bar NSAL Nuclear Safety Advisory Letter BAC Baffle plate cold OD Outside Diameter BAH Baffle plate hot OXP Over-expansion BLG Bulge PLP Possible Loose Part CL Cold Leg PWSCC Primary Water SCC CM Condition Monitoring SCC Stress Corrosion Cracking DNG Ding SG Steam Generator DNT Dent SGMP SG Management Program ECT Eddy Current Testing TEC Tube End Cold EFPM Effective Full Power Months TEH Tube End Hot EFPY Effective Full Power Years TS Tubesheet EPRI Electric Power Research Institute TSC Tubesheet Cold ETSS Exam Technique Spec Sheet TSH Tubesheet Hot FDB Flow Distribution Baffle TSP Tube Support Plate FO Foreign Object TTS Top of Tube Sheet FOSAR Foreign Object Search and Retrieval TW Through Wall HL Hot Leg VOL Volumetric indication (used to report ISPT In-Situ Pressure Test FO-wear in TP4-31)

L-2019-175 Page 8 of 8 Enclosure Appendix B - TP4-31 Listing of Indications Note: Designation used for tube support structures: TSPs: 01H thru 06H on the HL; 01C thru 06C on the CL.

FDB: BAH or BAC. AVBs: AV1 thru AV4 SG-A SG-B SG-B (contd)

ROW COL %TW LOCATION ROW COL %TW LOCATION ROW COL %TW LOCATION

=== === ========= === === === ======== === === === =====

25 12 12 AV2 +0.26 13 35 10 AV3 -0.93 35 49 9 02H -0.37 26 20 7 AV1 +0.30 13 42 10 AV1 -0.04 40 25 6 01C +0.43 30 16 7 AV2 +0.16 21 6 9 AV3 +0.23 43 37 11 04C +0.56 30 30 7 AV3 +0.00 23 50 13 AV3 +0.96 43 39 10 04C +0.64 30 80 9 AV2 +0.18 23 85 10 AV3 -0.10 44 38 18 04C +0.53 31 77 13 AV1 +0.28 26 64 17 AV2 +0.00 31 80 10 AV1 +0.30 18 AV3 +0.00 10 AV2 +0.24 26 68 10 AV3 +0.00 32 74 15 AV1 +0.05 26 71 8 AV2 +0.19 SG-C 14 AV2 +0.27 26 83 7 AV2 +0.25 12 AV3 +0.20 27 72 16 AV2 +0.20 ROW COL %TW LOCATION 32 76 9 AV4 -0.14 27 82 11 AV4 +0.18 === === === =========

33 72 14 AV3 -0.18 30 65 14 AV2 +0.15 12 4 13 AV4 +0.36 33 74 7 AV1 +0.14 8 AV3 +0.18 13 4 12 AV4 +0.37 35 67 10 AV4 -0.14 30 73 8 AV2 +0.00 22 7 8 AV2 +0.17 37 20 14 AV2 +0.26 13 AV3 +0.00 22 82 10 AV1 +0.33 12 AV1 +0.30 17 AV4 +0.00 22 83 11 AV4 +0.00 37 65 17 AV3 +0.00 31 13 12 AV2 +0.18 24 12 17 AV4 -0.09 40 49 11 AV4 -0.05 10 AV3 -0.16 26 82 13 AV1 +0.35 42 63 7 AV3 +0.71 9 AV4 +0.19 27 80 9 AV3 +0.25 29 25 20 AV4 -0.11 33 16 13 AV4 -0.07 27 81 9 AV1 +0.31 33 72 20 AV1 +0.23 33 62 11 AV2 -0.23 8 AV4 +0.15 37 65 28 AV2 +0.00 33 78 9 AV1 +0.18 30 15 15 AV1 +0.35 32 AV4 +0.00 8 AV2 +0.17 30 75 13 AV2 +0.65 37 71 26 AV2 +0.48 34 46 13 AV1 +0.29 31 80 7 AV3 +0.14 20 AV3 +0.35 12 AV2 +0.58 32 16 18 AV2 +0.28 27 72 22 AV1 -0.11 33 76 8 AV1 +0.26 ROW COL %TW LOCATION 34 46 27 AV2 -0.50 34 17 7 AV1 +0.09

=== === ======== 38 58 23 AV3 +0.23 34 53 10 AV1 -0.22 4 58 6 02H +0.48 30 AV4 -0.21 16 AV2 +0.22 10 62 8 04H +0.48 34 75 15 AV4 +0.00 11 86 7 04C +0.41 ROW COL %TW LOCATION 36 74 6 AV3 +0.02 13 4 9 BAH -0.29 === === === ======== 37 71 9 AV1 +0.33 18 86 11 BAC -0.31 19 86 10 BAH -0.22 37 73 7 AV3 -0.27 39 28 5 BAH +0.05 8 BAH -0.27 39 69 7 AV2 -0.11 35 70 9 BAH -0.40 40 68 5 AV2 +0.20 40 26 8 BAH -0.32 32 70 24 AV1 +0.31 6 BAH +0.00 22 AV3 +0.18 27 22 31 TSH -0.03 35 31 20 AV2 +0.31 5 12 10 04H +0.43 5 86 8 01H +0.66 ROW COL %TW LOCATION 8 3 16 02H -0.57 === === === =====

9 80 5 02H +0.46 35 75 12 06H +0.29 28 80 6 05H -0.54 28 82 7 BAH +0.51 31 60 17 02H -0.32