CP-202200200, (CPNPP) Unit 2 Refueling Outage 19 (2RF19) Steam Generator 180 Day Report
| ML22125A267 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 05/05/2022 |
| From: | Hicks J Luminant |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| CP-202200200, TXX-22041 | |
| Download: ML22125A267 (1) | |
Text
II Luminant CP-202200200 TXX-22041 May 5, 2022 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Jack C. Hicks Manager, Regulatory Affairs
Subject:
Comanche Peak Nuclear Power Plant (CPNPP)
Docket No. 50-446 Ref Unit 2 Refueling Outage 19 (2RF19) Steam Generator 180 Day Report
Dear Sir or Madam:
Comanche Peak Nuclear Power Plant (Vistra Operations Company LLC)
P.0. Box 1002 6322 North FM 56 Glen Rose, TX 76043 T 254.897.6725 10CFR50.55a TS 5.6.9 Vistra Operations Company LLC ("Vistra OpCo") hereby submits the Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 steam generator tube inspection report for 2RF19 as required by Technical Specification 5.6.9.
This communication contains no new commitments regarding CPNPP Unit 2.
Should you have any questions, please contact Jim Barnette at (254) 897-5866 or James.barnette@luminant.com.
Sincerely, JakC.llicks
Attachment:
180 Day Steam Generator Tube Inspection Report - Comanche Peak Unit 2 Cycle 19 c (email) -
Scott Morris, Region IV [Scott.Morris@nrc.gov]
Dennis Galvin, NRR [Dennis.Galvin@nrc.gov]
John Ellegood, Senior Resident Inspector, CPNPP Uohn.Ellegood@nrc.gov]
Neil Day, Resident Inspector, CPNPP [Neil.Day@nrc.gov]
Attachment to TXX-22041 Page 1 of 18 180 Day Steam Generator Tube Inspection Report -
Comanche Peak Unit 2 Cycle 19 DESIGN AND OPERATING PARAMETERS Steam Generator Design and Operating Parameters SG Model/ Tube Material/# SGs per unit W-D5/ Alloy 600TT / 4
- of tubes per SG / Nominal Tube Dia. / tube 4,570 / 0.750 in/ 0.043 in thickness Support Plate Style/ Material Broached Quatrefoil and Drilled Hole/
Stainless Steel Last Inspection Date December 2019 (2RF17)
EFPM since the last inspection 31.5 Total cumulative SG EFPY 25.5 Mode 4 initial entry November 12, 2021 Observed P/S Leak Rate since the last No leakage observed inspection and how it trended with time Nominal indicated value of Thot during Cycle 618 degrees F (This value was the highest and will be used as the conservative average of the 19 at full power four loops.)
Degradation mechanism sub population Potential high residual stress tubes in row 1 and 2 U-bend regions.
Deviations from SGMP guidelines since the None last inspection Steam Generator Schematic Schematic is attached. See next page.
Attachment to TXX-22041 Page 2 of 18 l.i 3!
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Attachment to TXX-22041 Page 3 of 18
- a. SCOPE OF INSPECTIONS PERFORMED ON EACH SG The primary side inspection included all tubes in all SGs, consisting of 100% full length bobbin, 100%
+POINT probe inspection of the hot leg top of tubesheet, and additional inspections of dents/dings, portions of the cold leg tubesheet, and special interest. The secondary side inspection included foreign object search and removal (FOSAR) after sludge lancing, Waterbox inspections, and an upper tube bundle inspection in SG 3.
100% Bobbin full length inspection of tubes in all four SGs (straight legs only in Rows 1 and 2).
100% Bobbin inspection of tubes identified as potentially having high residual stress.
100% Bobbin inspection of all prior indications of degradation and/or historical PLPs.
100% +POINT probe inspection of HL TTS from +3.00 inches/-15.00 inches (H* distance= 14.01 inches).
+POINT probe inspection HL TTS +3.00 inches/-15.00 inches of 100% of the peripheral tubes, including the open lane and T-slot, 2 pitches into the bundle. Data acquisition shall continue as required to assure that the required distance below the tubesheet (15.00 inches) is adequately covered. (this is covered by the item above, but is retained for information)
+POINT probe inspection CL TTS +3.00 inches/-3.00 inches of 100% of the peripheral tubes, including the open lane and T-slot, 2 pitches into the bundle.
+POINT inspection of all HL and CL TSP locations and CL TTS +3 inches/-3 inches in tubes identified as potentially having high residual stress.
100% +POINT probe inspection of the U-bends in Rows 1 and 2 (same tubes as bobbin program).
100% +POINT probe inspection of all dents/dings> 5.0 volts on HL and U-bend.
100% +POINT probe inspection of all dents/dings> 2.0 volts at and below TSP C7.
100% +POINT probe inspection of dents> 2.0 volts at H3 TSP.
100% +POINT inspection of tubes expanded at Preheater Baffle Plate (PBP) B.
100% +POINT probe inspection of tubes expanded at PBP D.
+POINT probe inspection of legacy loose parts and PLPs.
+POINT probe inspection of all I-code bobbin indications that are not resolved after history review.
Attachment to TXX-22041 Page 4 of 18
- b. THE NONDESTRUCTIVE EXAMINATION TECHNIQUES UTILIZED FOR TUBES WITH INCREASED DEGRADATION SUSCEPTIBILITY
+Point/Rotating probe (RPC) was utilized for all tubes with increased degradation susceptibility as described in the scope of inspections.
- c. FOR EACH DEGRADATION MECHANISM FOUND c.1 NONDESTRUCTIVE EXAMINATION TECHNIQUES UTILIZED Degradation Mechanism Technique Used Tube wear at A VBs Bobbin and RPC Tube wear at preheater baffle plates Bobbin and RPC Tube wear at quatrefoil tube support plates Bobbin and RPC Tube wear due to foreign object Bobbin and RPC Axial ODSCC at dents/dings Bobbin and RPC
Attachment to TXX-22041 Page 5 of 18 c.2 LOCATION, ORIENTATION, MEASURED SIZE, AND VOLTAGE RESPONSES Wear Indication at Support Structures SG1 SG2 SG3 SG4 Limiting/Total
<20%TW 135 47 54 342 279 Col Volts Ind
%TW Axial Cir.
Cir.
Location SG Row Length Width Degrees 1
35 16 0.99 WEAR 20 AV2 1
45 82 0.97 WEAR 20 AV4 1
45 87 1.12 WEAR 20 AV1 1
38 89 0.95 WEAR 20 AVl 1
38 90 0.94 WEAR 20 AV4 1
41 93 1.1 WEAR 20 AV3 1
23 108 0.91 WEAR 20 AV2 1
32 12 1.16 WEAR 21 AV2 1
40 20 1.12 WEAR 21 AV4 1
40 30 0.96 WEAR 21 AV4 1
40 31 1.19 WEAR 21 AV4 1
40 60 1.38 WEAR 21 AV4 1
39 78 1.15 WEAR 21 AV4 1
45 79 1.08 WEAR 21 AV3 1
38 89 1.08 WEAR 21 AV4 1
37 99 1.07 WEAR 21 AV3 1
38 99 1.09 WEAR 21 AVl 1
38 99 1.08 WEAR 21 AV2 1
31 103 1.08 WEAR 21 AV3 1
41 20 1.23 WEAR 22 AV3 Inch Probe
-0.35 Bobbin
-0.03 Bobbin
-0.38 Bobbin
-0.35 Bobbin
-0.03 Bobbin
-0.32 Bobbin
-0.06 Bobbin 0.00 Bobbin 0.03 Bobbin
-0.06 Bobbin
-0.03 Bobbin 0.15 Bobbin 0.35 Bobbin 0.06 Bobbin
-0.34 Bobbin 0.18 Bobbin 0.03 Bobbin 0.00 Bobbin 0.09 Bobbin
-0.06 Bobbin
Attachment to TXX-22041 Page 6 of 18 SG Row Col 1
40 31 1
40 31 1
43 77 1
42 88 1
35 100 1
28 105 1
30 11 1
31 12 1
40 19 1
43 86 1
39 89 1
41 95 1
35 101 1
34 102 1
36 16 1
40 30 1
40 45 1
49 56 1
45 84 1
39 17 1
41 20 1
30 56 1
45 79 1
43 87 1
41 88 1
46 89 Volts Ind 0.99 WEAR 1.3 WEAR 1.15 WEAR 1.09 WEAR 1.2 WEAR 1.15 WEAR 1.39 WEAR 1.45 WEAR 1.35 WEAR 1.39 WEAR 1.3 WEAR 1.34 WEAR 1.27 WEAR 1.2 WEAR 1.62 WEAR 1.34 WEAR 1.46 WEAR 1.41 WEAR 1.42 WEAR 1.44 WEAR 1.63 WEAR 1.66 WEAR 1.54 WEAR 1.47 WEAR 1.64 WEAR 1.55 WEAR
%TW Axial Cir.
Cir.
Location Inch Length Width Probe Degrees 22 AV2 0.00 Bobbin 22 AV3 0.00 Bobbin 22 AV4 0.06 Bobbin 22 AV3
-0.09 Bobbin 22 AV3 0.12 Bobbin 22 AV2 0.03 Bobbin 23 AV3 0.00 Bobbin 23 AV3 0.00 Bobbin 23 AV2 0.36 Bobbin 23 AV2 0.17 Bobbin 23 AV2
-0.09 Bobbin 23 AV3 0.32 Bobbin 23 AV4 0.00 Bobbin 23 AVl 0.03 Bobbin 24 AV3
-0.31 Bobbin 24 AV3
-0.11 Bobbin 24 AV2
-0.03 Bobbin 24 AV4
-0.03 Bobbin 24 AV3 0.12 Bobbin 25 AV3 0.00 Bobbin 25 AV2 0.36 Bobbin 25 AV2
-0.25 Bobbin 25 AV2 0.33 Bobbin 25 AV3
-0.03 Bobbin 25 AV2
-0.33 Bobbin 25 AV2
-0.06 Bobbin
Attachment to TXX-22041 Page 7 of 18 SG Row Col 1
39 91 1
34 102 1
30 12 1
37 16 1
40 20 1
40 30 1
40 43 1
45 84 1
38 99 1
35 101 1
43 81 1
43 87 1
46 89 1
43 81 1
45 87 1
46 31 1
45 79 1
34 102 1
39 17 1
39 20 1
46 83 1
34 13 1
46 31 1
45 84 1
38 89 1
41 94 Volts Ind 1.46 WEAR 1.44 WEAR 1.62 WEAR 1.96 WEAR 1.74 WEAR 1.59 WEAR 1.69 WEAR 1.72 WEAR 1.77 WEAR 1.75 WEAR 1.86 WEAR 1.9 WEAR 1.99 WEAR 2.11 WEAR 1.97 WEAR 2.24 WEAR 2.25 WEAR 2.14 WEAR 2.26 WEAR 2.4 WEAR 2.37 WEAR 2.77 WEAR 2.58 WEAR 2.76 WEAR 2.73 WEAR 2.6 WEAR
%TW Axial Cir.
Cir.
Location Inch Probe Length Width Degrees 25 AV4 0.00 Bobbin 25 AV2 0.03 Bobbin 26 AV2 0.00 Bobbin 26 AV2
-0.32 Bobbin 26 AV3 0.00 Bobbin 26 AV2 0.00 Bobbin 26 AV4 0.15 Bobbin 26 AV2 0.06 Bobbin 26 AV3 0.03 Bobbin 26 AV2 0.15 Bobbin 27 AV2
-0.06 Bobbin 27 AV2
-0.06 Bobbin 27 AV4
-0.09 Bobbin 28 AV3
-0.38 Bobbin 28 AV3
-0.09 Bobbin 29 AV4 0.19 Bobbin 29 AV4
-0.09 Bobbin 29 AV4 0.03 Bobbin 30 AV2
-0.12 Bobbin 30 AV2 0.00 Bobbin 30 AV2 0.09 Bobbin 31 AV2 0.00 Bobbin 31 AV2 0.08 Bobbin 31 AV4 0.15 Bobbin 31 AV2
-0.42 Bobbin 31 AV2
-0.03 Bobbin
Attachment to TXX-22041 Page 8 of 18 SG Row Col 1
33 102 1
44 25 1
45 26 1
45 83 1
38 16 1
37 17 1
41 90 1
42 94 1
36 99 1
40 43 1
40 20 1
40 43 1
1 69 2
30 11 2
40 86 2
34 13 2
35 97 2
40 29 2
44 89 2
48 69 2
34 13 2
44 89 2
36 99 2
6 1
2 6
2 2
4 114 Volts Ind 2.68 WEAR 2.83 WEAR 2.9 WEAR 2.98 WEAR 3.34 WEAR 3.4 WEAR 3.25 WEAR 3.08 WEAR 3.16 WEAR 4.21 WEAR 4.85 WEAR 5.44 WEAR 0.88 SAi 0.93 WEAR 1.2 WEAR 1.13 WEAR 1.18 WEAR 1.62 WEAR 1.38 WEAR 1.53 WEAR 2.07 WEAR 2.44 WEAR 2.8 WEAR 0.15 VOL 0.14 VOL 0.21 VOL
%TW Axial Cir.
Cir.
Location Inch Probe Length Width Degrees 31 AV2 0.03 Bobbin 32 AV2 0.00 Bobbin 32 AV2 0.00 Bobbin 32 AV2 0.09 Bobbin 33 AV2 0.00 Bobbin 33 AV2 0.03 Bobbin 33 AV2 0.03 Bobbin 33 AV2
-0.12 Bobbin 33 AV3 0.18 Bobbin 36 AV2
-0.15 Bobbin 38 AV2
-0.08 Bobbin 39 AV3
-0.38 Bobbin 62 0.19 50.8 H3 17.50
+Point 20 AV3 0.23 Bobbin 20 AV2 0.00 Bobbin 22 AV3
-0.03 Bobbin 22 AV2 0.00 Bobbin 23 AV3 0.00 Bobbin 23 AV3
-0.03 Bobbin 24 AV4 0.13 Bobbin 29 AV2
-0.03 Bobbin 30 AV2
-0.03 Bobbin 33 AV2 0.00 Bobbin 16 0.21 0.41 63 Cl 0.56
+Point 16 0.21 0.39 60 Cl 0.85
+Point 21 0.18 0.39 60 C4 0.44
+Point
Attachment to TXX-22041 Page 9 of 18 SG Row Col 2
3 114 2
6 2
3 41 85 3
49 42 3
24 107 3
33 103 3
33 87 3
41 87 3
30 105 3
41 87 3
32 12 3
38 98 3
43 82 3
34 101 3
33 103 3
43 82 3
43 82 3
6 79 3
40 48 3
40 49 3
21 so 4
34 97 4
35 14 4
27 so 4
38 71 4
35 82 Volts Ind 0.32 VOL 0.37 VOL 0.87 WEAR 0.89 WEAR 1.14 WEAR 1.2 WEAR 1.14 WEAR 1.16 WEAR 1.48 WEAR 1.55 WEAR 1.95 WEAR 2.31 WEAR 1.99 WEAR 2.96 WEAR 3.27 WEAR 2.91 WEAR 3.13 WEAR 2.78 SVI 0.34 SVI 0.14 SVI 0.84 VOL 0.97 WEAR 0.92 WEAR 1.19 WEAR 1.29 WEAR 1.37 WEAR
%TW Axial Cir.
Cir.
Location Inch Probe Length Width Degrees 28 0.24 0.46 71 C4 0.33
+Point 31 0.34 0.44 68 Cl 0.42
+Point 20 AV3
-0.06 Bobbin 20 AV4 0.00 Bobbin 21 AV2
-0.46 Bobbin 21 AVl 0.03 Bobbin 22 AV4
-0.12 Bobbin 22 AV2
-0.36 Bobbin 23 AV2
-0.36 Bobbin 25 AV3
-0.32 Bobbin 27 AV2 0.00 Bobbin 28 AV2
-0.45 Bobbin 28 AV4 0.00 Bobbin 31 AV2
-0.48 Bobbin 33 AV3 0.00 Bobbin 33 AV2
-0.39 Bobbin 34 AV3
-0.38 Bobbin 43 0.42 0.28 43 Cll 13.55
+Point 33 0.18 0.35 54 C2 5.66
+Point 18 0.35 0.49 75 C2 5.59
+Point 12 0.12 0.21 32 C2 0.65
+Point 20 AV2 0.00 Bobbin 21 AVl 0.06 Bobbin 21 AV4 0.37 Bobbin 21 AV2
-0.05 Bobbin 22 AV2
-0.03 Bobbin
Attachment to TXX-22041 Page 10 of 18 SG Row Col 4
37 84 4
37 84 4
44 43 4
44 43 4
34 77 4
26 69 4
32 71 4
44 44 4
44 44 4
44 44 4
44 44 Volts Ind
%TW 1.45 WEAR 23 1.66 WEAR 25 0.54 VOL 14 0.64 VOL 15 0.81 VOL 15 1.12 VOL 21 1.62 VOL 26 1.47 VOL 27 1.66 VOL 30 1.98 VOL 33 2.1 VOL 34 Axial Cir.
Cir.
Location Inch Probe Length Width Degrees AV2 0.03 Bobbin AV3 0.00 Bobbin 0.14 0.29 45 C2 2.27
+Point 0.13 0.23 35 C2 2.28
+Point 0.11 0.34 52 C2 0.50
+Point 0.19 0.40 62 C2 1.29
+Point 0.17 0.36 55 C2 0.53
+Point 0.22 0.32 49 C2 2.11
+Point 0.21 0.39 60 C2 2.03
+Point 0.16 0.40 62 C2 2.29
+Point 0.22 0.36 55 C2 2.29
+Point
Attachment to TXX-22041 Page 11 of 18 c.3 CONDITION MONITORING ASSESSMENT AND RESULTS, 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 The condition monitoring results for 2RF19 are presented in the table below for all detected degradation mechanisms. Any existing degradation mechanisms not found in the table below were not detected at 2RF19 and meet condition monitoring for structural and leakage integrity. Wear at drilled holes in the PBP and FOB were sized with the Pancake coil (ETSS 96911.1). Wear at broached holes in the TSPs were sized with the +POINT coil (ETSS 96910.1).
CPNPP 2RF19 Condition Monitoring Summary for Limiting Flaw Mechanism SG Row Col IND Loe 2RF19 CM Limiting Flaw Limit AVB Wear 1
40 43 PCT AV3 39%TW 66.8% TW, 0.5-inch flaw 96004.3 PBP Wear 1
49 56 WAR cs 17%TW 46.4% TW, 0.75-inch flaw 96911.1 TSP Wear 1
47 46 WAR C7 14%TW 54.3% TW, 1.125-inch flaw 96910.1 3
6 79 SVI Cll 43%TW 70.8% TW, 0.45-inch Foreign flaw 10908.5 Object Wear 66.2% TW for 0.25-inch 3
40 48 SVI C2 34%TW flaw 21998.1 Axial ODSCC at 1
1 69 SAi H3+17.5 62%TW 67.8% TW for 0.25-inch Freespan Dings flaw 128432 For volumetric wear flaws with pressure-only loading condition, tu be burst and ligament tearing (i.e., pop-through) are coincident, therefore, satisfaction of the tube burst criteria at 3~PNo also satisfies the accident induced leakage performance criteria (AILPC} at steam line break differential pressure.
Therefore, for AVB, PBP, TSP and Foreign Object wear, the SG structural and leakage performance criteria are satisfied for condition monitoring.
For the limiting sec flaws, the burst and ligament tearing are greater than the minimum burst and leakage integrity limits of 3909 psi and 2560 psi, respectively. This includes material property, burst relation, and NDE uncertainties at 0.95 probability and 50% confidence (95/50). Therefore, condition monitoring for sec mechanisms has been demonstrated.
SG Integrity Assessment Guidelines require condition monitoring results from the current inspection be compared to the OA from the previous inspection. This comparison identifies whether the underlying assumptions, input parameters, or methodology for performing OAs are conservative or require alteration prior to performing the next OA. Failure to meet CM requirements means that the projections of the prior OA were not conservative and that necessary corrective actions are to be identified. Even when CM requirements are met, this comparative review may identify adjustments to the OA inputs or assumptions.
Attachment to TXX-22041 Page 12 of 18 For wear mechanisms, a comparison of the previous OA to the 2RF19 inspection results is presented in the below table. Note for FOW, no foreign objects remain within the vicinity of the affected tubes, so no OA projection is provided.
For sec mechanisms, the previous OA evaluated the mechanisms below and demonstrated structural and leakage integrity to 2RF19. Existing and potential mechanisms were considered, with the potential mechanisms being selected based on the frequency of their historical occurrence in the Alloy 600TT fleet:
Existing Degradation Mechanisms (Prior to 2RF19)
- Circumferential PWSCC at BLG/OXP locations within the HL tubesheet
- Circumferential PWSCC at HL Tubesheet Expansion Transitions Previously Considered Potential Degradation Mechanisms
- Axial ODSCC at tube support plates for high stress tubes
- Circumferential ODSCC at top of tubesheet expansion transitions
- Axial PWSCC at top of tubesheet expansion transitions
- Axial ODSCC at the top of tubesheet expansion transitions and sludge pile None of these mechanisms were detected at 2RF19. For the detected sec mechanism (Axial ODSCC at Frees pan Dings), only two tubes had previously been affected by this mechanism in the A600TT industry.
An OA for axial ODSCC at freespan dings will now be included as an existing degradation mechanism. As part of the benchmarking efforts for this mechanism, a simulation was performed for the previous inspection period, 2RF16-2RF19, and it has been determined that structural and leakage integrity were predicted to be demonstrated throughout the 3-cycles.
Attachment to TXX-22041 Page 13 of 18 Comparison of Previous Wear OA Projections to 2RF19 Results Mechanism 2RF18 Projection {% TW) 2RF19 Limiting Flaw {% TW)
AVB Wear-Existing 55.3 39 AVB Wear-New 38.4 25 PBP Wear - Existing 42.6 17 PBP Wear - New 53.6 16 TSP Wear - Existing 51.1 14 TSP Wear - New 57.6 14 Based on the inspection data and the condition monitoring assessment, no tubes exhibited degradation exceeding the condition monitoring limits set forth in the 2RF19 DA. No tubes required in situ pressure or leak testing to demonstrate structural and leakage integrity. Therefore, the SG performance criteria for structural and leakage integrity were satisfied for all degradation mechanisms for the preceding CPNPP Unit 2 SG operating interval.
c.4 TUBES PLUGGED OR REPAIRED DURING THE INSPECTION OUTAGE.
- 2RF19 Plugging and Stabilization List SG Row Col Ind Location Plugging Basis Stabilizer?
1 1
69 SAi H3 Axial ODSCC No 2
1 95 High Stress Tube No 2
1 55 High Stress Tube No 3
6 79 SVI C11 Preventative No 3
40 48 SVI C2 Preventative Yes 3
40 49 SVI C2 Preventative Yes
Attachment to TXX-22041 Page 14 of 18
- d. ANALYSIS
SUMMARY
OF THE TUBE INTEGRITY CONDITIONS PREDICTED TO EXIST AT THE NEXT SCHEDULED INSPECTION The Operational Assessment for tube wear mechanisms was performed using conservative methods to project EOC flaw depths for each active mechanism. For detected wear, this includes burst relation, material property and NDE measurement uncertainties. For undetected wear, this includes burst relation and material property uncertainties. It was concluded that the projected EOC depth of the largest detected and assumed undetected flaw will remain below the calculated structural limits with sufficient margin at 2RF22. The limiting wear degradation mechanism is AVB wear, and it is predicted that the worst-case flaw would be no greater than SS.4%TW at the next planned inspection at 2RF22 (4.35 EFPY). This projection is less than the end of cycle structural limit of 69.4% TW. For volumetric flaws ligament tearing is coincident to burst. Therefore, since structural integrity against tube burst at 3*~PN0 was demonstrated, leakage integrity is expected to be maintained to at least 2RF22 as well.
The Operational Assessment for sec mechanisms was performed with assumed undetected flaws for each existing degradation mechanism. Based on the detection the results of the 2RF19 inspection, axial ODSCC at dents/dings is now an existing degradation mechanism.
The remaining existing degradation mechanisms are circumferential PWSCC at bulge/over-expansions and at the hot leg expansion/transition.
Fully probabilistic methods were used for the OA calculations with an acceptance criterion of 5.0% for POB, POL, minimum burst pressure requirement and the plant's accident induced leak rate limit. The evaluations include uncertainties associated with burst relation and tube material properties. Each
- evaluation assumed undetected flaws at 2RF19, and the operating interval until the next planned inspection. Accepted industry methods were used to develop the POD functions, undetected flaw populations, and growth rates for each SCC mechanism evaluated (typical default growth rates used).
Benchmarking ofthe fully probabilistic OA methods for existing degradation mechanisms was completed by comparing OA simulation results for prior outages with actual detection results. The predicted detection depths and quantities were compared to actual CPNPP Unit 2 inspection results. It was found that the number of detected indications is well characterized by the model results. Additionally, the measured flaw depths and lengths are reasonably represented by the predicted distributions (including the peak flaw versus the worst-case prediction distribution). Tnis benchmarking developed confidence that the simulation process will accurately and conservatively predict future SG conditions. For each SCC mechanism, the POB and POL were calculated to be below the 5.0% criterion which demonstrates structural and leakage integrity until the next planned inspections (2RF20 for axial ODSCC at dents/dings and 2RF22 for circumferential PWSCC at HL tubesheet). OA calculations were performed for axial ODSCC at dents/dings and circumferential PWSCC at HL tubesheet for 2.9 EFPY and 4.35 EFPY, respectively.
When combining predicted leakages from the OA calculations, and in considering CPNPP Unit 2 requirements associated with the H* alternate repair criteria, it was determined that an administrative leakage limit would not be needed for Cycle 20. This should be re-evaluated after the inspection at 2RF20.
Two SG channel head cladding anomalies are being tracked at CPNPP Unit 2 and were visually observed during 2RF19. The anomalies did not appear to change from the prior inspection. A corrosion rate evaluation has been performed for the larger of the two flaws. There is significant margin between the estimated flaw depth and the ASME Code allowable and no repairs are required.
Attachment to TXX-22041 Page 15 of 18 A total of 16 foreign objects remained in secondary side of the SGs following 2RF19. All of these objects were small parts and demonstrated by bounding calculations through tube wear projections to not adversely affect tube integrity until at least 2RF22.
The CM and OA for the CPNPP Unit 2 SGs at the 2RF19 outage follows the requirements of the SG Integrity Assessment Guidelines} and complies with requirements of NEl-97-06. It has been shown that all existing degradation mechanisms will maintain structural and leakage integrity until the next planned inspection, for each existing degradation mechanism. Potential mechanisms were also considered and are not expected to challenge the structural or leakage integrity performance criteria during the next operating interval, 2RF19-2RF22.
The forward-looking assessments demonstrate structural and leakage integrity until the next planned inspections (2RF20 for axial ODSCC at dents/dings and 2RF22 for the remaining degradation mechanisms}.
- e. NUMBER AND PERCENTAGE OF TUBES PLUGGED OR REPAIRED TO DATE, AND THE EFFECTIVE PLUGGING PERCENTAGE IN EACH SG The total number of plugged tubes in each SG is summarized in the table below.
- Tubes 2RF19 # Piugged Total # Plugged
% Plugging 1
4,570 1
24 0.53 2
4,570 2
35 0.77 3
4,570 3
24 0.53 4
4,570 0
19 0.42 Total 18,280 6
102 0.56
- f. SG SECONDARY-SIDE INSPECTION RESULTS Top of tubesheet sludge lancing with post-cleanliness inspection was performed in all SGs. The deposit removal amounts were 4.0 lbs, 4.5 lbs, 5.5 lbs, and 7.0 lbs in SGs 1, 2, 3, and 4, respectively.
Foreign object search and retrieval (FOSAR} inspections were performed at 2RF19. FOSAR and deposit inspections of the annulus/peripheral bundle, tubelane, and pre-defined in-bundle columns in all SGs was performed. Upper tube bundle visual inspection (TSP P} was performed in SG3 in pre-defined columns. TSP P was found to be in acceptable condition, with the support plate and quatrefoils free of deposit. Limited tube scale was observed at TSP P.
Attachment to TXX-22041 Page 16 of18 A total of 32 objects were found during FOSAR and 16 were retrieved. A summary of the FOSAR and sludge lancing is provided int. All remaining foreign objects were Priority 3 items.
CPNPP 2RF19 Foreign Object Summary No.
Description Row Col Metallic?
Retrieved?
L (In.) W (In.)
H (In.)
D (In.)
1001 Wire Bristle 49 79 y
y 0.38 0.1 0.05 0.05 1002 Wire Bristle 24 9-10 y
y 0.75 0.5 0.6 0.3 1003 Wire Bristle 6
1 y
y 0.38 0.1 0.05 0.05 1004 Other - Wire Mesh 27-28 46-47 y
y 0.2 0.2 0.1 1005 Other-Shim 28 46-47 y
y 0.3125 0.3125 0.4 Material 1006 Sludge Rock 9
47-48 N
N 0.3125 0.3125 0.4 1007 Scale 40-41 55-56 N
N 0.3125 0.1 0.1 1008 Sludge Rock 22-23 55-56 N
N 0.3125 0.2 0.2 1009 Sludge Rock 43 50-51 N
N 0.32 0.32 0.2 2001 Gasket Material 21 5-6 y
y 0.625 0.25 0.125 2002 Wire Bristle 13-14 3-4 y
y 0.75 0.02 3001 Other - Gasket 25-26 7-8 y
N 0.075 0.02 Thread 3002 Other-Shim 21 64 y
y 0.3 0.02 0.5 Material 3003 Other-Slag 41 20 y
y 0.25 0.06 0.3 3004 Scale 20 12 N
N 0.625 0.06 0.325 3005 Scale 47 32 y
y 0.125 0.05 0.125 3006 Sludge Rock 31 82-83 N
y 0.32 0.25 0.25 3007 Other-Shim 40 48-49 y
N 0.4 0.2 0.4 Material 4001 Sludge Rock 30-31 10-11 N
N 0.2 0.2 0.1 0.2 4002 Sludge Rock 42-43 63-64 N
N 0.75 0.1 0.2 0.2 4003 Wire Bristle 8-9 80-81 y
N 0.5 0.01
Attachment to TXX-22041 Page 17 of 18 No.
Description 4004 Sludge Rock 4005 Sludge Rock 4006 Other-mesh 4007 Wire Bristle 4008 Scale 4009 Scale 4010 Other-Shim Material 4011 Sludge Rock 4012 Wire Bristle 4013 Sludge Rock 4014 Other-Mesh Row Col Metallic?
44 23 N
17-18 6-7 N
49-50 37 y
49-50 47 y
48-49 52 y
44 43-45 y
25-26 45-46 y
27-28 44-45 N
18 111-y 112 9
19-20 N
44 43-44 y
Retrieved?
L (In.) W (In.)
H (In.)
D (In.)
N 0.3 0.2 0.25 N
0.25 0.2 0.25 y
0.625 0.625 0.2 y
0.5 0.03 N
0.5 0.1 N
2 0.0625 0.0625 y
0.75 0.125 0.5 N
0.4 0.15 0.2 y
0.75 0.06 N
0.312 0.312 0.25 y
1 0.35 0.0625 Preheater and Waterbox inspections were performed in all SGs. The SG Waterbox was found to be in good condition with no relevant degradation identified. The condition of the preheater/feedwater inlet Waterbox components were found in good condition with no anomalous or degraded conditions reported in any of the SGs. As a result of the inspection findings, there were no immediate recommendations made regarding any actions that should be taken prior to restart of Comanche Peak Unit 2. There are no changes or planned changes to plant operations or chemistry programs that would affect the integrity of the Waterbox components until the next planned inspection.
- g. FOR UNIT 2, THE PRIMARY TO SECONDARY LEAKAGE RATE OBSERVED IN EACH SG (IF IT IS NOT PRACTICAL TO ASSIGN THE LEAKAGE TO AN INDIVIDUAL SG, THE ENTIRE PRIMARY TO SECONDARY LEAKAGE SHOULD BE CONSERVATIVELY ASSUMED TO BE FROM ONE SG}
DURING THE CYCLE PRECEDING THE INSPECTION WHICH IS THE SUBJECT OF THE REPORT There was no SG primary-to-secondary side leakage present during Cycle 19.
Channel head cladding anomalies have been reported within SGl-CL and SG2-HL.
The cladding anomaly contained in SGl-CL is in the vicinity of the joint between the channel head shell and the tubesheet near the peripheral tube in Row 36 Column 100 on the cold leg side. The reported flaw is estimated to be approximately 5/8-inch long and approximately half as wide. Evidence of this cladding anomaly has been present as early as 2003.
Attachment to TXX-22041 Page 18 of 18 The cladding anomaly contained in SG2-HL is in the vicinity of the tube-to-tubesheet weld of Row 1 Column 109. The reported flaw is a small "pit-like" anomaly that is approximately 1/16-inch in diameter.
The discoloration is apparently caused by a small breech in the tubesheet cladding causing oxidation of the carbon steel base metal. This anomaly was first detected at 2RF16 and was not visible upon review of previous primary channel head visual inspections.
A re-inspection of these anomalies was performed during 2RF19 and showed no apparent change in size or character.
A 100% visual inspection oftube plugs in all four SGs has been performed from the primary side during CPNPP 2RF19. No anomalous conditions, such as a degraded tube plug or surrounding boron deposits, have been reported during performance of these visual inspections.
H. FOR UNIT 2, THE CALCULATED ACCIDENT INDUCED 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 INDUCED LEAKAGE RATE FROM THE MOST LIMITING ACCIDENT IS LESS THAN 3.16 TIMES THE MAXIMUM OPERATIONAL PRIMARY TO SECONDARY LEAKAGE RATE, THE REPORT SHOULD DESCRIBE HOW IT WAS DETERMINED; For condition monitoring, primary-to-secondary side leakage attributable to the portion of tubing below the alternate repair criteria depth must be multiplied by a factor of 3.16 and added to the total leakage from any other source. This sum is then to be compared to the allowable accident induced leakage. There was no SG primary-to-secondary side leakage present during Cycle 19 on which to apply the H* leakage factor. Therefore, the regulatory requirements relative to the alternate repair criteria have been satisfied.
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.
The tube slippage monitoring was conducted as part of the SG tube inspection program. Tube slippage is detected through bobbin coil examination. During 2RF19, as part of the tube inspection program, 100%
of the tubes were tested with the bobbin probe. No slippage was detected in any of the tubes inspected.