NRC 2013-0067, Spring 2013 Unit 1(U1R34) Steam Generator Tube Inspection Report
| ML13268A108 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 09/24/2013 |
| From: | Millen M Point Beach |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC 2013-0067, TS 5.6.8 | |
| Download: ML13268A108 (15) | |
Text
NEXT era**
ENERGY~
~
September 24, 2013 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Point Beach Nuclear Plant, Unit 1 Docket 50-266 Renewed License No. DPR-24 Spring 2013 Unit 1 (U1R34)
Steam Generator Tube Inspection Report Pursuant to the requirements of Point Beach Nuclear Plant (PBNP) Technical NRC 2013-0067 TS 5.6.8 Specification (TS) 5.6.8, "Steam Generator Tube Inspection Report," NextEra Energy Point Beach, LLC, is submitting the 180-day Steam Generator Tube Inspection Report. The enclosure to this letter provides the results of the spring 2013, Unit 1 (U1 R34) steam generator tube in-service inspections.
If you have any questions please contact Mr. Michael Millen, Licensing Manager, at 920/755-7845.
Very truly yours, NextEra Energy Point Beach, LLC Mike Millen Licensing Manager Enclosure cc:
Administrator, Region Ill, USNRC Project Manager, Point Beach Nuclear Plant, USNRC Resident Inspector, Point Beach Nuclear Plant, USNRC PSCW NextEra Energy Point Beach, LLC, 6610 Nuclear Road, Two Rivers, WI 54241
1.0 Introduction ENCLOSURE NEXTERA ENERGY POINT BEACH, LLC POINT BEACH NUCLEAR PLANT UNIT 1 STEAM GENERATOR TUBE INSPECTION REPORT U1R34 Point Beach Nuclear Plant (PBNP) Unit 1 has two Westinghouse Modei44F replacement steam generators (SG) with thermally treated Alloy 600 tubing. The inspection at U1 R34 was the first inspection in the 60 effective full power months (EFPM) interval.
The U1 R34 inspection scope and plan were based on the degradation assessment that was prepared prior to the refueling outage. Anti-Vibration bar (AVB) wear, tube support plate wear, mechanical wear due to maintenance activities, and primary water stress corrosion cracking (PWSCC) near the tube ends in the hot leg were the* only existing degradation modes in the SGs.
2.0 Scope of Inspections Performed 2.1 The inspection program for SG A consisted of:
- a. Bobbin Inspection-All Accessible Tubes (3209 tubes):
Rows 1 and 2-straight length inspection only (183 tubes)
Straight sections from the hot leg (183 tubes)
Straight sections from the cold leg (183 tubes)
Rows 3 and above - full length inspection (3026 tubes)
Rows 3 and 4 - straight sections plus U-bend from the hot leg ( 183 tubes)
Rows 3 and 4-straight sections from the cold leg (183 tubes)
Rows 5 and above - full length from the hot leg (2843 tubes)
- b. Motorized Rotating Pancake Coil (MRPC) Inspection(+ Point):
Hot Leg Top of Tubesheet +/- 3"- 100% of peripheral tubes (529 tubes)
Hot Leg Tubesheet Full Depth {TEH-TSH +3")- 50% of tubes (1605 tubes)
Cold Leg Top of Tubesheet +/- 3" -100% of peripheral tubes (529 tubes) 50% Tight Radius U-bends in Rows 1 and 2 (91 tubes) 50% of ding/dent indications >5V
- c. Upon completion of the initial inspection program, diagnostic and special interest (SI) inspections based on historical data and the results of the initial bobbin and rotating probe (+Point probe and pancake coil) inspections were performed to characterize and/or size any identified indications.
- d. Installed tube plugs were visually inspected and all plugs were dry.
Page 1 of 14
- e. NSAL 12-1 inspection of lower portion of the hot and cold leg channel heads were completed with no anomalies identified.
2.2 The inspection program for SG B consisted of:
- a. Bobbin Inspection -All Accessible Tubes (3206):
Rows 1 and 2-straight length inspection only (181 tubes)
Straight sections from the hot leg (181 tubes)
Straight sections from the cold leg (181 tubes)
Rows 3 and above-full length inspection (3025 tubes)
Rows 3 and 4-straight sections plus U-bend from the hot leg (183 tubes)
Rows 3 and 4-straight sections from the cold leg (183 tubes)
Rows 5 and above - full length from the cold leg (2842 tubes)
- b. MRPC Inspection(+ Point):
Hot Leg Top of Tubesheet +/- 3"- 100% of peripheral tubes (528 tubes)
Hot Leg Tubesheet Full Depth (TEH - TSH +3") - 100% of all tubes (3206 tubes)
Cold Leg Top of Tubesheet +/- 3"- 100% of peripheral tubes (528 tubes) 50% Tight Radius U-bends in Rows 1 and 2 (91 tubes) 50% of ding/dent indications >5V
- c. Diagnostic and special interest (SI) inspections based on historical data and the results of the initial bobbin and rotating probe (+Point probe and pancake coil) inspections were also conducted upon completion of the initial inspection program. No expansion beyond the planned inspection scope was required.
- d. Installed tube plugs were visually inspected and all plugs were dry.
- e. NSAL 12-1 inspection of lower portion of the hot and cold leg channel heads were completed with no anomalies identified in the lower channel head drain area. An instance of missing cladding in SG B has been previously reported.
2.3 Secondary Side The following secondary side work was performed in both SGs:
Sludge Lancing, FOSAR of hot and cold leg annulus, tube lane, and possible loose parts (PLP) verification, Following extended power uprate modifications, the listed components were visually inspected; internal feedring, j-nozzles, thermal sleeve, primary moisture separator, mid-deck extension, hatch, hinges, riser barrel, top hats, and externals of the feedring and J-nozzles. Ultrasonic testing (UT) measurements were performed on the feed ring and primary moisture separators, and swirl vanes for baseline information.
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3.0 Degradation Mechanisms Found The following degradation mechanisms were observed in the Point Beach Unit 1 SGs during U1 R34:
AVB wear continues to be an existing degradation mechanism in both SG, Wear at Tube Support Plates (TSP),
Mechanical wear above top of tubesheet due to insertion/removal of sludge lancing equipment.
4.0 NDE Techniques for Damage Mechanisms The following is the list of EPRI technique sheets used for detection for the degradation modes that may be present during the steam generator inspection in U1 R34.
AVB Wear 96004.1 TSP/FDB Wear 96004.1; 96910.1 Mechanical Wear 27091.2; 21998.1 PWSCC in Tubesheet and Tube Ends 20511.1A, 20510.1 c Loose Part Wear 27901.3-27907.3, 21998.1 Transition Zone ODSCC and sludge pile 128424A; 128431A; 21410.1C Axial ODSCC at Flow Baffle 128411, 128424, and 128431 Axial ODSCC at TSP and free span 128413, 128425, and 128432 Low Row U-bend ODSCC 10411.1A; 21410.1 C Ding/Dent ODSCC 24013.1A; 22841.3A; 22842.3C Low Row U-bend Axial PWSCC 96511.2;*99997.1 Transition Zone PWSCC 20511.1A; 20510.1 C, 20507.1 C, 20508.1A, Pitting in Sludge Pile 96005.2,21998.1 5.0 Service Induced Flaws 5.1 PWSCC A 50% sample of tubes in SG A, and 100% of the tubes in SG B, was +Point RPC probe tested for hot leg tube end cracking and any other anomalies that might be present inside the hot leg tubesheet area. The results showed no tubes had any reportable crack-like indications.
5.2 Mechanical Wear Indications at Anti-vibration Bar (AVB)
- a. Table 5-1 lists indications identified in U1 R34 and historical indications for a total of 104 indications in 58 tubes. U1R34 identified one hundred-two (102) indications in Page 3 of 14
fifty-seven (57) tubes in SG A with indications of wear at the AVBs. All one hundred two (102) AVB wear indications were sized with the bobbin coil. The remaining two (2) indications in one (1) are listed on table 5-1 for historical tracking purposes and were recorded as indications not recordable (INR) during U1 R34. None of these indications were determined to be repairable per engineering disposition and all remained in service.
Tables 5-1 and 5-2 show all AVB wear indications along with historical comparisons.
Table 5-1 AVB Wear History-SG A 2013 2011 2008 2007 2004 2001 1998 1995 Row Col Loc TW TW TW TW TW TW TW TW 22 8
AV3 5
4 3
3 AV4 4
5 3
32 14 AV2 6
6 4
AV3 9
8 7
7 5
3 14 11 AV4 8
9 5
7 33 18 AV3*
24 21 19 18 25 21 AV4 15 15 10 11 16 13 35 18 AV2 10 10 9
11 10 6
INR 9
37 20 AV4 8
38 22 AV2 9
8 7
7 AV3 10 11 9
10 12 6
10 8
AV4 8
8 6
6 40 25 AV1 7
6 6
AV2 9
8 7
9 6
5 9
6 AV3 9
9 7
40 27 AV3 8
8 6
8 5
4 6
5 34 33 AV1 13 13 8
14 10 10 5
11 AV2 17 11 6
11 7
7 7
10 31 35 AV4 9
33 36 AV4 12 33 37 AV3 7
7 5
AV4 13 12 10 14 9
13 7
8 29 41 AV2 10 45 41 AV1 9
9 7
10 6
6 7
6 AV4 11 10 8
8 7
6 7
6 40 42 AV1 11 10 7
14 12 13 23 45 42 AV1 10 10 10 14 35 43 AV3 10 10 9
8 AV4 13 13 11 9
38 43 AV1 28 27 27 24 23 19 12 11 AV2-26 22 19 17 16 AV2+
23 25 24 22 23 19 12 8
45 43 AV1 8
8 7
18 13 12 15 11 AV4 11 11 9
9 8
8 40 44 AV3 14 12 9
11 13 10 7
5 11 45 AV1 10 Page 4 of 14
Table 5-1 AVB Wear History-SG A 2013 2011 2008 2007 2004 2001 1998 1995 Row Col Loc TW TW TW TW TW TW TW TW 45 45 AV4 8
40 47 AV3 14 14 10 15 10 13 10 12 33 48 AV3 11 9
8 9
13 9
AV4 7
7 4
45 49 AV1 6
4 4
15 19 14 13 18 AV2 6
5 4
AV4 10 9
7 45 50 AV4 10 9
6 4
45 51 AV4 7
6 6
43 52 AV4 9
9 45 52 AV2 10 9
7 AV3 7
6 6
AV4 5
8 5
5 11 53 AV4 9
9 7
4 19 54 AV1 10 10 7
8 AV2 18 17 12 17 12 14 13 7
AV3 10 11 8
10 AV4 17 17 13 17 12 16 12 13 38 54 AV3 22 24 20 26 25 18 14 15 AV4 11 11 8
9 44 54 AV1 7
AV4 7
35 56 AV1 23 26 21 18 14 15 5
6 AV2 34 37 33 27 27 27 9
13 43 56 AV4 7
7 33 57 AV1 12 10 4
5 AV2 12 19 61 AV1 16 17 12 13 12 18 10 12 AV2 18 19 14 16 15 23 13 14 AV4 9
9 6
5 6
8 42 61 AV4 8
9 6
5 24 63 AV1 14 12 8
14 INR 9
AV2 18 12 AV3 20 16 AV4 9
31 63 AV2 17 16 13 18 20 14 9
12 AV3 11 10 7
11 10 5
5 2
34 65 AV3 12 13 9
5 9
6 1
AV4 20 17 14 11 15 12 6
7 33 66 AV1 19 18 16 14 20 14 9
8 AV2 15 15 13 10 13 11 9
4 AV3 6
5 5
4 5
5 4
4 40 66 AV1 9
9 32 68 AV1 7
12 10 9
AV2 10 10 8
9 Page 5 of 14
Row 39 34 39 27 32 33 32 31 32 29 26 26 24 15 Table 5-1 AVB Wear History-SG A 2013 2011 2008 2007 2004 2001 1998 1995 Col Loc TW TW TW TW TW TW TW TW 68 AV2 8
7 5
AV3 7
6 5
AV4 5
5 5
9 9
8 9
6 69 AV1 9
11 6
8 3
7 1
0 AV2 14 16 11 16 11 14 6
9 69 AV3 11 11 7
71 AV2 11 12 8
10 6
11 5
4 AV3 17 18 14 15 10 12 3
2 AV4 9
11 8
7 5
6 0
0 71 AV2 18 18 14 15 11 9
10 6
AV3 12 12 8
11 71 AV2 20 20 16 16 13 17 5
6 AV3 14 15 10 14 6
10 0
0 78 AV3 5
6 2
79 AV3 5
7 5
6 79 AV1 6
6 4
9 81 AV2 6
6 4
7 83 AV3 8
8 6
84 AV1 5
6 4
AV2 6
5 3
85 AV2 8
7 5
5 87 AV2 INR INR 5
AV3 INR INR 5
INR = indication not recordable
- b. Table 5-2 lists indications identified in U1 R34 and historical indications for a total of seventy eight indications (78) in fifty five tubes (55). U1 R34 identified seventy-four (74) indications in fifty-one (51) tubes in SG B with indications of wear at the anti-vibration bars. All AVB wear indications were sized with the bobbin coil. The remaining four (4) indications on four (4) tubes are listed on table 5-2 for historical tracking purposes and were recorded as INR during U1 R34. None of these indications were determined to require repair per engineering disposition and all remained in service.
The following table (Table 5-2) shows all AVB wear indications for SG B along with historical comparisons.
Table 5-2 AVB Wear History - SG B 2013 2011 2008 2007 2004 2001 1998 1995 Row Col Loc TW TW TW TW TW TW TW TW 24 13 AV2 8
8 7
4 28 13 AV2 7
9 7
29 13 AV2 6
8 32 14 AV2 7
9 7
3 14 15 AV3 7
8 8
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Table 5-2 AVB Wear History-SG B 2013 2011 2008 2007 2004 2001 1998 1995 Row Col Loc TW TW TW TW TW TW TW TW 33 16 AV1 4
6 4
4 33 17 AV2 9
11 8
4 34 17 AV2 9
11 8
5 34 18 AV2 7
8 5
5 35 18 AV2 7
9 6
3 38 22 AV1 9
10 7
6 AV2 10 25 23 AV3 6
8 6
35 24 AV4 10 31 25 AV4 6
9 6
5 26 28 AV2 8
10 41 29 AV1 8
7 5
1 AV4 8
8 6
1 42 31 AV4 10 10 7
6 32 32 AV3 12 14 10 13 13 12 8
7 AV4 8
10 7
7 6
6 42 32 AV1 12 13 11 23 33 AV1 12 9
8 12 11 6
8 8
AV2 18 16 14 16 15 13 16 11 AV3 25 25 24 26 25 17 19 18 AV4 6
5 4
6 42 33 AV1 7
9 7
6 19 36 AV3 8
9 8
8 9
9 6
6 29 40 AV2 8
9 8
28 41 AV4 8
8 7
6 32 44 AV3 6
5 5
9 8
7 5
4 45 44 AV1 7
8 6
16 14 14 12 13 AV2 6
8 5
32 46 AV1 8
8 6
AV2 16 16 14 17 15 11.
11 8
AV3 18 19 18 21 18 15 17 12 AV4 13 14 12 10 45 46 AV1 10 9
7 12 13 19 9
10 16 47 AV2 8
9 8
5 32 49 AV1 18 18 17 20 18 14 13 13 AV2 16 16 13 16 15 11 10 10 44 50 AV3 10 8
9 44 54 AV1 9
9 9
8 8
8 AV3 9
9 6
29 55 AV1 14 13 12 11 AV3 6
5 4
8 22 58 AV1 10 12 9
10 9
8 8
5 AV2 21 21 19 21 21 19 16 16 AV3 18 19 17 19 19 16 13 14 AV4 15 16 13 15 14 12 11 9
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Table 5*2 AVB Wear History
- SG 8 2013 2011 2008 2007 2004 2001 1998 1995 Row Col Loc TW TW TW TW TW TW TW TW 42 58 AV1 11 42 59 AV1 9
10 43 59 AV4 9
11 39 69 AV2 9
9 7
AV3 8
9 6
16 70 AV2 INR 8
17 70 AV3 9
8 32 70 AV1 15 14 12 13 11 14 4
5 AV2 17 20 16 19 17 17 14 12 33 71 AV1 19 19 18 20 19 17 13 10 AV2 11 11 9
10 10 6
AV3 7
8 4
16 73 AV2 INR 9
7 37 73 AV3 11 10 9
8 36 74 AV1 8
8 5
7 6
7 7
6 AV4 8
7 6
34 75 AV2 11 10 9
6 16 77 AV3 INR INR 6
18 77 AV3 INR 7
8 17 79 AV2 10 9
8 9
21 79 AV2 8
9 AV3 7
7 23 79 AV2 7
9 28 79 AV2 9
10 8
6 27 82 AV2 8
8 23 86 AV2 8
7 7
AV3 9
9 10 15 87 AV3 11 INR = ind1cat1on not recordable 5.3 Wear at Support Plates There were ten (1 0) Distorted Support Indications (DSI) codes reported by the bobbin probe and identified as wear at broached supports. There were six (6) tubes with wear at a single contact in SG A and three (3) tubes with wear at a single contact and one (1) tube with wear at double contacts in SG B.
The results of the sizing showed land contact wear at each of the broached support locations with wear depths ranging from 5% to 15% through-wall. Table 5-3 shows all TSP wear indications along with historical comparisons.
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Table 5-3 Wear at Tube Support Plates SG ROW COL 2013 2011 2008 2007 2005 2004 Location
%TW
%TW %TW %TW %TW %TW A
39 24 13 15 13 N/1 11 12 03C A
41 65 15 16 14 N/1 16 18 02C A
39 67 11 12 10 N/1 7
N/R 02C A
37 73 8
N/R N/R N/R N/R N/R 01C A
21 85 15 15 13 N/1 12 10 02C A
18 87 13 13 N/R N/R N/R N/R 02C B
34 18 15 13 12 N/R N/1 N/R 01H B
38 22 10 N/R N/R N/R N/R N/R 04C B
5 45 10 11 N/R N/R N/R N/R 05C B
39 69 5
5 N/R N/R N/R N/R 01C B
39 69 12 13 N/R N/R N/R N/R 01C N/1 = not inspected, N/R = not reported, TW = through-wall 5.4 PLP (Possible Loose Part)
Twenty (20) PLP indications were reported, nine (9) in SG A and eleven (11) in SG B.
Details are shown 'in Table 5-4.
Table 5-4 Possible Loose Parts Location SG Row Column Location Elevation A
2 52 TSC
+0.06" A
43 38 TSC
+0.12" A
24 68 TSH
+0.33" A
24 67 TSH
+0.42" A
26 53 TSH
+0.96" A
25 53 TSH
+0.85" A
26 52 TSH
+0.86" A
10 22 TSH
+0.23" A
9 22 TSH
+0.31" B
34 73 TSC
+0.87" B
34 73 TSC
+0.63" B
33 73 TSC
+0.86" B
1 25 TSC
+0.16" B
1 24 TSC
+0.02" B
20 36 TSH
+0.03" B
20 35 TSH
+0.00" B
25 27 TSH
+1.36" B
24 27 TSH
+0.71" B
24 26 TSH
+0.10" B
6 6
TSH
+0.16" Page 9 of 14
No degradation was observed in conjunction with these twenty (20) indications. Three (3) of the indications in SG A were not reported during the previous inspection in 2011. The indications at R26, C53; R25, C53; and R26, C52 were reported at the same elevation as reported during the 2011 inspection. The indications in SG B were not reported during the previous inspection in 2011.
All tubes bounding these indications were also tested with +Point RPC probe in the area of interest. Since no wear was associated with these PLP indications, no further action was required.
5.5 Historic Loose Part Wear U1 R34 inspection confirmed historical wear attributed to loose parts in SG Bat tube location R1 C5, described in Table 5-5. The wear indication was sized using the volumetric flaw standard using the +Point RPC probe with Electric Power Research Institute (EPRI) Technique ETSS 21998.1. The inspection results from wear sizing were classified as INR. The indication has been attributed to mechanical damage, presumably from a transient loose part or sludge lancing equipment, and shows no change beyond normal eddy current repeatability from cycle to cycle. The +Point RPC pancake coil did not detect any flaw-like response, only a small geometry change. The +Point RPC pancake coil may be detecting the residual from this change. From the eddy current data it is concluded that the condition of the tubing at these locations is likely small scuff marks with very minor tube deformation. Since the depth is below the repair criterion and further wear is unlikely, the tube was determined, by engineering disposition, to be acceptable to remain in service.
Table 5-5 Historic Loose Part Wear Through-Through-Through-Through-wall wall wall wall Location I Inch SG Row Column U1R34 U1R33 U1R31 U1R30 U1R33 B
1 5
INR 16 17 TSC I 0.33 5.6 Mechanical Wear Indications above the Top of Tubesheet Hot and Cold Legs There were seventeen tubes (17) with seventeen (17) previous indications in SG A and one (1) tube with a single indication in SG B reported in previous inspections. The majority of these indications were on the extreme outer periphery of the generator with indications attributed to mechanical wear above the top of the tubesheet. At this inspection, all indications were retested and were INR. The indications have been attributed to mechanical damage presumably from sludge lancing equipment and they show no change beyond normal eddy current repeatability from cycle to cycle. The pancake coil did not detect any flaw-like response, only a small geometry change. The +Point coil may be detecting the residual from this change. From the eddy current testing Summary of Tube Inspection Results April 2013 data it is concluded that the condition of the tubing at these locations is likely small scuff marks with very minor tube deformation. The U1 R34 inspection results at the location of indications that were identified in previous inspections are shown in Table 5-6. None of these indications were determined to be repairable per engineering disposition and all tubes listed remain in service.
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Table 5-6 Mechanical Wear Indications Through-Through-Through-Through-Through-Location I Inch SG Row Column Wall Wall Wall Wall Wall U1R34 U1R33 U1R31 U1R29 U1R28 U1R33 A
37 20 INR 2
2 4
4 TSH 0.74 A
41 28 INR 7
7 5
TSH 0.62 A
42 30 INR 11 6
5 5
TSH 0.56 A
43 33 INR 10 7
3 5
TSH 0.71 A
44 36 INR 2
5 4
6 TSH 0.70 A
45 41 INR INR 5
3 4
TSH 0.74 A
45 42 INR INR 2
1 3
TSH 0.79 A
45 43 INR 3
2 2
1 TSH 0.72 A
45 44 INR INR 4
3 4
TSH 0.64 A
45 45 INR 4
10 4
10 TSH 0.70 A
45 46 INR INR 3
2 7
TSH 0.71 A
45 47 INR 3
3 2
5 TSH 0.71 A
43 60 INR INR 11 7
7 TSH 0.61 A
42 63 INR 11 19 11 11 TSH 0.68 A
40 68 INR 7
TSH 0.63 A
33 78 INR INR 1
1 TSH 0.89 A
31 80 INR INR 9
4 3
TSH 0.70 B
1 92 NDF INR 6
7 9
TSH 6.19 6.0 Plugging No tubes were plugged during U 1 R34.
Table 6-1 Total Tubes Plugged and Plugging Percentage SGA SGB Total Tubes Plugged 5 of 3214 8 of 3214 Plugging Percentage 0.156%
0.249%
(note: The effective pluggmg percentage equals the pluggmg percentage.)
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7.0 Condition Monitoring Assessment Results.
All existing and potential degradation mechanisms identified in the Degradation Assessment were searched for according to the inspection plan. Four types of wear were detected. These wear indications were evaluated for acceptability according to the criteria specified in the Degradation Assessment.
AVBWear The previous operational assessment for SG A and SG B provided predictions for the depth of expected AVB wear at the end of Cycle 34. The deepest indication was predicted to be less than 43%
through-wall. The actual number of indications detected at U 1 R34 is 102 in SG A and 7 4 in SG B as described in Tables 5-1 and 5-2. The deepest indication measured was 34% through-wall. The growth rates are developed only for those current indications that were observed and.recorded in the previous inspection. The 95th percentile growth is used in the deterministic bounding prediction for future operation. The growth rate for SG A is the highest growth rate; therefore it is the bounding case. The 95th percentile growth rate from SG A is less than 3% per EFPY. SG B is much lower at just over 1% per EFPY. The bounding growth rate is applied to the maximum depth AVB indication for the operational assessment and the predicted depth is less than the condition monitoring limit.
Wear at Tube Support Plates Wear at tube support plates in SG A is described in Table 5-3. The wear depths in the five previously identified indications in SG A and four previously identified indications in SG B are small and essentially unchanged. The newly identified wear indications in SG A and SG Bare also small. All of the six (6) indications in SG A and the five (5) indications in SG B are well below the condition monitoring limit curve.
Mechanical Wear Mechanical wear indications are listed in Table 5-6. The indications have been attributed to mechanical damage presumably from sludge lancing equipment and they show no change beyond normal eddy current repeatability from cycle to cycle. The +Point RPC pancake probe did not detect any flaw-like response, only a small geometry change. The +Point RPC pancake probe may be detecting the residual from this change. From the ECT data it is concluded that the condition of the tubing at these locations is likely small scuff marks with very minor tube deformation. All indications are well below the condition monitoring limit.
Loose Parts wear The one tube with loose parts wear is described in Table 5-5. There were no foreign objects present near this indication, therefore it is expected that no further wear will occur. The indication was retested during this inspection and judged to be INR. The indication has been attributed to mechanical damage presumably from a transient loose part or sludge lancing equipment and shows no change beyond normal eddy current repeatability from cycle to cycle. The indication depth is well below the condition monitoring limit curve.
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PWSCC Indications at Tube End Two crack-like indications at hot leg tube ends were reported and required repair as a result of the U1 R33 SG eddy current inspection. These two tube locations (R1, C48 and R4, C41) were taken out of service with the installation of mechanical (rolled) tube plugs. Prior to plugging, the tubes were rolled to provide assurance against leakage and pull out if the cracking extended in future operation.
No crack-like indications were found during U1 R34.
8.0 Observed Leak Rates The primary-to-secondary leak rate from both SGs combined is in the range of 0.0 to 0.2 gallons per day.
The Unit 1 primary-to-secondary SG leakage remains constant and was evident prior to the spring 1991 outage. The leak may have existed since steam generator replacement. The current Unit 1 primary-to-secondary leak rate is too low to accurately differentiate leakage between individual SGs.
One hundred percent ( 1 00%) of the tubes in both SGs have been tested several times since this leakage has been detected and no degradation that would lead to leakage has been identified. The current leak rate has remained essentially the same for many cycles and is expected to remain at these low levels.
9.0 Secondary Side Inspections/Cleaning Sludge lancing was performed in both SGs.
A foreign object search was performed in SG A and SG B after sludge lancing. The inspection included the hot and cold leg annulus, tube lane and PLP verification.
In SG A, two (2) foreign objects were observed and removed. One was a piece of a gasket, while the second object was a sludge rock. Both pieces were removed. All PLPs were inspected with no foreign objects or anomalies observed.
In SG B, no foreign objects or anomalous conditions were observed. PLPs were inspected with no foreign objects or anomalies observed.
The general area of both SG steam drums were visually inspected and recorded. Areas of inspection included the hatch and hinges, extended mid-deck plate, vanes in the secondary moisture separators, flow diverters, downcomers, feedring brackets, center drain, and mid-deck supports. All accessible areas of the moisture carryover mods were inspected with no anomalies. All thirty five J-nozzles, feed ring and thermal sleeve were visually inspected using a video probe. All of the J-nozzles were visually inspected with no anomalous conditions recorded. The one hundred and twelve primary moisture separators (PMS) were visually inspected and recorded. All PMS appeared to be covered in a light coating of magnetite. No anomalies were observed during inspection. Informational UT thickness measurements were made on the feedring and eight (8) primary moisture separators of both SG A and SG B for trending. There were no abnormal thickness values or negative trends from the baseline measurements taken in U1 R33.
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10.0 Summary The predicted AVB wear depth at U 1 R36 is 42.4% through wall depth which is less than the bounding condition monitoring limit of 55% through-wall depth. There is no significant growth predicted for mechanical wear for the next two cycles. It is unlikely that any PWSCC indications at the tube ends that might develop in the next two operating cycles would exceed the structural or leakage performance criteria.
Based on the inspection results and operational assessment, the next inspection of the steam generator tubes will be at U1 R36.
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