CP-201101429, Twelfth Refueling Outage (2RF12) Steam Generator 180 Day Report

Twelfth Refueling Outage (2RF12) Steam Generator 180 Day Report

ML11306A012
Person / Time
Site:	Comanche Peak
Issue date:	10/12/2011
From:	Madden F Luminant Power, Luminant Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CP-201101429, TXX-11129
Download: ML11306A012 (39)

Text

MIN Luminant Rafael Flores Senior Vice President

& Chief Nuclear Officer rafael.flores@Luminant.com Luminant Power P 0 Box 1002 6322 North FM 56 Glen Rose, TX 76043 T 254 897 5550 C 817 559 0403 F 254 897 6652 CP-201101429 TXX-11129 Ref. # 10 CFR 50.55a October 12, 2011 U. S. Nuclear Regulatory Commission ATITN: Document Control Desk Washington, DC 20555

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT, DOCKET NO. 50-446 UNIT 2 TWELFTH REFUELING OUTAGE (2RF12) STEAM GENERATOR 180 DAY REPORT

Dear Sir or Madam:

By means of the enclosure to this letter, Luminant Generation Company LLC (Luminant Power) submits the Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 Model D5 steam generator tube inspection report for 2RF12 as required by Technical Specification 5.6.9.

This communication contains no new licensing basis commitments regarding Comanche Peak Unit 2.

Should you have any questions, please contact Mr. Jim Barnette at (254) 897-5866.

Sincerely, Luminant Generation Company LLC Rafael Flores By:

K222-a.*,

yred W.dMadden Director, Oversight & Regulatory Affairs Enclosure Lunminant Power, Comanche Peak Nuclear Power Plant, Steam Generator Condition Monitoring and Operational Assessment for Unit 2 April 2011 Outage (2RF12) c -

E.E. Collins, Region IV B. K. Singal, NRR Resident Inspectors, Comanche Peak I~lJ~

Luminant Power Comanche Peak Nuclear Power Plant Steam Generator Condition Monitoring and Operational Assessment for Unit 2 April 2011 Outage (2RF12)

Table of Contents Executive Summary..............................................................................................

4 1

Intro d uctio n................................................................................................

.. 5 1.1 Steam Generator Configuration...................................................................

5 1.2 Summary of Operation and Plan.................................................................

5 2

Steam Generator Outage Summary.............................................................

6 2.1 Primary Side Inspection Plan and Results....................................................

6 2.1.1 Base Scope Inspection..........................................................................

6 2.1.2 Inspection Expansion............................................................................

7 2.1.3 Inspection Results.......................................................................................

7 2.2 Tube Repair Summary.......................................................

............................... 7 2.3 Summary of Secondary Side Inspection & Maintenance.............................. 7 3

Condition Monitoring........................................

18 3.1 Existing Degradation Mechanisms.............................................................

18 3.1.1 Tube W ear at AVBs............................................................................

18 3.1.2 Tube W ear at Preheater Baffle Plates..................................................

18 3.1.3 Tube W ear Due to Loose Parts...........................................................

19 3.2 Potential Degradation Mechanisms...........................................................

19 3.3 Secondary Side Integrity............................................................................

20 3.4 Condition Monitoring Conclusion..............................................................

20 4

Operational Assessment............................................................................

27 4.1 Existing Degradation Mechanisms.............................................................

27 4.1.1 Tube W ear at AVBs.............................................................................

27 4.1.2 Tube W ear at Preheater Baffle Plates..................................................

28 4.1.3 Tube W ear Due to Loose Parts...........................................................

29 4.2 Potential Degradation Mechanisms...........................................................

29 4.2.1 Possible Loose Parts (PLP)..................................................................

29 4.3 Secondary Side Integrity............................................................................

31 4.4 Operational Assessment Conclusion........................................................

31 5

Classification of Degradation Mechanisms for the Next Inspection............... 37 5.1 Existing Degradation Mechanisms.............................................................

37 5.2 Potential Degradation Mechanisms...........................................................

37 6

References................................................................................................

38 2/38

List of Tables Table 2-1. Summary of Eddy Current Inspections Completed in 2RF12...........................

8 Table 2-2. Pivot Table of Inspection Results....................................................................

9 Table 2-3. Brief Explanation of Three-letter Codes Used for Inspection Results............ 10 Table 2-4. 2RF12 Tube Plugging Attributes...................................................................

11 Table 2-5. History of Tube Plugging in CPNPP Unit 2....................................................

12 Table 2-6. History of Sludge Removal from CPNPP Unit 2 SGs.....................................

13 Table 2-7. Summary of Loose Parts and Eddy Current PLPs from 2RF12..................... 14 Table 3-1. Summary of AVB Wear Indications in 2RF12...............................................

21 Table 3-2. AVB Wear Indications in Tubes Plugged in 2RF12.......................................

22 Table 3-3. Summary of Baffle Plate Wear Indications...................................................

23 Table 3-4. Summary of Loose Part Wear Indications...................................................

24 Table 4-1. AVB Indications - Trends of Number and Maximum Depth...........................

32 Table 4-2. Growth Rate of AVB Wear Indications...........................................................

33 Table 4-3. Limiting Growth Rate of AVB Wear Indications..............................................

34 Figure 3-1. Video captured image of a wear scar in a Row 6 tube................................

25 Figure 3-2. Foreign object that caused tube wear over FDB...........................................

26 Figure 4-1. Growth Rate of AVB Indications During Cycles 11 and 12...........................

35 Figure 4-2. Histogram and Cumulative Probability Distribution of AVB Indication Growth Rates During Cycles 11 and 12...................................................................

36 3/38

Executive Summary The primary side inspection of the Comanche Peak Unit 2 steam generators (SG) consisted of bobbin and +Point testing of a 50% sample population for all existing and potential degradation mechanisms and bobbin inspection of prior indications.

Temporary alternate repair criteria implemented in the current outage eliminated the need for inspecting four-inch long tubing close to the tube-end.

Secondary side activities included sludge lancing, video inspection, and foreign object search and retrieval (FOSAR).

Base scope inspection program was completed as planned. No expansion of inspection was necessary. Three tubes were plugged for wear at AVB locations, of which two had indications exceeding the repair limit of 40% in depth and the other was administratively plugged with indications which were below the repair limit.

No new degradation mechanisms were reported.

Structural and leakage performance criteria were satisfied prior to the current shutdown.

Hence the condition monitoring requirements are satisfied. An operational assessment of the current inspection results shows that the structural and leakage integrity will be satisfied during the next two operating cycles until the next planned inspection in April 2014 (2RF14). Skipping of SG inspection at 2RF13 depends on NRC approval of the license amendment request (LAR) for permanent alternate repair criteria (H*).

4/38

I Introduction Per NEI 97-06 (Reference 1), a condition monitoring assessment (CM), which evaluates structural and leakage integrity characteristics of the steam generator (SG) at the end of the last operating period, is to be performed following each inspection. This evaluation is "backward looking" and compares the observed SG tube eddy current indication parameters against leakage and structural integrity criteria commensurate with the draft Regulatory Guide 1.121 (Reference 2). Additionally, an operational assessment (OA),

or "forward looking" evaluation is used to project the inspection results and trends to confirm that the SG performance criteria will be met during the operating period until the next inspection.

This report documents the condition monitoring and operational assessment of the inspection results from the Comanche Peak 2RF12 inspection.

1.1 Steam Generator Configuration The Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 NSSS has four Westinghouse Model D-5 SGs each with 4570 thermally treated Alloy 600 U-tubes.

Each U-tube has a nominal outside diameter (OD) of 0.750 inch, a nominal tube wall thickness of 0.043 inch, and a straight length ranging from 303.73 inches (Row 1) to 305.49 inches (Row 49), based on the tube schedule drawing. The tubesheet is 21.23 inches thick with a full depth hydraulic expansion of the tubes in both the hot leg and the cold leg. Approximately 0.75 inch of the tube at both ends was tack expanded prior to tube end welding. On the hot leg side, the U-tubes are supported by seven (7) tube support plates (TSP).

A flow distribution baffle (FDB) plate located between the tubesheet and the first support plate helps distribute the secondary side flow over the tubesheet. On the cold leg side there are four (4) TSPs, six (6) preheater baffle plates and the FDB. The FDB and the lowest five preheater baffle plates are. 0.75 inch thick whereas the TSPs and the top preheater baffle plate are 1.12 inch thick. The FDB and the preheater baffle plates have round drilled holes whereas the TSPs have concave quatrefoil holes. All plates are made of type 405 stainless steel. In the U-bend, the tubes are supported by two (2) sets of chrome-plated Inconel anti-vibration bars (AVB).

To reduce tube vibration, 140 tubes in each SG were hydraulically expanded at the B and D preheater baffle plates. This field modification was performed before the initial startup of CPNPP Unit 2.

1.2 Summary of Operation and Plan The last inspection of these SGs, prior to 2RF12, was conducted at 2RF10 when the accumulated operating life was 13.04 effective full power years (EFPY).

During the 2RF1 1 outage, neither primary side nor secondary side inspection of the SGs was performed. CPNPP Unit 2 implemented a Stretch Power Uprate of 4.5% of the original power rating at the beginning of Cycle 12 in the fall of 2009. The uprate changed the core thermal power from 3458 MWt (101.5% condition) to 3612 MWt. The cumulative operating experience at the current (2RF12) inspection is 15.906 EFPY. The next two fuel cycles are planned to be 1.448 (Cycle 13) and 1.443 (Cycle 14) EFPY.

5/38

2 Steam Generator Outage Summary 2.1 Primary Side Inspection Plan and Results 2.1.1 Base Scope Inspection The 2RF12 inspection plan satisfied the requirements of both the Technical Specifications and the EPRI NDE Guidelines Revision 7 (Reference 3). The 2RF12 base scope inspection plan (for all SGs unless specified) included:

1) 55% full length bobbin inspection, including tubes with prior indications (see the next paragraph) and all tubes uninspected in 2RF10

2) 50% hot leg +Point inspection from 3 inches above to 17 inches below the top of the tubesheet (TTS) (see the next paragraph) including all tubes uninspected in 2RF10

3) 50% U-bend mag-biased mid-range +Point inspection of Rows 1 and 2 (all tubes uninspected in 2RF10)

4) 50% +Point inspection at expanded preheater baffle plates1 (all tubes uninspected in 2RF10)

5) 100% +Point inspection of_> 2 volt dents at H3 TSP

6) 50% +Point inspection of_> 5 volt dings and dents in the hot leg (all such dings and dents uninspected in 2RF10)

7)

Bobbin inspection of tubes at preheater baffle plates to monitor tube wear due to uprating implemented at the beginning of Cycle 12

8)

Special interest rotating pancake coil (RPC) (freespan signals without historical resolution, bobbin I-code indications)

9)

Slippage monitoring in support of the temporary alternate repair criteria (TARC)

10) 100% tube plug video inspection

11)

Top of the tubesheet and typical (periphery and T-slot) baffle plate B secondary side video inspection including foreign object search and retrieval (FOSAR)

12) Upper bundle video inspection (through Access Ports 1 and 2 only) in only one SG (SG4)

Tubes which were identified as possibly having elevated residual stress were included in the full length bobbin program (item 1 above) and the top of the tubesheet +Point program (Item 2).

1 Tube R42C94 in SG 1 was expanded at preheater baffle plate E (C4) in addition to plates B (C2) and C (C3). Hence support plate E is included in the inspection program when the tube R42C94 in SG 1 is selected for preheater baffle plate +Point inspection.

6/38

2.1.2 Inspection Expansion Based on the results of the base scope inspection and application of the industry guidelines, no expansion of inspection was necessary. Hence no inspection expansion was performed during 2RF12.

2.1.3 Inspection Results A summary of the completed inspection program is shown in Table 2-1.

Table 2-2 presents a filtered summary of the tube nondestructive examination (NDE) results, representing data relevant to the condition of the tubes; the data represent total database records, without deleting redundant records. Hence it should be used with caution. Table 2-3 provides a listing of the three-letter codes used to designate eddy current indications and a brief explanation of each.

Slippage monitoring was performed using automated analysis of the eddy current data.

The results were spot-checked by eddy current analysts. No slippage was detected in any of the tubes inspected.

2.2 Tube Repair Summary A total of 3 tubes were plugged during 2RF12. Table 2-4 summarizes the list of tubes plugged in each SG and the cause of plugging. The number of tubes plugged in each SG is listed in Table 2-5 chronologically.

As shown in the table, the cumulative total number of tubes plugged in all SGs is 81, which is equal to 0.44% of the total number of tubes.

2.3 Summary of Secondary Side Inspection & Maintenance The SG secondary side maintenance activities during 2RF12 consisted of sludge lancing, tube bundle video inspection, and FOSAR. These services were performed in all four SGs. In addition, upper bundle video inspection was performed in SG4.

A total of 29 pounds of sludge was removed from the four SGs.

This quantity is consistent with the prior history of sludge removal from CPNPP Unit 2. The sludge removal history is summarized in Table 2-6.

All possible loose parts (PLP) reported from eddy current inspection were reviewed for FOSAR.

Areas of the tube bundle accessible for retrieval include the top of the tubesheet and a large portion of the area over baffle plate B. A FOSAR was conducted for all PLPs located in these areas and over the flow distribution baffle plate A in the cold leg. The video inspection also resulted in the identification of parts located on the tubesheet and on baffle plate B. The parts judged to have possibly caused tube wear (based on size and location) were identified and eddy current inspection of the potentially affected tubes was conducted.

Table 2-7 shows a list of all the parts identified from various inspections and their disposition.

7/38

Table 2-1. Summary of Eddy Current Inspections Completed in 2RF12 Inspection Type SG1 SG2 SG3 SG4 Total 0.610 C/L Bobbin (40 ips) 2860 2715 2784 2897 11256 0.610 H/L Low Row Bobbin (40 ips) 393 393 401 400 1587 0.610 H/L Top of Tubesheet RPC 2290 2289 2290 2296 9165 0.580 Row 1 & 2 U-Bend RPC 114 114 114 114 456 0.610 C/L Expanded Baffle RPC 141 140 140 140 561 0.610 H/L Special Interest RPC 63 30 52 166 311 0.610 C/L Special Interest RPC 7

48 26 7

88 0.580 U-Bend Special Interest RPC 48 21 10 18 97 Total 5916 5750 5817 6'038 23521 8/38

Table 2-2. Pivot Table of Inspection Results Call \\ SG 1

2 3

4 Grand Total BLG 1

1 2

DFH 480 279 492 553 1804 DFS 5

13 1

3 22 DNG 660 334 586 645 2225 DNH 1

12 1

2 16 DNS 3

4 30 35 72 DNT 227 171 248 519 1165 DSH 5

3 7

11 26 DSS 4

5 2

11 INF 9

5 1

3 18 INR 103 71 81 127 382 MBH 5

16 3

5 29 MBM 68 138 144 149 499 NDD 4854 5027 4869 4835 19585 NDF 108 59 79 193 439 NQH 1

1 PCT 161 53 59 22 295 PID 1

1 2

PLP 3

11 1

5 20 PVN 1

6 5

12 RBD 10 17 14 11 52 RHW 1

1 2

RIC 257 69 61 101 488 RRT 2

2 RWS 2

1 3

SLG 1

4 4

WAR 7

5 2

4 18 Grand Total 6977 6301 6687 7229 27194 9/38

Table 2-3. Brief Explanation of Three-letter Codes Used for Inspection Results Call Brief Explanation BLG Bulge DFH Distorted freespan signal with prior history DFS Distorted freespan signal DNG Ding in freespan DNH Distorted signal at a ding with prior history DNS Distorted signal at a ding DNT Dent (ding at a support location)

DSH Distorted support signal with prior history DSS Distorted support signal INF Indication not found INR Indication not reportable MBH Manufacturing buff mark with prior history MBM Manufacturing buff mark NDD No degradation detected NDF No degradation found NQH Non-quantifiable signal with prior history PCT Percent (wall thinning )

PID Positive identification PLP Possible loose part PVN Permeability variation RBD Retest tube - bad data RHW Retest tube with AVB high wear standard RIC Retest tube - incomplete test extent RRT Retest tube - restriction RWS Retest tube with TSP wear standard SLG Sludge WAR Wear indication 10/38

Table 2-4. 2RF12 Tube Plugging Attributes SGID Outage Row Col Volts Deg Ind Per Chn Locn Inch1 PDia PType Attribute 2

U2RF12 27 8

3.49 0 PCT 44 P5 AV3

-0.18 0.61 ZBAZC AVB Wear 2

U2RF12 30 10 4.49 0 PCT 35 P2 AV2

-0.05 0.61 ZBAZC AVBWear(Admin) 3 U2RF12 39 84 5.53 0 PCT 42 P5 AV2 0

0.61 ZBAZC AVB Wear 11/38

Table 2-5. History of Tube Plugging in CPNPP Unit 2 Outage Date EFPY SG 1 SG 2 SG 3 SG 4 Total Percent Pre-service Pre-serv.

0.000 5

3 3

9 20 0.11%

2RF01 Nov-94 0.910 0

0 0

0 0

0.00%

2RF02 Mar-96 2.090 0

0 0

0 0

0.00%

2RF03 Nov-97 3.489 3

5 0

0 8

0.04%

2RF04 Apr-99 4.706 1

0 0

4 5

0.03%

2RF05 Oct-00 6.138 3

0 0

1 4

0.02%

2RF06 Apr-02 7.520 0

4 7

0 11 0.06%

2RF07 Oct-03 8.825 3

0 0

1 4

0.02%

2RF08 Apr-05 10.205 5

2 4

2 13 0.07%

2RF09 Oct-06 11.639 No SG Inspection 01 0.00%

2RF10 Apr-08 13.044 11 31 2

13 0.07%

2RF1 1 Oct-09 14.502 No SG Inspection 0

0.00%

2RF12 Apr-11 15.906 0

2 1

0 3

0.02%

Total 21 23 18 19 81 0.44%

Percent 0.46% 0.50% 0.39% 0.42%

0.44%

12/38

Table 2-6. History of Sludge Removal from CPNPP Unit 2 SGs Comanche Peak Unit 2 - Pounds of Sludge Removed RFO Date SG-1 SG-2 SG-3 SG-4 Total 1 Nov-94 2.5 3.0 3.0 3.0 11.5 2

Mar-96 No sludge lancing performed 3

Nov-97 3.7 4.0 4.5 6.0 18.2 4

Apr-99 3.0 4.0 3.0 3.0 13.0 5

Oct-00 5.5 3.5 5.5 3.5 18.0 6

Apr-02 4.0 6.0 3.0 2.0 15.0 7

Oct-03 No sludge lancing performed 8

Apr-05 10.0 8.0 7.51 9.0r 34.5 9

Oct-06 No sludge lancing performed 10 Apr-08 8.3 6.8 9.3 7.8 32.0 11 Oct-09 No sludge lancing performed 12 Apr-11 6.5 6.5 9.5 6.5 29.0 Total 43.4 41.8 45.3 40.8 171.2 13/38

Table 2-7. Summary of Loose Parts and Eddy Current PLPs from 2RF12 Page 1 of 4: SG1 Width Object Legacy Object Elevation First (Diameter Confirmed Removed Item Number SG Object Description Location (In)

Found by Row Column Leg Length Height for wire) by (YES/NO) (YES/NO) Resolution 1001 1 Scale TTS N/A Video 7

111 HL 0.625 0.25 0.02 N/A NO NO N/A Wire next to legacy part EC 1-Engineering 1002 1 01 TTS N/A Video 8

3 HL 0.5 N/A 0.03 N/A NO NO Disposition 1003 1 Screen mesh TTS N/A Video 4

1 HL 0.375 0.003 0.375 N/A YES NO N/A 1004 1 Sludge rock UTS N/A Video 43 22 CL 0.44 0.26 0.38 N/A YES NO N/A 1005 1 Screen mesh TTS N/A Video 1

89 CL 0.5 0.003 0.05 N/A YES NO N/A Engineering 1006 1 Hard sludge TTS N/A Video 19 63 HL 0.5 0.5 0.5 N/A NO YES Disposition Engineering 1007 1 Hard sludge TTS N/A Video 25 70 HL 0.7 0.5 0.5 N/A NO YES Disposition Engineering 1008 1 Hard sludge TTS N/A Video 23 71 HL 0.7 0.5 0.5 N/A NO YES Disposition Engineering 1009 1 Wire TTS N/A Video 43 56 HL 0.25 N/A 0.02 N/A NO NO Disposition Engineering 1010 1 Wire BP B (C2)

N/A Video 25 82 CL 0.5 N/A 0.02 N/A NO NO Disposition Engineering 1011 1 Wire bristle BP B (C2)

N/A Video 26 45 CL 0.75 N/A 0.01 N/A NO NO Disposition 1012 1 Wire lodged tube crevice BP B (C2)

N/A Video 26 37 CL 1.25 N/A 0.03 N/A YES NO N/A Engineering 1013 1 Wire BP B (C2)

N/A Wire 26 22 CL 0.15 N/A 0.02 N/A NO NO Disposition Legacy part (no change).

Rough Metal Strip wedged in Video /

place. Wedged in between NDE Engineering EC 1-01 1 R7C3, R8C2 and R8C4)

TTS 0.4

+Point 8

2 HL 3

0.3 0.04 History NO YES Disposition Video /

NDE Engineering EC 1-02 1 Same as EC 1-01 TTS 0.13

+Point 7

3 HL 3

0.3 0.04 History NO YES Disposition Video /

NDE Engineering EC 1-03 1 Same as EC 1-01 TTS 0.23

+Point 8

3 HL 3

0.3 0.04 History NO YES Disposition SG-SGMP-11-18, Revision 1 14/38

Table 2-7. Summary of Loose Parts and Eddy Current PLPs from 2RF12 Page 2 of 4: SG2 Width Object Legacy Object First Found (Diameter Confirmed Removed Item Number SG Object Description Location Elevation by Row Column Leg Length Height for wire) by (YES/NO) (YES/NO) Resolution Engineering 2001 2 Scale TTS N/A Video 46 44 HL 0.3 0.125 0.125 N/A NO NO Disposition 2002 2 Curl pushed out to annulus TTS N/A Video 41 21 HL 0.3 0.25 0.1 N/A YES NO N/A 2003 2 Metal Object in annulus TTS N/A Video 49 35 HL 0.75 0.2 0.1 N/A YES NO N/A Engineering 2004 2 Scale TTS N/A Video 3

107 HL 0.5 0.2 0.2 N/A NO NO Disposition Engineering 2005 2 Metal Object BP B (C2)

N/A Video 25 11 CL 0.25 0.062 0.062 N/A NO NO Disposition Wire in tube crevice (Legacy Engineering 2006 2 Item 2-003 identified in 2RF10) BP B (C2)

N/A Video 26 16 CL 0.25 N/A 0.062 N/A NO YES Disposition Metal curl, folded over and EC 2-01 wrapped in between tubes

+Point /

(2007) 2 (caused wear on tubes)

FDB (C1) 0.44

+Point 6

1 CL 3.25 0.11 0.045 Video YES NO N/A EC 2-02

+Point /

(2007) 2 Same as above (EC 2-01)

FDB (Cl) 0.64 Bobbin 6

2 CL 3.25 0.11 0.045 Video YES NO N/A Nothing was found by video EC 2-03 2 inspection TTS 0.15

+Point 5

27 HL N/A N/A N/A Video N/A N/A N/A N/A (No wear indicated by Engineering EC 2-04 2 +Point)

C3 0.37

+Point 49 46 CL N/A N/A N/A

+Point N/A N/A Disposition Blowdown support appears to be touching the tube near the location (First identified in Engineering EC 2-05 2 2RF10 as EC 2-09)

TTS 1.76

+Point 30 56 HL N/A N/A N/A Video N/A YES Disposition N/A (No wear indicated by Engineering EC 2-06 2 +Point)

C3 0.39

+Point 37 56 CL N/A N/A N/A

+Point N/A N/A Disposition SG-SGMP-11-18, Revision 1 15/38

Table 2-7. Summary of Loose Parts and Eddy Current PLPs from 2RF12 Page 3 of 4: SG3 Width Object Legacy Object First (Diameter Confirmed Removed Item Number SG Object Description Location Elevation Found by Row Column Leg Length Height for wire) by (YES/NO) (YES/NO) Resolution Engineering 3001 3 Wire bristle BP B (C2)

N/A Video 21 44 CL 0.3 N/A 0.006 N/A NO NO Disposition Engineering 3002 3 Wire bristle BP B (02)

N/A Video 23 81 CL 0.2 N/A 0.006 N/A NO NO Disposition Engineering 3003 3 Wire (legacy item 3-005 in 2RF10) BP B (C2)

N/A Video 24 67 CL 0.5 0.01 0.01

+Point NO YES Disposition Engineering 3004 3 Wire (legacy item 3-004 in 2RF10) BP B (C2)

N/A Video 25 82 CL 0.5 0.03 0.03

+Point NO YES Disposition Metal object (legacy item 3-003 in Engineering 3005 3 2RF10)

BP B (C2)

N/A Video 25 86 CL 0.3 0.3 0.25

+Point NO YES Disposition Metal object (legacy item first Engineering 3006 3 identified in 2RF08)

BP B (C2)

N/A Video 6

56 CL 0.5 0.5 0.5

+Point NO YES Disposition Wire (legacy item 3-002 identified Engineering 3007 3 in 2RF10)

BP B (C2)

N/A Video 15 56 CL 0.5 N/A 0.064

+Point NO YES Disposition Engineering 3008 3 Brittle material BP B (C2)

N/A Video 5

58 CL 0.125 0.125 0.125 N/A NO NO Disposition 3009 3 Slag BP B (C2)

N/A Video 5

58 CL 0.5 0.5 0.25 N/A YES NO N/A 3010 3 Wire bristle BP B (C2)

N/A Video 14 58 CL 0.75 0.005 0.005 N/A YES NO N/A Engineering 3011 3 Wire bristle BP B (C2)

N/A Video 8

55 CL 0.5 N/A 0.005 N/A NO NO Disposition Engineering 3012 3 Rubber material BP B (C2)

N/A Video 5

55 CL 0.75 0.25 0.1 N/A NO NO Disposition 3013 3 Metal Shard BP B (C2)

N/A Video 8

55 CL 0.375 0.5 0.3 N/A YES NO N/A Nothing was found by video EC 3-01 3 inspection TTS 0.12

+Point 5

33 HL N/A N/A N/A Video N/A N/A N/A SG-SGMP-11-18, Revision 1 16/38

Table 2-7. Summary of Loose Parts and Eddy Current PLPs from 2RF12 Page 4 of 4: SG4 Width Object Legacy Object First (Diameter Confirm Removed Item Number SG Object Description Location Elevation Found by Row Column Leg Length Height for wire) ed by (yes/no)

(YES/NO)

Resolution 4001 4 Wire mesh TSP L N/A Video 1

79 CL 0.4 0.05 0.4 N/A YES NO N/A 4002 4 Metallic object BP B (C2)

N/A Video 25 84 CL 1.25 0.3 0.50 N/A YES NO N/A 4003 4 Rubber BP B (C2)

N/A Video 25 21 CL 0.5 0.5 0.5 N/A YES NO N/A Engineering 4004 4 Wire BP B (C2)

N/A Video 26 104 CL 0.2 0.005 0.005 N/A NO NO Disposition UFO (Retrieval attempted, Engineering 4005 4 object fell in quatrefoil)

TSP P N/A Video 2

96 CL 0.25 0.15 0.15 N/A NO NO Disposition Engineering 4006 4 Scale TTS N/A Video 5

114 HL 1.5 0.03 0.03 N/A NO NO Disposition Engineering 4007 4 Scale TTS N/A Video 11 113 HL 1.5 0.03 0.03 N/A NO NO Disposition 4008 4 Sludge rock in annulus TTS N/A Video 34 49 HL 0.68 0.5 0.5 N/A YES NO N/A 4009 4 Sludge rock TTS N/A Video 46 27 HL 0.37 0.37 0.35 N/A YES NO N/A NDE History.

4010 4 Part (legacy part since 2RF08)

TTS N/A Video 34 55 HL 0.5 0.6 0.02

+Point NO YES Eng. Disp.

NDE History.

4011 4 Nail (legacy part since 2RF08)

TTS N/A Video 23 79 HL 2

0.2 0.2

+Point NO YES Eng. Disp.

4012 4 Metal shaving TTS N/A Video 48 30 HL 0.5 0.125 0.125 N/A YES NO N/A Engineering 4013 4 Consolidated scale/sludge TTS N/A Video 25 61 HL 0.75 0.5 0.5 N/A NO YES Disposition Same as 4010 (legacy item first Video /

NDE History.

EC 4-01 4 identified in 2RF08)

TTS 0.19

+Point 34 55 HL 0.5 0.6 0.02

+Point NO YES Eng. Disp.

Same as 4010 (legacy item first Video /

NDE History.

EC 4-02 4 identified in 2RF08)

TTS 0.06

+Point 35 55 HL 0.5 0.6 0.02

+Point NO YES Eng. Disp.

Same as 4011 (legacy item first Video /

NDE History.

EC 4-03 4 identified in 2RF08)

TTS 0.12

+Point 23 79 HL 2

0.2 0.2

+Point NO YES Eng. Disp.

Same as 4011 (legacy item first Video /

NDE History.

EC 4-04 4 identified in 2RF08)

TTS 0.25

+Point 22 80 HL 2

0.2 0.2

+Point NO YES Eng. Disp.

Same as 4011 (legacy item first Video /

NDE History.

EC 4-05 4 identified in 2RF08)

TTS 0.14

+Point 23 80 HL 2

0.2 0.2

+Point NO YES Eng. Disp.

SG-SGMP-11-18, Revision 1 17/38

3 Condition Monitoring Condition monitoring is the evaluation of the steam generators with respect to meeting the performance criteria for structural integrity, operating leakage and accident condition leakage prior to shut down, in light of the inspection results.

3.1 Existing Degradation Mechanisms Prior to 2RF12, the existing degradation mechanisms in the Comanche Peak Unit 2 SGs were tube wear at AVBs, tube wear at non-expanded preheater baffle plates, and tube wear due to loose parts. These mechanisms were reported during 2RF12; but no other (new) degradation mechanisms were reported.

3.1.1 Tube Wear at AVBs AVB wear has been reported at Comanche Peak Unit 2 SGs in prior inspections. A number of AVB wear indications were reported in each of the SGs during 2RF12. Table 3-1 provides a summary of the AVB wear indications in 2RF12.

Three tubes were plugged due to AVB wear during 2RF12.

Table 3-2 shows the list of AVB wear indications in the tubes plugged during 2RF12. Two of the indications (one each in SG2 and SG3) had through-wall (TW) depths above the repair limit of 40%. The TW depths of those indications were 44% and 42%.

Hence these tubes were plugged as per technical specification requirements. Another tube in SG2 had wear indications at four AVB locations, the deepest being 35% TW. An administrative decision was made by Luminant to plug this tube preventively. The maximum reported depth for AVB wear during 2RF12 was 44% TW.

As per the pre-outage degradation assessment (DA), Reference 4, the condition monitoring limit for AVB wear is 57% TW. The deepest indication reported was only 44% TW.

Hence the wear depths of the reported indications satisfy condition monitoring for burst strength. For primary-to-secondary leakage, the indicated depth of an OD-initiated flaw has to exceed 75% for any leakage to occur. Since all of the reported AVB wear indications had TW depths at/below 44%, primary-to-secondary leakage would not occur either at normal operation or at accident conditions. Thus the structural and leakage performance criteria (condition monitoring) are satisfied for the AVB wear indications.

3.1.2 Tube Wear at Preheater Baffle Plates Wear at preheater baffle plates has been observed at CPNPP Unit 2 in prior inspections. These have been very few in number and had negligible growth rates.

During 2RF10, two baffle plate wear indications were reported, one each in SGs 1 and

3. Wear indications at these same locations were reported in 2RF12 and had the same TW depths as in 2RF10. The baffle plate wear indications reported during 2RF12 are summarized in Table 3-3. The estimated depths of these indications, 7% and 6%, were far below the repair limit of 40% TW.

18/38

As per the pre-outage DA (Reference 4), the condition monitoring limit for baffle plate wear is 48% TW, based on bobbin sizing using a wear scar standard. For primary-to-secondary leakage, the indicated depth of an OD-initiated flaw has to exceed 75% for any leakage to occur. Since all of the reported baffle plate indications had TW depths well below 40%, leakage will not occur either at normal operation or at accident conditions. Thus the structural and leakage performance criteria (condition monitoring) are satisfied for the baffle plate wear indications.

3.1.3 Tube Wear Due to Loose Parts Loose parts wear indications were reported in two adjacent tubes in SG2.

The indications were on top of the flow distribution baffle plate A in the cold leg (Cl). The affected tubes, R6C1 and R6C2, are located at the periphery. There was one wear scar in R6C1 and two scars in R6C2. These locations were inspected using a +Point probe.

Inspection results are shown in Table 3-4. The depth estimates of the indications from

+Point inspection were 22% TW in R6C1 and 30% and 19% in R6C2. As a result of the eddy current inspection, a foreign object search was performed at the given location over the FDB and the object was retrieved from the SG. Figure 3-1 shows the video captured image of one of the wear scars in a tube. Figure 3-2 shows a picture of the foreign object that caused the tube wear. It was a metal curl, 3.25 inches in length and 0.11 inch in width and 0.045 inch in thickness. It was wedged between these two tubes.

Since the part was removed (tube wear at this location will not continue) and the depths of the indications were below the repair limit (40% TW), the tubes were left in service.

The axial extents of all three indications were 0.17 inch by eddy current indication. As per Table 3-1 of the degradation assessment (Reference 4), the condition monitoring limit for a volumetric indication of 0.3 inch axial length) is 67% TW by bobbin and 60%

TW by +Point measurement.

The difference is due to the higher NDE uncertainty associated with ETSS 21998.1 (used for sizing the flaws by +Point) compared to ETSS 96004.3 (used for bobbin sizing). Since the actual length and depths of the wear scars were much smaller than these values, there is a significant margin in the depth of these indications from both the plugging limit and the condition monitoring limit. For primary-to-secondary leakage, the indicated depth of an OD-initiated flaw has to exceed 75% for any leakage to occur. Since all of the reported loose parts wear indications had TW depths well below 75%, leakage will not occur either at normal operation or at accident conditions. Hence the structural and leakage performance criteria were satisfied for the loose part wear indications during Cycle 12.

3.2 Potential Degradation Mechanisms Potential degradation mechanisms are those mechanical and corrosive processes that are judged to have the potential to occur based on industry experience and/or laboratory data. None of the potential degradation mechanisms listed in the 2RF12 DA (Reference 4) was observed during the current outage. Hence the condition monitoring was satisfied for the potential degradation mechanisms.

19/38

3.3 Secondary Side Integrity Secondary side sludge lancing, video inspection over the tubesheet and over baffle plate B, and FOSAR at these locations were performed in each SG during 2RF12. A video inspection was performed in accessible locations where loose parts were known or suspected to exist based on inspections during prior outages. In addition, an upper bundle inspection was performed in SG4. Tube OD surface and TSP crevices were found to be clean with very little deposit accumulation.

No anomalous conditions adverse to structural integrity were reported from the video inspection. The FOSAR operation was performed over the tubesheet and over baffle plate B.

One object that had led to wear indications in two tubes over the flow distribution baffle plate A in the cold leg (C1) was retrieved. All of the PLP indications reported in the eddy current inspection over the tubesheet and plates A and B were subjected to FOSAR.

Further, objects identified during the video inspection were retrieved where appropriate.

Table 2-7 provides a summary of the results from the FOSAR operation.

3.4 Condition Monitoring Conclusion During the plant operation in Cycle 12, no primary-to-secondary leakage was detected based on N-16 monitors, condenser off gas monitors, and grab sample measurements.

Further, none of the eddy current indications were deep enough to cause primary-to-secondary tube leakage (all indications had depths below the condition monitoring limit).

Hence leakage integrity was maintained during Cycle 12.

During the 2RF12 outage, tube plugging was performed only for tube wear at AVB locations.

The condition monitoring (CM) limit for AVB wear is 57% TW depth (Reference 4). The deepest AVB wear indication reported during this outage was 44%

TW which is well below the CM limit. Since the TW depths of all indications were below the CM limit, they met the burst strength requirements in the condition monitoring criteria. Since these indications were well below 75% TW, leakage would not occur during normal operation or accident conditions.

In summary, each of the four SGs met the performance criteria (condition monitoring) during the operating cycle prior to shut down for 2RF1 2.

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Table 3-1. Summary of AVB Wear Indications in 2RF12 SGI SG2 SG3 SG4 Total Number of AVB Indications 160 48 56 22 286 Maximum Depth, % TW 33 44 42 26 44 Number of "New" Indications 6

3 2

4 15 Number of > 20% "New" Indications 0

0 0

0 0

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Table 3-2. AVB Wear Indications in Tubes Plugged in 2RF12 SGIDI RowI Coil Voltsj DegInd I Per[ Chn LocnI Inchl1 BegT [EndT 1 PDial PType Cal 2

27 8

3.041 01 PCT1 311 P21 AV2

-0.111 CTE I HTE 10.61 ZBAZC 71 2

27 8

3.491 01 PCT1 441 P5I AV3 1 -0.181 CTEI HTE 1 0.611 ZBAZC 71 2

30 10 3.59 0 PCT 31 P2 AV1 0 HTE CTE 0.61 ZBAZC 36 2

30 10 4.49 0 PCT 35 P2 AV2

-0.05 HTE CTE 0.61 ZBAZC 36 2

30 10 3.74 0 POT 32 P2 AV3 0

HTE GTE 0.61 7AZC 36 2

30 10 0.72 0 PCT 11 P2 AV4 0.49 HTE CTE 0.61 ZBAZC 36 3

39 84 5.53 0 PCT 42 P5 AV2 0

HTE CTE 0.61 ZBAZC 50 3

39 84 3.59 0 PCT 33 P2 AV3 0 HTE CTE 0.61 ZBAZC 50 3

39 84 1.68 0 PCT 20 P2 AV4 0.1 HTE CTE 0.61 ZBAZC 50 22/38

Table 3-3. Summary of Baffle Plate Wear Indications 23/38

Table 3-4. Summary of Loose Part Wear Indications SGID Outage Row Col Volts Deg Ind Per Chn Locn Inch1 BegT EndT PDia PType 2

U2RF12 6

1 1.05 114 PCT 22 6

C1 0.45 C1 C1 0.61 ZPS3C 2

U2RF12 6

2 1.79 101 PCT 3 0 6

C1 0.44 C1 C1 0.61 ZPS3C 2

U2RF12 6

2 0.85 108 PCT 19 6

Cl 0.84 Cl C1 0.61 ZPS3C 24/38

Object on upper left corner is the retrieval tool. The flow distribution baffle (FDB) is on the left side and the tube on the right side in the picture. The FDB crevice is free of any deposit buildup.

Figure 3-1. Video captured image of a wear scar in a Row 6 tube 25/38

The foreign object is a metal curl, bent into a shape resembling a pretzel. A small portion of a tube is seen on the right side in the picture.

Figure 3-2. Foreign object that caused tube wear over FDB 26/38

4 Operational Assessment Operational assessment is the forward looking evaluation to assess if the steam generators will meet the structural, operating leakage and accident condition leakage performance criteria until the next scheduled inspection.

4.1 Existing Degradation Mechanisms As discussed in Section 3.1, the existing degradation mechanisms reported during the 2RF12 inspection were tube wear at AVBs, tube wear at non-expanded preheater baffle plates, and wear due to loose parts.

4.1.1 Tube Wear at AVBs During 2RF12, two tubes were plugged for AVB wear as their TW depth exceeded the repair limit of 40%. In addition, a third tube with wear indications at four AVB locations (the deepest of these being 35%) was preventively plugged based on an administrative decision. The number of AVB indications in all SGs was a total of 286, compared to 275 reported at 2RF10. Thus the number of indications is reaching a plateau.

The maximum reported wear depth during the current outage is 44% TW compared to 34%

TW reported at 2RF10. Table 4-1 shows the trends of the number and the maximum reported depth of the AVB indications in each SG.

Although most indications did not grow in depth, some did, and a very few progressed above the repair limit. A portion of the high progression in a few indications is attributed to the uncertainty in the depth measurement by eddy current - when the uncertainties in the measurement in consecutive inspections affect in opposite directions, some high progressions and some negative progressions result.

A 4.5% power uprating was implemented in CPNPP Unit 2 at the beginning of Cycle 12. It is likely that the uprating also had an influence on the progression of AVB wear indications.

The growth rate of AVB indications is very low.

Figure 4-1 shows the growth rate distribution as a function of the indicated depth at the beginning of the period (during the last inspection at 2RF10). It may be noted that the growth rate is independent of the initial wear depth. There are a large number of negative values, which reflect the NDE uncertainty. The average growth of the AVB indications in the last two cycles was 0.15% TW, which assumes that the new indications grew to their current values from 0% TW depth at 2RF10. If the new indications are removed from the population, the average growth rate falls to -0.66% TW, with a standard deviation of 2.76% TW. Since the combined operating length of cycles 11 and 12 was 2.862 EFPY, the average growth per EFPY was -0.23% with a standard deviation of 0.965 %/EFPY. The growth rate at 95% probability and 50% confidence is 1.36 %/EFPY.

A histogram and a cumulative probability distribution of the growth rates during Cycles 11 and 12 are shown in Figure 4-2. The average and maximum growth rates for the last few cycles are listed in Table 4-2.

This table also shows the growth rates at 95% cumulative 27/38

probability and the 95% probability value at 95% confidence. The growth rate during the last two cycles at the 95% cumulative probability was 1.05 %/EFPY. The growth rate at 95% probability and 95% confidence during the same period was 1.48 %/EFPY.

The combined length of the next two fuel cycles is expected to be 2.89 EFPY. Hence using the 95/95 growth rate of 1.48 %/EFPY and the combined cycle length of 2.89 EFPY, the projected growth during the next two cycles is 4.28% TW.

The 95/95 growth rate of 1.48 %/EFPY multiplied by the combined cycle lengths during the last two cycles of 2.862% yields a two-cycle growth of 4.24% from 2RF10 to 2RF12.

The value conservatively projected at the conclusion of 2RF1O (Reference 5) was 6.43%. Thus the actual growth rate observed during Cycles 11 and 12 was less than the conservative estimate made previously.

The SG specific limiting growth rates (%TW/EFPY) in recent cycles are listed in Table 4-3. It lists the maximum growth rate of all AVB indications in each SG and the 95%

probability, 50% confidence growth rates in each SG (calculated using t distribution).

The data shows that there is no systematic trend that suggests high growth rates in any specific SG; instead the high growth rates are randomly distributed among the SGs in different cycles. Based on the 95% probability, 50% confidence values, there was a small increase in the growth rate in the last two cycles in SG3 and SG4 compared to the prior two cycles. In the other two SGs, there was a more appreciable change in the last two cycles, one decreasing (SG1) and the other increasing (SG2). The highest 95/50 growth rate was 2.25 %/EFPY (in SG2). Using this value and the combined operating durations of the next two cycles (2.89 EFPY) yields a projected growth rate of 6.50%

TW in the next two cycles.

Since the projected growth rate for the next two cycles estimated on the basis of growth rates in individual SGs (6.50%) is higher than the value estimated based on all SGs combined (4.28%), the higher value of 6.5% is used in this operational assessment to assess the operability of the SG in the next two cycles. The deepest AVB indication returned to service after 2RF12 was 33% TW. Applying the estimated growth rate of 6.5% in the next two cycles, a 33% indication (largest indication left in service after 2RF12) will grow to 39.5% TW at 2RF14. As noted in the degradation assessment, the condition monitoring limit for AVB wear is 57%. Hence at the next inspection during 2RF14, there will be considerable margin from the condition monitoring limit for the AVB indications. Moreover, the projected depth of the AVB wear indications is much smaller than the throughwall penetration required for primary-to-secondary leakage. Thus the AVB wear indications will meet the performance criteria during the next two operating cycles.

4.1.2 Tube Wear at Preheater Baffle Plates During 2RF12, two baffle plate wear indications were reported, one each in SGs 1 and

3. The baffle plate wear indications reported during 2RF12 are summarized in Table 3-3. The estimated depths of these indications were 7% (SG1 R49C56) and 6% (SG3 R45C55).

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The depths of these indications during the prior inspection in 2RF10 were identical to their current depths. The growth rate of the baffle plate indications was 0% TW. The indication in SG1 R49C56 was inspected at 2RF08 with an estimated depth of 5% TW.

Hence in the two cycles prior to 2RF10, this indication grew by 2% TW. The indication in SG3 R45C55 was also inspected at 2RF08 and had an estimated depth of 7% TW.

Hence in the two cycles prior to 2RF10, this indication grew by -1% TW. The negative growth reflects the uncertainty in the depth estimate by eddy current. Thus the average growth rate of the two indications in four cycles was 0.5% TW and the maximum growth rate was 2% TW. A power uprating was implemented in CPNPP Unit 2 at the beginning of Cycle 12. Comparison of the current data with the prior inspection results shows that the uprating had no impact on the growth of baffle plate wear indications.

The 95 percentile growth rate during the next two cycles is conservatively projected to be twice the maximum growth rate during the last four cycles.

This yields a projected 95%

growth value of 4% in two cycles.

The largest of the baffle plate indications was 7% in depth. Adding a growth value of 4%, it is projected to be 11% TW at 2RF14. The projected depth is far below the condition monitoring limit of 48% (Reference 4). The projected depth of these wear indications is much smaller than the throughwall penetration required for primary-to-secondary leakage. Hence the structural and leakage integrity will be met for the baffle plate wear mechanism during the next two operating cycles.

4.1.3 Tube Wear Due to Loose Parts As discussed in Section 3.1.3, a number of loose parts were reported from FOSAR.

These parts have accumulated over the twelve cycles of plant operation. Those objects that could be retrieved have been removed from the SGs.

A detailed engineering evaluation of the parts remaining in the SGs was made by Westinghouse as documented in Reference 6. It concluded that there would be no threat to tube integrity from the parts remaining in the SGs for at least two fuel cycles of operation. Hence tube integrity will be maintained for degradation from loose parts wear during the next two cycles.

4.2 Potential Degradation Mechanisms 4.2.1 Possible Loose Parts (PLP)

A number of PLP indications were reported at the top of the tubesheet in the hot leg (HTS) and/or over baffle plates A and D in the cold leg (Cl and C3) in all steam generators. All PLP locations accessible to FOSAR were video inspected and if any objects were found, the objects were either retrieved or disposed on the basis of an engineering assessment. This section addresses the PLP indications with no coincident tube wear indication in the vicinity, and there is no information regarding an object coincident with the PLP or the confirmation of its presence.

The prior experience at Comanche Peak had indicated that +Point inspection can result in a significant number of false PLP calls. At 2RF08, a large sample of the PLP data 29/38

was reviewed to quantify the extent of false calls.

The sample included the PLPs reported at the top of the tubesheet in all SGs and those over baffle plate B in SG 3.

Most of the +Point inspection over baffle plate B in all SGs was performed as a result of the foreign objects observed from FOSAR and hence were in tubes adjacent to the observed objects. In SG 3, this +Point inspection scope was expanded to include tubes adjacent to PLPs (to "box in" PLPs); SG 3 was selected for this reason. Of the 23 PLP indications reported over the tubesheet in all SGs, objects were found adjacent to 12 of the tubes. There were no objects in the vicinity of the remaining 11 tubes with PLPs.

Hence 48% of the reported PLPs over the tubesheet were false calls. Forty-five PLP indications were reported over baffle plate B in SG 3. Of these, 16 were false calls.

Thus overall, approximately 40% of the PLP indications reported in the sample population were false calls.

Based on the above data, it was judged at 2RF08 that a large number of PLP indications reported over baffle plates D and H (C3 and C6) were false calls. It was also likely that several of the others, especially over baffle plate H, represented scale that had fallen on to the plate rather than foreign objects.

Since these areas are not accessible for video inspection, confirmation of the actual condition has not been possible. If loose parts carried into the SG through feedwater are responsible for any of the PLP calls over these upper baffle plates, the objects are likely to be smaller and lighter than those observed over baffle plate B since those objects would have been transported to the higher elevation after having overcome the normal gravitational settlement over baffle plate B. The lighter and smaller objects tend to be less damaging to tubes. Based on these considerations, it was concluded in 2RF08 that most of the PLP indications at these baffle plate locations were benign and would not affect tube integrity.

The inspection results from 2RF10 and 2RF12 substantiate the above conclusion since no loose parts wear coincident with the 2RF08 PLP locations was reported at C3 or C6. Moreover, all of the PLP calls at C6 reported in prior inspections have disappeared in the 2RF12 inspection. Only two (new) PLP calls were reported in the higher baffle plates (C3) during 2RF12.

Over baffle plate H (C6), tubes have been plugged in SG 3 for loose part wear during 2RF08 and 2RF06. Four of these tubes are adjacent tubes in the same column (33). It is likely that the same object is responsible for the wear indications in these tubes. It is also possible that this object may affect other tubes in the vicinity of the plugged tubes in future cycles. However, the wear rate as derived from the plugged tubes is small.

Tubes in Column 33 adjacent to those previously showing wear indications were inspected during 2RF10 and found to have no wear at baffle plate H (C6). Tubes in Columns 32, 33, and 34 in adjacent rows were inspected using +Point during 2RF12.

Neither tube wear nor PLP calls were reported from this inspection. Hence based on inspections in 2RF10 and 2RF12, loose parts wear in adjacent tubes over baffle plate H (C6) appears to have been arrested. Therefore, no leakage is expected during normal operation or at accident conditions. Operational assessment related to loose part wear was discussed in Section 4.1.3. It showed that performance criteria are expected to be met for two operating cycles until 2RF14.

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4.3 Secondary Side Integrity Secondary side sludge lancing, video inspection over the tubesheet and over baffle plate B, and FOSAR at these locations were performed in each SG during 2RF12. In addition, upper bundle inspection was performed in SG4 via access ports 1 and 2.

Tube OD surface and TSP crevices were found to be clean with very little deposit accumulation.

No anomalous conditions adverse to structural integrity were reported from the video inspection. The FOSAR operation was performed over the tubesheet and over baffle plate B. In addition, a foreign object was retrieved from the top of flow distribution baffle plate A in the cold leg. The PLP reported in the eddy current inspection were subjected to FOSAR. Further, objects identified during the video inspection were retrieved where appropriate.

4.4 Operational Assessment Conclusion The condition of the CPNPP Unit 2 SG tubes, as indicated by the condition monitoring evaluation (Section 3) and the repair actions during 2RF12, has been subjected to operational assessment with respect to the acceptability of the SGs to provide service with satisfactory structural integrity and leakage integrity until the next inspection at the end of Cycle 14.

The condition monitoring evaluation concluded that no challenge with respect to either leakage or tube burst was present.

Hence no in situ leak or pressure testing was necessary during 2RF12. It may be noted that all SGs had two continuous cycles of operation without inspection prior to 2RF12. Evaluation of tube wear at baffle plates shows that significant margin from plugging limit will be present during the next two cycles and hence the performance criteria will be met.

Three tubes were plugged during 2RF12, all due to tube wear at AVB locations.

Progression of AVB wear indications during 2RF12 was consistent with prior history.

Based on an operational assessment, significant margin against structural and leakage integrity limits will be present during the next two cycles of operation.

An assessment of the potential loose parts wear from parts known to remain in the SGs concluded that the performance criteria will be met during the next two cycles.

In summary, the operational assessment leads to the conclusion that structural and leakage integrity of the SGs will be maintained during the next two fuel cycles, until the next planned inspection at the end of Cycle 14 (2RF14).

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Table 4-1. AVB Indications - Trends of Number and Maximum Depth Trend of AVB Wear Indications Reported in Recent Inspections Inspection Number of AVB Indications Maximum depth, %TW SG1 SG2 SG3 SG4 SG1 SG2 SG3 SG4 2RF05 127 Note 1 Note 1 15 39 Note 1 Note 1 42 2RF06 Note 1 37 46 Note 1 Note 1 34 30 Note 1 2RF07 138 Note 1 Note 1 14 47 Note 1 Note 1 35 2RF08 157 43 50 18 37 34 31 25 2RF09 No SG inspection performed at 2RF09 2RF1O 157 47 541 18 341 321 321 25 2RF1 1 No SG inspection performed at 2RF1 1 2RF12 1601 48 561 22 33 441 42 26 Note 1: This SG was not inspected during this refueling outage.

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Table 4-2. Growth Rate of AVB Wear Indications Aggregate AVB Wear Growth Rate Summary Period SGs AVB Indication growth, %TWIEFPY Ending Inspected Average Maximum 95%CPDF 950/195%

2RF04 1, 2, 3, 4 0.93 8.22 4.50 4.48 2RF05 1, 4 0.97 4.93 4.50 6.28 2RF06 2, 3 0.74 2.49 4.19 3.57 2RF07 1, 4

-0.10 7.07 2.42 2.43 2RF08 1, 2, 3, 4 0.92 5.80 3.62 3.71 2RF09 None No SG inspection performed at 2RF09 2RF10 1, 2, 3, 4 0.06 2.47 1.41 1.41 2RF11 None No SG inspection performed at 2RF11 2RF12 1, 2, 3, 4

-0.23 6.64 1.05 1.48 33/38

Table 4-3. Limiting Growth Rate of AVB Wear Indications AVB Wear Indication Limiting Growth Rate Summary for Each SG Period Maximum growth, %TW/EFPY 95% prob. growth, %TW/EFPY Ending SG1 SG2 SG3 SG4 SG1 SG2 SG3 SG4 2RF04 8.22 8.22 3.29 6.28 4.04 5.88 3.28 6.02 2RF05 4.88 Note 1 Note 1 4.93 3.6 Note 1 Note 1 5.47 2RF06 Note 1 2.23 2.49 Note 1 Note 1 2.19 1.43 Note 1 2RF07 7.07 Note 1 Note 1 1.86 2.26 Note 1 Note 1 2.23 2RF08 5.80 2.61 3.72 3.62 4.18 1.92 2.35 2.58 2RF09 No SG inspection performed at 2RF09 2RF10 2.11 2.471 1.76 1.06 1.371 1.44 1.21 0.99 2RF1 1 No SG inspection performed at 2RF1 1 2RF12 2.45 6.64 3.49 0.701 1.071 2.25 1.27 1.05 Note 1: This SG was not inspected during this refueling outage.

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AVB Indication Growth from 2RF1O to 2RF12 20 0

LL EL 4

0 L..

C)

N E

0 15 10 0

0 0

0 0

0000 00 0

000 0

0 00 0

0000 0

0 0

000 0000 0

o oo 000 0

0 0

0 0 0 0

0

-5 000 0

0 0 0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0 0 o 0 0 0

000 0000 0

0 0

0 0

0 0 0 0

0 0

0 00 0

0 0

0 0

0 0

0 0

0 0

0

-10 0

5 10 15 20 25 30 35 40 Indication Depth at 2RF10, % TW Figure 4-1. Growth Rate of AVB Indications During Cycles 11 and 12 35/38

AVB Wear Growth Rate in Cycles 11 and 12 200 o

o o

o 100%

90%

160 80%

o*70%

In*

0

.2120 60 50%O 80 40%

EE M

30%

zU 40 20%

10%

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 6.8 Upper End of Growth Bin Range, %/oIEFPY Frequency

-e-Cumulative %

Figure 4-2. Histogram and Cumulative Probability Distribution of AVB Indication Growth Rates During Cycles 11 and 12 36/38

5 Classification of Degradation Mechanisms for the Next Inspection Based on the results of the prior and current inspections through 2RF12 and the industry experience to-date, the degradation mechanisms in CPNPP Unit 2 SGs are classified as follows. This is a good starting point for the next degradation assessment (DA); however, additional industry guidelines and operating experience during the interim period must be taken into account in the development of the next DA.

5.1 Existing Degradation Mechanisms The existing degradation mechanisms in the CPNPP Unit 2 SGs as of 2RF12 are:

1) Tube wear at AVBs

2) Tube wear at preheater baffle plates

3) Tube wear due to loose parts 5.2 Potential Degradation Mechanisms The potential degradation mechanisms in the CPNPP Unit 2 SGs as of 2RF12 are:

1) Axial ODSCC at tube support plates

2) Axial and circumferential ODSCC at the top of the hot leg tubesheet

3) Axial and circumferential PWSCC at BLG/OXP locations within the hot leg tubesheet

4) Axial PWSCC at Row I and 2 U-bends.

37/38

6 References

1.

"Steam Generator Program Guidelines," NEI 97-06 Revision 2, May 2005.

2.

"Bases for Plugging Degraded PWR Steam Generator Tubes," Draft Reg. Guide 1.121, August 1976.

3.

"Steam Generator Management Program: Pressurized Water Reactor Steam Generator Examination Guidelines: Revision 7," EPRI 1013706, October 2007.

4.

Westinghouse Letter WPT-17498, "Comanche Peak Nuclear Power Plant Unit 2 2RF12 Steam Generator Degradation Assessment," March 10, 2011.

5.

Westinghouse Letter WPT-17208, "Comanche Peak Nuclear Power Plant Units 1

& 2 2RF10 Steam Generator Condition Monitoring and Operational Assessment Report," July 18, 2008.

6.

Westinghouse Letter WPT-17517, "Comanche Peak Nuclear Power Plant Unit 2 Engineering Disposition of Steam Generator Foreign Objects in 2RF12," May 6, 2011.

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