L-PI-10-099, Unit 2 180-Day Steam Generator Tube Inspection Report

Unit 2 180-Day Steam Generator Tube Inspection Report

ML103190514
Person / Time
Site:	Prairie Island
Issue date:	11/12/2010
From:	Schimmel M Northern States Power Co, Xcel Energy
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-PI-10-099
Download: ML103190514 (132)

Text

12 November 2010 L-PI-10-099 TS 5.6.7 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Unit 2 Docket 50-306 License No. DPR-60 2010 Unit 2 180-Day Steam Generator Tube Inspection Report In accordance with Prairie Island Nuclear Generating Plant (PINGP) Unit 2 Technical Specification 5.6.7 "Steam Generator Tube Inspection Report", Northern States Power Company, a Minnesota corporation (NSPM), doing business as Xcel Energy submits the enclosed report of steam generator tube inspections performed during the 2010 refueling and maintenance outage on Unit 2.

Summary of Commitments This letter contains no new commitments and no revisions to existing commitments.

Mark A. Schimmel Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc: Administrator, Region III, USNRC Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC Department of Commerce, State of Minnesota 1717 Wakonade Drive East

• Welch, Minnesota 55089-9642 Telephone: 651.388.1121

ENCLOSURE 1 Prairie Island Nuclear Generating Plant Unit 2 2010 Steam Generator Tube Inspection Report In accordance with Prairie Island Nuclear Generating Plant (PINGP), Unit 2 Technical Specification 5.6.7, Northern States Power Company, a Minnesota corporation (NSPM),

doing business as Xcel Energy submits this report of steam generator tube inspections performed during the 2010 refueling and maintenance outage on Unit 2 (2R26).

PINGP Unit 2 has two Westinghouse Model 51 Steam Generators (SGs) with approximately 51,500 square feet of heat transfer. Each SG has 3,388 mill annealed Alloy 600 u-tubes manufactured by Blairsville and Huntington which have an outside diameter of 0.875 inch and a nominal wall thickness of 0.050 inch. The tubes are configured in a square pitch of 1.281 inches with 46 rows and 94 columns. The tube u-bends vary in radius from 2.1 875 inches for a row 1 tube to 59.844 inches for a row 46 tube. The tube straight length is 378.230 inches for all tubes in the bundle. Rows 1 and 2 were subject to in situ stress relieving using Westinghouse thermal treatment process during the May 2000 refueling outage. The tubes were roll expanded at each tube end for approximately 2.75 inches leaving an open tubesheet crevice.

The tubesheet is A-508 Class 2 material 21.0 inches thick with Weld Deposit lnconnel cladding 0.188 inches thick (minimum) and a tube extension beyond the clad of 0.2 inches for an overall thickness of 21.4 inches. The tubes are supported by seven A-285 Grade C drilled tube support plates (TSPs) 0.750 inches thick and two anti-vibration bars (AVBs). The original AVB design consisted of two square (0.387" x 0.387")

lnconnel 600 bars with a alphatized chrome-plated surface, with a 44' bar nested in a 136' bar that intersected the tubes between one and four times. The replacement AVB design consisted of two hinged rectangular (0.750" x variable) stainless steel bars set at 25' and 60' from the centerline axis of the tube bundle that intersected the tubes between two and four times.

PINGP Unit 2 has a Technical Specification (T.S.5.5.8.f.2.b) approved repair method of hardroll expanding non-sleeved portions of tubes in the (hot leg) tubesheet in order to apply the F* and EF* criteria. Figure Iprovides an illustration of the original equipment manufacturers (OEM) tube-to-tubesheet configuration and each of the three possible reroll elevations (ARI, AR2 and ARE) utilized at PINGP.

TOP OF TUBESHEET 1

OEM AR I AR2 ARE ROLL ADD'L REUOU 'I ADWl REROLL 2 ADD'L ELEVATED REROLL Hydraulk expansion k optional and may or may not exist I- ' 1 f SCALE: NlA LOC: PIWP -- UNIT2 D W BY; $AR T I N : STEAM GEN WESHEET ELEVAIlONS I REV: 02 Figure 1 Reroll Configuration Page 2 of 131

Italicized text represents technical specification excerpts. Each excerpt is followed by the appropriate information intended to address each specific requirement and also includes additional details based on benchmarking recent submittals and Staff requests for additional information of peer Licensees. A legend of codes and field names is included at the end of the report.

5.6.7 Steam Generator Tube Inspection Report

a. A report shall be submitted within 180 days after initial entry into MODE 4 following completion of an inspection performed in accordance with the Specification 5.5.8, Steam Generator (SG) Program.

Initial entry into MODE 4 occurred on May 19, 2010, dictating submittal of this report on or before November 15,2010.

The report shall include:

1. The scope of inspections performed on each SG, Table 1 and the text that follows, provides the scope of inspections performed during 2R26.

TABLE 1 SCOPE TECHNIQUE S/G 21 S/G 22 Full Length0 Bobbin 100%(3109) 100%(3114)

Rows 1 through 4 U-Bends MRPC@ 100% (348) 100% (349)

Rows 5 through 8 U-Bends MRPC@ 33% (115) 33% (125)

Hot Leg Tubesheets MRPC@ 100%(3109) 100%(3114)

Hot Leg Roll Plugs MRPC@ 25% (73) 25% (66)

Cold Leg Tubesheets MRPC@ 20% (622) 20% (624)

Supplemental@and PID MRPC@ 100% (613) 100% (528)

Baseline new Re-Rolls ~obbin/MR~C@ 100% (439) 100% (315)

Post In Situ Pressure Test MRPC@ 100% (1) NIA Plug Visual 100% (279) 100% (274)

Upper InternalsO Visual NIA 100%

Top of Tubesheet@ Visual NIA 100%

PLPO Visual 1 9 General Notes:

The scope of inspections is provided as a percentage followed by the total number of tests parenthetically where practical.

For clarity, only three digit codes that require supplemental MRPC@testing and utilized during 2R26 are included in Q below.

DNT is called at 2 2.0 Volt, and all the other codes in O below (DSI, INR, MBM, NQI, PLP and PSI) do not have a voltage calling criteria.

Specific Notes:

0 Except the bend portion of rows 1 through 4 u-bends.

Supplemental MRPC@testing (including the +point@coil) was based on bobbin results to inspect all, DNI, TSP DNT r 2.OV, Freespan DNT 2 5.OV, DSI, TSP INR 2 1.5V, MBM, NQI, PLP (Bound MRPC PLP's), PSI, Cold Leg Thinning 2 40% or <

40% and r 1.5V signalslindications to detect latent tube degradation, to refutelconfirm, to characterize (axial, circumferential or volumetric) andlor obtain additional length and depth measurements.

O Inspection of upper internals included the Swirl Vane Moisture Separators, Feed Ring Hangers, Holes, and Plugs, Upper Transition Girth Weld, Thermal Sleeve, Magnetic Particle Examine of the Feedwater Nozzle, Ultrasonic inspections of Feed Ring Tee, and Feedwater to Reducer Welds Downcomer, and other upper bundle components per NRC Generic Letter 97-06.

@ Tube lane and periphery of the tube bundle inspected using Camera Transporter System.

O Locating new possible loose part (PLP) indications for investigation and possible removal based on eddy current results.

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4 0

t

2. Active degradation found, Primaw Side lns~ections-Thinning, wear, outside diameter stress corrosion cracking (ODSCC) and primary water stress corrosion cracking (PWSCC) were found in both SGs during 2R26 and are captured within the corrective action process. These Mechanisms have been previously reported.

Secondary Side lns~ections - None found

3. Nondestructive examination techniques utilized for each degradation mechanism, Table 2 and the text that follows, provides the Electric Power Research Institute (EPRI) Examination Technique Specification Sheet (ETSS) (techniques) utilized during 2R26 for existing and potential degradation and proactive sampling.

TABLE 2 MECHANISM ORIENTATION LOCATION TECHNIQUE Wear Volumetric AVBa, TLBD0 and TSPa 96004.3 Rev. 12 Wear Volumetric FOIPLPO 27091.2 Rev. 0 Pitting Volumetric Sludge Pile0 96005.2 Rev. 9 Thinning Volumetric Non-dented TSPO and Sludge Pile0 96001.1 Rev. 11 HotO and Cold@ Leg Tubesheet IGNSCC Axial Crevice, Freespan Dent (25V)Q and 21409.1 Rev. 6 TSP Dent (>2V)Q IGNSCC Axial Sludge Pile0 128413 Rev. 2 IGNSCC Axial Non-dented (<2V) Freespana 128412 Rev. 2 IGNSCC Axial Freespan Dent (22V & <5V)O 24013.1 Rev. 2 128411 Rev. 2 and IGNSCC Axial Non-dented (<2V) TSPO GL 95-05 IGNSCC Circ. Roll Transition0 and TSP Dent (>2V)0 21410.1 Rev. 6 Hot@and Cold@ Leg Tube End and PWSCC Axial 2051 Rev. 8 HotO and Cold@ Leg Roll Transition PWSCC Axial TSP Dent (22V)O 20511.1 Rev. 8 PWSCC Axial U-bend@ 96511.2 Rev. 16 PWSCC Axial Hot Leg Roll Plug Transition@ 99-TR-FSW-01O@

Hot@and Cold@ Leg Tube End and PWXC Circ. 20510.1 Rev.

HotO and Cold@ Leg Roll Transition PWSCC Circ. TSP Dent (22V)O 20510.1 Rev. 7 PWSCC Circ. U-bend0 96511.2 Rev. 16 PWSCC Circ. Hot Leg Roll Plug Transition@ 99-TR-FSW-010@

O Active is synonymous with the term "existing" degradation that is found in the EPRl Steam Generator Integrity Assessment Guidelines. Therefore the classical definition applies (i.e.,

one historical or current indication equates to active).

.O Potential degradation based on internal and external operating experience on steam generators with similar designs, operating conditions and materials.

@ Proactive Sampling is used to challenge engineering assumptions such as material susceptibility or when the Arrhenius equation predicts susceptibility in a future sequential period. These samples are considered informational sample plans that are not subject to the periodicity requirements of T.S.5.5.8.d.3.

@ 99-TR-FSW-010 Rev. 00 "Appendix H Qualification for Eddy Current Testing Steam Generator Mechanical Tube Plugs" ABBCE, November 2,1998.

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4. Location, orientation (if linear), and measured sizes (if available) of service induced indications, Tables 3 and 4 provide the location and measured size of each reported indication in each steam generator respectively for degradation found during 2R26 that was sized with the bobbin coil. All the tubes in these two tables were returned to service using the depth based criteria for tube repair.

Tables 5 and 6 provide the location, orientation and length (if available) of each reported indication in each steam generator respectively for degradation found during 2R26 that is located below the F* distance of a tube that has never been repaired by the rerolling process. These tubes are considered F*O tubes and all the tubes in the two tables were returned to service using the F* Alternate Repair Criteria (ARC) without any additional rerolling during 2R26.

Tables 7 and 8 provide the location, orientation and length (if available) of each reported indication in each steam generator respectively for degradation found during 2R26 (or known to exist from previous inspections) that is located below the F* distance of a tube that was repaired by rerolling in a previous outage at the first reroll repair location (approximately 3.75" to 5.00" above the tube end). These tubes are considered F*l tubes and all the tubes in the two tables were returned to service using the F* ARC without any additional rerolling during 2R26.

Tables 9 and 10 provide the location, orientation and length (if available) of each reported indication in each steam generator respectively for degradation found during 2R26 (or known to exist from previous inspections) that is located below the F* distance of a tube that was repaired by rerolling in a previous outage at the second reroll repair location (approximately 5.75" to 7.00" above the tube end).

These tubes are considered F*2 tubes and all the tubes in the two tables were returned to service using the F* ARC without any additional rerolling during 2R26.

Tables 11 and 12 provide the location, orientation and length (if available) of each reported indication in each steam generator respectively for degradation found during 2R26 (or known to exist from previous inspections) that is located below the Ef* distance of a tube that was repaired by rerolling in a previous outage at the elevated reroll repair location (approximately 16.38" to 18.38" above the tube end).

These tubes are considered EF* tubes and all the tubes in the two tables were returned to service using the EF* ARC without any additional rerolling during 2R26.

Tables 13 and 14 provide the location, orientation and length of each reported indication in each steam generator respectively for degradation found during 2R26 that is located within (and in some cases also below) the F* distance of a tube that has never been repaired by rerolling in a previous outage. These tubes were successfully repaired during 2R26 at the first reroll repair location (approximately 3.75" to 5.00" above the tube end). These tubes are considered new F*l tubes and all the tubes in the two tables were returned to service using the F* ARC with a new reroll installed during 2R26.

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Tables 15 and 16 provide the location, orientation and length (if available) of each reported indication in each steam generator respectively for degradation found during 2R26 (or known to exist from previous inspections) that is located within (and in some cases also below) the F* distance of a tube that was either successfully repaired by rerolling in a previous outage or failed the acceptance criteria during the current outage at the first reroll repair location. These tubes were successfully repaired during 2R26 at the second reroll repair location (approximately 5.75" to 7.00" above the tube end). These tubes are considered F*2 tubes and all the tubes in the two tables were returned to service using the F* ARC with a new reroll installed during 2R26.

Tables 17 and 18 provide the location, orientation and length (if available) of each reported indication in each steam generator respectively for degradation found during 2R26 (or known to exist from previous inspections) that is located within (and in some cases also below) the F* distance of a tube that was successfully repaired by rerolling in a previous outage at the second reroll repair location. These tubes were successfully repaired during 2R26 at the elevated reroll repair location (approximately 16.38" to 18.38"above the tube end). These tubes are considered EF* tubes and all the tubes in the two tables were returned to service using the EF*

ARC with a new reroll installed during 2R26.

Tables 19 and 20 provide the location, orientation (if linear) and measured sizes (if available) of indications in each steam generator respectively for tubes exceeding the plugging or repair criteria during 2R26. These tubes were all removed from service by plugging during 2R26.

A legend of fields and codes with briif explanations is provided at the end of this enclosure for ciarifiation purposes.

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TABLE 3 Page 9 of 131

TABLE 3 Page 10 of 131

TABLE 3 Page 11 of 131

TABLE 3 Page 12 of 131

TABLE 4 Page 13 of 131

TABLE 4 Page 14 of 131

TABLE 4 Page 15 of 131

TABLE 4 Page 16 of 131

TABLE 5 STEAM GENERATOR 21 HISTORICAL F*O Page 17 of 131

TABLE 5 STEAM GENERATOR 21 HISTORICAL F*O Page 18 of 131

TABLE 5 STEAM GENERATOR 21 HISTORICAL F*O Page 19 of 131

TABLE 5 STEAM GENERATOR 21 HISTORICAL F*O Page 20 of 131

TABLE 6 Page 21 of 131

TABLE 6 Page 22 of 131

TABLE 6 STEAM GENERATOR 22 HISTORICAL F*O Page 23 of 131

TABLE 6 156 158 13 88 1.67 SAN TRH -1.83 -1.75 0.08 157 159 9 . 90 , 0.77 SAl TRH -2.62 -2.54 0.08 158 160 6 91 1 0.89 SAN TRH -2.58 -2.50 0.08 159 161 7 91 , 1.09 SAI TRH -2.62 -2.54 0.08 160 162 6 , 94 1.17 MAN TRH -2.66 -2.58 0.08 161 163 , 7 94 0.88 . SAN TRH -2.54 -2.43 0.11 Page 24 of 131

TABLE 7 Page 25 sf 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*1 Page 26 of 131

TABLE 7 Page 27 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F

• l Page 28 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*1 Page 29 of 131

Page 30 of 131 TABLE 7 Page 31 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*l Page 32 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*l Page 33 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*1 Page 34 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*1 Page 35 of 131

Page 36 of 131 TABLE 7 STEAM GENERATOR 21 HISTORICAL F1l Page 37 of 131

Page 38 of 131 TABLE 7 STEAM GENERATOR 21 HISTORICAL F*l Page 39 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*l Page 40 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*1 Page 41 of 131

Page 42 of 131 TABLE 7 STEAM GENERATOR 21 HISTORICAL F*l Page 43 of 131

Page 44 of 131 TABLE 7 Page 45 of 131

I TABLE 7 Page 46 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*l Page 47 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*l Page 48 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F

• l Page 49 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*1 Page 50"of 131

Page 51 of 131 TABLE 7 Page 52 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F*1' Page 53 of 131

TABLE 7 STEAM GENERATOR 21 HISTORICAL F'1 1 1093 1 '14401 23 1 74 1 IBH 1 -0.90 I 1 I Page 54 of 131

TABLE 7 I

Page 56 of 131

Page 57 sf 131 Page 58 of 131 TABLE 8 STEAM GENERATOR 22 HISTORICAL F*l Page 59 of 131

Page 60 of 131 TABLE 8 Page 61 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F*l Page 62 of 131

TABLE 8 Page 63 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F*l Page 64 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL Ffl Page 65 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F'1 328 383 12 45 1 SAD 1BH 4.90 329 384 13 ] 45 1 1.78 1 SAN 1BH 25 08 0.1 7 Page 66 sf 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F*1 Page 67 of 131

TABLE 8 Page 68 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F*l Page 69 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F*1 Page 70 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F*1 Page 71 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F*l 1 558 1672 1 12 1 6 0 1 ] SAD 1 1BH -0.99 1 I Page 72 of 131

Page 73 of 131 TABLE 8 STEAM GENERATOR 22 HISTORICAL F'1 Page 74 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F*1 Page 75 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F"1 Page 76 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F*l Page 77 of 131

Page 78 of 131

TABLE 8 STEAM GENERATOR 22 HISTORICAL F*l Page 80 of 131

TABLE 9 Page 81 of 131

TABLE 9 STEAM GENERATOR 21 HISTORICAL F*2 Page 82 of 131

TABLE 9 STEAM GENERATOR 21 HISTORICAL F*2 Page 83 of 131

TABLE 9 STEAM GENERATOR 21 HISTORICAL F*2 Page 84 of 131

Page 85 of 131 TABLE 9 STEAM GENERATOR 21 HISTORICAL F.2 Page 86 of 131

Page 87 .of 131 TABLE 9 STEAM GENERATOR 21 HISTORICAL F*2 Page 88 of 131

Page 89 of 131 TABLE 9 STEAM GENERATOR 21 HISTORICAL F*2 1 209 1 480 1 5 j 70 1 2.64 j MAN 1 2BH J -3.45 j -3.23 1 0.22 j Page 90 of 131

TABLE 9 STEAM GENERATOR 21 HISTORICAL F*2 Page 91 of 131

TABLE 10 STEAM GENERATOR 22 HISTORICAL F*2 Page 92 of 131

TABLE 10 STEAM GENERATOR 22 HISTORICAL F*2 Page 93 of 131

TABLE 10 STEAM GENERATOR 22 HISTORICAL F"2 Page 94 of 131

TABLE 10 STEAM GENERATOR 22 HISTORICAL F*2 Page 95 of 131

TABLE 10 Page 96 of 131

Page 97 of 131 TABLE 11 Page 98 of 131

TABLE 12 I TUBE # I IND # I 1 1 21 STEAM GENERATOR 22 HISTORICAL EF*

ROW I COL I VOLTS I PCT ( LOCATION I ELEV-FROM 22 SAD EBH -14.14 ELEV-TO 1 LENGTH 1 1 2 21 22 3.13 MAN EBH -9.42 2 3 14 40 SAD EBH -14.25 7

2 4 14 40 0.20 SAN EBH -1 1.86 2 5 14 40 1.49 SAN EBH -9.57 3 6 13 41 MAD EBH -14.15 3 7 13 41 0.37 SAN EBH -10.53 Page 99 of 131

TABLE 13 STEAM GENERATOR 21 NEW F.1 Page 100 of 131

TABLE 13 STEAM GENERATOR 21 NEW F.1 Page 101 of 131

TABLE 13 STEAM GENERATOR 21 NEW F*1 Page 102 of 131

TABLE 13 STEAM GENERATOR 21 NEW F*1 Page 103 of 131

Page 104of "11 TABLE 13 STEAM GENERATOR 21 NEW F*l Page 105 of 131

TABLE 13 STEAM GENERATOR 21 NEW F'1 Page 106 of 131

TABLE 14 STEAM GENERATOR 22 NEW F"1 Page 107of 131

TABLE 14 STEAM GENERATOR 22 NEW F'4 TRH 0.07 1 0.16 1 0.09 1 Page 108 of 131

TABLE 14 STEAM GENERATOR 22 NEW F*l 1 133 1 144 ] 34 1 4 9 1 0.81 1 SAI I TRH I 4.06 1 0.05 ]

Page 109 of 131

TABLE 14 STEAM GENERATOR 22 NEW F"1 Page 110 of 131

TABLE 14 STEAM GENERATOR 22 NEW F 1 Page 111 of 131

Page 112 of 131 TABLE 15 I

I Page 113 of 131

TABLE 15 STEAM GENERATOR 21 NEW F.2 36 J 95 ] 6 1 25 1 0.36 j SAl llBH I 1.17 1 1.20 j 0.03 37 96 1 10 25 1 1 SAD ] 1BH -1.29 4 1 Page 114 of 131

TABLE 15 STEAM GENERATOR 21 NEW F*2 Page 115 sf 131

TABLE 15 Page 116of 131

TABLE 15 I

Page 117 of 131

TABLE 15 STEAM GENERATOR 21 NEW F.2 Page 118 of 131

TABLE 16 STEAM GENERATOR 22 NEW F'2 Page 119 of 131

TABLE 16 STEAM GENERATOR 22 NEW F*2 56 95 13 86. SAD 1BH -1.32 56 96 . 13 86 . 0.50 , MA1 , 1BH 1.47 1.59 0.12 Page 120of131

TABLE 17 STEAM GENERATOR 21 NEW EF*

Page 121 of 131

TABLE 17 STEAM GENERATOR 21 NEW EF*

Page 122 of 131

TABLE 18 STEAM GENERATOR 22 NEW EF' 5 14 17 80 2.03 SAN 2BH -0.93 -0.75 0.18 ,

5 15 17 , 80 0.36 SAI 2BH 1.14 1.26 0.12 Page 123 of 131

TABLE 19 STEAM GENERATOR 21 NEW PLUGS Page 124 of 131

TABLE 19 STEAM GENERATOR 21 NEW PLUGS Page 125 of 131

TABLE 19 STEAM GENERATOR 21 NEW PLUGS Page 126 of 131

TABLE 19 STEAM GENERATOR 21 NEW PLUGS Page 127 of 131

TABLE 20 STEAM GENERATOR 22 NEW PLUGS Page 128 of 131

5. Number of tubes plugged or repaired during the inspection outage for each active degradation mechanism, Table 21 provides the number of tubes plugged and repaired during 2R26.

TABLE 21

6. Total number and percentage of tubes plugged or repaired to date, Table 22 provides the total number and percentage of tubes plugged and repaired to date.

TABLE 22 PLUG F*O F*l F*2 EF*

S/G SG 21 SG 22 SG 21 SG 22 SG 21 SG 22 SG 21 SG 22 SG 21 SG 22 TOTAL 321 290 191 161 1506 1063 348 182 47 11

, PERCENT 1 9.47% 8.56% 5.64% 4.75% 44.45% 31.38% 10.27% - 5.37% 1.39% 0.32% .

7. The results of condition monitoring, including the results of tube pulls and in-situ testing, Condition monitoring and operational assessment evaluations of steam generator tubing at Prairie Island Unit 2 were performed without the need for tube pulls. The observed severity of degradation at the end of Cycle 25 was evaluated to determine if structural and leakage integrity requirements were maintained. The expected severity of tubing degradation at the end of Cycle 26 was projected to determine if required structural and leakage integrity margins will be maintained during the next cycle of operation. The scope of this evaluation included all forms of observed degradation.

I The observed degradation at the EOC 25 outage was evaluated in a manner consistent with NEI 97-06 and EPRl guidance. Observed degradation did not i present serious challenges to the deterministic (3AP or 1.4 SLB) structural margin requirement at the end of the last cycle of operation or challenge required leakage integrity limits under postulated accident conditions. A conservative approach to I operational assessment leads to a similar expectation for the next cyde of operation. I E

Condition monitoring structural and leakage integrity requirements were met for the last cycle of operation. In situ pressure testing of a freespan axial ODSCC in tube Page 129 of 131 P

R3C38 was successfully completed. Operational assessments using both simplified and advanced techniques show that structural and leakage integrity requirements will be maintained over the next inspection cycle. These analyses were performed for a cycle length of 1.75 EFPY. The expected cycle length is 1.714 EFPY. The projected SLB leakage at EOC 26 is entirely from degradation left in service according the F* and EF* alternate repair criterion. The projected steam line break (SLB) leakage is 0.40 gpm in SG 21 and 0.27 gpm in SG 22.

8. The effective plugging percentage for all plugging and tube repairs in each SG, There have been no repairs performed on these SGs that affect the heat transfer area; therefore the effective plugging percentage is equivalent to that reported in Table 22.

9. Repair method utilized and the number of tubes repaired by each repair method, and During 2R26 the Technical Specification (T.S.5.5.8.f.2.b) approved repair method of hardroll expanding non-sleeved portions of tubes in the (hot leg) tubesheet in order to apply the F* and EF* criteria was applied. Table 23 summarizes the number of tubes repaired at each elevation during 2R26.

TABLE 23

~ - ~ - --

ELEVATION SG 21 SG 22 .

1 R e ~ a iLocation r 270 228 2"(' Repair Location 120 56 Elevated Repair Location 18 5

10. The results of inspections performed under Specification 5.5.8.d.3 for all tubes that have flaws below the F* or EF* distance, and were not plugged. The report shall include: a) identification of F* and EF* tubes, and b) location and extent of degradation.

The inspection results of tubes returned to service using the F* and EF* ARC'S were provided in Tables 5 through 18 of item 4 above. Table 24 summarizes the current cumulative number of tubes with the F* and EF* ARC applied and returned to service.

TABLE 24 I ELEVATION I SG 21 1 SG 221 Page 130 of 131

LEGEND OF FIELDS AND CODES FIELD EXPLANATION TUBE # Distinct ROWICOL combination within each Table IND # Distinct ROWICOULOCATION combination within each Table ROW Row number of tube location COL Column number of tube location VOLTS Measured Voltage PCT Measured percent or three digit code - see below LOCATION Affected landmark - see below ELEV-FROM Measurement in inches from the centerline of the landmark to the center of the bobbin coil indication or the lower edge of the rotating coil indication ELEV-TO Measurement in inches from the centerline of the landmark to the upper edge of the rotating coil indication LENGTH Calculated Length (ELEV-TO - ELEV-FROM)

FIELD CODE EXPLANATION PERCENT DNT Dent DSI Distorted Support signal with lndication INR lndication Not Reportable IRR Inadvertent ReRoll MAD Multiple Axial indications not Detectable MA1 Multiple Axial lndications MAN Multiple Axial indications No change MBM Manufacturing Burnish Mark MCD Multiple Circumferential indications not Detectable MVl Multiple Volumetric Indications NQI Non-Quantifiable lndication PLP Possible Loose Part PSI Possible Support lndication SAD Single Axial indication not Detectable SAI Single Axial lndication SAN Single Axial indications No change SCD Single Circumferential indication not Detectable SCN Single Circumferential indication No change SVI Single Volumetric lndication SVN Single Volumetric indication No change 0-100 As measured percent through wall LOCATION TEH Tube end hot (primary face)

YRH original Tube Roll Hot leg 1BH 1 additional reroll Bottom roll transition Hot leg 2BH 2"d additional reroll Bottom roll transition Hot k g EBH Elevated reroll Bottom roll transition Hot leg TSH Tube sheet hot (secondary face)

O?H  ? =First through Seventh tube support plate on hot leg side NV?  ? = First through Fourth anti-vibration bar 0%  ? = First through Seventh tube support plate on cold leg side TSC Tube sheet cold (secondary face)

TEC Tube end cold (primary face)

Page 131 of 131