CP-201800215, Submittal of Nineteenth Refueling Outage (1RF19) Steam Generator 180 Day Report

Submittal of Nineteenth Refueling Outage (1RF19) Steam Generator 180 Day Report

ML18128A191
Person / Time
Site:	Comanche Peak
Issue date:	04/19/2018
From:	Sewell S Vistra Energy, Vistra Operations Company
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CP-201800215, TXX-18022
Download: ML18128A191 (14)

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\ m Luminant Steven K. Sewell Senior Director, Engineering & Regulatory Affairs Luminant P.O. Box 1002 6322 North FM 56 Glen Rose, TX 76043 o 254.897.6113 CP-201800215 TXX-18022 ATIN: Document Control Desk Ref 10 CFR 50.55a U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 04/19/2018

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT DOCKET NO. 50-445 UNIT 1 NINETEENTH REFUELING OUTAGE (1RF19) STEAM GENERATOR 180 DAY REPORT

Dear Sir or Madam:

By means of the enclosure with this letter, Vistra Operations Company LLC (Vistra OpCo) submits the Comanche Peak Nuclear Power Plant (CPNPP) Unit 1 steam generator tube inspection report for 1RF19 as required by Technical Specification 5.6.9.

This communication contains no new licensing basis commitments regarding Comanche Peak Unit 1.

If you have any questions regarding this submittal, please contact Jim Barnette at (254) 897-5866 or James.barnette@luminant.com.

Sincerely, Enclosure - Comanche Peak Nuclear Power Plant 1RF19 Steam Generator 180 Day Report 6555 SIERRA DRIVE IRVING, TEXAS 75039 0214-812-4600 VISTRAENERGY.COM

TXX-18022 Page 2 of 2 c - Kriss Kennedy, Region IV Margaret M. O'Banion, NRR Balwant K. Singal, NRR Resident Inspectors, Comanche Peak

Enclosure with TXX-18022 Comanche Peak Nuclear Power Plant 1RF19 Steam Generator 180 Day Report CPNPP (Report is 10 pages, the attachment to the report is 2 pages; 12 pages in total)

This report is being submitted pursuant to TS 5.6.9, "Steam Generator Tube Inspection Report," to provide the results of the most recent CPNPP Unit 1 Replacement Steam Generator (RSG) inservice inspection.

Page 1 of 10

Enclosure with TXX-18022 Steam Generator Configuration Comanche-Peak Unit 1 is a four-loop Westinghouse pressurized water reactor plant equipped with Delta 76 replacement steam generators (RSGs) that were installed during the 121h refueling outage (1RF12). The Attachments to this Enclosure (Figure 1-1 and Figure 1-2) provide drawings depicting major components and inspection openings of the Delta 76 RSGs. The RSGs each have 5532 U-tubes made of thermally treated Alloy 690 (A690TT). Each U-tube has a nominal outside diameter of 0.750 inch, a nominal wall thickness of 0.043 inch (except tubes in Rows 1 and 2, which have a nominal thickness of 0.044 inch), and a straight length ranging from 398.944 inches (Row 1) to 409.344 inches (Row 108). The tubes are arranged in a triangular pitch of 1.030 inches in 108 rows (parallel to the tube lane) and 131 columns. The distance between adjacent rows is 0.515 inch and between adjacent columns is 0.892 inch. The U-bend radii range from 3.09 inches (Row 1) to 58.195 inches (Row 108). The tubesheet is 24.315 inches thick, including the 0.25-inch cladding at the bottom (primary coolant side). The tubes have full depth hydraulic expansion within the tubesheet.

Above the tubesheet, the tubes are supported by ten (10) tube support plates (TSP) which are 1.125 inches thick. The TSPs have trefoil broached holes and are made of stainless steel (Type 405). The elevation of the lowest TSP at its midpoint is 20.56 inches above the top of the tubesheet. The distance between adjacent TSPs (center to center) is 39.00 inches. In the U-bend, the tubes are supported by four (4) sets of stainless steel (Type 405) anti-vibration bars (AVB). The AVBs have a rectangular cross section of 0.48-inch x 0.14-inch thickness with chrome plating.

Each SG has 18 primary separators and a single-tier secondary separator consisting of six banks of demister vanes in a parallel orientation. The feedwater is discharged into the SG through 38 spray nozzles attached to the elevated (in relation to the feedwater nozzle) feedring. Each spray nozzle has 156 holes of 0.27-inch diameter. The feedring has an inside diameter (ID) of 9.75 inches and the spray nozzles have an ID of 2.323 inches. Above the lower deck plate and at its rim, a six-inch-high wall exists. This structure functions very much like a loose parts weir in preventing most of the loose parts and foreign objects in the upper drum from entering the downcomer annulus. This structure has a very positive impact on preventing loose parts from reaching the tube bundle and thus protecting the tubes from loose parts wear.

Inspection Summary The inservice inspection of the RSGs was completed by Westinghouse Electric Company (WEC) during the Unit 1 Refueling Outage 19 (1RF19). Initial entry into MODE 4 after the inspection was achieved on November 2, 2017.

The CPNPP Un it 1 Cycle 19 operating period was 492.79 effective full power days (EFPD), or 1.35 effective full power years (EFPY). The cumulative operating history of the RSGs since their installation at 1RF12 is 9 .83 EFPY. No eddy current inspection was performed during 1RF17 or 1RF18, and no inspection is planned during 1RF20 or 1 RF21. The next scheduled eddy current inspection is during the 1RF22 outage. This evaluation concludes that at the CPNPP Unit 1, End of Cycle Page 2 of 10

Enclosure with TXX-18022 (EOC)-19 condition, all observed eddy current indications of SG tube degradation satisfied the performance criterion requirements, and that all projected indications of degradation are expected to satisfy performance criterion requirements at EOC-22. The conditional burst probability for the returned to service indications will not exceed the limit of 5% when evaluated against the performance criterion of 3760 psi and the probability of leakage at accident conditions will not exceed 5%. A deterministic Operational Assessment (OA) approach per the EPRI Steam Generator Management Program: Steam Generator Integrity Assessment Guidelines, Revision 4 was used. The OA also considered postulated missed indications at the 1RF16 inspection for the population of tubes not inspected at 1RF19 and concludes that such postulated indications will not challenge structural or leakage integrity at EOC-22. Prior to 1RF19 two tubes were plugged. In SG3, R32 C90 was plugged in the factory. At 1RF16, R13 C17 in SG4 was plugged due to a foreign object wedged between the tube and stayrod at the hot leg to the Top of the Tube Sheet (TTS).

No tubes were plugged at 1RF19, therefore, the active tube count per SG following 1RF19 is:

SG1: 5532 SG2: 5532 SG3: 5531 SG4: 5531 For the combined inspection programs of 1RF16 and 1RF19, the Technical Specification requirement to inspect 100% of all tubes is satisfied as a 50% full length bobbin program was performed at both inspections. The 50% inspected at 1RF19 were not inspected at 1RF16. The condition of the SGs has met all industry and regulatory structural and leakage integrity requirements.

Section 1 of this report describes the scope of inspections performed.

Section 2 contains the inspection results, which include:

• Degradation mechanisms found;

• Nondestructive examination techniques utilized for each degradation mechanism;

• Number of tubes plugged during the inspection outage for each degradation mechanism;

• Number and percentage of tubes plugged to date;

• The results of condition monitoring, including the results of tube pulls and in-situ testing; Section 3 contains the location, orientation (if linear), and measured sizes (if available) of service induced indications.

Page 3 of 10

Enclosure with TXX-18022 Section 1: Scope of Inspections Performed The inspection plan for 1RF19 satisfied the requirements of Section 3.4 of the EPRI SG examination guidelines; all SGs were inspected. The following was the initial inspection plan:

• 50% bobbin coil inspection using a 0.610-inch diameter probe, full length in Rows 4 and above; plus 50% bobbin coil inspection using a 0.610-inch diameter probe in the vertical straight leg section (hot leg and cold legs) of Rows 1, 2, and 3

• 50% +POINT probe inspection using a 0.580-inch diameter probe in Li-bends of Rows 1, 2, and 3 on the same tubes tested with bobbin; this inspection extends from top TSP to top TSP

• 20% +POINT probe inspection of the hot leg top-of-tubesheet (TTS) region from

+/-3 inches about the TTS in all SGs. Due to reporting of a possible pit-like indication at another plant with A690TT tubing, this program was biased to the expected sludge deposition region at the TTS. This region was conservatively bounded by a 29-inch radius about the center of the tubesheet face.

• 50% +POINT probe inspection of all dents/dings >5V(1) in all SGs. Note: whether the signal is located in the freespan or within a TSP, the signal is identified as ONG from bobbin coil analysis ..

• +POINT probe inspection of hot and cold leg TTS region at the periphery and tube lane regions (loose part concern). This program included a three (3) tube deep pattern in any row or column on the periphery and a two (2) tube deep pattern in any row or column along the tube lane.

• +POINT probe special interest inspection as necessary including; o Any freespan bobbin I-code (DNI, FSI, etc.) or distorted indication in the tubesheet (DTI) o Any bobbin I-code at a TSP (OSI) or AVB intersection o Possible loose parts/foreign object (PLP) signals including all immediately surrounding tubes until PLP signals are no longer reported (i.e., "boxing")

• Video inspection of hot and cold leg channel head bowls as recommended per Westinghouse Nuclear Safety Advisory Letter (NSAL) NSAL 12-1. In addition, the channel head video inspection included the Z-seam (tubesheet to channel head) weld region based on operating experience (OE) from another plant.

• Tube plug video inspection.

• Upper tube bundle video inspection in SG 3 focused on deposit formation documentation in the trefoil lobes.

• Foreign Object Search and Retrieval (FOSAR) of the TTS periphery and tube lane region (1 ): sec at freespan dings is judged non-relevant, similarly, freespan wear is judged non-relevant in the absence of foreign objects. The recommended +POINT probe Page 4 of 10

Enclosure with TXX-18022 inspection of >5V dings is performed to satisfy the full length testing requirement, to establish that foreign objects are not present, and to confirm that wear is not present in

>5V dings at support structures.

Eddy Current Inspection Program Expansion Per the Degradation Assessment, localized bobbin program expansions were required for observed TSP wear. This expansion was performed to establish that a localized flow condition resulting in higher than expected tube vibrations are not present. Based on the observed TSP wear depths the bobbin program expansion was a 3-tube deep box around the affected tube. No additional wear indications were reported from this expansion.

The total percentage of tubes tested full length with bobbin for SGs 1 through 4 are 51.8%,

51.7%, 52.9%, and 51.6%. Localized +POINT probe expansions to bound the extent of observed PLPs was also performed. This protocol included a 2-tube box around newly reported PLPs and a 1-tube box around historic PLPs.

Page 5 of 10

Enclosure with TXX-18022 Section 2: Inspection Results Degradation Mechanisms Found and Nondestructive Examination Techniques Utilized for Each Degradation Mechanism:

Indications suggestive of the following degradation mechanisms were detected in the CPNPP1 1 RF19 inspection:

• Wear at TSPs (service induced)

A total of seven (7) tubes were reported to contain fretting wear indications at 1RF19; one (1) was reported at 1RF16 and again reported at 1RF19. Of these tubes, six (6) exhibited "normal" TSP wear indications, where normal is considered a tapered depth profile over the length of the indication. The other indication, observed on R62 C118 at 06H in SG1 was associated with a burr at the edge of the TSP. This unique wear has been reported at other plants with RSGs manufactured at similar times as the CPNPP1 RSGs. Here a small burr or lip of raised metal is found on the edge of TSP contact land and is an artifact of the TSP buffing operation. These indications have similar axial and circumferential length reports. In many cases, as is the case with R62 C118, the burr can be evidenced in +POINT probe 150 kHz frequency data. With continued operation and if the vibrational amplitude of the tube is sufficient, the wear may progress to the land. When this occurs the wear depth growth rate will be dramatically reduced as the contact area between the tube and TSP will be greatly increased. As wear is a constant energy process driven by the forcing function provided by the secondary side flaw conditions this increase in contact area will result in a decrease in the volume removed and thus depth growth rate.

The Table below provides a summary of the 1RF19 observed TSP wear indications.

The deepest indication depth as measured from the bobbin coil amplitude using the guidance of examination technique specification sheet (ETSS) 196043 is 16%TW.

+POINT probe based depths are also provided in the table below; the bobbin and

+POINT based depths are very similar. A review of the prior bobbin inspection data was performed to help to determine time of initiation and growth period.

CPNPP TSP Wear Indications Reported at 1RF19 SG Row Column Location Elevation Bobbin +POINT Axial History History

%TW %TW Length Data Precursor (inch) Review Year 1 62 118 06H -0.69 14 16 0.14 2008 No 2 21 15 08C -0.6 16 10 0.18 2008 Yes 3 105 63 08H 0.03 15 12 0.23 2008 Yes 3 6 114 07C 0.65 16 14 0.43 2013 Yes 3 6 118 08C -0.49 17 17 0.46 2008 No 3 55 121 09C -0.41 16 18 0.47 2013 (a) 4 25 127 08C -0.61 11 10 0.25 2008 No (a): Reported during normal analysis in 2013.

Page 6 of 10

Enclosure with TXX-18022

• Foreign Object Wear at TSPs One (1) tube (R40 C30 at 09C in SG3) was reported to contain a wear indication suspected to be caused by a foreign object which was no longer at this location.

Analysis of the +POINT probe low frequency data confirmed no foreign material. The indication is located on the side of the land, just off of the contact point. The indication was depth sized at 18%TW using the volumetric (VOL) standard and guidance of ETSS 21998. The axial and circumferential dimensions of the wear were 0.20 inch axial and 0.18 inch circumferential. These dimensions better coincide with the dimensions of the flat bottom holes of the American Society of Mechanical Engineers (ASME) standard.

Thus use of the VOL standard will result in a conservative assessment of depth as the VOL standard flaws will produce lesser amplitude response for equal depth compared to the flat bottom holes of the ASME standard. Prior evaluations of +POINT probe geometry sizing capabilities show that the +POINT probe will overestimate the dimensions of volumetric flaws thus use of the as-reported dimensions will result in a conservative integrity assessment.

Note that while foreign object induced tube wear was observed at 1RF19, continued observation of this mechanism is dependent upon material ingress, thus, this mechanism is judged potential for 1RF22. The classification as existing or potential does not affect the 1RF22 eddy current inspection scope or the requirement to apply qualified techniques for detection.

FOSAR inspection of the top of tubesheet region in all four (4) SGs has established that no foreign objects potentially detrimental to tube integrity are present at the top of tubesheet region annulus or tube lane regions upon return to power. The peripheral and tube lane eddy current +POINT probe have established that no metallic objects are present in the highest tube gap velocity regions of the TTS.

Disposition Techniques for Identified Degradation Mechanisms Depth measurement of structure wear indications by bobbin is accepted as a method for evaluation against the 40% TW depth repair criteria. An administrative repair limit of

<40% TW may be imposed to support the planned operating interval until the next scheduled eddy current inspection. The typical practice applied for disposition of volumetric degradation attributed to foreign objects/loose parts wear with the PLP remaining is to plug the tube as the presence of the object can affect the depth sizing. If the object is not present, the indication can be depth sized against the Technical Specification repair limit.

Tube Repair Due to Data Quality:

No tubes were plugged due to data quality at 1RF19. In SG1 a OSI signal was reported from bobbin coil analysis on R22 C126 at 10H. An approximate 1.7 volts ding signal was present in the 2008 bobbin data at this location. It is suspected that deposit accumulation, combined with the dent signal, produced a resultant which was subsequently reported from the auto analysis screening. The bobbin coil response was not consistent with typical TSP OSI signals confirmed as wear from +POINT probe Page 7 of 10

Enclosure with TXX-18022 analysis; the signal included only a slight phase angle shift from the 2008 data. As this location was reported as a OSI it was subsequently inspected with a

+POINT probe; no degradation was reported.

In response to the observed deposit condition, the 20 tubes with the largest deposit signal amplitudes in SG1 and SG4 were inspected with a +POINT probe to ensure that the deposit condition was not influencing detection capabilities. If the largest deposit signal on that tube was located at a location other than 1OH, all TSP elevations above the location were also examined. No degradation was reported.

Total Number and Percentage of Tubes Plugged to Date:

A total of two tubes have been plugged in U1 RSGs. The two plugged tubes account for 0.01 % of the total tubes in U1 RSGs. Tube R32C90 in SG3 was plugged in the factory.

List of All Plugged Tubes through CPNPP 1RF19 Plug Repair No Date SG Row Col Volts Deg Ind Per Chn Locn lnchl Attribute Pre- Factory 1 3 32 90 plug service 2 1RF16 4 13 17 4.8 83 PLP 11 TSH 0.16 Preventive Channel Head Visual Inspection Results The hot leg and cold leg primary side channel heads in each SG were visually inspected during the current outage. The inspections were prompted by industry experience at two (2) plants that identified wastage of the carbon steel channel head pressure boundary as result of a breach in the channel head stainless steel cladding and/or in the divider plate-to-channel head cladding. The visual inspection results did not identify any anomalies or degradation of the cladding or welds. A general scan of the tube-to-tubesheet weld region and Z-seam areas were also performed. At several locations, an elevation consistent with the nozzle drain plug elevation, and just below the Z-seam weld, reddish surface deposits were observed. No visible degradation of the cladding was evident. Considering that two (2) distinct elevations within the channel head were associated with these deposits it is suspected that the deposits are an artifact of the reactor coolant system (RCS) water levels within the SG during various hold points as the RCS was drained down to mid-loop. Visual verification and general inspection of all previously plugged locations was also performed.

Page 8 of 10

Enclosure with TXX-18022 Results of Condition Monitoring (CM), including the results of tube pulls and in-situ testing:

As all reported TSP wear flaw depths are less than the CM limit depth for tapered TSP wear of 56% TW, the structural integrity performance criterion is satisfied. For volumetric degradation The EPRI Steam Generator Management Program: Steam Generator Program Integrity Assessment Guideline, Revision 4 states that burst and tearing pressures are consistent. Thus as the burst pressure of all reported volumetric degradation is >3760 psi since the reported depths are less than the CM depth, which is greater than the steam line break pressure differential of 2560 psi, leakage integrity is also satisfied. The reported axial dimension of the volumetric indication presumed to be associated with foreign object wear is less than the structural equivalent depth of a tapered TSP wear indication, thus the tapered wear SL limit can be applied in this case. Depth sizing of this indication is based on ETSS 21998. Therefore, the as-reported depth of 19%TW must be adjusted using the sizing performance uncertainty of ETSS 21998 to be compared with the TSP tapered wear SL. The ETSS 21998 performance includes a systematic component described by a linear regression with y-intercept of 5.81 %TW, slope of 1.02, and standard error of 6.28% TW. At 95%

probability the NOE adjusted depth is 35.6% TW. As this depth is less than the SL for tapered wear, the structural integrity performance criterion is satisfied.

No tube pulls or in-situ testing was performed during 1RF19.

Page 9 of 10

Enclosure with TXX-18022 Section 3: Indication Listing Outage SG Row Col Volts Deg Ind Per Chn Loe Inch Crlen Ceg Crwid Beg End Pdia Ptype UlRF19 1 62 118 0.13 127 PCT 14 P4 06H -0.69 TEC TEH 0.61 CBAFN U1RF19 1 62 118 0.2 91 WAR 16 P4 06H -0.69 0.32 29 0.19 06H 06H 0.61 NPSMR U1RF19 2 21 15 0.16 154 PCT 16 P4 08C -0.6 TEC TEH 0.61 CBAFN U1RF19 2 21 15 0.1 121 WAR 10 P4 08C -0.6 0.14 26 0.17 08C 08C 0.61 NPSMR U1RF19 3 6 114 0.17 138 PCT 16 P4 07C 0.65 TEC TEH 0 .61 CBAFN U1RF19 3 6 114 0.16 76 WAR 14 P4 07C 0.5 0.25 26 0.17 07C 07C 0 .61 NPSMR U1RF19 3 6 118 0.18 127 PCT 17 P4 08C -0.49 TEC TEH 0.61 CBAFN UlRF19 3 6 118 0.21 79 WAR 17 P4 08C -0.49 0.43 29 0 .19 08C 08C 0.61 NPSMR U1RF19 3 55 121 0.16 137 PCT 16 P4 09C -0.41 TEC TEH 0.61 CBAFN U1RF19 3 55 121 0.22 132 WAR 16 P4 09C -0.6 0.18 29 0 .19 09C 09C 0.61 NPSMR U1RF19 3 105 63 0.16 143 PCT 15 P4 08H 0.32 TEC TEH 0.61 CBAFN U1RF19 3 105 63 0.13 76 WAR 12 P4 08H 0.4 0.23 31 0.2 08H 08H 0.61 NPSMR U1RF19 3 40 30 0.15 75 VOL 19 P4 09C -0.4 0.2 28 0 .18 09C 09C 0.61 NPSMR U1RF19 3 40 30 0.18 61 DSS Pl 09C -0.4 TEC TEH 0.61 CBAFN U1RF19 4 25 127 0.1 146 PCT 11 P4 08C -0.61 TEC TEH 0.61 CBAFN U1RF19 4 25 127 0.1 64 WAR 10 P4 08C -0.61 0.26 22 0 .14 08C 08C 0 .61 NPSMR Page 10 of 10

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