ML080870429

2007 Steam Generator Tube Inspection Report

ML080870429
Person / Time
Site:	Cook
Issue date:	03/18/2008
From:	Jensen J Indiana Michigan Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
AEP:NRC:8691
Download: ML080870429 (9)

Text

Indiana Michigan Power INDIANA Cook Nuclear Plant MICHIGAN One Cook Place Bridgman, Ml 49106 POWER AEP.com A unitof American Electric Power March 18, 2008 AEP:NRC:8691 Docket Nos.: 50-315 50-316 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop O-P 1-17 Washington, DC 20555-0001 Donald C. Cook Nuclear Plant Units 1 and 2 2007 STEAM GENERATOR TUBE INSPECTION REPORT Technical Specification (TS) 5.6.7 of Appendix A, to the Donald C. Cook Nuclear Plant (CNP) Unit I and Unit 2 Operating Licenses requires that following the completion of an inspection perforlned in accordance with TS 5.5.7, Steam Generator (SG) Program, an inspection report be submitted within 180 days after initial entry into Mode 4. CNP Unit 2 entered Mode 4 on November 2, 2007. This report details specific attributes of the inspection in accordance with TS 5.6.7. Consistent with these requirements, the 2007 SG Tube Inspection Report is attached.

This letter contains no new or revised commitments. Should you have any questions, please contact Mr. James M. Petro, Jr., Regulatory Affairs Manager, at (269) 466-2491.

Sincerely, Site Support Services Vice President SLA/rdw Attachment 2007 Steam Generator Tube Inspection Report Enclosures

1. 2007 Unit 2 Steam Generator (SG) Inspection Scope

2. Inspection Methods for Applicable Degradation Mechanisms 14-o y 7

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U. S. Nuclear Regulatory Commission AEP:NRC:8691 Page 2 c: J. L. Caldwell, NRC Region III K. D. Curry, Ft. Wayne AEP, w/o attachment/enclosures J. T. King, MPSC, w/o attachment/enclosures MDEQ - WHMD/RPS, w/o attachment/enclosures NRC Resident Inspector P. S. Tam, NRC Washington, DC

Attachment to AEP:NRC:8691 2007 STEAM GENERATOR TUBE INSPECTION REPORT Acronyms/Definitions 0#C Identifier for the cold leg support plates (i.e., 07C is the 7 1h support plate on the cold leg side of the steam generator) 0#H Identifier for the hot leg support plates (i.e., 04H is the 4kh support plate on the hot leg side of the steam generator)

%TW Percent Through-Wall

+PointTM Plus Point (rotating coil inspection probe)

ASME American Society of Mechanical Engineers CL Cold Leg Dent A local reduction (plastic deformation) in the tube diameter due to a buildup of corrosion products (magnetite)

Ding A local reduction (plastic deformation) in the tube diameter caused by manufacturing, support plate shifting, vibration, or other mechanical means.

EFPM Effective Full Power Months EPRI Electric Power Research Institute FDB Flow Distribution Baffle HL Hot Leg ID Inside Diameter IGA/SCC Intergranular Attack/Stress Corrosion Cracking Manufacturing A tubing condition where localized tubing imperfections were removed in the Burnish Mark tubing mill or fabrication shop by buffing and are detectable due to the effects of cold working and localized wall thinning OD Outside Diameter PLP Possible Loose Part - Indication code used to identify a potential foreign object on the secondary side of the steam generators

Attachment to AEP:NRC:8691 Page 2 PWR Pressurized Water Reactor PWSCC Primary Water Stress Corrosion Cracking Rxx/Cyy Typical identification scheme for a tube location coordinate corresponding to Row xx and Column yy SG Steam Generator TEC Tube End Cold TEH Tube End Hot TS Technical Specification TSP Tube Support Plate TTS Top of Tubesheet U-bend Area of curved tubing between the uppermost support plates on the hot and cold leg side of the steam generator Introduction UNIT I During September and October of 2006, SG inservice inspections were conducted on the Unit I SGs. The inspection results were reported Linder AEP:NRC:7691, dated February 27, 2007 (ADAMS Accession Number ML070660516). Based upon the results of that inspection, and in accordance with the provisions of TS 5.5.7, the next Unit 1 SG inspection is scheduled for the Fall of 2009.

UNIT 2 During September and October of 2007, SG inservice inspections were conducted on the Unit 2 SGs. This inspection constituted the seventh inspection of the replacement SGs since they were placed in service in 1989. The inspection results are reported in this attachment. Based upon the results of that inspection, which identified no significant degradation, and the provisions of TS 5.5.7, the next Unit2 SG inservice inspection is scheduled for the Fall of 2010.

Unit 2 SG Description Each of the four replacement Westinghouse model 54F SGs contain 3592 thermally treated alloy 690 tubes with an OD of 0.875 inches, and a nominal wall thickness of 0.050 inches. All tubes

Attachment to AEP:NRC:8691 Page 3 in the eight innermost rows were thermally stress relieved after bending, and the bundle has an increased tube bend radius to further reduce residual stress in the U-bend area.

The tube support structures consist of seven 1.12 inch thick support plates with quatrefoil-shaped tube holes, and six anti-vibration bars that are located in the U-bend region of the tubes. There is also an FDB located between the tubesheet and the first support plate. The FDB is 0.75 inches thick with octafoil-shaped tube holes. The support plates, anti-vibration bars, and the FDB are made of type 405 stainless steel.

The tubesheet is composed of ASME SA-508 Class 2a low alloy steel forging material and is 21.18 inches thick (without cladding). The primary side of the tubesheet is clad with 0.20 inches of Inconel, making the overall nominal tubesheet thickness with cladding, 21.38 inches. Tubes are hydraulically expanded into the tubesheet, with the exception of eight tubes. The eight tubes lack hydraulic expansion in either the HL or CL tubesheet due to a manufacturing oversight.

A. The scope of inspections performed on each SG Primary Side Inspection Scope At the time of the 2007 inspection, the Unit 2 SGs had accumulated 132.6 EFPM of operation.

TS 5.5.7.d.2 notes that the first sequential inspection period begins after the first inservice inspection. Accordingly, the accumulated EFPM does not include the first cycle of operation.

The 2007 inspection scope was established to ensure the inspection requirements of TS 5.5.7.d.2 for the first 144 EFPM inspection period, when coupled with previous inservice examination scope, was accomplished. Based upon the scope of inspections completed to date, Unit 2 has satisfied the TS 5.5.7.d.2 requirements to inspect 100% of the tubing within the first sequential period. The 2007 inspection scope is summarized in Enclosure 1.

Bobbin Coil The full length examination of each SG included three separate inspection plans. The tubing in rows 4-47 was examined along the full length (tube end to tube end) using the bobbin coil.

Row 3 tubes were inspected using the bobbin coil in a candy cane fashion. For example, from the HL tube end to the uppermost support on the CL, and then from the CL tube end to the uppermost CL support. Similarly, tubes in rows 1-2 were inspected using an examination plan that included a combination of bobbin coil straights (HL tube end to uppermost HL support, CL tube end to uppermost CL support) and rotating coil inspections from the uppermost HL support to the uppermost CL support, to complete an overall examination of the associated tubes.

In total, these inspection plans addressed the full length inspection of 2077 (57.8%) tubes in SG 21 (1808+74+195), 2073 (57.7%) tubes in SG 22, 2062 (57.4%) tubes in SG 23, and 2075 (57.8%) tubes in SG 24.

Attachment to AEP:NRC:8691 Page 4 Rotating Coil Rotating coil inspections were performed under three distinct inspection plans. A nominal 20%

HL TTS examination was conducted in each SG. In addition, a rotating coil was used to inspect the U-bend area of 100% of the inservice rows 1-2 tubes in each SG. The rotating coil was also used to inspect the "special interest" population (e.g., samples of historical indications and indications from the bobbin coil examination that required additional characterization).

Visual Plug Examination 100% of the installed tube plugs were inspected using a remote camera to confirm plug location and condition. No abnormal conditions were identified during this examination.

Secondary Side Inspection Scope Post-sludge lancing remote visual inspections were completed on each SG at the TTS. Areas targeted included the divider lane, bundle periphery, and select inner bundle passes. In addition, foreign object search and retrieval efforts were performed based upon eddy current inspection results.

Steam drum inspections were performed in SG 22 and SG 23 with a focus on the feedring header/supports, J-nozzles, and the moisture separator units. No abnormal conditions were identified during these inspections.

B. Active degradation mechanisms found Active degradation mechanisms as defined by EPRI PWR SG Examination Guidelines (Revision 6) and the Donald C. Cook Nuclear Plant SG Program include:

• A combination of 10 or more new indications (> 20% TW) of thinning, pitting, wear (excluding loose part wear), or impingement and previous indications that display an average growth rate > 25% of the repair limit in one inspection-to-inspection interval in any one SG,

• One or more new or previously identified indications (> 20% TW) which display a growth equal to or greater than the repair limit in one inspection-to-inspection interval, or

• Any crack indication (OD IGA/SCC or primary-side stress corrosion cracking).

No active degradation mechanisms were identified during the 2007 examination.

C. Nondestructive examination techniques utilized for each degradation mechanism Nondestructive examination techniques focused on the degradation mechanisms and are listed in .

Attachment to AEP:NRC:8691 Page 5 D. Location, orientation (if linear), and measured sizes (if available) of service induced indications Identifier indication Type Tube Location Orientation Size (%TW) 21 TSP Wear R6/C53 05H, -0.63" Axial 5 21 TSP Wear R6/C53 06H, -0.61" Axial 12 21 TSP Wear R6/C54 04H, -0.64" Axial 8 21 TSP Wear R6/C54 05H, -0.62" Axial 7 21 TSP Wear R6/C51 06H, -0.62" Axial 11 23 TSP Wear R4/C56 06H, -0.61" Axial 11 24 TSP Wear R7/C54 06H, -0.59" Axial 9 E. Number of tubes plugged during the inspection outage for each active degradation mechanism No tubes were plugged during the 2007 inspection.

F. Total number and percentage of tubes plugged to date The following table identifies the current total number and percentage of tubes plugged for each SG:

SG Identifier Number of Tubes/SG Number of Plugged Tubes Plugging Percentage (%)

SG 21 3,592 11 0.028 SG 22 3,592 5 0.139 SG 23 3,592 6 0.167 SG24 3,592 4 0.111 Total 14,368 16 0.111 G. Results of condition monitoring, including the results of tube pulls and in-situ testing Evaluation of the indications found during the 2007 inspection indicate that the condition monitoring requirements for structural and leakage integrity, as specified in TS 5.5.7, were satisfied.

The indications of interest were limited to seven support plate wear indications. The largest of these indications was sized at 12% TW. The condition monitoring limit for tube support wear detected is approximately 41% TW. Comparisons to the established limit and the as-found indications confirmed that none of the indications approached the condition monitoring limit.

Condition monitoring requirements were met for the previous cycle of operation.

The inspection found no indications that met the criteria for in-situ pressure testing and no tubes were required to be pulled.

Enclosure 1 to AEP:NRC:8691 Page I 2007 Unit 2 Steam Generator (SG) Inspection Scope

-Eiaioiiintion Effent SG 21I÷ . -*SG 22 . SG-23--: :- SG

'2 . ." Notes -'

Technique Exam-Count Exam Countl Exam Count Exam Count.

Bobbin Full Length 1808 1814 1813 1808 Rows 4-47 TEC/TEH Bobbin Full Length (candy 74 66 69 71 Row 3 cane) 07CTEH & 07CTEC Bobbin Straight Lengths 195 193* 190 196t Row 1 & 2 07HTEH & 07CTEC Rotating TTS 724 720 725 728 Population was 20%

Coil +/- 3" (minimum) of inservice tubes Rotating Row 1-2 195 193 190 196 Population was 100% of Coil U-bends inservice tubes, 07C07H Rotating HL TTS 40 57 35 9 Special Interest:

Coil HL FDB -- 4 -- -- Bounding exams surrounding CL TTS -- 38 .

-- new/historical PLPs/Dings Rotating HL Tubesheet ..-- 4 -- Special Interest:

Coil CL Tubesheet -- 4 -- -- Tubes not fully expanded Rotating Various 64 34 46 59 Special Interest:

Coill Bobbin Sampling Visual Plug NA 2 10 12 8 No new plugs installed during Examination this examination

• Total includes one row 2 tube examined with an extent greater than 07CTEH & 07CTEC Total includes four row 2 tubes examined with extents greater than 07CTEH & 07CTEC to AEP:NRC:8691 Page I Inspection Methods for Applicable Degradation Mechanisms Deraat" Location Pryobe Type- ....

D:Degr"eDu tion .. ri*ng*

Mlechianism .j:ecnique) egaaonspectioneu?

2f Wear TSP Bobbin Yes Wear Anti-Vibration Bars Bobbin No Wear Full Length of Tubing with specific targeted area Bobbin, No (Loose Part) (TTS) +PointTM, Visual Thinning Tube Support & Sludge Pile Bobbin No Pitting Sludge Region Bobbin No IGA/SCC (OD) Non-Dented Tube Supports, Freespan, Dings < 5.OVolts Bobbin, No Tube Supports, Freespan, Sludge Pile, Tubesheet, +PointTM Expansion Transitions, Low Row U-bends, Dents/Dings, Foreign Object Wear, Manufacturing Burnish Marks PWSCC (ID) Low Row U-bends, Expansion Transitions, Dents/Dings +PointTM No