ML071350249

Steam Generator Tube Plugging Report

ML071350249
Person / Time
Site:	Millstone
Issue date:	05/08/2007
From:	Price J Dominion Nuclear Connecticut
To:	Document Control Desk, NRC/NRR/ADRO
References
07-0342
Download: ML071350249 (6)

Text

Dominion Nudear Connecticut, Inc. minionlll DoEhj Millstone Power Station Rope Ferry Road, Waterford, CT 06385 4AY 0 8 2007 U.S. Nuclear Regulatory Commission Serial No. 07-0342 Attention: Document Control Desk NSLS/RWM RO Washington, D.C. 20555 Docket No. 50-423 License No. NPF-49 DOMINION NUCLEAR CONNECTICUT. INC.

MILLSTONE POWER STATION UNIT 3 STEAM GENERATOR TUBE PLUGGING REPORT This special report is being submitted pursuant to the requirements of Plant Technical Specifications 4.4.5.5.a and 6.9.2. Plant Technical Specification 4.4.5.5.a requires a special report documenting the number of steam generator (SG) tubes plugged be submitted to the commission within 15 days following completion of each inservice inspection of the SG tubes.

The eddy current inspections conducted at the end of cycle 11 were completed on April 24, 2007. Attachment I to this letter contains tables that summarize the number of tubes examined and identify tubes removed from service as a result of the examination.

The scheduled inspections were performed in Steam Generators B and D. All operational tubes within the B and D steam generators, a total of 11,170, were inspected with bobbin probes. Additionally, an augmented sample of 7,010 tube locations was inspected in the B and D steam generators utilizing rotating probes incorporating plus point coils. The plus point probe provides superior detection of both circumferential and axial cracks, and has been qualified per the Steam Generator Examination Guidelines, Appendix H, for the detection of cracking mechanisms. The rotating probe inspections were performed in areas of special interest including hot leg expansion transitions, low row U-bends, tubesheet overexpansions, and dents, as well as locations where the bobbin probe response was ambiguous.

There were no repairs required for the B Steam Generator. Four tubes were removed from service in the D Steam Generator. Eddy current testing identified flaws greater than or equal to the plugging limit in one (1) tube. The plugging limit is defined within Technical Specifications as an imperfection depth of 40 percent nominal tube wall thickness or greater. Three additional tubes were removed from service on a discretionary basis. The basis for plugging the four tubes is as follows:

One tube was identified with foreign object wear, sized at 47 percent throughwall, exceeding the Technical Specification plugging limit. The foreign object was removed.

A second tube was identified with wear from the same foreign object, sized at 25 percent throughwall. The tube was discretionarily removed from service.

Two tubes were identified with anti-vibration bar (AVB) wear, sized at 37 and 38 percent throughwall respectively, and discretionarily removed from service.

Serial No. 07-0342 MP3 Steam Generator Tube Plugging Report Page 2 of 2 All tubes were removed from service by the installation of Framatome Alloy 690 Rolled Mechanical Tube Plugs on April 24, 2007 and April 25, 2007.

The inspection results for the steam generators resulted in a classification of C1 for Steam Generator B and 02 for Steam Generator 0. No sample expansion was required since 100 percent of the tubes in Steam Generator D were scheduled for examination.

The complete results of the steam generator tube inspection will be submitted within 12 months in accordance with Technical Specification 4.4.5.5.b.

If you should have any questions regarding this submittal, please contact Mr. David W.

Dodson at (860) 447-1791, extension 2346.

Very truly yours, J YA nPrice

~Vice President - Millstone Attachments: 1. Steam Generator Tube Plugging Report Commitments made by this letter: None.

cc: U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Mr. J. D. Hughey Project Manager, Millstone Unit No. 3 U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8B33 Rockville, MD 20852-2738 Mr. S. M. Schneider NRC Senior Resident Inspector Millstone Power Station

Serial No. 07-0342 Docket No. 50-423 ATTACHMENT I MILLSTONE POWER STATION, UNIT NO. 3 STEAM GENERATOR TUBE PLUGGING REPORT MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC.

Serial No. 07-0342 MP3 Steam Generator Tube Plugging Report Attachment I / Page 1 of 3 TABLE I - MILLSTONE 3 RFO1I ECT

SUMMARY

SG B SG D Total Number of Tubes (SG B and D only) 5,622 5,548 11,170 Number of Tubes Inspected FIL w/Bobbin Probe 5,153 5,067 10,220 Number of Tubes Inspected w/Bobbin Probe Cold Leg 469 481 950*

Straights and Hot Leg Candy Canes Previously Plugged Tubes 4 78 82 Number of Tubes Incomplete w/Bobbin Probe due to 0 0 0 Obstruction Number of Tube Inspections w/MRPC (Total) 3,390 3,620 7,010

• Hot Leg Transitions - Original Scope (tubes) 2,813 2,813 5,626

• Hot Leg Transitions - Scope Expansion (tubes) 0 0 0

• Hot Leg OXP (+3 / -17) (tubes) 65 136 201 9Row I and 2 U-Bends - Original Scope (tubes) 244 239 483

• Row I and 2 U-Bends - Additional Scope (tubes) 0 0 0

• U-Bends - Additional Scope (locations) 0 0 0 eHot Leg Misc. Special Interest - Diagnostic Exams 176 201 377 and from Previous History (tubes) oCold Leg Transitions - Scope Expansion (tubes) 0 0 0

• Cold Leg Misc. Special Interest - Diagnostic Exams 44 26 70 and from Previous History (tubes) eU-bend. Special Interest - Diagnostic Exams and 4 8 12 from Previous History (tubes)

.PLP / SVI Bounding Special Interest (examinations) 44 197 241 Number of OXP Locations Examined (locations) 115 292 407 Number of OXP Locations L_.28.3 V Examined 14 52 66 (locations)

Number of OXP Locations < 28.3 V Examined 101 240 341 (locations)

Number of OXP Locations from TTS (+3 / -3) (locations) 17 106 123 Tubes with Max AVB Wear > 40 % 0 0 0 Tubes with Max AVB Wear >20% but <40% 15 23 38 Tubes with Max AVB Wear <20% 28 47 75 Tubes with Max SVI / VOL> 40 % 0 1 1 Tubes with Max SVI / VOL>20% but <40% 1 4 5 Tubes with Max SVI / VOL<20% 0 1 1 Tubes Plugged as a result of SVI / VOL> 37 % 0 1 1 Tubes Plugged as a result of AVB Wear > 37 % 0 2 2 Tubes Plugged as a result of an Obstruction 0 0 0 Tubes Plugged on a discretionary basis 0 3 3 Total Tubes Plugged as a Result of this Inspection 0 4 4

• For 244 tubes in Steam Generator (SG) B and 239 tubes in SG D, straight legs were examined with bobbin probes, U-bends with MRPC

Serial No. 07-0342 MP3 Steam Generator Tube Plugging Report Attachment I / Page 2 of 3 TABLE 2 - TUBES PLUGGED DURING RF1 1 FOR FOREIGN OBJECT WEAR ( > 40%)

D SG (ONLY)

ROW COLUMN  % THROUGHWALL 53 80 47%

TABLE 3- DISCRETIONARY TUBES PLUGGED DURING RF1I FOR FOREIGN OBJECT WEAR D SG (ONLY)

ROW COLUMN  % THROUGHWALL 52 79 25%

TABLE 4 - DISCRETIONARY TUBES PLUGGED FOR AVB WEAR DURING RFlI D SG (ONLY)

ROW COLUMN  % THROUGHWALL 43 75 38%

28 115 37%

Serial No. 07-0342 MP3 Steam Generator Tube Plugging Report Attachment 11 Page 3 of 3 TABLE 5 - TOTAL TUBES PLUGGED TO DATE SGA " SG B SG C SG D TOTAL Fabrication 1 2 2 0 5 Preservice 2 1 1 1 5 RFO1 1 0 0 1 2 RF02 4 - 0 - 4 RF03 0 - 5 5 RFO4 6 - 1 0 7 RFO5 - 1 - 10 11 MID CYCLE - - 2 - 2 RFO6 12 - 2 - 14 RFO7 - 0 - 51 51 RFO8 8 - 3 - 11 RFO9 - 0 - 10 10 RF10 2 - 0 - 2 RF11 - 0 - 4 4 TOTAL _36 4 11 82 133 TABLE 6 - ACRONYMS AVB Anti-Vibration Bar ECT Eddy Current Test F/L Full Length MRPC Motorized Rotating Pancake Coil OXP Over-expansions PLP Possible Loose Part RFO Refueling Outage SG Steam Generator SVI Single Volumetric Indication TTS Top of Tubesheet VOL Volumetric Indication