ML20212F598

Discusses Predecisional EC Eddy Current Exam of SG Tubing & Sleeves Conducted on 970926.Meeting Re Methods & Practices Used for Eddy Current Exam.Agenda,Attendance List,Licensee Presentation & Apparent Violations Encl

ML20212F598
Person / Time
Site:	Arkansas Nuclear
Issue date:	10/31/1997
From:	Howell A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:	Hutchinson C ENTERGY OPERATIONS, INC.
References
EA-97-382, NUDOCS 9711050026
Download: ML20212F598 (92)

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NUCLEAR REGULATORY COMMIS0'ON

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REGION IV

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AR LINGTON, T r XAS M0118064 October-31, 1997 EA 9,7 382 4

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C, Randy Hutchinson, Vice President

Operations :

~ Arkansas Nuclear One.

Entergy Ope'ations, Inc. -

1 1448 S.R. 333

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Russellville, Arkansas 72801-0967

SUBJECT:

s Pf t. DECISIONAL ENFORCEMENT CONFERENCE - EDDY CURRENT EXAMINATION OF STEAM GENERATOR TUBING

Dear Mr. Hutchinson:

This' refers to the Predecisional Enforcement Conference conducted in the Region IV office

on September 26,1997. This meeting related to the methods and practices used for eddy

' current examination of steam generator tubing and sleeves, y

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1The agenda, attendance list, licensee's presentation, and apparent violation are included as (enclosures."

'In accordance with Section 2.790 of the NRC's " Rules of Practice," Part 2, Title 10, Code of Federal Regulations, a copy of this letter will be placed in the NRC's Public Document

. Room..

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Should you have any questions concerning this matter, we will be pleased to discuss them with you.

- Sincer ly, jQ 0

,t rthur T. Ho il 11, Dir i

Division of Reactor Safety

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PREDECISIONAL ENFORCEMENT CONFERENCE ATTENDANCE LICENSEE / FACILITY Entergy Operations, Inc. / Arkansas Nuclear One DATE/ TIME -

September 26,1997, Noon LOCATION NRC Region IV, Arlington, Texas j

EA NUMBER 97-382 NRC & LICENSEE REPRESENTATIVES NAME (PLEASE PRINT)

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- Welded S leeves............................................

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- Enforcement Perspective..............................

Dwight Mims Conclusion..........................................................

Randy Hutchinson i

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- Industry peer review

~

Members included -

- 7 LevelIII ECT analysts

- Vendor, other utilities, EPRI

~

~

- Involved with Appendix "H" development Conclusion

- IGA sizing technique met provisions of Appendix "H"

- Defect morphology must be volumetric

- Tube pull to confirm technique

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Implementation

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- ANO revie4 and approval

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ANO EngineeringIleport l-Engineering. Standard.

. - Regression technique ~used IR13_(Fall 1996)

~

- 470 tubes sized 37 tubes with defects 240% TW plugged 433 tubes with 470 indications sized at < 40% TW

- Ensured defects were volumetric

~ !

33% of tubesheet indications examined with rotating pancake coil (RPC)

- Technique not used outside tubesheet-

- 3 tubes (with 11 indications) removed during 1R13 Validate technique for generic use ECT results in generator comparable to results outside generator

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Implementati n o

- Examination of removed tubes Burst testing conducted All burst at 210,000 psig No tube sheet employed Substantial structural margin exists Destructive examination

' Different technique than previously used Flaws opened by mechanical fatigue method Flaw depths determined by SEM metallography Dep.ths did not correlate well with ECT results

- Tubes left in service with IGA indications Depths not accurately determined

- Some may exceed TS limit (40% TW)

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Deviation from guidelines-

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4 Morphology differences

- Potential contributors Differences in destructive examination techniques

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- Potentialcauses

~~- Deviation from EPRI data distribution guidelines

- Variations in ECT amplitudes

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- ; Adequacy of EPRI Appendix "H" Revision 4 l

- Differences in destructive examination techniques

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- Revision to LER planned ~

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Both OTSGs declared inoperable.

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-TS 3.U.3 entered I

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Initiated Condition Report

- April 9,1997 t

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- April 11,1997

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- Exigent TS change request submitted.

- May 7,1997

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TS change approved

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implemented ~

IGA sizing administratively precluded

- August 13,1997

~

Altemate Repair Criteria (ARC) submitted by BWOG

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- No structural or leakage chellenges

- Resolves TS compliancc issues

- Maintains current design basis margins

- Eliminates unnecessary reduction of RCS flow Y

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- Burst pressures 210,000 psig

- UTS precludes tube. rupture

- Conservative leak rate estimates bounded by safety analysis

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- Inservice IGA flaws bounded by pulled tubes

- Freespan indications plugged

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- Conclusion No structural or leakage concern

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- Qualification data set

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Appropriatelyselected'

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- Use of data from other plants is accepted practice

- Qualification process met provisions of nppendix "H"

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- Appropriate. processes were used in the development and -

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No structural or leakage concerns i

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The performance of sizing qualification, usmg data that did "o

not conform to'the fequirements of the selected qualification methods,; was identified to licensee personnel.

on August 8,1997, as.an apparent violation of Criterion IX of Appendix B to 10CFR50

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{ Safety Consequenceg-Actual and Potential

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- UTS precludes tube rupture-

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- Inservice IGA flaws bounded by pulled tubes f

- Freespan indications plugged

- Steam generator safety functions maintained Flaws do not represent a structural or leakage concern o Conclusion

- No actual, low potential safety consequences

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Conclusion:==

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. - Reasonable and' prudent approach:

Sized in UTS only - substantial structural margin Use of knowledgeable industry peer panel to evaluate qualification process

- No violation s

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total bf210 tubes ~ were documentid during ~a Refueling Outage 2R12 revie^w of2F96-1 eddy ^ current data history, as containing.

flaw indications in excess ofthe 40percentplugging or repair limitofthe TechnicalSpecifications

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Inspection Report Concern o

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--2F96-1 analysis appropriate >

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Chronology ~

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Removed 2 tubes

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- Preventive plugging limits

- December 1996 -Initiated Condition Report

- Tubes were identified as having been previously " missed" during the ECT analysis process in 2R11

- March 25,1997 - Presented results from root cause analysis and corrective actions to NRC

- 2R12 (May o - June 9,1997)- Applied corrective actions identified in Root Cause and INPO Audit

- Improved POD

- May 21,1997 - Received NCV for 2R11 missed indications

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- Operation assessments used to' address safe operation

- ECT changes implemented in 2F96-1 Eliminated manufacturing buff mark (MBM) calls

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User friendly analysis guidelines Independent resolution for 2R12

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Surveillance ofoversight process

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Outage 2F96-1. Atotal of210 tubes were documented during a Refueling Outage 2R12. review of 2F964 eddy current datahistory,;as containing flaw' indications in excess. of the 40 percent plugging:or repair limit of the -

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- L_ow potential safety significance Low regulatory significance

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- EGM 96-003 (attachment 2, case 3, scenario 1 & 2) -

LevelIV violation possible

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- Furtherconsiderations

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violation l

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Self-identified Corrective actions prompt and thorough Improvement made independent of regulatory / enforcement process a

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Failure to takeprompt ' corrective actionsprior to returning to service potentially defective : sleeved tubes exhibiting weldzone

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Inspection Report Concerns-The acceptance in 1995 ofcontractor-proposed "use-as-is" dispositionsfor eddy current examination identified weld anomalies in installed Unit 2 sleeves

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1 c1992 ^

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s Sleeve topical sulunitted and!TS cliange approved.

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- 1992-1995-Prairie Island and Zion installed Tungsten Inert Gas (TIG) welded sleeves

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- October 1995 (2R11)

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Unit 2 installed 725 TIG welded sleeves Identified indications by ECT j

Condition report initiated to address ECT indications

- 28 indications accepted for use-as-is based on ultrasonic testing (UT), visual-testing (VT) and ECT methods 4

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- Tubes removed to verify

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- ABB-CE analysis ofpulled tubes confirmed indica ~ tion's were'

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installation-inducedi

- Root Cause evaluation. performed Improper cleaning of tube:

ABB-CE evaluated structural adequacy of the affected welds

- ANO initiated a Condition Report and performed an Operational Assessment for sleeves left in service with indications Discussed Operational Assessment with NRC Staff

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- November 26,1996'

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~ ANO submitted TS change to utilize the revised topical

- May 20,1997 Received Safety Evaluation Report (SER) on TIG welded sleeves

- May 1997 (2R12) - Applied new topical 20% plus point ofsleeves and 100% of previous indications Re-analysis of previously installed sleeves Repaired 1 of the 28 tubes due to weld zone indications

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anticipated welding flaws r

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Generator 11tbe Repair:Using L~eak[ Tight Sleeves, dated July;1992 A

Section:1.0. Introduction-

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- After sleeves are installed and inspec'ted; a baseline examination is" performed using eddy current (ET) techniques. The ET.exaniination -

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serves as baseline to determin'e if there.is sleeve degradation'in later operating years..

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sleeving in order to ilemonstrate'the acceptabilits of the : sleeving:

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Pressure tisting sleeve without bursting l

~ Corrosion test to ensure no loss of functional integrity; Code. design requirements -

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NDE to levels of detectability required to show structural adequacy

' - Specifies periodic ET examination required to verify structural adequacy j

i Items listed applp to qualification parameters and are not acceptance l

criteria for field sleeve installation J

Section 4.5.7 Xondestructive Examination

- Multi-frequencp eddy current method will^e used to perform a base line examination of the installed sleeves for future reference

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- The sleeve to tube weld!joi!its are qualifie'd by process control.

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s Checks 'are made to ensure.that the welds meet these design 1 -

1 requirements. The welding; current and voltage are recorded. The

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L recordings are examined after the: welding sequence has.been completed to verify that the essential parameters are met..

- All welds will be examined using ultrasonic (UT) inspection. On a j

. periodic basis, or if any abnormal conditions are suspected, a visual examination will also be made.

- All sleeves will be examined with eddy current following the installation process. This method will ~ provide 'a volumetric examination of the pressure boundary, including the appropriate segments of the sleeve, parent tube, and weld.

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The objective 6f this examina' tion is to establish baseli,neidata on:

ihe pressure boundafy of the:sibeve tube ' assembly

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' Qualifications have been carried out on sleeved tube samples for' detecting

^as little as a 20% thiough wall flaw.

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sleeve installation m

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. Expansion tool and process Weld parameters UT Post weld heat treat.

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IssueLDescription 7

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- 725. ABB-CE TIG. welded sleeves! installed-

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- Plus point probe used for baseline inspection for installed sleeves

' 73 tubes identified

- Condition reports written

- Arc strikes evaluated with VT Evaluations performed ANO UT Level III, ANO Metallurgist, ANO Lead Design Engineer, ANO Welding Engineer, Corporate Welding Engineer Mock-up. testing performed

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- 3 tubes plugged based on ECT indications.

- 28 had ECT indications called weld zone indications (WZI) (10) and geometric anomalies (GEO)(18)

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~2R-11tWZI/GEO Indications 3 Process controls indicated' sleeve installation good 1

Evaluation of plus point indications.

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~UT/VT methods qualified to evaluate structural member (weld)

Indications gonsidered a'cceptable v

No evidence ofsurface flaws from VT UT confirmed fusion and weld width No presence ofindications on UT '

- Subsequent work post-Prairie Island confirmed conclusions made in 2R11 Post 2RI 1 - Data reviewed'using Prairie Island guidelines

- 1 of 28 indications identified for repair in subsequent refueling outage

- Based on location relative to weld centerline Satisfied RG 1.121 structural and leakage requirements

- Bounded by Prairie Island indications

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Enit 2 Welded Sleeves z

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Corrective Actions forECT indications identified in 2R11

~

. -: Condition Reports to assess indications i

~

~

2 Confirmed indications were repaired

- Condition Report for Prairie Island indications Operability Assessment performed

- Root Cause Evaluation performed

- NDE techniques evaluai.ed

~

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- Appendix"H" Qualification

- Revised TS to reflect revised topical

- Plugged 1 tube in 2R12 based on new acceptance criteria

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Safety Perspective.

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- Sleeves acceptable ~for service based on process control parameters

- 100% inspection performed and evaluated to confirm structural adequacy

- Digital UT - confirmed fusion and weld width VT-no surface flaws present Plus Point - three tubes with weld zone indications plugged

- Subsequent testing and analysis confirmed that the 28 indications met structural and leakage requirements 1/28 required repair based on new acceptance criteria

- Conclusion Low safety significance t

's e

~

~

~

Unit 2 Welded Sleeves

=

_

= _ _

RelatedNRC Correspondence

_ Staff review of weld defects in CE designed SG tube sleeves

~

f(February 10,1997)

Historically, ECT was performed on all welds to provide a baseline for future comparisons with ISI There were no specified initial acceptance criteria for the ECT results 4

CE demonstrated adequate leakage and structural integrity exists for previously installed sleeves that possibly contain upper weld defects j

- NRC staff concluded CE and the affected licensees have taken appropriate steps to ensure adequate integrity of CE designed welded SG tube sleeves

- SER (May 20,1997)

Sleeve welds were historically accepted based on VT and UT examinations.

ET was used for an initial baseline inspection for comparison with later required periodic inspections

~

^

rnit 2 Welded SIseves

~

~

_ = = = - _

= _

' Conclusion

- Sleeve welding parameters indicated proper installation

- Indications were identified during NDE

- Evaluation ofindications and sleeving process performed

- ECT, UT, and VT used to evaluate acceptability of sleeves Tubes plugged based on results ofexams

- Technical basis existed tojustify sleeves as is Complete fusion Sufficient weld width No surface flaws

- Subsequent testing and analysis confirmed that none of the indications were structurally significant

- Structural integrity maintained

- Prompt corrective actions were taken

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W Enforcement Perspective-Dwight Mims Director, Nuclear Safety e

_s Unit 2 Welded Sleeves

=

i Failure to take prompt corrective actions prior;to returning to service potentially' defective sleeved tubes exhibiting weld zone eddy current indications l

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Sleeve welding parameters indicated proper installation Indications were identified during NDE Evaluation ofindications and sleeving process performed 100% ECT, UT, and VT used to evaluate acceatability of.

sleeves Technical basis existed to justify sleeves as is

~

o Subsequent testing and analysis confirmed that none of the o

indications were structurally significant Structuralintegrity maintained o

,7 v

~

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~

Unit 2 Welded Sleeves:

_..._--,..-e..

-_m.,

Safety Consequences - Actual and Potential-Sleeves acceptable based on process control parameters NDE techniques used were evaluated

^

Digital UT - confirmed fusion and weld width VT-no surface flaws presents.

Plus Point - three tubes with indications plugged

~

Steam generator safety functions maintained Met structural and leakage requirements Conclusion o

- No actual, low potential safety consequences l

~

1

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,,--b, Unit 2 Welded Sleeves

_ _

_=

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- - Conclusion

~

- Complied with topical report Technicallyjustified

~

Reasonable, safe for initial installation

- No structural or leakage concerns Consistent with others using sleeves NRC acknowledged - not a safety issue

- No violation

~~

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Conclusion Randy Hutchinson Vice-President, ANO

Eritergy Operations, Inc.

2-ENC 101URL4 APPARENT VIOLATION l

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APPARENT VIOLATION f

PREDECISIONAL ENFORCEMENT CONFERENCE

ENTERGY OPERATIONS, INC., ARKANSAS NUCLEAR ONE

- SEPTEMBER 26,1997 C.

1 NOTE:

THE APPARENT VIOLATIONS DISCUSSED AT THIS PREDECISIONAL ENFORCEMENT CONFERENCE ARE SUBJECT TO FURTHER REVIEW AND MAY BE REVISED PRIOR TO ANY RESULTING ENFORCEMENT ACTION.

~<

APPARENT VIOLATION A.

Criterion IX of Appendix B to 10 CFR Part 50 states, in part,

• Measures shall be establish 3d to assure that special processes, including... nondestructive testing, are controlled and accomplished... using qualified procedures in accordance with applicable codes, standards, specifications, criteria, and other special requirements.

Contrary to the above, the following examples were noted where the practices used p

to qualify the bobbin coil eddy current examination technique (that was used during the Unit 1 Refueling Outage 1R13 in September and October 1990 to size the depth 4,

^'9 of intergranular attack in steam generator tubing in the upper tube sheet region) were not in full conformance with the i.clected qualification method; i.e.,

Appendix H of Electric Power Research Instituto Report TR 106589.V1, "PWR Steam Generator Examination Guidelines: Revision 4," Volume 1:

Contrary to the above:

1.

Paragraph H2.2.1(c) in Supplement H2 to Appendix H of Electric Power Research Institute Report TR 106589-V1 states, " Test sample damage mechanism morphology and dimensions used to construct qualification data set Grading units shall be based on steam generator operating experience as inferred from tube pulls where practical." The qualification data set for siring depth of intergrariular attack was, however, only partially based on Arkansas Nuclear One, Unit 1, steam generator operating experience. Forty seven of thu 53 total data points used for the qualification were obtained from Crystal River 3. The tube location and morphology of the Crystal River 3 intergranular attack were different to the intergranular attack to be sized at Arkansas Nuclear One, Unit 1 (i.e., tube free span and pit-like in configuration versus the Arkansas Nuclear One, Unit 1, upper tube sheet crevice location and patch like configuration).

2.

Paragraph H2.2.2(b) in Supplement H2 to Appendix H of Electric Power Research Institute Report TR 106589 V1 requires, in part, that at least 2/3 (rou ided to the nearest whole number) of the flawed grading units data set elements shall have a maximum true depth equal to greater than 60% of the nominal tebe wall thickness, with the data set uniformly distributed over the depth range of 00% to 100% through wall. However, only 7 of the 53 qualification data points used by the licensee had maximum true depths equal to or greater than 60% of the nominal tube wall thickness.

NOTE:

THE APPARENT VIOLATIONS DISCUSSED AT THIS PREDECISIONAL ENFORCEMENT CONFERENCE ARE SUBJECT TO FURTHER REVIEW AND MAY BE REVISED PRIOR TO ANY RESULTING ENFORCEMENT ACTION.

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3 APPARENT VIOLATION

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I B.

Section 4.4.5.4b. of the Unit 2 Technical Specifications requires steam generator tubes which exceed the plugging or repair limit to be plugged or repaired before determining the steam generator to be operable. Section 4.4.5.4a.7 of the Unit 2 Technical Specificatluns defines the plugging or repair limit as an Imperfection depth ti -

e.;ual to 40 percent of the nominal parent tube thickness.

. Contrary to the above, licensee reevaluation of prior Outage 2F961 bobbin coil 1

examination history (for tubes found by May 1997 Refueling Outage 2R12 eddy

. current examinations to contain flaws requiring removal of the tubes from service) v identified 78 tubas in Steam Generator A and 132 tubes in Steam Generator B for which the Refueling Outage 2R12 eddy curIent analysts assigned imperfection depths.In excess of 40 percent of the nominal parent tube thickness.

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P CV.

NOTE:

. THE APPARENT VIOLATIONS DISCUSSED AT THIS PREDECISIONAL ENFORCEMENT CONFERENCE ARE SUBJECT TO FURTHER REVIEW AND MA Y BE REVISED PRIOl; TO ANY RESULTING ENFORCEMENT ACTION.

4

.x.

.i APPARENT VIOLATION Criterion XVI of Appendix B to 10 CFR Part 50 states, in part, " Measures shall be C.

A established to assure that conditions adverse to quality, such as failures, g,'

malfunctions, deficiencies,' deviations, defective material and equipment, and nonconformances are promptly identified and corrected...."

Contrary to the above, the licensee failed to take prompt corrective action in November 1995, during Refueling Outage 2R11, prior to returning potentially defective Unit 2 sleeved tubes to service. Corrective action (an operability

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~ assessment) was not implemented until March 27,1996.

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e n

NOTE:

THE APPARENT VIOLATIONS DISCUSSEO AT THIS PREDECISIONAL 3

w ENFORCEMENT CONFERENCE ARE SUBJECT TO FURTHER REVIEW AND MA Y BE REVISED PRIOR TO ANY RESULTING ENFORCEMENT ACTION.

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