RNP-RA/07-0107, Steam Generator Tube Inspection Report

Steam Generator Tube Inspection Report

ML073110281
Person / Time
Site:	Robinson
Issue date:	11/01/2007
From:	Castell C Progress Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RNP-RA/07-0107
Download: ML073110281 (14)

Text

Progress Energy TS 5.6.8 Serial: RNP-RA/07-0107 NOV ,0 1 20071 United States Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261/LICENSE NO. DPR-23 STEAM GENERATOR TUBE INSPECTION REPORT Ladies and Gentlemen:

In accordance with the H. B. Robinson Steam Electric Plant (HBRSEP), Unit No. 2, Technical Specifications (TS) Section 5.6.8, "Steam Generator Tube Inspection Report," Carolina Power and Light Company, also known as Progress Energy Carolinas, Inc., submits the attached report.

The attachment to this letter provides the steam generator tube inspection report information for Refueling Outage 24 (RO-24) required by TS Section 5.6.8.

If you have any questions concerning this matter, please contact me.

Sincerely, Curt Castell Supervisor - Licensing/Regulatory Programs (Interim)

CAC Attachment c: NRC Resident Inspector, HBRSEP Dr. W. D. Travers, NRC, Region II M. G. Vaaler, NRC, NRR Progress Energy Carolinas, Inc.

Robinson Nuclear Plant

/Uaf 3581 West Entrance Road Hartsville, SC 29550 KiA&4

Attachment to Serial: RNP-RA/07-0107 Page 1 of 13 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 REFUELING OUTAGE 24 STEAM GENERATOR TUBE INSPECTION REPORT This report summarizes the Steam Generator (SG) Tube Inspection Program and the results of the examination that was performed at the H. B. Robinson Steam Electric Plant (HBRSEP),

Unit No. 2, during Refueling Outage 24 (RO-24), as required by the HBRSEP, Unit No. 2, Technical Specifications (TS) Section 5.6.8, "Steam Generator Tube Inspection Report."

Eddy Current (EC) Examination of the tubes on the three installed steam generators was performed during RO-24 in the spring of 2007. The spring of 2007 examinations included the population of tubes in service which were not inspected in the spring of 2004. The RO-24 examinations end the 90 effective full power month (EFPM) inspection interval.

Scope of Inspections The SG Tube Inspection Program during RO-24 included the use of multi-frequency Bobbin coil and motorized Rotating Coil or Plus Point Coil (RPC) probes. Bobbin coil examinations were performed on approximately 50% of tubes in the three Steam Generators full length except for Rows 1 and 2 which were inspected from the tube end to top tube support on both Hot Leg (HL) and Cold Leg (CL). A selection of tubes identified as lead indicators to screen for outside diameter intergranular attack/stress corrosion cracking (ODSCC) at the tube support locations based on industry operating and inspection experience were also inspected with Bobbin coil technology.

RPC, also referred to as Plus Point or +Point, examinations were performed in the three Steam Generators on approximately 50% of the row 1 and 2 U-bends as well as approximately 50% of the tubes on the hot leg at the top of tube sheet from 4 inches above the tube sheet to 2 inches below tube sheet. Periphery tubes (i.e., exterior two rows) were inspected on hot leg and cold leg sides including the tube lane in the SGs from 4 inches above tube sheet to 2 inches below tube sheet. Hot leg tubes that contain bulges, over expansions or dents in the tube sheet regions were inspected from 4 inches above the tube sheet to 17 inches below the top of tube sheet.

Additional RPC inspections included a sample of previously identified indications as well as hot leg and cold leg bobbin "I-code" indications that could represent potential degradation of the tube wall (including U-bends), and the unexpanded tube (SG "A" RI C47 cold leg tube sheet [CTS])

and partially expanded tube (SG "B" R25C10 CTS). Inspections by RPC were performed on surrounding tubes to bound the tubes exhibiting possible loose parts (PLP) signals identified during this inspection effort.

Attachment to Serial: RNP-RA/07-0107 Page 2 of 13 Steam Generator "A" Test Plans Base Plan Tests Comments Bobbin Full Length Bobbin Cold Leg 1633 R5-45 06H-CTE Bobbin Cold Leg 96 R3-4 Bobbin Cold Leg R1-2 182 Hot Leg Bobbin R1-4 278 Straight Length Bobbin Total Tubes 1911 RPC Cold Leg/Hot Leg 10 Previous Sample Dents Cold Leg 1 Non-expanded Tubesheet Cold Leg/Hot Leg 40 Wear % Indications Previous Non-quantifiable Hot Leg/Cold Leg 15 Signal (NQS) (Benign)

Hot Leg Row 1-2 U-Bend 93 Hot Leg 1886 Top of Tubesheet Previous PLP and Bounding Hot Leg 40 Tubes Cold Leg 450 Top of Tubesheet Expanded Scope PLP, Loose Part Signal Cold Leg/Hot Leg 75 (LPS), Loose Part Indication (LPI) Bounding +Point Cold Leg/Hot Leg 43 Wear Scar, Sizing +Point Hot Leg 1 Special Interest Cold Leg 7 Special Interest

Attachment to Serial: RNP-RA/07-0107 Page 3 of 13 Steam Generator "B" Test Plans Base Plan Tests' Comments Bobbin Full Length Bobbin Cold Leg 1666 R5 - 45 06H-CTE Bobbin Cold Leg 108 R3-4 06C-CTE Bobbin Cold Leg 183 R1-2 06H-HTE Bobbin R1-4 291 Straight Length Bobbin Total Tubes 1957 RPC Cold Leg 458 Top of tubesheet (TTS)

Cold Leg/Hot Leg 19 Previous Non-quantifiable Signal (NQS) (Benign)

Cold Leg/Hot Leg 32 Previous Sample Dents Hot Leg/Cold Leg 34 Wear % indications Cold Leg/Hot Leg 124 Previous PLP & Bounding Hot Leg TTS 1948 TTS Hot Leg Row 1-2 U-Bend 92 Expanded Scope Cold Leg/Hot Leg 288 PLP, LPS, LPI Bounding

+Point Cold Leg/Hot Leg 39 Wear Scar, Sizing +Point Hot Leg 3 Special Interest Cold Leg 5 Special Interest

Attachment to Serial: RNP-RA/07-0107 Page 4 of 13 Steam Generator "C" Test Plans Base Plan Tests Comments Bobbin 06H-HTE Hot Leg Rl-4 283 Full Length Bobbin Cold Leg 1634 R5 -45 06H-CTE Bobbin Cold Leg 101 R3-4 06C CTE Bobbin Cold Leg 182 R1-2 Bobbin Total Tubes 1917 RPC Cold Leg/Hot Leg 23 Previous Sample Dents Cold Leg/Hot Leg 23 Previous NQS Hot Leg/Cold Leg 11 Wear % Indication Hot Leg/Cold Leg RI -2 U Bend 92 Hot Leg 1898 TTS Cold Leg 474 TTS Hot Leg/Cold Leg 33 Previous PLP & Bounding Expanded Scope Hot Leg/Cold Leg 114 PLP, LPS, LPI Bounding

+Point Hot Leg/Cold Leg 12 Wear Scar, Sizing +Point Hot Leg 5 Special Interest Bobbin Sizing Anti-vibration Hot Leg/Cold Leg 3 Br(V)Wa Bar (AVB) Wear Cold Leg 6 Special Interest

Attachment to Serial: RNP-RA/07-0107 Page 5 of 13 Active Degradation Mechanisms Active degradation is defined in report EPRI 1003138, "Pressurized Water Reactor Steam Generator Examination Guidelines," Revision 6, October 2002. The criteria attributed to active degradation are:

a) A combination of 10 or more new indications (> 20% through-wall) of thinning, pitting, wear (excluding loose part wear), or impingement and previous indications that display an average growth rate equal to or greater than 25% of the repair limit in one inspection-to-inspection interval in any one steam generator.

b) One or more new or previously identified indications (_ 20% through-wall) which display a growth equal to or greater than the repair limit in one inspection-to-inspection interval.

c) Any crack indication (outside diameter intergranular attack/stress corrosion cracking or primary-side stress corrosion cracking).

The only observed degradation with potential growth is the anti-vibration bar (AVB) wear in Steam Generator "C" and support wear in the three steam generators.

The provisions for steam generator tube repair are located in Technical Specification 5.5.9.c which states:

Tubes found by inservice inspection to contain flaws with a depth equal to or exceeding the following criteria shall be plugged: 47% of the nominal tube wall thickness if the next inspection interval of that tube is 12 months, and a 2% reduction in the repair criteria for each 12 month period until the next inspection of the tube.

Based on a planned inspection interval of two operating cycles (approximately 3 years) the appropriate tube repair criteria is 43% through-wall indication for these two wear mechanisms.

Criterion a) would be satisfied with ten new indications with greater than 20% through-wall or an indication greater than 20% through-wall that was growing faster than 25% of the repair criteria in an inspection interval. Neither the AVB wear nor the tube support wear indications identified in RO-24 were found in more than 2 new locations with a depth greater than 20% through-wall.

The maximum wear depth for these mechanisms is 25% for the support wear mechanism. The measured growth rate for this indication was 7% in the interval between the two most recent inspections. The previous inspection interval and the current inspection interval is 2 operating cycles or 3 years. The measured wear rate is less than the 10.75% growth increase criteria which was obtained from 25% of the 43% through-wall repair criteria.

Criterion b) would be satisfied if there were a previous indication of greater than 20% through-wall with a measured wear rate in excess of its repair criteria. The maximum AVB wear identified prior to RO-24 was 14% which does not meet the 20% through-wall criteria. The maximum support wear previously identified was 25% through-wall in Steam Generator "A" and

Attachment to Serial: RNP-RA/07-0107 Page 6 of 13 23% through-wall in Steam Generator "B." The maximum wear rate measured for either of these indications was 1% through-wall for a 3 year inspection interval which is significantly less than the tube repair criteria.

Criterion c) would be satisfied if there were any crack indications. There were no crack-like indications identified in the RO-24 inspections. Therefore, this criterion does not apply.

Nondestructive Examination Techniques There has been no indication of corrosion related degradation in any of the HBRSEP, Unit No. 2, steam generators. Volumetric indications of various types of wear have been previously identified such as:

S Anti-Vibration Bar Wear 0 Tube Support Wear S Potential Maintenance Equipment Wear S Loose Parts Wear Industry experience has indicated the possibility of other types of indications, which were included in the RO-24 inspection plan.

0 Primary-side stress corrosion cracking (PWSCC) 0 Pitting S Outside diameter intergranular attack/stress corrosion (ODSCC)

The Nondestructive Examination (NDE) techniques utilized were taken from the EPRI quality assured database (EPRIQ) and are listed below.

Mechanism Location/Detail Technique Wear Mechanical, Bobbin (Examination Technique Loose Parts Specification Sheet [ETSS] 96001.1)

+Point (ETSS 21998.1)

Wear AVB Bobbin (ETSS 96004.2)

Wear Supports Bobbin (ETSS 96004.2)

ODSCC Circumferential at +Point (ETSS 21410.1)

TTS ODSCC Axial at TTS +Point (ETSS 21409.1)

PWSCC Circumferential at +Point (ETSS 20510.1)

TTS & below PWSCC Axial at TTS & below +Point (ETSS 20511.1)

ODSCC Axial at Sludge pile, Bobbin (ETSS 96008.1) free span supports +Point (ETSS 21409.1)

Attachment to Serial: RNP-RA/07-0107 Page 7 of 13 Mechanism Location/Detail Technique ODSCC or PWSCC Axial row 1 and row 2 +Point (ETSS 96511.2, 96511.1)

U-bend ODSCC or PWSCC Circumferential row 1 +Point (ETSS 96511.2, 96511.1) and row 2 U-bend Pitting TTS Bobbin (ETSS 96005.2)

+Point (ETSS 21998.1)

ODSCC or PWSCC Sample of dents +Point (ETSS 96703.1)

Service Induced Indications The measured wear depths for the indications are listed in the following table. Most indications have not changed in depth beyond expected measurement uncertainty since the 2004 inspection.

Indications that had significant depth or were associated with a loose part were plugged, as discussed later in this report.

Steam Generator "A" Row Column  % Depth Location Inches 1 1 13 CTS 13.72 7 1 18 CTS 0.68 7 1 14 CTS 0.69 1 2 13 CTS 13.74 11 2 17 CTS 0.54 1 3 17 CTS 15.66 13 3 16 CTS 0.45 1 4 18 CTS 15.78 16 4 19 CTS 0.41 16 4 13 CTS 0.84 1 5 16 CTS 15.76 1 6 17 CTS 15.57 23 7 17 CTS 0.5 26 9 16 CTS 0.5 23 14 23 HTS 0.05 33 15 16 CTS 0.48 37 20 15 HTS 0.63 40 25 18 CTS 0.47 40 25 14 CTS 0.68 42 30 13 HTS 0.63 42 30 14 HTS 0.95

Attachment to Serial: RNP-RA/07-0107 Page 8 of 13 Steam Generator "A" Row Column  % Depth Location Inches 42 30 16 CTS 0.47 43 33 14 CTS 0.56 43 33 13 CTS 0.57 44 36 18 CTS 0.64 44 36 15 CTS 1.69 43 37 15 CTS 0.55 43 37 16 CTS 1.75 33 41 22 HTS 0.1 34 41 23 HTS 0.09 45 41 17 CTS 0.61 27 44 21 05C -0.75 45 47 15 CTS 2.72 45 47 18 CTS 6.77 45 52 18 CTS 0.57 45 52 19 CTS 0.63 45 52 15 CTS 3.78 41 53 27 HTS 0.07 24 54 24 03H -0.72 44 57 16 CTS 0.6 44 57 20 CTS 0.61 44 57 13 CTS 1 44 57 16 CTS 1.97 44 57 13 HTS 0.67 44 57 15 HTS 1.11 43 60 19 CTS 0.61 42 63 15 CTS 0.62 42 63 18 CTS 0.7 42 63 12 HTS 0.64 40 68 17 HTS 0.65 40 68 17 HTS 0.73 36 74 13 HTS 0.62 31 80 16 CTS 0.59 26 84 15 CTS 0.61 23 86 17 CTS 0.61 23 86 13 CTS 3.16

Attachment to Serial: RNP-RA/07-0107 Page 9 of 13 Steam Generator "A" Row Column  % Depth Location Inches 19 87 16 CTS 7.69 1 89 14 HTS 15.54 11 91 18 CTS 0.56 11 91 17 CTS 0.67 7 92 15 CTS 0.61 Steam Generator "B" Row Column  % Depth Location Inches 1 1 13 CTS 9.13 1 1 17 CTS 12.1 1 1 21 CTS 12.63 1 1 1.4 CTS 13.1 1 1 17 CTS 15.15 2 1 15 CTS 5.49 2 1 17 CTS 10.17 2 1 17 CTS 11.64 6 1 15 CTS 0.48 7 1 13 CTS 0.64 7 1 13 CTS 1.12 7 1 16 CTS 12.4 11 2 17 CTS 0.56 16 4 17 CTS 0.5 23 7 14 HTS 0.68 26 9 19 HTS 0.62 25 11 24 04C -0.64 29 14 31. FBH 0.46 30 14 15 FBH 0.42 30 14 22 FBH 0.44 29 15 36 FBH 0.43 7 16 18 CTS 16.11 33 17 20 FBH 0.72 37 20 17 HTS 0.6 37 20 15 CTS 0.51 37 20 15 CTS 0.53 40 25 22 CTS 0.51

Attachment to Serial: RNP-RA/07-0107 Page 10 of 13 Steam Generator "B" Row Column  % Depth Location Inches 40 25 20 CTS 0.53 40 26 16 CTS 0.51 4 32 20 CTS 3.11 4 32 18 CTS 6.12 2 41 18 CTS 1.19 2 42 27 CTS 1.59 3 44 32 HTS 0.24 3 44 23 HTS 0.41 34 44 26 HTS 0.07 3 45 19 CTS 1.42 4 47 16 CTS 1.42 4 47 16 CTS 1.44 4 48 17 CTS 1.59 4 48 28 CTS 3.27 5 48 28 CTS 1.67 4 49 20 CTS 1.5 5 49 27 CTS 1.69 4 50 16 CTS 1.76 11 53 26 CTS 1.27 43 60 18 CTS 0.58 27 65 19 03H 0.08 1 67 25 06C -0.54 1 67 24 06C 0.61 40 67 13 CTS 0.52 40 68 18 CTS 0.51 34 76 21 CTS 1.83 33 78 16 CTS 0.63 33 78 18 CTS 0.64 26 84 17 CTS 0.67 23 86 19 CTS 0.65 16 89 21 CTS 0.6 1 92 12 HTS 2.02 1 92 16 HTS 2.88 1 92 15 HTS 13.91 2 92 14 CTS 11

Attachment to Serial: RNP-RA/07-0107 Page 11 of 13 Steam Generator "C" Row Column  % Depth Location Inches 7 1 15 CTS 0.6 44 38 17 HTS 0.55 37 45 10 03A 0 37 45 10 04A 0 34 50 23 HTS 0.02 34 51 20 HTS 0.05 35 51 18 HTS 0.08 44 57 17 HTS 0.56 44 57 16 HTS 1.21 44 57 18 CTS 0.65 35 61 7 02A -0.38 35 61 5 03A -0.13 35 61 5 04A 0.11 38 62 6 02A -0.29 38 62 15 03A -0.32 33 75 21 03H -0.89 35 75 17 CTS 1.49 33 78 14 HTS 0.66 2 91 38 CTS 0.05 3 91 25 HTS 0.39 Abbreviations:

CTS Cold leg top-of-tubesheet HTS Hot leg top-of-tubesheet FBH Flow distribution baffle on hot leg side 02A Anti-vibration bar 2 03A Anti-vibration bar 3 04A Anti-vibration bar 4 02C Cold leg second support plate 02H Hot leg second support plate 03C Cold leg third support plate 03H Hot leg third support plate 04C Cold leg fourth support plate 04H Hot leg fourth support plate 05C Cold leg fifth support plate 05H Hot leg fifth support plate 06C Cold leg sixth support plate 06H Hot leg sixth support plate

Attachment to Serial: RNP-RA/07-0107 Page 12 of 13 Number of Tubes Plugged A total of six tubes were plugged during the RO-24 Steam Generator inspection/repair effort.

These six tubes were damaged due to loose parts wear. Loose parts wear is tube wall thinning caused by the interaction between foreign objects and the outside surfaces of the tubes. In Steam Generator "B" there were five tubes plugged and staked. In Steam Generator "C" one tube was plugged, no loose part was present and therefore no stake was required. The wear depth ranged from 20% to 38% through-wall.

The only observed degradation with potential growth was the Anti-Vibration Bar (AVB) wear in Steam Generator "C" and support wear in each of the steam generators. As discussed previously, the results of the RO-24 inspection do not warrant classifying these mechanisms as active degradation mechanisms. Therefore, none of the 6 tubes plugged during RO-24 were determined to be damaged as a result of any active degradation mechanisms.

Tubes Plugged to Date The HBRSEP, Unit No. 2, steam generators were replaced in 1984 with Westinghouse Model 44F steam generators with alloy 600 thermally treated tubes. The current analysis supports up to 6% tube plugging. Prior to RO-24 there were 26 plugged tubes. With the 6 tubes plugged in RO-24 there are a total of 32 plugged tubes out of a population of 9642 for the three steam generators. This brings the total plugging to 0.3% as compared to the analysis limit of 6%.

Condition Monitoring The maximum depths of the wear indications detected are demonstrated to be below the condition monitoring limits defined in the degradation assessment. Therefore the condition monitoring limits are satisfied for tube integrity. The assessment of the secondary side inspection results demonstrated that any remaining loose part was sufficiently small that wear would not cause a violation of the condition monitoring limit during the next two operating cycles.

Tube Pulls There were no tube pulls in RO-24.

Insitu Testing There was no insitu pressure testing in RO-24.

Indications Detected in the Upper 17 inches of the Tubesheet Region Eddy current data for the hot leg tube sheet region was screened for indications of bulges, over-expansions, and dents. The tubes with these indications that were part of the inspection

Attachment to Serial: RNP-RA/07-0107 Page 13 of 13 population were inspected to 17 inches below the top of the tube sheet. No degradation was identified in this 17 inch region.

Evaluation of Operational Cycle Primary to Secondary Leakage Rate There was no measured primary to secondary leakage in the cycle preceding RO-24; therefore there is no corresponding calculated accident leakage to report.