RA-22-0201, Refuel 24 Steam Generator Tube Inspection Report Pursuant to Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revision 1, Revised Frequencies for Steam Generator Tube Inspections

Refuel 24 Steam Generator Tube Inspection Report Pursuant to Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revision 1, Revised Frequencies for Steam Generator Tube Inspections

ML22202A007
Person / Time
Site:	Catawba
Issue date:	07/21/2022
From:	Hare M Duke Energy Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RA-22-0201
Download: ML22202A007 (9)

Text

{{#Wiki_filter:Mandy Hare tl_~ DUKE Manager Nuclear Support Services Catawba Nuclear Station ~ ENERGY~ Duke Energy CN03CH I 4800 Concord Rd York, SC 29745 803.701.2218 Mandy.Hare@duke-energy.com Serial: RA-22-0201 July 21, 2022 United States Nuclear Regulatory Commission ATTN : Document Control Desk Washington, DC 20555-0001 Catawba Nuclear Station, Unit No. 2 Docket No. 50-414 / Renewed License No. NPF-52

Subject:

Catawba Unit 2, Refuel 24 Steam Generator Tube Inspection Report Pursuant to Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revision 1, "Revised Frequencies for Steam Generator Tube Inspections" Ladies and Gentlemen: By letter dated March 4, 2022 (ADAMS Accession No. ML22010A281) , the U.S. Nuclear Regulatory Commission (NRC) issued Amendment Numbers 311 and 307 to the Renewed Facility Operating Licenses for CNS, Units 1 and 2, respectively. Amendments 311 and 307 revised Technical Specification 5.6.8, "Steam Generator (SG) Tube Inspection Report," based on Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revision 1, "Revised Frequencies for Steam Generator Tube Inspections." Pursuant to TSTF-577, Revision 1, a SG tube inspection report satisfying the revised TS 5.6.8 requirements is being provided to the NRC staff because a 100% inspection during CNS Unit 2, Refuel 24 (i.e., before adopting TSTF-577) is being credited as the beginning point of the new inspection period. The Enclosure to this letter contains the SG tube inspection report for CNS Unit 2, Refuel 24 in accordance with the revised TS 5.6.8 reporting requirements. This submittal contains no regulatory commitments. Should you have any questions concerning this letter, or require additional information, please contact Ryan Treadway, Manager - Nuclear Fleet Licensing, at 980-373-5873. Sincerely, 7>7 1.3. J-{aAJ-,, Mandy Hare Manager Nuclear Support Services, Catawba Nuclear Station

U.S. Nuclear Regulatory Commission Page 2 RA-22-0201

Enclosure:

Catawba Unit 2, Refuel 24 Steam Generator Tube Inspection Report cc: (w/ Enclosure) L. Dudes, NRC Regional Administrator, Region II Z. Stone, NRC Project Manager, NRR J.D. Austin, NRC Senior Resident Inspector, Catawba Nuclear Station

U.S. Nuclear Regulatory Commission RA-22-0201 Enclosure Catawba Unit 2, Refuel 24 Steam Generator Tube Inspection Report

Steam Generator Tube Inspection Report Catawba Nuclear Station Unit 2 EOC-24 April 2021 Location: 4800 Concord Road, York South Carolina 29745 NRC Docket No. 50-414 \ License No. NPF-52 National Board No. 173 Commercial Service Date: August 19, 1986 Owner: Duke Energy Corporation 526 South Church St. Charlotte, N.C. 28201-1006 Revision 0 Prepared By: Dan Mayes Checked By: Marie Turner Approved By: Etienne Fonteneau

TSTF-577 supplement to Catawba Nuclear Station Unit 2 EOC 24 Steam Generator Tube Inspection Report Pursuant to Catawba technical specification 5.6.8 and industry guidance the following information is provided:

Background

Catawba Nuclear Station utilizes a Recirculating Steam Generator (RSG) design for primary to secondary heat transfer. There are four preheat steam generators with reactor coolant flow divided among them. The Catawba Unit 2 RSGs are Model D5, manufactured by Westinghouse and are original to the station. Each steam generator has 4578 tubes constructed of thermally treated Inconel Alloy 600 (I-600) with an outside diameter of 0.750 inches and nominal wall thickness of 0.043 inches. The tubes are hydraulically expanded full depth of the tubesheet, complete from the primary to secondary face, and flush seal welded at the primary face. On the secondary side, the tubes are supported in the hot leg by seven quatrefoil broached tubes support plates (TSP) and the drilled flow distribution baffle (FDB). The cold leg is supported by five quatrefoil broached tube support plates, five drilled preheater baffles (PB) and the drilled flow distribution baffle arranged vertically along the SG above the tubesheet. There are two sets of square nested anti-vibration bars per steam generator to support the u-bends. Figure 1 provides a visual representation of the SGs. The preheater acts to collect most foreign objects. No deviations have been taken from industry guidelines. The nominal Thot is ~617 degrees Fahrenheit. There has been no detectable primary to secondary leakage since the last inspection at EOC-24.

a. The scope of inspections performed on each SG See report ADAMS accession number ML21214A160.

b. The nondestructive examination techniques utilized for tubes with increased degradation susceptibility.

All currently known tubes with increased degradation susceptibility have been plugged.

c. For each degradation mechanism found:

1. The nondestructive examination techniques utilized.

See report ADAMS accession number ML21214A160.

2. The location, orientation (if linear), measured size (if available), and voltage response for each indication. For tube wear at support structures less than 20 percent through-wall, only the total number of indications needs to be reported.

See report ADAMS accession number ML21214A160.

3. A description of the condition monitoring assessment and results, including the margin to the tube integrity performance criteria and comparison with the margin predicted to exist at the inspection by the previous forward-looking tube integrity assessment.

See report ADAMS accession number ML21214A160. The table below shows the comparison with the margin predicted to exist at the inspection by the previous forward-looking tube integrity assessment to the current as found degradation Degradation EOC-23 Projection (%TW) EOC-24 As found (%TW) AVB Wear 53.2 36 Broached TSP 49.5 34 Wear Drilled TSP wear 24.2 11 FO wear See below 43 No growth is typically considered for FO wear indications provided that the wear-initiating object is no longer being in the tube vicinity for these indications. Therefore, there is no comparison to a projected depth needed as performed for other tube wear mechanisms since no OA with growth was performed for EOC-23 for historical foreign object wear indications over the past operating cycle. No crack like indications were identified during EOC-24

4. The number of tubes plugged [or repaired] during the inspection outage.

See report ADAMS accession number ML21214A160.

d. An analysis summary of the tube integrity conditions predicted to exist at the next scheduled inspection (the forward-looking tube integrity assessment) relative to the applicable performance criteria, including the analysis methodology, inputs, and results.

The operational assessment for wear was determined deterministically for the worst-case flaw.

Degradation Maximum depth projected OA Limit Growth rate Projected Wear at next inspection (%TW) (%TW/EFPY) EFPY (%TW) AVB 52 63.5 2.051 4.5 Broached TSP 57.1 58.4 3.42 4.5 Drilled 31 59 3.42 4.5 1=95th percentile 2=maximum The maximum measured wear indication from foreign objects returned to service is 33%TW. None of the foreign object wear indications that were left in service were found to have a PLP present that would represent a continued mechanism for wear on the tube. As such, growth on these indications is assumed to be zero over the next inspection interval. Therefore, by virtue of meeting CM, OA is met for three cycles for foreign object wear. The operational assessment for stress corrosion mechanisms was determined probabilistically. Below are the results: Degradation Cycles Number of POB POL 90/50 LR flaws (%) (%) (gpm) Axial ODSCC at TSP 3 2 3.339 3.246 0.009 Circumferential PWSCC 3 1 N/A 0 0 within tubesheet Axial ODSCC in freespan 3 3 1.069 0.061 0

e. The number and percentage of tubes plugged [or repaired] to date, and the effective plugging percentage in each SG.

See report ADAMS accession number ML21214A160.

f. The results of any SG secondary side inspections.

See report ADAMS accession number ML21214A160. Approximately 8000 pounds of iron is contained in the four steam generators by iron transport at EOC-24.

g. For Unit 2, the primary to secondary LEAKAGE rate observed in each SG (if it is not practical to assign leakage to an individual SG, the entire primary to secondary LEAKAGE should be conservatively assumed to be during the cycle preceding the inspection which is the subject of the report.

See report ADAMS accession number ML21214A160.

h. For Unit 2, the calculated accident leakage rate from the portion of the tubes below 14.01 inches from the top of the tubesheet for the most limiting accident in the most limiting SG. In addition, if the calculated accident leakage rate from the most limiting accident is less than 3.27 primary to secondary leakage rate, the report shall describe how it was determined: and

It was previously reported (ADAMS accession number ML21214A160) that there was no calculated leakage. Upon start up Catawba unit 2 was power limited. To return the unit to full power the unit will raise Tave and therefore Thot by ~2 degrees F. At the elevated Thot of 619 degrees F, no leakage is calculated for the first two cycles 25 and 26; leakage is only projected for the last cycle 27. The leakage was determined probabilistically using Westinghouses Full Bundle Model software. The leakage for the last cycle was projected to be 0.009 gpm. The new administrative limit was calculated as follows:

                           = 0.10417        / 3.27 - 0.009      = 0.02286       = 32.9

i. For Unit 2, the results of monitoring for tube axial displacement (slippage). If slippage is discovered, the implications of the discovery and corrective action shall be provided.

See report ADAMS accession number ML21214A160.

Figure 1 - Catawba Unit 2 Elevation Map AV 2 AV 3 AV 1 AV 4 Westinghouse Model D5 Tube Information: Number of tubes: 4578 Flush 08H 09C Tube Material: Alloy 600 TT Nominal Diameter: 0.750 Nominal Wall: 0.040 49 rows and 114 columns Tube Support Information: 07H 10C TSP Type: quatrefoil broached FDB Type: drilled round hole PB type: drilled round hole Material: ferritic SS AVB Information: 06H 11C AVB Type: Square Material: Chrome Plated Inconel 05H 12C 04H 13C 14C 15C 03H 16C 02H 17C 18C 01H 19C TSH TSC TEH TEC}}