ML17333A956

Generator U1R97 Condition Monitoring & Operational Assessment.

ML17333A956
Person / Time
Site:	Cook
Issue date:	07/21/1997
From:	INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:
Shared Package
ML17333A955	List: ML17333A954 ML17333A956 ML17333A957
References
AEP:NRC:1166AI, NUDOCS 9707300003
Download: ML17333A956 (34)

Text

ATTACHMENT 1 TO AEP:NRC: 1166AI COOK STEAM GENERATOR U1R97 CONDITION MONITORING AND OPERATIONAL ASSESSMENT 9707300003 97072i PDR ADQCK 050003l.5 P PDR

t ATTACHMENT1 TO AEP:NRC:1166AI Table of Contents 1.0 Introduction 2.0 Executive Summary 3'.0 Secondary Side Pressure Test at EOC-15 4.0 Evaluation of Tube Degradation at EOC-15 5.0 Tube Integrity Evaluation at EOC-15 13 6.0 Cycle 16 Operability Review 20 Page 2 of 26

ATTACHMENT1 TO AEP:NRC:1166AI I .0 Introduction The Cook Unit 1 steam generators were inspected with various types of eddy current testing methods at the EOC-15 1997 scheduled outage. The inspection was the most thorough ever performed at Cook Unit 1, and included the following for each steam generator:

o 100% full length BC 100% full depth hot leg tubesheets from TEH to TSH + 3" with RPC o 20% full depth cold leg tubesheets from TEC to TSC + 3" with RPC o 100% U-bend exam of rows 1 and 2 (expanded to row 3 in one SG) with RPC o Inspection of distorted or non-quantifiable BC signals with RPC Inspection of all dents at support plates with bobbin voltage ) 5.0 volts Inspection of all support plate residuals that could mask a BC signal o 100% plus point inspection of all inservice HEJ sleeves 2.0 Executive Summary A number of different tube degradation mechanisms were identified and characterized by the ECT methods utilized during the inspection. In some cases, a non-qualified sizing technique may have been utilized to aid in the characterization of the indications for in-situ selection processes and verification of tube integrity. Results of the ECT and this assesment noted no indications were of such severity that the steam generators would not have maintained tube integrity for the EOC-15, based upon RG 1.121 requirements. The evaluation for tube integrity mainly focused on leakage, as the location of the of majority the indications within the tubesheet eliminated the tube rupture concern. Based upon the in-situ testing performed during the U1R97, the steam generator tubes maintained adequate margin against tube rupture under bounding conditions and also against the allowable leakage under postulated accident conditions for cycle 15 operation.

Based upon the results of in-situ testing, the population of indications at EOC-15, historical review of past ECT data, and evaluations presented in this report, the Unit 1 steam generator tubes will maintain adequate margin against tube rupture and accident leakage requirements specified in RG 1.121 through the end of the current cycle (cycle 16).

3.0 Secondary Side Pressure Test at EOC-15 Based upon the shutdown leakage values that were calculated by plant monitoring equipment, a secondary side pressure test was performed on all four steam generators to pinpoint primary-secondary side leakage identified during operation. The testing was performed by holding a nitrogen overpressure on the secondary side which created a delta P of approximately'400 psi'.

The estimated breakdown of the leak rates prior to shutdown, was as follows:

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3 ATTACHMENT1 TO AEP:NRC:1166AI SG 11 - 25.63 gpd SG 12 - 0.59 gpd SG13- 2.31gpd SG 14- 1.13 gpd The results, of the test were consistent with the calculated leak rates obtained during operation, in that most leakage observed during the test was observed in SG 11. The following table is a summary of the leaking locations and the status of the tubes during cycle 15 operation.

Table 3-1 Identified Leaking Locations During Secondary-Primary Pressure Testing

'G Row Column Leak Evaluation Tube Status/Likel Source 16 27 Dri in HEJ Sleeve/Tra d residual water 18 37 Dri in Hard Rerolled 1995/Reroll Joint 31 37 Dri in HEJ Sleeve/Tra d residual water 20 41 Dri in Rerolled 1995/ODSCC TSH 47 Dri in Inservice Tube/PWSCC U-bend 54 Dri in Rerolled 1995/Reroll Joint 20 71 Dri in Rerolled 1995/Reroll Joint 13 31 Moist Rerolled 1995/Reroll Joint 44 1 dri /25 sec. Rerolled 1995/Reroll Joint 50 1 dri /3 min. Rerolled 1995/Reroll Joint 14 29 19 1 dri Inscrvice Tube/ODSCC TSH 26 48 1dri /2min. Inservice Tube/ODSCC TSH 30 49 1dri /6 min. Inservice Tube/ODSCC TSH

• - Location was dripping from C/L only; 4.0 Evaluation of Tube Degradation at EOC-15 4.1 PWSCC in U-bends The original U1R97 scope for the U-bend inspection was a 100% inspection of rows 1 and 2 in SG 11. During the previous outage, a sample inspection was conducted in one SG (SG 14) for U-bend PWSCC, using a rotating coil technique. No indications were detected at that time.

Based upon the detection of axial and circumferential indications in row 1 of SG 11, the U1R97 scope was expanded to encompass 100% of the row 1 and 2 U-bends in the remaining steam generators. This inspection identified six, eight, and eight tubes with indications in SGs 11, 12, and 13, respectively. No indications were detected in SG 14, which was consistant with inspection results from the previous outage.

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ATTACHMENT1 TO AEP:NRC:1166AI SG 11 also had two detected indications in the row 2 U-bend, therefore, the scope of the inspection was conservatively expanded in that steam generator to 100% of row 3 tubes. As expected, no row 3 indications were detected in the U-bend region. No other SGs contained row 2 U-bend indications.

The following table summarizes the information pertaining to the PWSCC indications that were detected in the low row U-bend region.

Table 4-1 U-bend Indication Data SG Row Column Location of Orientation of RPC Size of Indication Indication Volta e Indication 47 07C + 5.06" Circumferential 17.71 0.84"/111'1 1 43 07H + 8.86" Circumferential 4.32 0.54 "/714 45 07H + 5.22" Circumferential 2.80 0.55 "/72'.65 84 07H + 10.2" Circumferential 7.89 "/86'.22" 69 07H + 14.1" Axial 2.06 86 07H + 6.06" Axial 2.84 0.28" 72 07H + 9.81" Circumferential 2.58 0.35 "/46'.33" 12 1 73 07H + 10.02" Axial 1.61 07H + 10.68" Circumferential 2.27 0 35 "/46o 79 07H + 9.75" Axial 1.24 0.45" 80 07H + 4.20" Axial 3.42 0.40" 82 07H + 9.12" Axial 3.82 0.33" 12 1 84 07H + 8.81" Axial 79 0.27" 85 07H + 8.74" Axial .66 0.30" 07H + 9.56" Axial 1.62 0.30" 86 07H + 8.60" Axial .89 0.27" 07H + 9.37" Axial 1.57 0.30" 21 07H + 4.32" Circumferential 0.85 23 07H + 9.66" Circumferential 3.27 "/112'.48"/63'.77 27 07H + 4.34" Circumferential "/102'.50" 13 1 31 07H + 4.19" Axial 6.34 40 07H + 3.80" Circumferential 16.30 0.68 "/89'.73 Same plane 21.20

"/96'.60 77 07H + 6.99" Circumferential 5.06 81 07H + 10.95" Circumferential 11.32 86 07H + 10.49" Axial 18.09 "/79'.78"/102'ocation 1-47 in SG 11 was selected as a in-situ test candidate b-.cause it was a known leaking location and offered an indication with a (relatively) high voltage magnitude and length. Location 1-40 in SG 13 was selected for in-situ testing because it was the next bounding indication for characterization of leakage through a U-bend circumferential indication. The axial indications, locations 1-86 in SG 13 and 1-80 in SG 12 were Page 5 of 26

ATTACHMENT1 TO AEP:NRC:1166AI selected as the bounding axial indications in the U-bend, based upon voltage and length.

The following table represents the locations tested and the results of the testing.

Table 4-2 Results of U-bend In-situ Testing SG Row Column Indication Pressure Test Results ( d)

NOP MSL13 3x NOP 47 Circ. 0.0 0.71 13.56 12 80 Axial 0.0 0.0 0.0 13 40 Circ 0.0 0.0 0.0 86 Axial 11.84 44.84 628.9 Based upon these results, all of the indications met the structural requirements of RG 1.121, with respect to tube burst. In order to address accident leak rates at EOC-15, all of the U-bend circumferential indications were conservatively assigned an accident leak rate of 0.71 gpd, even though location 1-40 had zero leakage and bounded the remaining population of circumferential indications. The U-bend axial indications were assigned a conservative leak rate of 44.84 gpd for each indication, except for location 1-80, where testing showed zero leakage, and bounded the remaining population of axial indications.

4.2 PWSCC in OEM Roll Transition The TSH inspection included all of the inservice OEM roll transition regions of the tubes in the hot leg. The inspection detected a total of 635 tubes with axial PWSCC type indications, distributed as follows: 171 in SG 11, 128 in SG 12, 248 in SG 13, and 88 in SG 14.

The number of indications was much larger than expected. This is attributed to the enhanced ECT inspection technique utilized in the current outage and the previously identified issues with the analysis of the Cecco-5 data in the previous inspection. The indications were typical in size and characterization to those previously detected in the Unit 1 steam generators. No indications were characterized as being of sufficient severity to potentially not meet the leakage requirements of RG 1.121, nor were they expected to be, based upon in-situ testing at other PWR SGs and laboratory testing.

However, due to the sheer magnitude of the population of tubes affected and as a baseline for Unit 1, in-situ test candidates were chosen based upon the largest voltage, axial length and location within the roll transition. These indications are not a concern for rupture due to confinement within the tubesheet but two indications were conservatively selected for in-situ testing to quantify the population's 'eakage Page 6 of 26

ATTACHMENT1 TO AEP:NRC:1166AI contribution during accident conditions. The following table provides the indications and the results of the testing.

Table 4-3 Results of PWSCC in Roll Transition In-situ Testing SG Row Column Location of RPC Length Results of In-situ Testin Indication Volta c NOP MSLB 3 x NOP 11 3 59 BRT + 0.14" 8.39 0.41" 0.0 0.0 N/A 25 64 BRT + 0.19" 4.97 0.45" 0.0 0.0 N/A Based upon the results of the in-situ testing pe;formed on axial PWSCC in OEM roll transitions, no leakage at EOC-15 is attributed to these types of indications. This further supports the industry's data that these indications are very tight and leakage of this type is very minute.

4.3 PWSCC in Reroll Roll Transition The RPC inspection of inservice rerolled tubes identified a total of 55 locations that developed new axial PWSCC in the reroll roll transition. The appearance of this damage mechanism is not unexpected due to the increased stress applied to the tube during the process. It also confirms the need for continuing inspection of rerolled tubes in future inspections.

The breakdown of the locations is as follows: 16 in SG 11, 4 in SG 12, 29 in SG 13, and 6 in SG 14. These indications were screened utilizing voltage, length and proximity to the roll transition as criteria for selection of in-situ pressure testing. The majority of the population had very small lengths and the voltages were < 1.5 volts from RPC.

Locations 11-35 in SG 11 and 21-25 in SG 12 were selected as the best in-situ candidates based upon the aforementioned screening criteria. These indications bounded the remaining population of tubes with this type of degradation.

Table 4-4 Results of PWSCC in Reroll Roll Transition Inwitu Testing SG Row Col Location of RPC Length Results of In-situ Testin Indication Volta e NOP MSLB 3 x NOP 11 35 BRT + 0.34" 5.52 0.21" 0.0 4.2 N/A 12 21 25 BRT + 0.12" 11.16 0.36" 0.0 0.0 N/A Based upon the results of the in-situ testing performed on axial PWSCC in reroll roll transitions, a conservative accident leak rate of 4.2 gpd is applied to these indications detected at EOC-15, even though the testing of location 21-25 bounded the remaining population of indications.

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ATTACHMENT1 TO AEP:NRC:1166AI 44 ODSCC in Crevice/TTS During the full depth inspection of the hot leg tubesheet region, indications were also identified at or near the secondary face of the tubesheet by both bobbin coil and RPC techniques. Some of these indications were large in signal voltage response from both examinations. These indications were assessed to determine their impact on SG tube integrity for the last cycle. The total number of tubes with indications detected was 829, with 245 in SG 11, 99 in SG 12,206 in SG 13, and 287 in SG 14.

The indications were axial in nature, except for four indications that were reported as circumferential in SG 12. This is not believed to truly be the case, as there is no stress in the unexpanded portion of the tubes to initiate a circumferential indication, as well as no denting in these locations. Based upon previous tube pull specimen metallography from Unit 1 for OD degradation in this region, axial indications closely lined up and extending around the circumference of the tube can appear to be a circumferential indication by ECT techniques. In addition, these four indications exhibited the same type ECT signal identified with the tube pull specimens.

A historical review of the largest indications from 1995 bobbin inspection has shown that these indications were present, but were not confirmed by the Cecco probe inspection performed at that time. A re-analysis of the Cecco data from the EOC-14 was conducted during the current inspection using improved analysis techniques. The re-analysis identified that a large number of indications were not confirmed or detected during the previous inspection. The largest indications were also traced back to the 1994 RPC inspection (0.080" coil). Most had a very small ECT response which is believed to be the precursor to the indications that were detected during the current inspection. This investigation confirms that these indications do not have a significant growth rate and the majority are considered "two-cycle" indications. The data is contained in Table 4-5.

Location 20-41 in SG 11, and locations 26-48, 29-19, and 30-49 in SG 14 were selected for in-situ testing based upon the results of the secondary side hydro test, RPC voltage response, axial length, and their proximity to the top of the secondary face of the tubesheet. Additional indications, 16-8, and 14-40 in SG 12 and 9-71 in SG 13 were selected and tested to bound the. results obtained from the leaking tubes. These tubes were also selected based upon the size of the indications, voltage response, magnitude, size in length, and proximity to the top of the tubesheet.

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CHMENT 1 TO AEP:NRC:1166AI Table 4-5 Largest ODSCC Indications in TS/Crevice Region SG Row Col Location of Orientation of RPC 1997 RPC Size of 1997 Bobbin 1995 Bobbin 1995 Cecco 5 1994 RPC Historical Indication Indication Voltage Indication Voltage and Call Historical Review Re-analysis Review 0.080" cofl) 12 55 TSH - 5.08" 9.70 0.63" NDD NDD Haw Prcscnt w/ deposit NDD influences 12 56 TSH - 3.06" Axial 14.83 .0.49" NDD NDD Flaw Present NDD 11 13 57 TSH - 7.41" Axial 13.98 1.74" NDD NDD Flaws Present wl deposit NDD TSH - 6.26" Axial 0.62" influenccs 14 29 TSH - 0.27" Axial 0.97" DTI 1.29 volts Flaw Present Flaw Present Haw Present 20 41 TSH - 0.51" Axial 9.03 0.84" DTI 5.32 volts Haw Present Flaw Present Haw Present 14 TSH + 0.00" Circ. 1.33 2.1 NDD Haw Present Haw Present 0.43 "/574 12 42 TSH + 0.00" Circ. 1.62 "/273'.69"l221'.4 NDD Flaw Prcscnt Flaw Present 0.92 "/1214'DD 12 34 TSH - 3.96" Axial 2.22 "/0.53" NDD NDD Haw Present 12 16 TSH - 0.67" Axial 0.80" DTI 4.16 volts Haw Present Haw Present Flaw Present 16 45 TSH - 1.69" Axial 2.69 0.76" DTI 1.23 volts NDD Haw Present NDD TSH - 2.38" 2.89 0.79" 38 31 TSH - 0.81" Axial 2.12 OA4" NQI 1.35 volts Haw Present Haw Present wl deposit NDD influence 69 TSH - 0.41" Axial 3.51 0.94" NDD Haw Present Flaw Present NDD 13 4 28 TSH - 1.08" 2.15 1.65" N 10.96 volts Flaw Present Haw Present NDD 71 TSH - 1.80" Axial 2.19 4.11" NDD Flaw Present Haw Present NDD 16 TSH - 0.80" Axial 2.91 0.43" N 11.97 volts Flaw Present Flaw Present wl de sit influence Flaw Present 17 TSH - 0.92" 3.62 1.03" N 14.37 volts Haw Present Flaw Present wl de sit influenc Flaw Present 61 TSH - 0.58" Axial 2.03 0.52" NDD Flaw Present Flaw Present w/ de sit influenc Flaw Present 14 10 17 TSH - 0.79" 2.41 0.75" N 14.08 volts Haw Present Flaw Prcscnt wl de sit influencc Flaw Present 19 TSH - 0.69" Axial 2.48 1.01" DTI 9.90 volts Flaw Present Haw Present w/ de sit influence Flaw Present 15 TSH - 1.03" Axial 0.54" N 13.38 volts Haw Present Haw Present Flaw Prcscnt 16 32 TSH + 0.24" Axial 4.18 0.37" NDD Flaw Present Flaw Present wl deposit influence Flaw Present and distorted b dent 17 31 TSH - 2.94" Axial 2.38 0.83" NDD NDD Haw Present NDD 21 34 TSH - 0.56 Axial 5.01 0.71" DTI 3.78 volts Flaw Present Flaw Present wl d>> sit influence Haw Present 24 31 TSH - 1.01" 13.6 1.10" N 15.02 volts NDD Haw Present Flaw Present 26 48 TSH - 0.96" Axial 8.29 1.20" N 13.56 volts Flaw Present Flaw Present Haw Present 29 19 TSH - 1.00" Axial 3.22 1.23" N 16.15 volts Flaw Present Haw Present wl de sit influencc Flaw Present 30 49 TSH - 0.80" 3.22 0.84" N 14.42 volts Flaw Present Haw Present Haw Present 30 56 TSH - 0.85" Axial 5.52 0.96" DTI 4.41 volts Flaw Present Flaw Present wl de sit influenc Flaw Page 9 of 26

1 ATTACHMENT1 TO AEP:NRC:1166AI The results of the testing, contained in the Table 4.6 below, bound the large population of indications that were detected at EOC-15 in this region. For axial indications with RPC voltages )3 volts, a conservative leak rate of 7.5 gpd is assigned to each indication, for those indications ( 3 volts, based upon the testing, a leak rate of zero was assigned. Additionally, for circumferentially oriented indications, no leak rate is assigned, based upon the testing performed. The leak rates are factored into the total

'steam generator leakage based upon the population of indications and their voltage, for each steam generator.

Table 4-6 Results of ODSCC in Tubesheet Region In-situ Testing SG RoN'ol Location of RPC Length Results of In-situ Testin Indication Volta e NOP MSLB 3xNOP 20 41 TSH - 0.51" 9.03 0.84" 1.7 7.5 317.3 12 16 TSH - 0.67" 2.94 0.80" 0.0 0.0 0.0 14 40 TSH - 0.00" 1.62 1.03 "/154'.11" 0.0 0.0 0.0 13 71 TSH - 1.80" 2.19 0.0 0.0 0.0 14 26 48 TSH + 0.29" 1.35 TSH - 0.96" 8.19 1.20" 0.0 0.0 0.0 29 19 TSH - 1.00" 3.22 1.23" 0.0 0.0 0.0 30 49 TSH - 0.80" 3.22 0.0 0.0 0.4 4.5 ODSCC at TSPs The required calculations for the as-found conditions of the steam generators, with respect to the population of ODSCC type indications at hot leg support plate intersections, was performed. The calculated probability of burst is well below the required 1 x 10 threshold. Additionally, the associated leak rates are consistent with previous calculations performed for Unit 1 and are also well below the allowable 8.4 gpm limit. The largest bobbin coil indication at a TSP detected during the inspection was 1.73 volts. The calculated leak rates were factored into the total limiting steam generator for EOC-15 leakage evaluation. The results of the calculations are contained in Table 4-7 below.

Table 4-7 Results of TSP ODSCC ARC Calculations for ROC-15 SG Number of Conditional Leak Probability of Burst Indications Rate Results Results

( d) 369 607.5 1.56 x 10 12 169 361.5 9.72 x 10 13 '60 164.4 6.02 x 10 14 355 583.8 1.56 x 10 Page10of 26

ATTACHMENT1 TO AEP:NRC:1166AI 4.6 Cold Leg Thinning Based upon the size of the detected cold leg thinning during U1R97, no indications were a concern with respect to tube integrity requirements. No contribution to leakage at EOC-15 is attributed to this type of tube degradation.

4.7 AVB Wear Based upon the size of the detected AVB wear during U1R97, no indications were a concern with respect to tube integrity requirements. No contribution to leakage at EOC-15 is attributed to this type of tube degradation.

4.8 HEJ Sleeves 4.8.1 Sleeves with Indications Sleeves that had indications detected by the plus point above the hard roll region of the HEJ were also considered as potential candidates for in-situ pressure testing. The indications at the upper expansion transition are of particular interest because of the potentially short leak path through the top of the sleeve through the flaw and into the secondary side. A summary of the indications that were detected in the HEJs above the hard roll region of the HEJ joint and were considered as in-situ candidates, is contained in Table 4.8. Two locations were selected for in-situ pressure testing. Tubes 33-23 and 17-31 in SG 13 were tested based upon the relative size, type, and location of the indications within the upper region of the joint.

Table 4-8 HEJ Sleeve Indication Data Row Col Location '97+Pt Orientation Size Voltage 1995 Review 31 UEZ 1.06 Circ. .44"/77'ECCO-5 0.29"/46 NDD 19 27 UUE 1.64 Axial .30" NDD 20 44 UUE 4.74 Circ. NDD 20 51 URT 1.92 Circ. .15"/27'DD 29 36 UUE 3.04 Circ. .3 1 "/42o Circ. PTI 33 20 UUE 1.66 Circ. .23"/30'44"/77'25"/46'24"/38' NDD 38 64 UEZ 1.61 Circ. NOD 15 24 UUE 2.49 Circ. NDD Axial 41) NDD 16 29 UUE 3.24 Circ. .44"/77'26" NDD 12 16 49 UUE 5.30 Axial NDD 16 78 UUE 4.56 Circ. .28"/38'44"/78o NDD Circ. NDD 20 43 UUE 2.18 Circ. .28"/38'19"/25'25"/46'TI NDD 20 44 UUE 0.67 Circ. NDD 21 24 UUE 2.41 Circ. NDD Page 11 of 26

<l ATTACHMENT1 TO AEP:NRC:1166AI Table 4-8 HEJ Slccve Indication Data (cont.)

SG Row Col Location c97+Pt Orientation Size CECCO-5 Voltage 1995 Review 5 22 UUE 1.62 Circ. NDD 5 53 URT 1.53 Circ. NDD

.50"/66'4'/58'26"/35'6"/35'4" Circ. NDD 11 53 URT 1.81 Circ NDD 13 15 54 UUE 5.77 Axial NDD

!.:17';:.': ';:::3.l:'::,::::."':!:":,':UUEic:.'";'ll c,;.'.31::,37:;::;:; l,;::;,';,',,Circ,':,,';:;~'.':;.:".."::,.:.:::.:,:.'.",'::::,4.1. /54."':::,:::::,::'.,".".'5::'NDD:;::;::i::.."c";

22 65 URT 0.77 Circ 35"/46'7"/23o NDD 23 45 URT 1.62 Circ NDD

""i33"' '.'239"':4"::.URT;.:l'.',!!i'.0c9,6;;3:~'-';.  ;'4::::::.i!'.Circ';:i'.:;t;;.":.;:;:!7.,'.;;23! /3,.1~'s':.,.'g';.'.:g<'i".".:::NDD!i:;:i$;;'::-'.;

Neither of the locations developed any leakage during the pressure testing, which included equivalent pressures for NOP, MSLB, and 3 x NOP conditions.

Based upon these results, the sleeves with indications were conservatively assigned a leak rate for EOC-15 equivalent to the licensing basis leak rate for a HEJ sleeve, or 0.0046 gpd per sleeve.

1 4.8.2 Sleeves with No Indications Based upon the results of the secondary side hydro testing, the two sleeved locations in SG 11 that were identified as having minimal leakage (Table 1-1),

were in-situ pressure tested to verify integrity of the joints within the sleeve.

Both tubes were full tube tested to a room temperature pressure equivalent to 3 x NOP at temperature, with no signs of leakage during any portion of the test.

Based upon these results, the assumed leakage for these two locations during a MSLB for EOC-15 is assumed to be the licensed leak rate of 0.0046 gpd per sleeve.

4.9 Rerolled Tubes Exhibiting Leakage Three in service re-rolled locations were noted as leaking during the secondary side hydro test. These locations were in-situ pressure tested to quantify the leak rate during postulated accident conditions. The locations and the results of the test are noted in Table 4-9. Tube 18-37 in SG 11 exhibited significantly more leakage during both the pressure and in-situ tests than the other re-roll leaking tubes. Additional review was performed to account for this difference. A review of 1995 ECT and reroll data noted tube 18-37 had a typical size flaw prior to re-roll operations. Post reroll ECT indicated that the re-rolL operations had increased the flaw size. 1997 ECT data noted that the flaw size had again increased during the previous cycle to the point of being throughwall. Reroll installation data confirmed that the tube had a marginally acceptable diametrical expansion that was unable to provide a leaktight seal. Comparisons between tube 18-37 and the other leaking Page12of 26

ATTACHMENT1 TO AEP:NRC:1166AI locations determined that tube 18-37 had less expansion than the other two tubes. ECT results noted this indication also had a much larger voltage than the other leaking locations. It is believe that the combination of these factors account for the higher leakrate observed from tube 18-37.

A review of the diametrical expansion data of all previously installed rerolls was performed. 119 locations were identified as having marginal expansion and were re-rerolled. Additionally, an ECT review was conducted to identify any similar indications to tube 18-37. This review identified two other tubes with similar ECT indications, but which had exhibited no leakage during the hydro test. These tubes were selected for in-situ testing in order to verify the integrity of the remaining population of rerolled tubes.

Post reroll leak testing was also performed to assure the success of the reroll process. No leaking tubes were found during this test.

Table 4-9 Summary of Rerolled Tubes In-situ Tests Pressure Test Results ( d)

SG Row Col Location Volta e NOP MSLB 3xNOP 11 18 37 LRT SAI Q BRT - 1.67" 18.91 100.7 196.6 N/A Re-test 37.8 58.1 N/A 13 4 44 LRT MAI BRT - 1.67" 14.40 0.9 1.7 N/A 8 31 LRT MAI BRT - 1.74" 7.60 0.0 0.0 N/A 24 24 RT MAI Ci BRT - 1.67" 8.09 0.0 0.0 0.0 3 70 RT MAI Q BRT - 1.98" 14.83 0.0 0.0 0.0 Based upon these results, a conservative leak rate of 196.6 gpd was assigned to reroll locations that were leaking during the secondary side hydro test, except for those that have specific in-situ test results. The remaining reroll indications were bounded by the testing of locations 24-24 and 3-70 in SG 13, which exhibited zero leakage during both pressure tests. The licensed accident leak rate value of 0.000423 gpd per in service reroll location was applied to the remaining population of rerolled tubes at EOC-15.

5.0 Tube Integrity Evaluation at EOC-15 5.1 Burst Capability The indications evaluated against the tube rupture requirements of RG 1.121 were in-situ tested up to bounding equivalent pressures of 3 x NOP. These indications were in the U-bend region and at the top of the hot leg tubesheet. None of the indications tested ruptured during the test, and those that leaked during the test did not leak beyond the capacity of the test system (1 gpm MSLB equivalent) and are classified as not ruptured. Therefore, at EOC-15, there were no tubes that would have ruptured under postulated accident conditions, nor under bounding 3 x NOP conditions. Therefore, the Unit 1 steam generators met the requirements of RG 1.121 for tube integrity for cycle 15 ~

Page l3 of 26

ATTACHMENT1 TO AEP:NRC:1166AI 5.2 Total Leakage Evaluation The total leakage evaluation is based upon a cumulative assessment approach that assigns conservative leak rates based upon in-situ pressure test results to each damage mechanism, or licensed non-leak tight repair technique (HEJs and rerolled tubes).

Tables 5-1 through 5-4 itemize the leak rates for each steam generator during EOC-15.

The bounding steam generator was SG 11 with a postulated leak rate under accident conditions of 0.69 gpm, well within the allowable 8.4 gpm 10CFR100 limits. Table 5-5 is a compilation of all in-situ testing performed and the results of each test.

Page 14 of 26

ATTACHMENT1 TO AEP:NRC:1166AI CATEGORY Number of Leak Rate Leak Rate Category Locations ( d) Total er T e Total ~

Tubes with HEJ sleeves (s26 nb s)

Sleeves In-situ Tested 2 0.00 0.00

~ Sleeves w/ Ind. above Hard Roll Region 7 0.0046 0.03 Remainin Sleeves 817 0.0046 3.76 3.79 Tubes Previously Rerolled (245 tubes)

RR w/ OEM RT Indications > 14 volts 3 58. 10 174.30 RR w/ OEM RT Indications 8-14 volts 3 1.70 5.10 Remaining Rerolled Tubes 223 0.000423 0.09 New Indications in Reroll RT 16 4.20 67.2 246.69 PWSCC in OEM RT (174 ind. in 171 fllbCS)

Indications In-situ Tested 2 0.00 0.00 o Remainin RT Indications 172 0.00 0.00 0.00 ODSCC at TSPs 369 Calculated per GL 9545 607.50 U-bend PWSCC (6 irxl. in 6 tubes)

Circumferential Indications 0.80 3.20 o Axial Indications In-situ Tested 44.80 89.60 o Remainin Axial Indications 0.00 0.00 92.80 TTS ODSCC (263 ird. in 245 ntbcs)

Circ. Oriented Indications 0 0.00 0.00 Axial Indications > 3 volts 5 7.50 37.50 Axial Indications ( = 3 volts 258 0.00 0.00 37.50 Cold Le Thinnin (100ind.insot bcs) 0.00 0.00 0.00 AVB Wear (s i~. tn5 tUbcS) 0.00 0.00 0.00 Steam Generator Total ( d) 988.28 Steam Generator Total ( m) 0.69 Page 15 of 26

ATTACHMENT1 TO AEP:NRC:1166AI CATEGORY Number of Leak Rate Leak Rate Category Locations ( d) Total er T e Total Tubes with HEJ sleeves <<so n as>

e Sleeves w/ Ind. above Hard Roll Region 7 0.0046 0.03 Remainin Sleeves 173 0.0046 0.80 0.83 Tubes Previously Rerolled (t t7 tub s)

~ RR w/OEM RT Indications >14 volts 0 58. 10 0.00

~ RR w/ OEM RT Indications 8-14 volts 1 1.70 1.70 RR w/ OEM RT Indication In-situ Tested 1 0.00 0.00

~ Remaining Rerolled Tubes 110 0.000423 0.05

~ New Ind. in Reroll RT In-situ Tested 1 0.00 0.00 u Remainin New Ind. in Reroll RT 4 4.20 16.80 18.55 PWSCC in OEM RT (128 ird. in 128 tubes) u RT Indications 128 0.00 0.00 0.00 ODSCC at TSPs 169 Calculated per GL 95-05 361.50 U-bend PWSCC (10 ind. in 8 tubes) u Circumferential Indications 0.80 0.80 Axial Indications In-situ Tested 0.00 0.00

~ Remainin Axial Indications 44.80 358.40 359.20 TTS ODSCC (99 ind. in 9t tubes) u Circ. Oriented Indications In-situ Tested 1 0.00 0.00 u Remaining Circ. Oriented Indications 3 0.00 15.00 u Axial Indications > 3 volts 0 7.50 0.00 Axial Indications ( = 3 volts 95 0.00 0.00 0.00 Cold Le Thinnin (89 ind. in 74 tubes) 0.00 0.00 0.00 AVB Wear (29 ind. in 21 tubes) 29 0.00 0.00 0.00 Steam Generator Total ( d) 740.08 Steam Generator Total ( m) 0.51 Page 16of 26

ATTACHMENT1 TO AEP:NRC:1166AI CATEGORY Number of Leak Rate Leak Rate Category Indications ( d) Total er T e Total Tubes with HEJ sleeves (459 tubes)

Sleeves In-situ Tested 2 0.00 0.00

~ Sleeves w/ Ind. above Hard Roll Region 8 0.0046 0.04

~ Remainin Sleeves 449 0.0046 2.07 2.11 Tubes Previously Rerolled (493 tubes) e OEM RT Indications In-situ Tested 3 0.00 0.00 o RR w/ OEM RT Indications ) 14 volts 0 5

58.10 0.00 o RR w/ OEM RT Indications 8-14 volts 1.70 8.50 Remaining Rerolled Tubes 456 0.000423 0.19 e New Indications in Reroll RT 29 4.20 121.80 130.49 PWSCC in OEM RT (251 ind. in 248 tubes)

RT Indications 251 0.00 0.00 0.00 ODSCC at TSPs Calculated per GL 95-05 164.40 U-bend PWSCC (9'. in8 tubes)

Circ. Indications In-situ Tested 0.00 0.00 Remaining Circ. Indications 0.80 4.80

~ Axial Indications In-situ Tested 0.00 0.00 Remainin Axial Indications 44.80 44.80 49.60 TTS ODSCC (231ind. in206tubes) e Circ. Oriented Indications 0 0.00 0.00 e Axial Indications In-situ Tested 1 0.00 0.00

~ Axial Indications ) 3 volts 3 7.50 30.00 Axial Indications ( = 3 volts 227 0.00 0.00 30.00 Cold Le Thinnin (61 ind. in 55 tubes) 61 0.00 0.00 0.00 AVB Wear (66 i~. Ill40 tubes) 66 0.00 0.00 0.00 Steam Generator Total ( d) 376.60 Steam Generator Total ( m) 0.26 Page 17 of 26

t ATTACHMENT1 TO AEP:NRC:1166AI CATEGORY Number of Leak Rate Leak Rate Category Locations ( d) Total er T e Total Tubes with HEJ sleeves (374 tubes)

~ Sleeves w/ Ind. above Hard Roll Region 0 0.0046 0.00

~ Remainin Sleeves 374 0.0046 1.72 1.72 Tubes Previously Rerolled (t09 nb s) e RR w/ OEM RT Indications >14 volts 0 58.1 0.00 RR w/ OEM RT Indications 8-14 volts 1 1.70 1.70 Remaining Rerolled Tubes 102 0.000423 0.04 e New Indications in Reroll RT 6 4.20 25.2 26.94 PWSCC in OEM RT (88 ind. in 88 tubes)

RT Indications 88 0.00 0.00 0.00 ODSCC at TSPs 355 Calculated per GL 9545 583.80 U-bend PWSCC e Circ. Indications 0.80 0.00

~ Axial Indications 44.80 0.00 0.00 TTS ODSCC (300 ind. in 287 tubes)

Circ. Oriented Indications 0 0.00 0.00 o Axial Indications In-situ Tested 3 0.00 0.00 Axial Indications > 3 volts 6 7.50 45.00

~ Axial Indications ( = 3 volts 291 0.00 0.00 45.00 Cold Le Thinnin (74 ird. in 69 tubes) 74 0.00 0.00 0.00 AVB Wear (23 ind. in 13 tubes) 23 0.00 0.00 0.00 Steam Generator Total ( d) 657.43 Steam Generator Total ( m) 0.45 Page 18 of 26

ATTACHMENT1 TO AEP:NRC:1166AI Table 5-5 Summary of All In-situ Tests by Damage Mechanism Cook 1 U1R97 Pressure Test Results ( d)

SG Row Col Location Reason for Test NOP MSLB 3 x NOP 11 1 47 U-Bend U-Bend PWSCC, leaker* 0.0 0.8 13.6 13 1 40 U-Bend U-Bend PWSCC 0.0 0.0 0.0 0.0 0.0 0.0 13 1 86 U-Bend U-Bend PWSCC 11.8 44.8 628.9 12 1 80 U-Bend U-Bend PWSCC 0.0 0.0 0.0 11 16 27 Sleeve A arent leaker* 0.0 0.0 0.0 11 13 13 31 33 17 37 23 31 Sleeve Sleeve Sleeve PTI PTI I

A arent leaker*

HEJ sleeve HEJ sleeve 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 11 12 12 20 16 14 41 8

40 ODSCC ODSCC ODSCC I

TSH, leaker*

TSH TSH 1.7 0.0 0.0 7.5 0.0 0.0 317.3 0.0 0.0 14 26 48 ODSCC TSH, leaker" 0.0 0.0 0.0 ei 0.0 0.0 0.0 14 14 13 29 30 9

19 49 71 ODSCC ODSCC ODSCC II TSH, leaker*

TSH, leaker*

TSH 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.0 ll 18 37 RT Leakin rerolled tube* 100.7 196.6 N/A Retest 37.8 58.1 N/A 13 4 44 RT Leakin rerolled tube* 0.9 1.7 N/A 13 8 31 RT Leakin rerolled tube* 0.0 0.0 N/A 13 24 24 RT Similar si nal to 11-R18C37 0.0 0.0 N/A 13 30 70 RT Similar si nal to 11-R18C37 0.0 0.0 N/A 11 11 35 RRT New PWSCC in RRT 0.0 4.2 N/A 12 21 25 RRT New PWSCC in RRT 0.0 0.0 N/A 11 3 59 RT PWSCC in OEM RT 0.0 0.0 N/A 11 25 64 PWSCC in OEM RT 0.0 0.0 N/A

- Observed Leaking Under Hydro Test Page 19 of 26

I ATTACHMENT1 TO AEP:NRC:1166AI

.0 Cycle 16 Operability Review 6.1 Assessment of Tube Rupture at EOC-16 Based upon the results of the ECT inspection performed during U1R97, tube burst under bounding worst case conditions at EOC-16 is not a concern.

Based upon the types and characteristics of the indications detected during the EOC-15 inspection, it is expected that the population of indications, as well as the severity of the indications, will bound future cycles at Unit 1. The majority of all large flaws (most of

, which are not a concern for tube burst due to location) are classified as "two-cycle" flaws, based upon review of historical data and the fact that the U-bends that had indications had not previously been inspected with a rotating technique. Therefore, the growth rate of the most limiting indications is based upon two cycles of operation and is not considered a concern for one cycle.

Due to the enhanced techniques utilized during the most recent inspection, and reanalysis of historical data from previous inspections, the indications detected at EOC-15 should bound any indications found in future inspections at Unit 1. The probability of detection is also increased due to the use of the enhanced ECT techniques and analyst site specific testing/training, both of which contribute to decreasing the likelihood of returning a significant indication to service for cycle 16.

The bounding indications for tube burst (U-bend PWSCC and TTS ODSCC) were in-situ tested to the room temperature equivalent bounding pressure differentials and did not rupture. Therefore, the likelihood of tube rupture under bounding RG 1.121 pressures (3 x NOP), is not a concern for these types of indications at EOC-16, and future inspections.

6.2 Assessment of Projected Leakage at EOC-16 Using the results of the ECT inspection performed at EOC-15, as well as the results from the in-situ pressure testing, an evaluation was performed for estimated leakage under postulated accident conditions on the last day of cycle 16. The leakage assessment uses the information obtained at EOC-15 to conservatively bound the leakage. Tables 6-1 through 6-4 provide the overall summary of the cumulative estimated leak rates for each steam generator at EOC-16, during MSLB conditions.

The estimates show that SG 11 is the bounding steam generator.

Results show that the estimated cumulative leak rates for each steam generator are limited to well below the primary-to-secondary technical specification limit (8.4 gpm in a faulted loop during a potential steam line break event).

Page20of 26

ATTACHMENT1 TO AEP:NRC:1166AI HEJ Sleeve Contribution Based upon the results of the in-situ pressure testing of HEJ sleeves at EOC-15, the projected contribution of HEJ sleeves to the leak rate is based on the number of in service sleeves and the licensed accident leak rate of 0.000423 gpd per sleeve.

Rerolled Tubes Based on the results of the ECT inspection and the re-evaluation of suspect rerolled tubes, the EOC-16 projected contribution to accident leakage is based on the number of rerolled tubes returned to service and the associated licensed leak rate value. Because there are two different types of in service rerolls (Westinghouse and FTQ, the more conservative higher FTI leak rate will be used for all rerolled tubes left in service for cycle 16. This leak rate is 0.001081 gpd per reroll.

PWSCC in OEM Roll Transition Because of the results of the ECT inspection, and the continuing progression of this tube degradation on Unit 1, it is anticipated that as many as 300 new indications may be present at EOC-16, with 75 in each SG. However, based on the testing performed at EOC-15 on the'largest indications, the associated accident leak rate is zero.

Additionally, based upon the ECT techniques used at EOC-15 compared to those used in past inspections, it is judged that the worst indications were present at EOC-15.

Because of the increased probability of detection of both large and smaller flaws at EOC-15, the indications expected to be seen, at EOC-16 will be bounded by those at EOC-15 which when in-situ tested, exhibited zero leakage.

ODSCC at Tube Su ort Plate Intersections The required calculations were performed for both the probability of tube burst and accident leak rate, in accordance with GL 95-05 and WCAP 14277. The results are contained within the following tables. These results are consistent with previous Unit 1 analyses and are well within the allowable limits. The leak rates calculated as part of this evaluation are the largest contributor to the total projected leak rate at EOC-16.

This is mostly due to the fact that the correlation between bobbin coil voltage response and predicted leak rate does not meet the 5% criteria. If such a correlation existed, the leak rates would be expected to be a fraction of the values currently calculated.

Page 21 of 26

ATTACHMENT1 TO AEP:NRC:1166AI U-bend PWSCC Due to the results of the U1R97 inspection and the industry's experience with this type of tubing degradation, it is expected that some small population of indications will exist at EOC-16. However, based upon the inspection techniques used at EOC-15, the fact that these indications were the first ever detected at Unit 1, and that the U-bends had not been previously examined with a rotating technique, the indications at EOC-15 should bound future populations of indications with respect to structural integrity. As a conservative measure, numbers of indications were postulated at EOC-16 to provide additional leakage to the projected cumulative leak rate.

ODSCC at Tubesheet Seconda Face Based upon the results of the U1R97 inspection and plant specific experience with this type of tubing degradation, it is expected that a population of indications will exist at EOC-16. However, due to the inspection techniques used at EOC-15, the projected indications should be bounded by the largest detected at EOC-15 that were also traceable to the 1994 RPC inspection. As a conservative measure, numbers of indications were postulated at EOC-16 to provide additional leakage to the projected cumulative leak rate for each steam generator.

Assessment at EOC-16 Based upon the requirements of RG 1.121 and the Draft Reg. Guide for Condition Monitoring and Operational Assessments, a similar assessment will be performed at the EOC-16 for the conditions of the steam generators. It is the intent to apply the results of the in-situ testing at EOC-15 to the indications detected at EOC-16 for evaluation of both the need to in-situ test, as well as the structural implications of different types of tubing degradation that will be detected at EOC-16. Similar ECT techniques and ranking of indication severity will be employed to ensure that proper comparisons and inferences can be made.

Page 22 of 26

ATTACHMENT1 TO AKP:NRC:1166AI CATEGORY Number of Leak Rate Leak Rate Category Locations ( d) Total er T e Total Tubes with HEJ sleeves Inservice Sleeves 817 0.0046 3.76 3.76 Tubes with Reroll Repair Inservice Rerolls (Westinghouse + FTI) 331 0.001081 0.36 o Estimated New Indications in Reroll RY 22 4.20 92.4 92.76 PWSCC in OEM RT Pro'ected Indications 75 0.00 0.00 0.00 ODSCC at TSPs 575 Calculated per GL 95-05 1386.86 U-bend PWSCC Circ. Indications Expected 0.80 3.20 Axial Indications Ex ected 44.80 89.60 92.80 TTS ODSCC Circ. Oriented Indications Expected 0 0.00 0.00 Axial Indications ) 3 volts Expected 5 7.50 37.50 Axial Indications ( = 3 volts Ex ected 258 0.00 0.00 37.50 Steam Generator Total ( d) 1613.68 Steam Generator Total ( m) 1.12 Page23 of 26

ATTACHMENT1 TO AKP:NRC:1166AI CATEGORY Number of Leak Rate Leak Rate Category Locations ( d) Total er T e Total Tubes with HEJ sleeves Inservice Sleeves 173 0.0046 0.80 0.80 Tubes with Reroll Repair Inservice Rerolls (Westinghouse + FTI) 224 0.001081 0.24 Estimated New Indications in Reroll RT 8 4.20 33.60 33.84 PWSCC in OEM RT Pro'ected Indications 75 0.00 0.00 ODSCC at TSPs 259 Calculated per GL 95-05 681.11 U-bend PWSCC o Circ. Indications Expected 0.80 0.80 Axial Indications Ex cted 44.80 403.20 TTS ODSCC o Circ. Oriented Indications Expected 0 0.00 0.00 Axial Indications ) 3 volts Expected 0 7.50 0.00

(

Axial Indications = 3 volts Ex ected 95 0.00 0.00 0.00 Steam Generator Total ( d) 1119.75 Steam Generator Total ( m) 0.78 Page 24 of 26

1 ATTACHMENT1 TO AEP:NRC:1166AI CATEGORY Number of Leak Rate Leak Rate Category Locations ( d) Total er T e Total Tubes with HEJ sleeves Inservice Sleeves 449 0.0046 2.07 2.07 Tubes with Reroll Repair Inservice Rerolls (Westinghouse + FTI) 596 0.001081 0.64 Estimated New Indications in Reroll RT 35 4.20 147.00 147.64 PWSCC in OEM RT o Pro'ected Indications 75 0.00 0.00 0.00 ODSCC at TSPs Calculated per GL 9545 345.24 U-bend PWSCC Circ. Indications Expected 0.80 5.60 Axial Indications Ex ected 44.80 89.60 95.20 TTS ODSCC Circ. Oriented Indications Expected 0 0.00 0.00 Axial Indications ) 3 volts Expected 3 7.50 22.50

(

Axial Indications = 3 volts Ex ected 227 0.00 0.00 22.50 Steam Generator Total ( d) 612.65 Steam Generator Total ( m) 0.43 Page25of 26

I ATTACHMENT1 TO AKP:NRC:1166AI CATEGORY Number of Leak Rate Leak Rate Category Locations ( d) Total er T e Total Tubes with HEJ sleeves Inservice Sleeves 374 0.0046 1.72 1.72 Tubes with Reroll Repair Inservice Rerolls (Westinghouse + FTI) 146 0.001081 0.16 Estimated New Indications in Reroll RT 8 4.20 33.60 33.78 PWSCC in OEM RT o Pro'ected Indications 75 0.00 0.00 0.00 ODSCC at TSPs 526 Calculated per GL 9545 1243.63 U-bend PWSCC Circ. Indications Expected 0.80 4.00 o Axial Indications Ex cted 44.80 179.20 183.20 TTS ODSCC Circ. Oriented Indications Expected 0 0.00 0.00 Axial Indications ) 3 volts Expected 9 7.50 67.50 Axial Indications ( = 3 volts Ex cted 291 0.00 0.00 67.50 Steam Generator Total ( d) 1529.83 Steam Generator Total ( m) 1.06 Page 26 of 26