ML083090396

End of Cycle 18 Steam Generator Tube Inspection Report

ML083090396
Person / Time
Site:	Millstone
Issue date:	10/24/2008
From:	Jordan A Dominion, Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML083090396	List: ML083090396
References
08-0627
Download: ML083090396 (14)

Text

Dominion Nuclear Connecticut, Inc.

Millstone Power Station S Dominion Rope Ferry Road, Waterford, CT 06385 OCT 2 4 2008 U.S. Nuclear Regulatory Commission Serial No. 08-0627 Attention: Document Control Desk NSS&L/MLC RO One White Flint North Docket No. 50-336 11555 Rockville Pike License No. DPR-65 Rockville, MD 20852-2738 DOMINION NUCLEAR CONNECTICUT. INC.

MILLSTONE POWER STATION UNIT 2 END OF CYCLE 18 STEAM GENERATOR TUBE INSPECTION REPORT In accordance with the Millstone Power Station Unit 2 (MPS2) Technical Specification (TS), Section 6.9.1.9, Dominion Nuclear Connecticut, Inc., hereby submits, the End of Cycle (EOC) 18 Steam Generator Tube Inspection Report. The report is submitted within 180 days after initial entry into MODE 4 following completion of an inspection performed in accordance with TS 6.26, Steam Generator (SG) Program.

The report includes the following:

a. The scope of inspections performed on each SG,

b. Active degradation mechanisms found,

c. Nondestructive examination techniques utilized for each degradation mechanism,

d. Location, orientation (if linear), and measured sizes (if available) of service induced indications,

e. Number of tubes plugged during the inspection outage for each active degradation mechanism,

f. Total number and percentage of tubes plugged to date, and

g. The results of condition monitoring, including the results of tube pulls and in-situ testing.

If you have any questions or require additional information, please contact Mr. William D.

Bartron at (860) 444-4301.

Sincerely, A. J. ,:dkdan Site VP - Millstone A- 0(-17

ýAw

Serial No. 08-0627 Docket No. 50-336

Enclosures:

(1)

Commitments made in this letter: None.

cc: U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Ms. C. J. Sanders NRC Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08-B3 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No. 08-0627 Docket No. 50-336 ENCLOSURE Millstone Power Station Unit 2 End of Cycle 18 Steam Generator Tube Inspection Report MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 1 of 11 End of Cycle 18 Steam Generator Tube Inspection Report Millstone Power Station Unit 2 (MPS2) is a two loop Combustion Engineering (CE) pressurized water reactor (PWR) with Babcock and Wilcox (B&W) replacement Steam Generators (SGs). Each SG was designed to contain 8523 U-bend thermally treated Inconel 690 tubes. One hot leg tubesheet hole in SG 1 was plugged during construction and the opposing cold leg hole was not drilled, thus SG 1 has 8522 tubes. The tubing is nominally 0.750 inches outside diameter with a 0.0445 inch nominal wall thickness.

During replacement SG fabrication, the tubes were installed using a two-step hydraulic expansion process over the full depth of the 21.06 inch thick tubesheet. The tubesheet was drilled on a triangular pitch with 1.0 inch spacing. There are 141 rows and 167 columns in each SG. To minimize small radius U-bends, tubes in rows 1 through 3 were installed using a staggered arrangement. This resulted in the termination of tubes at different locations between the hot and cold legs. For these rows, the tube identification follows the hot leg row/column naming convention. Secondary side tube support structures include seven lattice grid supports on the vertical section of the tubes and twelve fan bar assemblies on the U-bend section of the tubes. All lattice grid supports are full supports. SG replacement was completed in the fall of 1992 during MPS2's Refueling Outage 11 (2R1 1). The new SGs have accrued 9.762 Effective Full Power Years (EFPY) of operation as of the End of Cycle (EOC) 18 (April 2008). The 910 MW unit operates with a hot leg temperature of 601 degrees Fahrenheit.

The MPS2 SG eddy current testing (ECT) conducted at EOC 18 was completed on April 24, 2008. Initial entry into Mode 4 following completion of the inspections occurred on May 12, 2008. The examinations, personnel, and equipment conformed to the requirements of NEI 97-06, Rev. 2, Steam Generator Program Guidelines; EPRI Pressurized Water Reactor Steam Generator Examination Guidelines, Rev. 6; and MPS2 Technical Specifications (TSs).

In accordance with MPS2 TSs, a SG tube inspection report is required. TS Section 6.9.1.9 states:

A report shall be submitted within 180 days after initialentry into MODE 4 following completion of an inspection performed in accordancewith TS 6.26, Steam Generator(SG) Program. The report shall include:

a. The scope of inspectionsperformed on each SG, For both SG 1 and SG 2, a 100% full length bobbin coil examination was scheduled to be performed on all tubes from the tube end of the hot leg (TEH) to the tube end of the cold leg (TEC). This was accomplished for the majority of the tubes. The remaining tubes were examined from 07C to TEH, 07C to TEC, 07H to TEH, or 07H to TEC to complete the full length bobbin inspection. See Attachment 1, "Acronyms," for explanation of acronyms. See Attachment 2, "Millstone Power Station Unit 2 Steam Generator Arrangement," for illustration of steam generator component locations.

Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 2 of 11 For both SG1 and SG 2, the rotating pancake coil (RPC) examinations included a 140 tube sample of hot leg tubesheet expansion transitions (TSH +3"/-3") in the periphery area of each SG. In addition, a total of 1012 (438 in SG 1 and 574 in SG 2) locations were examined with RPC. These locations included 2R15 and 2R16 historical locations which consisted of previously reported bulges (BLG), dings (DNG), dents (DNT), non-quantifiable historical indications (NQH), partial tubesheet expansion (PTE), possible loose part (PLP),

percent through-wall indications (%TW), and volumetric indications (VOL). These locations also included 2R1 8 bobbin coil special interest (SI) locations of ding (DNG), dent (DNT) distorted expansion indications (DEI), deposit (DEP), loose part indications (LPI),

non-quantifiable indications (NQI), possible loose parts (PLP), various hot leg and cold leg bounding locations, and tubes that were observed with flex gasket material protruding from the tube ends. The inspection summary is documented in Table 1.

Table 1 - Millstone 2R18 ECT Summary SG 1 SG 2 Total Number of Tubes (SG 1 and SG 2) 8,522 8,523 17,045 Number of Tubes Inspected F/L w/Bobbin Probe 8,522* 8,523* 17,045 Previously Plugged Tubes 0 0 0 Number of Tubes Incomplete w/Bobbin Probe due to Obstruction 0 0 0 Number of Inspections w/MRPC (Total) 578 714 1292

• Hot Leg Transitions - Original Scope (tubes) 140 140 280 eHot Leg Transitions - Scope Expansion (tubes) 0 0 0

• Hot Leg Misc. Special Interest - Diagnostic Exams and from 75 92 167 Previous History (locations)

• Cold Leg Transitions - Original Scope (tubes) 0 0 0

• Cold Leg Transitions - Scope Expansion (tubes) 0 0 0 sCold Leg Misc. Special Interest - Diagnostic Exams and from 98 144 242 Previous History (locations) oU-Bends - Original Scope (locations) 0 0 0 eU-bend. Special Interest - Diagnostic Exams and from 51 97 148 Previous History (locations) oPLP / SVI Bounding Special Interest (locations) 214 241 455 Tubes with Max FB Wear > 40 % 0 0 0 Tubes with Max FB Wear >20% but <40% 0 0 0 Tubes with Max FB Wear <20% 2 2 4 Tubes with Max SVI / VOL / WAR> 40 % 2 0 2 Tubes with Max SVI / VOL / WAR>20% but <40% 2 10 12 Tubes with Max SVI / VOL / WAR<20% 3 1 4 Tubes Plugged as a result of SVI / VOL / WAR> 37 % 2 0 2 Tubes Plugged as a result of no qualified sizing 5 0 5 Tubes Plugged as a result of FB Wear > 37 % 0 0 0 Tubes Plugged as a result of an Obstruction 0 0 0 Tubes Plugged on a discretionary basis (loose part wear with part 1 2 3 not removed) I I I Total Tubes Plugged as a Result of this Inspection 8 2 10

• For 102 tubes in SG 1 and 260 tubes in SG 2, the bobbin exam was a combination of two examinations from opposite legs with overlap at the upper support structure.

Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 3 of 11

b. Active degradationmechanisms found, Two mechanical tube degradation mechanisms - fan bar wear and foreign object wear were identified during this examination. There was no evidence of any corrosion-related degradation.

c. Nondestructive examination techniques utilized for each degradation mechanism, Table 2 identifies the examination techniques utilized for each identified degradation mechanism.

d. Location, orientation (if linear), and measuredsizes (if available)of service induced indications, Table 3 identifies the service induced indications reported during the examination.

e. Number of tubes plugged during the inspection outage for each active degradationmechanism, In SG 1, seven wear indications were reported. Five were located at the tubesheet interface and not in the freespan and were caused by a transient loose part. Since there was no qualified technique for sizing indications at this location, all five tubes were removed from service by plugging. Two additional indications were located above the cold leg secondary side tubesheet interface and were caused by loose part wear. The loose part that caused the wear could not be removed by Foreign Object Search and Retrieval (FOSAR). The maximum depth sizing for these two indications was 67% and 58%. Both tubes along with a third adjacent tube were removed from service by plugging and stabilization. These three tubes box the loose part that could not be removed.

In SG 2, a wear indication was located above the hot leg secondary side tubesheet interface and was caused by a loose part. The maximum depth sizing was 11% TW. The loose part, a piece of flexitallic gasket, was still present and could not be removed. The tube with the wear indication along with an adjacent tube also in contact with the foreign object, were both removed from service by plugging and stabilization.

f. Total number and percentage of tubes plugged to date, and A total of eight tubes were plugged in SG 1 during this outage and none had been previously plugged. Eight of 8522 tubes or 0.094% of the tubes in SG 1 have been plugged to date. A total of two tubes were plugged in SG 2 during this outage and none had been previously plugged. Two of 8523 tubes or 0.024% of the tubes in SG 2 have been plugged to date.

g. The results of condition monitoring, including the results of tube pulls and in-situ testing.

Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 4 of 11 No tubes were pulled and no in-situ pressure tests were performed. The condition monitoring assessment concluded that the structural integrity, operational leakage and accident induced leakage performance criteria were not exceeded during the operating interval preceding 2R18.

Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 5 of 11 Table 2- Degradation Mechanisms and Available Inspection Techniques Degradation Location Likelihood Detection Best Estimate Sizing Technique, Tech. Sizing Tech. Sizing Technique, 2R18 Sample Size Mechanism of Near- Technique, ETSS Technique POD ETSS Number Correlation Regression Coef. Personnel Sizing Term Number (r2) (slope, intercept) Std Err (%TW)

Initiation Wear Tube to Tube Contact Low Bobbin, 96004.3 1.0 (>10%TW) Bobbin, 96004.3 0.98 0.96, 2.92 3.52, 0.86 100%, full length bobbin 0.98 (>40%TW) in both SGs

+Point, 96910.1 1.0 (>21%TW) +Point, 96910.1 0.92 1.01, 4.3 6.68, NA bobbin identified points of interest, +point / 0.115" 0.115", 96911.1 0.115", 96911.1 0.92 1.22, 0.07 7.49, 3.22 exams in both SGs 00 Wear Tube at Fan Bar Medium Bobbin, 96004.3 1.0 (>10%TW) Bobbin, 96004.3 0.98 0.96, 2.92 3.52, 0.86 1 %, full length bobbin (existing mechanism) 0.98 (>40%TW) in both SGs

+Point, 96910.1 1.0 (>21%TW) +Point, 96910.1 0.92 1.01, 4.3 6.68, NA bobbin identified points of interest, +point / 0.115" 0.115", 96911.1 0.115", 96911.1 0.92 1.22, 0.07 7.49, 3.22 exams in both SGs Wear Tube at Foreign Object Medium Bobbin, 96005.2 0.98 (>20%TW) Bobbin, 96005.2 0.17 0.27, 28.42 13.36, 1.73 100%, full length bobbin (existing mechanism) 0.88 (>40%TW) in both SGs

+Point, 96910.1 1.0 (>21%TW) +Point, 96910.1 0.92 1.01, 4.3 6.68, NA 0.115", 96911.1 0.115", 96911.1 0.92 1.22, 0.07 7.49, 3.22 +point/ 0.115" diagnostic exams Pitting Tube at Secondary Side Low Bobbin, 96005.2 0.98 (>20%TW), Bobbin, 96005.2 0.17 0.27, 28.42 13.36, 1.73 100%, full length in both Sludge/Deposits 0.88 (>40%TW) SGs Thinning Tube at support Low Bobbin, 96001.1 0.96 (>20%TW), Bobbin, 96001.1 0.74 0.97, -6.61 13.20, 0.89 100%, full length in both structures 0.98 (>40%TW) SGs Impingement Tube at support Very Low NA NA NA NA NA NA NA structures

[GA/SCC (OD) Tube Freespan, Non Very Low Bobbin, 96008.1 1.0 (>20%TW), Bobbin, 96008.1 0.55 0.74, 9.56 20.62, NA 100%, full length in both Volumetric/AxialDented Support 0.89 (>40%TW) SGs Intersections, Sludge Regions SCC (OD) Tube Freespan, Dented Very Low +Point, 21409.1 1.0 (>35%TW), +Point, 21409.1 0.15 0.33, 25.61 17.88, NA bobbin identified points of Axial and/or and Non Dented Support 0.98 (axial) 0.95 (% degraded area) (% degraded (% degraded (% degraded interest, +point exams in circumferential Intersections, Sludge (circ) area) area) area) both S&s Regions, Expansion Transition SCC (OD) Freespan including Very Low Bobbin, 24013.1 0.95 (>60%TW), NA NA NA NA 100%, full length bobbin Circumferential Dent > 5.0 volt in both SGs SCC (OD) Expansion Very Low +Point, 21410.1 1.0 (>42%TW) +Point, 0.02 0.13, 60.1 24.50 bobbin identified points of Transition 0.7 (<41%TW) 21410.1 interest, +point exams in both SGs Volumetric Freespan Medium +Point, 21998.1 1.0 (>10%TW) +Point, 21998.1 0.88 1.02, 5.81 6.28 +point/ 0.115" diagnostic exams

Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 6 of 11 Table 2 - Degradation Mechanisms and Available Inspection Techniques (continued)

Degradation Location Likelihood Detection Best Estimate Sizing Technique, Tech. Sizing Tech. Sizing Technique, 2R18 Sample Size Mechanism of Near- Technique, ETSS Technique POD ETSS Number Correlation Regression Coef. Personnel Sizing 2

Term Number (r ) (slope, intercept) Std Err (%TW)

Initiation SCC (OD) Dented Structural Very Low +Point, 22401.1 1.0 (>53%TW) +Point, 22401.1 0.02 1.3, 74.55 14.44 bobbin identified points of Supports interest, +point exams in

+Point, 22842.1 1.0 (44%TW) +Point, 22842.1 0.56 0.52, 0.03 0.26 both SGs SCC (ID) Tube Expansion Very Low +Point, 20510.1 0.96 (>30%TW) +Point, 20510.1 0.77 0.82, 2.83 7.69 +Point diagnostic exams Circumferential Transition, Within (%degraded area) (% degraded (% degraded (% degraded Tubesheet, Dents, Near area) area) area)

Seal Weld, Plugs +Point, 96701.1 0.67(21-41%TW) +Point 96701.1 0.85 0.84, 10.32 9.56 1.0 (>42%TW)

CC (ID) Tube Expansion Very Low +Point, 20511.1 1.0 (>37%TW) +Point, 20511.1 0.29 0.36, 18.91 7.60 +Point diagnostic exams Axial Transition, Within (%degraded area) (% degraded (% degraded (%degraded Tubesheet, Dents, Tack area) area) area)

Expansion, Plugs, <2.Ov Bobbin, 96012.1 Dents at TSP / Freespan

+Point, 96703.1 1.0 (>17%TW) +Point, 96703.1

(% degraded area) 0.83 0.90, 0,77 10.06 (Axial Length) 0.83 1.00, 0.13 0.28 5CC (ID) Low Row U-bends Very Low +Point, 96511.3 1.0 (>27%TW) +Point, 96511.3 0.22 0.34, 31.96 17.61, NA bobbin identified points of Axial and/or interest, +point exams in circumferential both SGs PWSCC Axial Dents Very Low +Point, 96703.1 1.0 (>10%TW) +Point, 96703.1 0.98 0.90, 7.56 15.28 Bobbin identified points of interest Wear Circumferential Groove Medium +Point, 27901.0 1.0 (>31%TW) +Point, 27901.0 0.98 1.05, -1.97 2.30 Additional diagnostic wear (foreign object Axial Groove +Point, 27902.0 1.0 (>8%TW) +Point, 27902.0 1.0 0.98, 1.89 2.32 techniques for loose part not present) Tapered Football +Point, 27903.0 1.0 (>21%TW) +Point, 27903.0 1.0 0.97, 2.80 2.11 sizing (freespan) Tapered Round Hole +Point, 27904.0 1.0 (>32%TW) +Point, 27904.0 0.98 1.00, 0.48 1.99 Flat Wear +Point, 27905.0 1.0 (>7%TW) +Point, 27905.0 1.0 1.09, -4.31 2.05 Tapered Wear +Point, 27906.0 1.0 (>11%TW) +Point, 27906.0 1.0 0.96, 1.67 1.43 45 deg. Tapered Wear +Point, 27907.0 1.0 (>13%TW) +Point, 27907.0 0.98 1.05, -2.10 2.59 Corrosion Support Structures Very Low Bobbin, no NA NA NA NA NA 100%, full length in both Induced Tube specific ETSS SGs Denting Plug Installation Plug/Tube Interface Low Engineering review plug installation parameters and plug video after installation; Use to date of 1-690 welded plugs. SG 1 Deficiencies

Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 7 of 11 Table 3 - Service Induced Indications SG I ROW COL VOLTS DEG PCT CHN LOCATION ELEVFROM 2 7 0.25 0 20 P5 TSH -0.07 3 8 0.15 0 13 P5 TSH -0.02 4 9 0.08 0 7 P5 TSH -0.02 5 10 0.08 0 8 P5 TSH -0.02 8 11 0.37 0 27 P5 TSH 0.09 40 155 0.37 115 11 P2 F06 -1.71 76 141 0.94 0 58 6 TSC 0.24 78 141 1.31 0 67 6 TSC 0.11 140 93 0.43 112 12 P2 F08 -0.54 SG 2 ROW COL VOLTS DEG PCT CHN LOCATION ELEVFROM 37 120 0.31 78 9 P2 F07 -0.7 28 5 0.25 0 29 6 01C -2.59 29 4 0.19 0 25 6 01C -1.86 40 81 0.17 79 30 6 TSH 0.12 59 10 0.16 0 23 6 01C -6.8 98 143 0.11 0 26 6 TSH 8.51 99 80 0.43 76 11 P2 F06 1.31 118 41 0.15 0 11 6 TSH 12.43 119 42 0.17 80 29 6 TSH 12.78 123 46 0.13 64 27 6 TSH 17.61 124 45 0.20 75 31 6 TSH 19.23 125 48 0.3 81 37 6 TSH 19.38 126 49 0.34 93 39 6 TSH 19.82

Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 8 of 11 Attachments Attachment Title 1 Acronyms 2 Millstone Power Station Unit 2 Steam Generator Arrangement

Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 9 of 11 Attachment I Acronyms B&W Babcock & Wilcox BLG Bulge CHN Channel COL Column DEG Degrees DEP Deposit DNG Ding DNT Dent ECT Eddy Current Testing EFPY Effective Full Power Years ELEV Elevation ETSS Examination Technique Specification Sheet FB Fan Bar F/L Full Length FOSAR Foreign Object Search and Retrieval IGA Intergranular Attack LPI Loose Part Indication MBM Manufacturing Burnish Mark MP 2 Millstone Unit 2 NQH Non-Quantifiable Historical Indication NQI Non-Quantifiable Indication OXP Over Expansion PCT Percent Through-Wall PLP Possible Loose Part POD Probability of Detection PTE Partial Tubesheet Expansion

%TW Percent Through-Wall RPC Rotating Pancake Coil SCC Stress Corrosion Cracking SG 1 Steam Generator Number 1 SG 2 Steam Generator Number 2 SLG Sludge SSI Secondary Side Inspection SVI Single Volumetric Indication TEC Tube End Cold-leg TEH Tube End Hot-leg TSC Top of Tube Sheet Cold-leg TSH Top of Tube Sheet Hot-leg VOL Volumetric Indication WAR Wear Indication

Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 10 of 11 Attachment 2 Millstone Power Station Unit 2 Steam Generator Arrangement

Serial No.16-127 Request for Withholding Proprietary Information Enclosure 6 Page 2 of 2 Serial No. 08-0627 Docket No. 50-336 EOC18 SG Tube Inspection Report Page 11of11

[REDACTED]