arkansas nuclear one unit one steam generators tube to tube wear

8/3/2019 Arkansas Nuclear One Unit One Steam Generators Tube to Tube Wear

1/42

ANO1 Steam Generators

NRC PresentationArkansas Nuclear One Unit One Steam Generators

Tube to Tube Wear

1

Entergy/AREVA INC.

January 2012


2/42


Entergy

Jaime McCoy Engineering Director

Danny Hughes EP&C Supervisor

Dan Meatheany SG Program Owner

Steve Brown Corporate SG Program Owner

2

Bob Clark - Licensing

AREVA INC.

Jeff Fleck

Jim Begley Jeff Grigsby

Mike Boudreaux

John Remark


3/42


Agenda

Opening Remarks Jaime McCoy

Outage Results Dan Meatheany

Damage History Mike Boudreaux

3

Questions

Closing Comments Jaime McCoy

Root Cause John Remark


4/42


Opening Comments

4

Engineering Director


5/42

EOTSG Description

15 Tube Support Plates

External FW and EFW Rings

Floating TSP/Tie Rod


5

TSP are Trefoil Broach SS Aspirating Port in 10th Span

Upper and Lower Shroud

Orifice Plate in Downcomer

FW into Downcomer

EFW Penetrates Shroud

52 Tie Rods Concentric Circles


6/42


ANO1 EOTSG Inspections

Generators replaced in fall of 2005 (1R19) First ISI was spring 2007 (1R20)

Second ISI was fall 2008 (1R21)

6

Third ISI was spring 2010 (1R22) Fourth ISI was fall of 2011 (1R23)


7/42


Inspection Scope

IR23 Inspection Scope 100% bobbin full length of tubes

X-Probe of affected tubes around tie rods

7

X-Probe of special interest (SI) locations

A similar scope of 100% Bobbin and X-Probe SI

was conducted in 1R20 and 1R21

Outage 1R22 was a limited scope of tubessurrounding tie rods for tie rod bowing

All special interest has been performed with the

X-Probe


8/42


Time Line for Identification of Tube-to-Tube

Wear Started ANO1 inspection on 10/20/2011

Analysis and repair complete on 10/26/2011

8

Notified by Exelon and AREVA on 11/07/2011about Tube-to-Tube wear

Re-analyzed 100% of the 1R23 data using auto

analysis and performed a review of historical data

Revised CMOA acceptable to operate for 3

cycles

Initiated root cause effort


9/42


Attributes of Tube-to-Tube Wear 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

Typically located in a radial pattern 30 45 from the center of

9

Present in adjacent tubes (groups of two or three) unless near

the detection threshold

In adjacent tubes the indications face one another at the same

elevation and are the same length and depth range

Indications occurring in a triangular pattern show two

indications in one tube and one indication in each of the other

two tubes

Symmetrically tapered to a maximum depth in the center


10/42


Reanalysis for Tube-to-Tube Wear

Diagnosis of this condition at TMI led to animmediate notification and reanalysis of the

ANO inspection data

10

automated algorithm with a reporting threshold

of 0.35 volts, which equates to 6% TW (0.50 voltsequates to 8% TW)

All identified indications were further reviewedfor the attributes defined for Tube-to-Tube wear


11/42


Reanalysis for Tube-to-Tube Wear

Identified tube-to-tube wear indications werereviewed in all prior inspections to concisely

define history and develop growth data

11

+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 Depths were assigned to all indications in 1R20,

1R21 and 1R23 inspections


12/42


Tube-to-Tube Wear Inspection Findings

A total of 126 indications in 122 tubes were identifiedwith tube-to-tube wear

EOTSG A: 48 indications in 48 tubes

12

Wear depths range from 5% to 26% through wall

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


13/42


13


14/42


14


15/42


Tube-to-Tube Wear Inspection Findings

Average Depth

of New

Indications at

Average

Depth

Repeat

Largest

1R23 New

Indication

Largest

1R23

Indication

15

at 1R23SG A 9%TW 8%TW 16%TW 16%TW

SG B 8%TW 10%TW 11%TW 26%TW


16/42


16


17/42


17


18/42


18


19/42


Growth History for Two Largest Indications

19


20/42


Condition Monitoring Satisfied

Utilized maximum depth and conservative lengthfor 3 delta P conditions

Substantial margin against accident leakage and

20

LBLOCA loading conditions evaluated and also

satisfied, conservatively assuming 180 degree

circumferential extent of wear


21/42


21


22/42


Operational Assessment Summary

Mixed arithmetic/monte carlo method utilized

Cycle length 4.13 EFPY (three fuel cycles)

Used maximum growth over previous cycle

22

Significant margin to leakage and burst(>10%TW margin)

LBLOCA evaluation also demonstrates

significant margin


23/42


ANO Unit 1 Inspection History

23

Mike Boudreaux


24/42


Absolute Drift Indications

Absolute Drift Indications (ADI) are eddy current

signals from the bobbin probe which have only

an absolute channel response and are caused

24

, ,

MBMs and material property changes Historically service related degradation in PWR

Steam Generators have produced both

differential and absolute channel responses andMBMs and material property changes have

produced only an absolute channel response


25/42


25


26/42


26


27/42


ADI Reporting Process (Bobbin Probe)

The reporting process for ADIs has been

consistent since 1R20 to support historical review

The reporting criteria for absolute indications is

27

. .

the most common source MBMs

The analysis rules allow reporting below this

threshold if the indication is flaw-like

Resolution analysts review the production calls aswell as evaluate the indications for change using

a criteria of 10 degree phase shift and > 0.50

volt increase in amplitude


28/42


Reporting Process (X-Probe)

The reporting process has been consistent since

1R20

The analysis requirements are prescriptive

28

e repor ng cr er a nvo ves no par cu ar

thresholds and there are reporting codes for linear

and volumetric indications otherwise No

Degradation Found (NDF)

Resolution analysts review the production callsand assign a final call as they deem appropriate

with concurrence


29/42


Reporting History for Tube-to-Tube Wear

SG A Tube-to-Tube Wear Indications Reported by Outage

Category 1R20 1R21 1R23

Primary Not available 4 17

Secondary Not available 3 22

Resolution 1 1 17

29

o a resen

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

Primary Not available 26 27

Secondary Not available 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


30/42


Analysis Process Review

An average of 21% of the Tube-to-Tube wear indications

have been reported over the past inspections

An average of 57% of the Tube-to-Tube wear indications

were below the ADI re ortin threshold over the ast

30

inspections This total of 78% means that, on the average, 20% of the

reportable ADIs were not reported over the past

inspections

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


31/42


Analysis Process Review

A review of the indications shows that both the

production, resolution and IQDA analysts have

mischaracterized the indications in one fashion or

31

Production - either by not reporting them ormischaracterizing them

Resolution either by deleting them or

mischaracterizing them IQDA either by not questioning deleted

indications or agreeing with the

mischaracterization


32/42


Review of Tube R116-T029 Reporting History

1R20

Reported as an NQI on bobbin and VOL on X-Probe

1R21

32

Reported by production as ADI on bobbin and SVI and

MBM on X-Probe

Resolution stated it was anomaly or geometry and

changed call to NDF with IQDA agreement

1R23 Reported by production as ADI on bobbin and

changed to NQS based on history and did not receive

an X-Probe test


33/42


Review of Tube R117-T029 Reporting History

1R20

Not reported on bobbin though signal was present

1R21

33

Reported by production as ADI on bobbin and SVI and

MBM on X-Probe

Resolution stated it was anomaly or geometry and

changed call to NDF with IQDA agreement

1R23 Reported by production as ADI on bobbin and

changed to NQS based on history and did not receive

an X-Probe test


34/42


Summary for R116-T029 and R117-T029

Hindsight review would indicate that these indications

should have been investigated further

34

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


35/42


Resolution Analysis Team Structure (1R23)

The primary and secondary resolution teams were

from different companies

The IQDA was from the secondary analysis

35

There were 5 primary & 6 secondary resolution

analysts and 2 IQDA all certified Level III QDA

The resolution process requires a minimum of two

resolution and one IQDA analysts to deletedegradation


36/42


Resolution Analysis Team Experience (1R23)

PositionExperience

(# Jobs)

Primary Resolution 1 16



36



Secondary Resolution 1 2






Independent QDA 1 8

Independent QDA 2 14


37/42


Potential to Mask Other Degradation

As the steam generators age there is a possibility for

another form of degradation to initiate at a Tube-to-Tube

wear site

It is unlikel that the absolute si nal from the wear scar

37

will mask other degradation since that degradation islikely to produce a differential signal and differential

channels are unaffected by Tube-to-Tube wear signals

New degradation will result in a change in the signal

which will require the indication to be further tested

No other attributes of the Tube-to-Tube wear scar are

likely to affect eddy current signal response for bobbin,

X-Probe or RPC


38/42


ANO Unit 1 1R24

38

Dan Meatheany


39/42


Purpose of Inspections

Confirm apparent cause and analysis inputs

Determine magnitude of tie rod bow

Determine if free-span wear exists on tubes

39

Determine if denting exists on tubes around tie

rods

Evaluate the Tube-to-Tube wear


40/42


Current Scope of 1R24 Inspection Plans

Bobbin test of surrounding tubes for all 52 tie

rods in both steam generators

Inspect all previously identified Tube-to-Tube

40

.


41/42


Questions ?

41


42/42


Closing Comments Jaime McCoy

42

arkansas nuclear one unit one steam generators tube to tube wear

Documents