ML120250111

Licensee Slides Arkansas Nuclear One, Unit 1 - Steam Generators Tube to Tube Wear

ML120250111
Person / Time
Site:	Arkansas Nuclear
Issue date:	01/25/2012
From:	AREVA, Entergy Nuclear Operations
To:	Peter Bamford Plant Licensing Branch 1
Bamford, Peter J., NRR/DORL 415-2833
Shared Package
ML120250090	List: ML120250105 ML120250111
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Download: ML120250111 (42)

Text

ANO1 Steam Generators NRC Presentation Arkansas Nuclear One Unit One Steam Generators Tube to Tube Wear Entergy/AREVA INC.

January 2012 1

ANO1 Steam Generators 3/4 Entergy Jaime McCoy - Engineering Director Danny Hughes - EP&C Supervisor Dan Meatheany - SG Program Owner Steve Brown - Corporate SG Program Owner Bob Clark - Licensing 3/4 AREVA INC.

Jeff Fleck Jim Begley Jeff Grigsby Mike Boudreaux John Remark 2

ANO1 Steam Generators 3/4 Agenda Opening Remarks - Jaime McCoy Outage Results - Dan Meatheany Damage History - Mike Boudreaux Outage Plans for 1R24 - Dan Meatheany Questions Closing Comments - Jaime McCoy Root Cause - John Remark 3

ANO1 Steam Generators Opening Comments Jaime McCoy Engineering Director 4

ANO1 Steam Generators EOTSG Description 9 15 Tube Support Plates 9 External FW and EFW Rings 9 Floating TSP/Tie Rod 9 TSP are Trefoil Broach SS 9 Aspirating Port in 10th Span 9 Upper and Lower Shroud 9 Orifice Plate in Downcomer 9 FW into Downcomer 9 EFW Penetrates Shroud 9 52 Tie Rods Concentric Circles 5

ANO1 Steam Generators ANO1 EOTSG Inspections 3/4 Generators replaced in fall of 2005 (1R19) 3/4 First ISI was spring 2007 (1R20) 3/4 Second ISI was fall 2008 (1R21) 3/4 Third ISI was spring 2010 (1R22) 3/4 Fourth ISI was fall of 2011 (1R23) 6

ANO1 Steam Generators Inspection Scope 3/4 IR23 Inspection Scope 100% bobbin full length of tubes X-Probe of affected tubes around tie rods X-Probe off special interest (SI)

(S ) locations 3/4 A similar scope of 100% Bobbin and X-Probe SI was conducted in 1R20 and 1R21 3/4 Outage 1R22 was a limited scope of tubes surrounding tie rods for tie rod bowing 3/4 All special interest has been performed with the X-Probe 7

ANO1 Steam Generators Time Line for Identification of Tube-to-Tube Wear 3/4 Started ANO1 inspection on 10/20/2011 3/4 Analysis and repair complete on 10/26/2011 3/4 Notified by Exelon and AREVA on 11/07/2011 about Tube-to-Tube wear 3/4 Re-analyzed 100% of the 1R23 data using auto analysis and performed a review of historical data 3/4 Revised CMOA - acceptable to operate for 3 cycles 3/4 Initiated root cause effort 8

ANO1 Steam Generators Attributes of Tube-to-Tube Wear 3/4 Located in the middle of the 9th span which is also the middle of the entire tube and some (far fewer) indications in the middle of the 8th span 3/4 Typically located in a radial pattern 30- 45 from the center of the tubesheet 3/4 Present in adjacent tubes (groups of two or three) unless near the detection threshold 3/4 In adjacent tubes the indications face one another at the same elevation and are the same length and depth range 3/4 Indications occurring in a triangular pattern show two indications in one tube and one indication in each of the other two tubes 3/4 Symmetrically tapered to a maximum depth in the center 9

ANO1 Steam Generators Reanalysis for Tube-to-Tube Wear 3/4 Diagnosis of this condition at TMI led to an immediate notification and reanalysis of the ANO inspection data 3/4 The reanalysis was conducted with an automated algorithm with a reporting threshold of 0.35 volts, which equates to 6% TW (0.50 volts equates to 8% TW) 3/4 All identified indications were further reviewed for the attributes defined for Tube-to-Tube wear 10

ANO1 Steam Generators Reanalysis for Tube-to-Tube Wear 3/4 Identified tube-to-tube wear indications were reviewed in all prior inspections to concisely define history and develop growth data 3/4 Using the correlation between bobbin and

+Point voltages for TMI Tube-to-Tube wear, a calibration curve was developed for the ANO1 bobbin data to estimate depth based upon

+Point voltage from EPRI 27905.3 3/4 Depths were assigned to all indications in 1R20, 1R21 and 1R23 inspections 11

ANO1 Steam Generators Tube-to-Tube Wear Inspection Findings 3/4 A total of 126 indications in 122 tubes were identified with tube-to-tube wear EOTSG A: 48 indications in 48 tubes EOTSG B: 78 indications in 74 tubes 3/4 Wear depths range from 5% to 26% through wall 3/4 Indications have initiated with time None were present in the preservice inspection and none have disappeared since initiation 79 were present in the first inspection 11 new indications were in the second inspection 36 new indications were in the fourth inspection 12

ANO1 Steam Generators 13

ANO1 Steam Generators 14

ANO1 Steam Generators Tube-to-Tube Wear Inspection Findings Average Depth Average Largest Largest of New Depth 1R23 New 1R23 Indications at Repeat Indication Indication 1R23 Indications Depth Depth at 1R23 SG A 9%TW 8%TW 16%TW 16%TW SG B 8%TW 10%TW 11%TW 26%TW 15

ANO1 Steam Generators 16

ANO1 Steam Generators 17

ANO1 Steam Generators 18

ANO1 Steam Generators Growth History for Two Largest Indications 19

ANO1 Steam Generators Condition Monitoring Satisfied 3/4 Utilized maximum depth and conservative length for 3 delta P conditions 3/4 Substantial margin against accident leakage and structural limits (>20%TW) 3/4 LBLOCA loading conditions evaluated and also satisfied, conservatively assuming 180 degree circumferential extent of wear 20

ANO1 Steam Generators 21

ANO1 Steam Generators Operational Assessment Summary 3/4 Mixed arithmetic/monte carlo method utilized 3/4 Cycle length 4.13 EFPY (three fuel cycles) 3/4 Used maximum growth over previous cycle 3/4 Significant margin to leakage and burst

(>10%TW margin) 3/4 LBLOCA evaluation also demonstrates significant margin 22

ANO1 Steam Generators ANO Unit 1 Inspection History Analysis of ADIs Mike Boudreaux 23

ANO1 Steam Generators Absolute Drift Indications 3/4 Absolute Drift Indications (ADI) are eddy current signals from the bobbin probe which have only an absolute channel response and are caused by numerous variables variables, most commonly; flaws flaws, MBMs and material property changes 3/4 Historically service related degradation in PWR Steam Generators have produced both differential and absolute channel responses and MBMs and material property changes have produced only an absolute channel response 24

ANO1 Steam Generators 25

ANO1 Steam Generators 26

ANO1 Steam Generators ADI Reporting Process (Bobbin Probe) 3/4 The reporting process for ADIs has been consistent since 1R20 to support historical review 3/4 The reporting criteria for absolute indications is 0 50 volts and > 0.50 0.50 0 50 inches in length to address the most common source - MBMs 3/4 The analysis rules allow reporting below this threshold if the indication is flaw-like 3/4 Resolution analysts review the production calls as well as evaluate the indications for change using a criteria of 10 degree phase shift and > 0.50 volt increase in amplitude 27

ANO1 Steam Generators Reporting Process (X-Probe) 3/4 The reporting process has been consistent since 1R20 3/4 The analysis requirements are prescriptive 3/4 The Th reporting ti criteria it i iinvolves l no particular ti l thresholds and there are reporting codes for linear and volumetric indications - otherwise No Degradation Found (NDF) 3/4 Resolution analysts review the production calls and assign a final call as they deem appropriate with concurrence 28

ANO1 Steam Generators Reporting History for Tube-to-Tube Wear SG A Tube-to-Tube Wear Indications Reported by Outage Category 1R20 1R21 1R23 Not available Primary 4 17 Not available Secondary 3 22 Resolution 1 1 17 Total Present 15 23 48 Not Reported 0.49 volts 11 18 23 0.50 volts 3 0 2 SG B Tube-to-Tube Wear Indications Reported by Outage Category 1R20 1R21 1R23 Not available Primary 26 27 Not available Secondary 25 41 Resolution 15 18 23 Total Present 64 67 78 Not Reported 0.49 volts 40 31 28 0.50 volts 9 7 6 29

ANO1 Steam Generators Analysis Process Review 3/4 An average of 21% of the Tube-to-Tube wear indications have been reported over the past inspections 3/4 An average of 57% of the Tube-to-Tube wear indications were e e be below o tthee ADI reporting epo t g tthreshold es o d o over e tthe e past inspections 3/4 This total of 78% means that, on the average, 20% of the reportable ADIs were not reported over the past inspections 3/4 The absence of a differential channel response, to indicate a flaw-like condition, coupled with a reporting threshold of 0.50 volts are the primary contributing factors to the percentage of indications reported 30

ANO1 Steam Generators Analysis Process Review 3/4 A review of the indications shows that both the production, resolution and IQDA analysts have mischaracterized the indications in one fashion or another over the past inspections Production - either by not reporting them or mischaracterizing them Resolution - either by deleting them or mischaracterizing them IQDA - either by not questioning deleted indications or agreeing with the mischaracterization 31

ANO1 Steam Generators Review of Tube R116-T029 Reporting History 3/4 1R20 Reported as an NQI on bobbin and VOL on X-Probe 3/4 1R21 Reported R t db by production d ti as ADI on b bobbin bbi and d SVI and d

MBM on X-Probe Resolution stated it was anomaly or geometry and changed call to NDF with IQDA agreement 3/4 1R23 Reported by production as ADI on bobbin and changed to NQS based on history and did not receive an X-Probe test 32

ANO1 Steam Generators Review of Tube R117-T029 Reporting History 3/4 1R20 Not reported on bobbin though signal was present 3/4 1R21 Reported R t dbby production d ti as ADI on b bobbin bbi and d SVI and d

MBM on X-Probe Resolution stated it was anomaly or geometry and changed call to NDF with IQDA agreement 3/4 1R23 Reported by production as ADI on bobbin and changed to NQS based on history and did not receive an X-Probe test 33

ANO1 Steam Generators Summary for R116-T029 and R117-T029 3/4 Hindsight review would indicate that these indications should have been investigated further The tubes are side by side The indications are at the same elevation The bobbin voltage was > 2 volts The X-Probe signal was volumetric in nature Voltage change was > 0.5 volts from 1R20 outage 34

ANO1 Steam Generators Resolution Analysis Team Structure (1R23) 3/4 The primary and secondary resolution teams were from different companies 3/4 The IQDA was from the secondary analysis company 3/4 There were 5 primary & 6 secondary resolution analysts and 2 IQDA - all certified Level III QDA 3/4 The resolution process requires a minimum of two resolution and one IQDA analysts to delete degradation 35

ANO1 Steam Generators Resolution Analysis Team Experience (1R23)

Experience Position

(# Jobs)

Primary Resolution 1 16 Primary Resolution 2 5 Primary Resolution 3 25 Primary Resolution 4 11 Primary Resolution 5 9 Secondary Resolution 1 2 Secondary Resolution 2 4 Secondary Resolution 3 7 Secondary Resolution 4 5 Secondary Resolution 5 9 Secondary Resolution 6 3 Independent QDA 1 8 Independent QDA 2 14 36

ANO1 Steam Generators Potential to Mask Other Degradation 3/4 As the steam generators age there is a possibility for another form of degradation to initiate at a Tube-to-Tube wear site 3/4 Itt iss unlikely u e y tthat at the t e absolute abso ute ssignal g a from o tthe e wear ea sca scar will mask other degradation since that degradation is likely to produce a differential signal and differential channels are unaffected by Tube-to-Tube wear signals 3/4 New degradation will result in a change in the signal which will require the indication to be further tested 3/4 No other attributes of the Tube-to-Tube wear scar are likely to affect eddy current signal response for bobbin, X-Probe or RPC 37

ANO1 Steam Generators ANO Unit 1 1R24 Inspection Plan Dan Meatheany 38

ANO1 Steam Generators Purpose of Inspections 3/4 Confirm apparent cause and analysis inputs 3/4 Determine magnitude of tie rod bow 3/4 Determine if free-span wear exists on tubes around tie rods 3/4 Determine if denting exists on tubes around tie rods 3/4 Evaluate the Tube-to-Tube wear 39

ANO1 Steam Generators Current Scope of 1R24 Inspection Plans 3/4 Bobbin test of surrounding tubes for all 52 tie rods in both steam generators 3/4 Inspect all previously identified Tube-to-Tube wear > 00.35 35 volts 40

ANO1 Steam Generators Questions ?

41

ANO1 Steam Generators Closing Comments - Jaime McCoy 42