L-2017-070, Refueling Outage SL1-27 Steam Generator Tube Inspection Report

Refueling Outage SL1-27 Steam Generator Tube Inspection Report

ML17117A334
Person / Time
Site:	Saint Lucie
Issue date:	04/27/2017
From:	Snyder M Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2017-070
Download: ML17117A334 (8)

Text

APR 2 7 2017 L-2017-070 10 CFR 50.55a 10 CFR 50.36 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Re: St. Lucie Unit 1 Docket No. 50-335 Refueling Outage SL1-27 Steam Generator Tube Inspection Report Attached is the St. Lucie Unit 1 Technical Specification 6.9.1.12 steam generator tube inservice inspection report for the fall2016 refueling outage (SL1-27). This submittal was made within 180 days after the initial entq into hot shutdown following the completion of the steam generator inspection that was performed in accordance with TS 6.8.4.1, Steam Generator (SG) Program.

Please contact Ken Frehafer at (772) 467-7748 should you have any questions regarding this submittal.

V eq truly yours, MJS/KWF

Attachment:

St. Lucie Unit 1 Steam Generator Tube Inspection Report for SL1-27 cc: USNRC Regional Administrator, Region II USNRC Senior Resident Inspector, St. Lucie Nuclear Plant Florida Power & Light Company 6501 S. Ocean Drive, Jensen Beach, FL 34957

L-2017-070 Enclosure Page 1 of 7 Enclosure SL1-27 Steam Generator Tube Inspection Report

==

Introduction:==

The enclosed Steam Generator Tube Inspection Report for St. Lucie Unit 1 is submitted for the inspection of the replacement steam generators (RSGs) during refueling outage 27 (hereafter referred to as the SL1-27 inspection/outage), as required by plant Technical Specification section 6.9.1.12.

Per the St. Lucie Unit 1 Tech Spec section 6.8.4.l.d.2, the second sequential period is 108 EFPMs.

The inspection during SL1-27, performed in accordance with Tech Spec section 6.8.4.l.d, was the 2nd inspection of the RSGs in the second sequential period, and the 6th ISI inspection since installation of the RSGs in 1997.

The plant Tech Spec requirement to inspect 50% of the tubes by the refueling outage nearest the midpoint of the period was met by the SL1-25 inspection. No primary-side inspection was performed during the SL1-26 outage. At unit shutdown for the SL1-27 inspection, the RSGs had operated for approximately 16.51 EFPY (198.18 EFPM) since installation. This included operation for approximately 1.331 EFPY (15.97 EFPM) during Cycle 25 and 1.334 EFPY (16.00 EFPM) during Cycle 26. Initial entry into Hot Shutdown following completion of the SL1-27 inspection was made on November 3, 2016.

St. Lucie Unit 1 is a 2-loop Combustion Engineering designed NSSS with RSGs manufactured by B&W Canada. The RSGs were fabricated using Inconel composition Alloy 690 thermally-treated tubes. Each RSG contains 8,523 U-tubes arranged in 141 rows and 167 columns. The tubes have a nominal OD of 0.75", a nominal wall thickness of 0.045", and have a triangular pitch arrangement. The tube bundle is supported by 7 horizontal lattice grid supports (LGS) along the straight lengths of tubes; the U-bend region is also supported by 10 fan bar supports (FBS) and 2 connector bar supports, all fabricated of stainless steel. The primary-side channel head has a stay cylinder as well as divider plates which provides flow separation between the inlet and outlet plenums. Tubes in rows 2 & 3 have the smallest U-bend radii. The general arrangement of the tube bundle supports including the FBS, CBS and horizontal LGS is shown in Appendix B. References to historical SG Tube Inspection Reports are provided in Appendix A along with acronyms and abbreviations used in this report. The inspection of the RSGs during the SL1-27 outage met the inspection requirements of the St. Lucie Unit 1 Tech Specs, NEI 97-06 and the referenced EPRI Guidelines.

A. Scope of Inspections Performed on each SG Primary-side:

• 100% full-length bobbin probe exam of all active tubes

• Array probe exam of peripheral tubes (high flow regions) in hot and cold legs (HL/CL) in each RSG, and low-row tubes (rows 1-4) along the tube free lane. (Peripheral tubes are defined as the 2 outermost tubes exposed to the annulus, all tubes in Rows 1-4 along the tube-free lane, and the innermost 2 tubes adjacent to the outermost edge of the stay cylinder.) The exam extent was from 01H to TTS-3.

• 30% tube sample of tight-radius U-bends of Rows 2 & 3 using the +Point' probe. The U-bend test extent was the portion of tubing between the uppermost horizontal LGS. (The selected tube sample was different from the 30% sample which was inspected during SL1-25.)

• 100% of all previously-identified DNG/DNT indications in the U-bend and at hotleg horizontal LGS locations with +Point'; at least 50% of all previously-identified DNG/DNT indications > 5 Volts at HL freespan locations with +Point'; and all newly-reported DNG/DNT indications that meet the above reporting criteria for previously-identified DNG/DNT indications with +Point'.

• +Point' and/or array probe exams of all tubes with previously-identified possible loose part (PLP) indications, from TTS +/- 3 inches.

L-2017-070 Enclosure Page 2 of 7

• Diagnostic +Point' examination at other special interest locations as required based on the results of the bobbin coil and array coil data.

• Visual inspection of all installed tube plugs in each RSG.

• Channel head bowl scan visual inspection of each RSG per recommended actions in Westinghouse NSAL 12-1 "Steam Generator Channel Head Degradation" January 5, 2012.

Secondary-side:

• Visual inspection of the Steam Drum / Upper Internals was performed in SG 1A. This included a sample of the primary and secondary separators.

B. Active degradation mechanisms found Wear at tube supports and historical PLP wear at the TTS were the active (existing) degradation mechanisms identified during the SL1-27 RSG inspection. Specifically, the degradation mechanisms were:

• Wear at fan bar supports (FBS)

• Wear at lattice grid supports (LGS)

• Historical PLP wear on 2 tubes at the HL TTS location Wear at CBS locations was not found in SL1-27. No indication was identified that was due to a corrosion degradation mechanism. There was no new degradation from foreign objects.

C. Nondestructive examination techniques utilized for each degradation mechanism Table 1 is a list of the EPRI Examination Technique Specification Sheets (ETSS) used for tube degradation detection and sizing, as needed, during the SL1-27 inspection.

Table 1 NDE Degradation Mechanism ETSS Technique Location/Description Status Wear at Support Structures 96004.1 Rev. 13 1 Bobbin Existing (LGS, FBS, CBS) (differential mix channel)

Wear at Support Structures 96004.2 Rev. 13 2 Bobbin Existing (LGS, FBS, CBS) (absolute mix channel)

Foreign Object Wear (PLP) 3 Bobbin Potential 27091.2 Rev. 2 (Object not present) 4 +Point' Wear at LGS Structures Existing 96910.1 Rev. 10 Wear at U-bend Supports 5 +Point' Existing 10908.4, Rev. 1 (FBS, CBS) 27901.1 Rev 1, 27902.1 Rev 2, 27903.1 6 +Point' PLP Wear (morphology dependent) Potential Rev 1, 27904.1 Rev 2, 27905.1 Rev 2, 27906.1 Rev 1, 27907.1 Rev 2 PLP Wear (based on technique 7 Array Potential 20400.1, Rev. 5 extension)

L-2017-070 Enclosure Page 3 of 7 D. Location, orientation (if linear), and measured sizes (if available) of service induced indications Listings of all service-induced indications identified during the SL1-27 inspections are provided below in Tables 2a, 2b and 2c.

Table 2a: Wear at Lattice Grid Supports (LGS):

SG Row Col %TW Location SG Row Col %TW Location A 64 11 15 04C -1.34 B 1 146 12 06C -1.45 A 97 144 9 01C -1.58 B 2 127 13 05C +0.48 A 97 144 23 02C -1.60 B 107 138 12 05H +1.45 A 107 138 10 02C -1.51 B 133 60 14 02C -1.39 A 116 37 14 06H -0.54 B 139 92 16 04H -1.59 A 139 74 14 03H -0.92 Table 2b: Wear at Fan Bar Supports (FBS):

SG Row Col %TW Location SG Row Col %TW Location A 67 92 11 F09 -2.41 B 93 90 15 F04 -1.26 A 82 105 11 F06 +0.80 B 102 67 11 F07 -1.12 A 86 91 14 F06 +1.32 B 108 91 10 F04 -1.23 A 87 94 12 F04 +1.27 B 108 91 12 F05 +1.05 A 87 94 14 F06 +1.34 B 108 91 12 F08 -1.36 A 87 94 14 F07 +1.47 B 123 94 12 F08 +0.81 A 101 74 14 F05 -0.89 B 132 65 10 F05 +1.11 A 101 74 14 F06 +1.82 B 132 65 11 F07 -1.14 A 104 79 12 F07 +1.36 B 137 64 11 F06 -0.85 A 118 61 11 F05 +0.93 B 137 64 11 F07 -0.91 A 118 61 11 F06 -0.95 A 118 61 15 F07 -1.21 A 118 61 11 F08 -1.31 A 121 66 12 F03 -1.09 A 121 66 11 F04 -1.06 A 121 66 12 F05 -0.54 A 121 66 18 F06 +1.45 A 121 66 11 F08 -1.11 A 121 66 11 F09 -1.26 A 126 83 13 F07 +1.27 A 126 83 11 F08 +1.36 Table 2c: Historical Wear due to PLP:

SG Row Col %TW Location B 137 78 17 TSH +0.37 B 139 78 14 TSH +0.54

L-2017-070 Enclosure Page 4 of 7 Apart from the items in Table 2c, there were no new degradation from PLP/foreign objects. As mentioned previously, wear at CBS locations was not found in SL1-27. No indication was identified that was due to a corrosion degradation mechanism.

E. Number of tubes plugged during the inspection outage for each active degradation mechanism The number of tubes plugged for each active degradation mechanism is summarized below in Table 3:

Table 3 - Tubes Plugged1 during SL1-27 inspection outage Degradation Mechanism2 SG 1A SG 1B Total Wear at Fan Bar Supports (FBS) 3 1 4 Wear at Lattice Grid Supports (LGS) 1 0 1 Wear at Connector Bar Supports (CBS) 0 0 0 Wear due to PLP/foreign objects 0 0 0 Total 4 1 5

1. The tubes plugged in SG 1A during SL1-27 were: R97C144, R87C94, R118C61 and R121C66. The tube at R108C91 was plugged in SG 1B.

2. No tube had wear which exceeded the Tech Spec limit ( 40%TWD). The tubes plugged were taken out of service to support the operational assessment until the next primary-side inspection in SL1-30. (A primary-side inspection is not planned for the SL1-28 or SL1-29 outages.)

F. Total number and percentage of tubes plugged to date The total number and percentage of tubes plugged to-date in each SG is summarized below in Table 4:

Table 4 - Cumulative Tube Plugging Summary following the SL1-27 Inspection SG Total Plugged  % Plugged 1A 101 1.19%

1B 54 0.63%

G. The results of condition monitoring, including the results of the tube pulls and in-situ testing All SG tubes inspected during the SL1-27 outage met the condition monitoring (CM) requirements for structural and leakage integrity. No evidence of corrosion degradation was detected. No primary-to-secondary leakage was noted since the last inspection. No indications were found to exceed the structural limits. The next inspection is planned for the SL1-30 outage. (A primary-side inspection is not planned for the SL1-28 or SL1-29 outages.)

1. The largest wear indications at lattice grid support (LGS) locations in each SG were 23%TWD and 16%TWD, in SG 1A and 1B, respectively. All detected LGS wear indications fell below the CM limit for burst and leakage. One (1) tube in SG 1A (none in SG 1B) was plugged due to wear at a LGS location to support the operational assessment to the next inspection. The list of LGS Wear indications in SL1-27 is provided in Table 2a.

2. The largest wear indications at fan bar support (FBS) locations in each SG were 18%TWD and 15%TWD, in SG 1A and 1B, respectively. All detected FBS wear indications fell below the CM limit

L-2017-070 Enclosure Page 5 of 7 for burst and leakage. Three (3) tubes in SG 1A and one (1) tube in SG 1B were plugged due to wear at FBS locations to support the operational assessment to the next inspection. The list of FBS Wear indications in SL1-27 is provided in Table 2b.

3. No wear indications were found at U-bend connector bar support (CBS) locations. Two (2) historical PLP wear indications at the TTS in SG 1B measured 14% and 17% in SL1-27 using the

+Point' probe. There has been no growth in these 2 PLP wear indications since they were first reported. The list of historical PLP wear indications is provided in Table 2c.

4. During the Steam Drum / Upper Internal components inspection, no sign of damage, degradation, erosion or corrosion was observed.

5. No degradation was found during the visual inspection of the primary-side channel head bowl. No corrosion-related degradation was identified anywhere in the channel head of the SGs. All previously-installed tube plugs were confirmed to be in their correct locations, and showed no visible signs of leakage based on the visual examination. No degradation of the tube plugs was identified.

In summary, all wear indications detected in SL1-27 met CM requirements. As a result, no tubes required in-situ pressure testing for burst or leakage, and no tube pulls were required. Therefore, all tubes met the structural and leakage integrity requirements of the St. Lucie Unit 1 Tech Specs.

H. The effective plugging percentage for all plugging in each SG No tube repair methods (i.e. sleeving) are approved for St. Lucie Unit 1 that would have an effect on the effective plugging percentages. Therefore, the applicable effective plugging percentage is synonymous with the % Plugged entries shown in Item F above.

L-2017-070 Enclosure Page 6 of 7 APPENDIX A - Additional Information References to historical SG Tube Inspection Reports SG ISI # EOC Outage NRC ADAMS Accession No.

1 EOC-15 SL1-16 ML003684169 2 EOC-16 SL1-17 ML012390098 3 EOC-18 SL1-19 ML053190206 4 EOC-21 SL1-22 ML091120207 5 EOC-24 SL1-25 ML14127A008 6 EOC-26 SL1-27 (current report)

Abbreviations and Acronyms CBS Connector Bar Support CL Cold Leg CM Condition Monitoring DNG/DNT Dings/Dents EOC26 End-of-cycle 26 (or SL1-27 inspection)

EFPM Effective Full Power Months EFPY Effective Full Power Years EPRI Electric Power Research Institute ETSS Examination Technique Specification Sheet FBS Fan Bar Support HL Hot Leg ISI In-service Inspection LGS Lattice Grid Support NSSS Nuclear Steam Supply System OD Outside Diameter PLP Possible Loose Part RSG Replacement Steam Generator SG Steam Generator TSH Tubesheet Hot TTS Top of Tubesheet TWD Through Wall Depth

L-2017-070 Enclosure Page 7 of 7 APPENDIX B - General arrangement of St. Lucie Unit 1 RSG Tube Bundle Supports Note: Seven horizontal lattice grid support (LGS) elevations are labeled sequentially from bottom to top as 01 H to 07H (or 01 C to 07C) according to the following table. There is no baffle plate.

Horizontal LGS designation Tube Support 1 2 3 4 5 6 7 Hot Leg 01H 02H 03H 04H OSH 06H 07H Cold Leg 01C 02C 03C 04C osc 06C 07C i l