ML070870675

Meeting Slides, Entergy Meeting with NRC, Topic: Waterford 3 Batwings

ML070870675
Person / Time
Site:	Waterford
Issue date:	03/22/2007
From:	Entergy Operations
To:	Office of Nuclear Reactor Regulation
References
Download: ML070870675 (39)

Text

Entergy Meeting with NRC Topic: Waterford 3 Batwings March 22, 2007 Purpose o.Communicate our technical understanding of the Batwing condition

o. Review analysis that support safe operation of the plant oo. Review the mitigation actions that been taken oo. Discuss preliminary plans for mid-cycle inspection 1

Agenda

1. Introduction Bob Murillo 8:00-8:05 (5)

2. Current Status Joe Kowalewski 8:05-8:15 (10)

3. RF13 and RF14 RCA Rex Putnam 8:15-8:40 (25)

4. Eddy Current Results Bill Cullen 8:40-9:05 (25)

5. W3 and Ginna Bill Cullen 9:05-9:30 (25)

BREAK 9:30-9:45 (15)

6. Batwing Analysis* Jeff Hall 9:45-10:10 (25)

7. Wrap-Around Bar Welds* Jeff Hall 10:10-10:35 (25)

8. Loose Part Considerations* Jeff Hall 10:35-11:00 (25)

BREAK 11:00-11:05 (5)

9. Mid-Cycle Inspections Rex Putnam 11:05-11:30 (25) io. Summary Joe Kowalewski 11:30-11:35 (5)

Presentation contains Proprietary information Current Status Joe Kowalewski GM Plant Operations, Waterford 3 2

Current Status Plant Performance since Startup Tritium Grab Samples Radio-isotopic analyses SG Loose Parts Monitor Third sensor installed as a temporary change No impacts or adverse trend identified Startup transients 3

SG Loose Parts Monitor Continuous monitoring of SG secondary for loose parts Memory feature captures and saves impacts Baseline is trended State-of-Art Monitor Areva LPMS VI components Sensors meets Reg. Guide 1.133 Sensitivity validated by calibrated hammer 0.5 Ibm impact should alarm Slow rise in overall energy would also alarm 4

A AREVA DF'SW I -.- I Cho-el Pain Aý 29 AD go ePa-t MIN 5.00 - F ro F 12 RW 1004hEI49ttýtI P194S Leroth Post 14 F13.061 GooAfte Ioo

.2i*a0 11 2.LA Pre~00 Ratio 5iadox-cl MI MW0011 FRts 001110 sa[v]

w 5

Coto Room -8/1/07I

" Codc aS i-yl - 5otg 11/30/07 6

RF1 an RF4B Condtio an SRo 7

8 Batwing Support Structure w'"I'll 9

Bawn Supor Structure*

RF13 (4/05) Batwing Findings oýSG #2 batwing #9 shifted down op. Detected by eddy current signals op-Confirmed by visual inspection 10

RF13 Corrective Action Plan Displaced batwing was a new degradation mechanism Caused by fatigue failure at the batwing notch due to flow induced vibration Mitigated by a plugging and stabilization strategy Final corrective action was to accept the condition As-Is" Additional inspections were performed in RF14 to confirm analytical assumptions Wear model was determined to be conservative Tbar POr.

Id tw*s mnof tHis Potsntal ligamnnt from ihifted brokeni betwing iupport bars 11

RF14 (11/06) Batwing Findings SG#I inspections found no batwing damage SG#2 inspections found additional batwing damage - all associated with the stay cavity 18 additional batwings broke at the notch 2 batwings also broke at the diagonal bar weld 2 batwing to wrap-around bar welds broke One of these had also broken at the batwing to slotted bar notch connection, the other had an intact notch The batwing with both the broken (upper) vveld and (Imer) notch had dropped several i[IC[ICS i(ItO the tUbe bUndle 12

RF14 Causal Determination for SG#2 Different SG degradation mechanisms from RF 13 Two loose segment,,, two broken wrap-ýI[_C)Uncl bar vvelds, and a batwing displaced into the tube bundle Batwings in the stay cavity area failed due to cyclic fatigue Low margin in the design fm the actual forces being applied Susceptibility of batwings to FIV identified in 1984 VV3 plugged in(-] stabilized 142 tubes in each SG' cluring Cycle 1 RF13 caused progressive clarnage on adjacent batwings Batwing wrap around bar welds failed due to being of poor quality and not meeting original design requirements One of the welds that failed had an intact batwing notch at the slotted bar connection in the stay cavity area Mock-up Batwing Response 13

Final Corrective Action o,. Batwing wrap around bar welds

" Accessible welds in SG#2 were re-welded

" The dropped batwing was mitigated by stabilizers and Sentinel plugs

" One batwing in SG#1 had single sided welds and was mitigated by stabilizers and Sentinel plugs.

" Additional Sentinel plugs installed at top of tube bundle and the eighth eggcrate for defense- in-depth

o. Batwing degradation is stay cavity

" Plugged to no-load contact force point (16.4 year wear point for limiting twisted batwing)

" Mitigated by stabilizers and Sentinel plugs

" Additional Sentinel plugs installed around the stay cavity as defense-in-depth measure RF14 CA Plan (Continued) oo. Defense in depth

" Third loose parts transducer installed on SGs

" Administrative limit of 15 gpd primary to secondary leakage

" Mid-cycle outage to perform addition inspections to confirm assumptions oo. Final corrective action - accept "as-is"

- Administratively open pending permanent installation of the third transducer 14

SIG - 32 TUBE REPAIR HISTORY RF13ANDRF14- REV4 WaterfordRFO14WTR33410 L 124 LOM STABILUI

• 7 STAY MTSTION

. I LONG5OhILUE 0Y LE W A4 11 772 P. ,..i 5

Tub*

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-1 .. ..--.

I~PI r 115 IAý..

Summary SG#2 batwing upper welds failed due to being poor quality, short, and single sided SG#2 Batwings in the stay cavity area were damaged due to FIV All damage was repaired or mitigated (Plugs, stabilizers, and Sentinel plugs) in support of accepting "as-is" Robust defense in depth was established to protect active tubes by a combination of:

Sentinel plug strategy that bOUnds batwing degradation mechanism Installation of a nevv SG Loose Parts Monitor Additional administrative limits including 15 glad secondaty leakage Mid-cycle jnspectioný to confirm analysis assumptions, 15

Objective 0 Compare observed'eddy current wear depth results from RF13 (2005) and RF14 (2006) and wear growth rates to determine impact of operation with failed batwings

" Examine the nature of R67 C99 tube wear 0 Establish a basis that ECT is not necessary for mid-cycle timeframe

• Provide general overview of SG condition for mechanisms other than batwings 16

Historical Wear Growth Rates Average Growth Rates Outage SG Overall Eggcrates BW1 BW2-8 BW9 BW9 BW9 Growth (non SC) (SC)

RF12 31 0.60% 1.40% 2.20% 0.30% 2.40% 2.80% 2.30%

32 1.70% 0.00% 0.60% 1.90% 2.80% 2.20% 3.10%

RF13 31 1.10% 3.10% 0.00% 0.80% 3.30% 0.00% 3.80%

32 1.60% 1.40% 1.20% 1.70% 1.40% 3.20% 0.70%

• RF14 31 0.00% 1.70% 0.00% 0.00% 0.00% 1.00 0.00%

32 0,00% 0.00% 0.00% 0.00% 2.50% 2.40% 2.60%

33

)Westinghouse Historical Wear Growth Rates Maximum Growth Rates Outage SG Overall Eggcrates BW1 BW2-8 BW9 BW9 BW9 Growth (non SC) (SC)

RF12 31 13% 7% 12% 13% 13% 11% 13%

32 10% 9% 9% 10% 10% 6% 10%

RF13 31 20% 11% 8% 16% 20% 8% 20%

32 22% 13% 22% 17% 20% 17% 20%

rRýFý14 31 13% 10% 8% 13% 13% 2% 113%

32 23% 3% 4% 8% 23% 23% 16%

34 OWestinghouse 17

Comparison of BW9 Growth Distributions: RF13 vs RF14 BMI W- .. ~ " MDtamo I C14-- N- C .4 SC C13 I

- .N-SC C3 Ow %TW 35 WBts?1ngt11u56 SG32 Growth Rate Summary 0 Slight increase in growth rates observed for Cycle 13 compared to Cycle 12; slight decrease in growth rates observed for Cycle 14 compared to Cycle 13

• Cycle 14 operation at EPU appears to have had no influence upon growth rates

• Largest growth for Cycle 14 (23%) observed on R3 C1 at BW9; Cycle 13 growth was 17%. Location was stabilized and plugged RF14 (55%TW)

• RPC testing of R3 C1 shows batwing not dropped, wear at edge (horizontal bar) and tapered 36 Westingtouse 18

Dropped Batwing Wear oAt RF14, five tubes adjacent to original failed batwings were deplugged; no new or additional wear with batwing in dropped elevation

• AII stay cavity tubes out to Row 70 were RPC tested at BW9 location to determine if non-detected wear (bobbin) was present by RPC inspection oNo conclusive evidence of wear in dropped elevation was found

• Largest stay cavity wear growth for Cycle 14 was 16% (R67C99) and occurred prior to batwing drop Westinghouse SG32 R67 C99 at BW9 OThe attenuation model does not include localized alignment/fitup conditions OTube vibration alone can be a source of wear

• No other tubes in the vicinity of R67 C99 have wear scars; RP 3 experience showed "strings" of wear scars over multiple rows in columns 82, 83, and 84 0

Conclusion:

Wear on R67 C99 is due to localized alignment/fitup and is not related to failed batwing 38 eWestinghouse 19

R67 C99 Wear Profile 1 39 OWesflngbouse SG32 Wear Map: BW1 and BW9 Waterfwd Tubesheet Map SG 32 RF14 Bes. Tubes *BW9 wea ABWi Wear 0 15 30 45 60 75 90 106 120 135 150 165 Croum n 40 fWestingouse 20

Wear Observations

• BW9 wear is primarily located near center area of stay cavity, at peripheral regions and near edge of partial eggcrates and not generally throughout SG

• R67 C99 wear and growth is isolated and not related to batwing in its dropped condition

• Only RF14 wear depth >40%TW was outside of stay cavity (R3 Cl) 41 westinghouse SG32 Distribution of Wear Depths SG32 Distribution of Wear Depths for All Structures, All Columns

-- O-,ut6We-% Al -o-onn60014 -- - -- tnve % Co- 5 to 114

-,,- M0.*Ie % CM 1-61 am 115-175 -.-- Outni.tve %Al Cok- RF13 100.00%

50.00%

80.00%

70.00%

60.00%

00.0M%-

40.00%

30.00%

20.00% -

10.00%

0.00%

DIN 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 &b.r Bin (%TW) 42 GWesfinghouse 21

Conclusions Regarding Observed Wear

• Distribution of wear depths from stay cavity (Row 62 to 114) are identical to non-stay cavity locations and overall SG distribution

" Scuff marks on perforated plate suggest Cycle 14 batwing failures occurred during operation oDeplugged tubes show no new wear (1 + cycles) oStrong basis to anticipate RF15 wear will be consistent with past observations, supporting conclusion that mid-cycle ECT is not necessary ORF15 maximum simulated wear depth 48%TW 4:

)Westinghouse Overall SG Condition o18.12 EFPY at RF14; Plugging due to ECT indications; SG31 5.54%, SG32 3.10%, very low SGTP for 18.12 EFPY 9 Majority of ECT based plugging due to eggcrate axial ODSCC; no required ISPT, deepest eggcrate ODSCC depth of about 60%TW; 180 to 220 confirmed eggcrate ODSC predicted for RF15

• Distribution of eggcrate ODSCC lengths and +Pt amplitudes consistent for last 3 inspections

• Cycle 15 OA predicts margins for all mechanisms 4

)Westinghouse 22

Summary of Overall SG Condition

" Historical wear growth rates have not been adversely impacted by EPU or the observed batwing damage

• R67 C99 tube wear was caused by localized batwing alignment/fitup and not the dropped batwing

• Batwing related tube wear is consistent between stay cavity area and non-stay cavity areas, indicating no systemic wear related differentiation

• Based on empirical wear growth rates and wear simulation model, mid-cycle eddy current inspection is not necessary

• SCC mechanisms are predictable

• Cycle 15 OA predicts margins for all mechanisms 45 AfWestinghouse 23

Objective

• Recap of Ginna significant contributing events and show differences for Waterford condition

• Compare flow conditions for the two plants to show that normal flow velocity conditions-for peripheral TTS and central cavity are not similar 0 Review historic burst and collapse testing

• Establish that a cascading tube damage event is not a credible event for a C-E SG in upper bundle region

~ *r',"

. . - 48

>~ ~Wstrngo~sf 24

Ginna Recap

• The 1982 Ginna tube rupture event scenario is not directly relatable to Waterford

- Repeated large mass foreign object impacts over extended axial lengths causing localized, high residual stresses and imbalanced tube loadings leading to fatigue at ITS with subsequent cascading damage

- Initial object impact could cause significant damage thus acting as an initiator for the fatigue event

- Peripheral TTS region is subject to thermal growth effects and tubesheet rotations introducing bending stresses not present at upper bundle region 49

)Westinghouse Ginna Recap

• Objects were remnants of J-nozzle replacement in 1975 (up to 1/2" thick x 6 x 4 inches)

• Tube plugging in vicinity of rupture as early as 1976; ruptured tube had ECT indications in 4/1981 inspection, rupture occurred 2/1982, thus not a rapidly propagating event 50 1 )Westinghouse 25

Comparison of Conditions

• Waterford wear scar length is limited to a maximum of 4 inches, does not involve repeated impacts by large objects, and does not involve change in material properties which in turn result in imbalanced loadings

• Flow conditions and densities are not consistent

- pV 2 comparison shows greatly reduced tube excitation potential for Waterford

• Tube stiffness and unsupported lengths are not consistent 51

)Westinghouse Comparison of pV 2 Temp Normal Velocity Fluid Condition pV2 Ratio Top of Tubesheet 440F 10-12 ft/sec Liquid N/A R38 C88 BW9 540F 2.66 ft/sec Two phase 28.3 R38 C88 BW5 540F 10.72 ft/sec Two phase 2.4 R34 C98 BW9 540F 0.94 ft/sec Two phase 285 R34 C98 BW5 540F 11.47 ft/sec Two phase 2.6 R24 C106 BW1 540F 1.96 ft/sec Two phase 231 R24 C106 BW5 540F 12.29 ft/sec Two phase 3.4 2

Crossflow velocities, and thus, normally oriented pV terms decay quickly once 12 inside tube bundle "Westingouse 26

Tube Support Differences

• Ginna: 50 inch cantilever length from 1st TSP to TTS, minimum tube to tube gap of 0.4 inch

• Waterford: Row 38: 24.8 inches from 07EC to batwing intersection, 0.25 inch tube to tube gap

• After 2 chemical cleanings, unlikely that tubes are fixed, postulated free end not likely to be excited like a cantilever beam

• Maximum free end displacement of 0.23 inch for lattice configuration 53 O)Westinghouse Tube Support Differences

<I Failed batwings expected to channel more flow vertically due to reduced restriction (open spaces) 54 O )Westinghouse 27

Historic Burst/Leakage Testing

• 75%TW, tapered wear scars, burst pressures of 5000 to 7200 psi at 650F (0.048 wall tubing)

- "Burst" was a localized opening, no tearing of base metal

@1 00%TW tapered wear scars used for leakage testing at 1350, 1750, and 1300 psid, sequentially

- 1300 psid leak rates (following 1750 psid) returned to near the 1350 psid rates

- Little or no gross deformation during pressure differential increase 55 OWestinghouse Historic Collapse Testing 090%TW, tapered wear scars, 2500-2525 psi collapse pressures (0.042 wall tubing)

• Limiting Waterford sec-pri differential = 980 psi

• Collapse occurred over about a 10 second period

• Collapse was localized to wear scar only

==

Conclusion:==

Tapered wear scars do not represent a burst or collapse potential 56 I)Westinghouse 28

Collapse Testing (2007)

• Bounding wear scar shapes at limited secondary to primary pressure differential (980 psi) 04 inch long, uniformly deep wear scars

- Localized collapse at 85%TW; wear scar "creased", tube mostly retained its shape

- Limited change in cross section to flow

- No anticipated change in axial load bearing capability due to large remaining wall thickness OControl samples using 1.5 degree wear tapers still to be tested 57 OWestinghouse Test Configuration N 00 t

W000 I" r 000 00000000 00 0000 00000~0 0000 4Wesflnghouse 29

2007 Collapse Test 59 Summary 0 Event details surrounding Ginna event are not a direct comparison with a wear only scenario

• pV 2 comparison is a minimum of about 30 times less for batwing/tube intersection compared to TTS; flow is mainly axially oriented in central cavity

• Large prying forces are not realistic for a worn/thinned batwing due to inherent weak point associated with wear on batwing; batwing would likely fail in fatigue at first tube in a large amplitude mode due to preexisting wear 60 wefsfingbouse 30

Summary (cont'd)

• At RF14 and RF13, in Columns 50 to 126 and Rows less than 90, no tubes reported with wear at 07C/H through 10C/H, thus no significant crossflow velocities in this area

" Half of BWI-BW9 wear is at BW5; vertically oriented flow

• Maximum free end displacement of 25 inch tube extension is 0.23 inch, or less than tube to tube gap of 0.25 inch

• Extreme wear scars do not cause complete tube collapse

• A "cascading tube damage event" within the original preventive plugging region is not a credible event for mainly axially oriented flow 61 efts1lnghouse Preventive Plugging Map 08 Partial EC provides additional support starting at Row 49 OWestinghouse 31

32 Mid-Cycle Inspection Presentation Objectives

" Review purpose of mid-cycle outage inspections

" Review scoping decision for removing degraded batwings

" Review key assumptions of critical analyses

" Identify needed mid-cycle inspections needed to verify assumptions are conservative Inspection Purpose Purpose Of Mid-Cycle Inspection

• Obtain data to consider removing degraded batwings in a future outage

• Monitor progress of batwing degradation mechanisms Assure conservatism of critical analyses and key assumptions Verify acceptability of current configuration 33

Batwing Removal m- Tooling required a new access hole along the tube lane Po.Stay Rod is located in the tube lane

" Tooling to cut and remove stay rod

" Must capture by-products of cutting P,. Significant technical issues and first of a kind evolution

. Risk of additional SG damage PP.Decision to not implement during mid-cycle outage

" Existing analysis and plugging/stabilization is acceptable

" Degraded batwing removal may be considered at a future outage 34

Key Analysis Assumptions io-Actual eddy current results were used to establish wear growth rates, dropped batwing wear, and wear distribution.

oo-Cyclesim was used to establish largest expected RF15 wear depths. Cycle 15 Operational Assessment predicts margins for all mechanisms

" Assumption - no additional batwings have slipped into the tube bundle

" Inspection - visual exam to verify no upper weld failures for batwings in stay cavity area Key Analysis Assumptions PP-Ginna tube rupture event analysis involved the repeated impacts of a large mass foreign object over several years. Batwing degradation mechanisms do not result in large mass foreign objects

" Assumption - no large mass foreign objects

" Inspection - foreign object search and retrieval 35

6Asupto - twste-- bawn foce can reul in -ino 36

Key Analysis Assumptions oý Broken batwing analyses evaluated acceptability of tube impacts and wear, including normal and accident condition

" Assumption - maximum weight/size of broken batwing

" Inspection - visual exam to verify no large batwing segments are formed in stay cavity area and to remove any segments that can be accessed Expected Batwing Condition SG# 1

" Upper batwing welds should be intact.

" Stay cavity damage is not expected, but may be observed.

" Should a batwing break at the notch connection, a progressive mechanism would be expected and damage similar to that observed in SG#2 could result.

SG#2

" Upper batwing welds/clips and wrap around bar should be intact.

" Stay cavity batwing damage is expected to propagate since the degradation mechanisms have not been arrested.

" No indications of gross tube deformation or large batwing segments are expected.

" Additional Batwing related loose segments may be found 37

Seodr InU.speto Scope Seodr viua exa of upe batwings.

0 veif no uppe batin wedci falue in sta cait area veif no grs s deorato twstn 60of a aroun ba.

Foeg obec se rc an 6retr ieval

• S

" to veif no. lag mass foegI bj csae rs n

" to 6 re ov acesil foeg objects Seodr viua inpcto .a.eaof lowe sta cavit to moio bawn degrada6tion

• 0 to verify no inictin of grs tub deforatio to veif that no larg batwi se -g gmet haefre nsa cait are an reov semet tha ma - y e acesil 6riar Insecio Scp Attnute wear moe wa-eiidt eosraiei 6RF14- 5- 6 S 6. 6 I~~

No-sa cait 6r bawig - n6. exece to fai3-l a- Rous supor structu.re6~ ~

Lo fo fresaple 38

Summary Joe Kowalewski GM Plant Operations, Waterford 3 Summary oý Robust engineering analyses and expertise have developed clear understanding of Batwing condition P.-Compelling defense in depth accounts for uncertainties and continued safe operation is assured o.Planned mid-cycle inspections provide additional conservatism 39