ML20151Z048

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Rev 0 to Welding Project Employee Concern Evaluation Rept WP-11-BFN, Surface Grinding of Welds at Browns Ferry Nuclear Plant
ML20151Z048
Person / Time
Site: Browns Ferry  Tennessee Valley Authority icon.png
Issue date: 04/04/1987
From: Lewis J, Pate B, Rose J
TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20151Z000 List:
References
WP-11-BFN, WP-11-BFN-R, WP-11-BFN-R00, NUDOCS 8808290147
Download: ML20151Z048 (9)
v • d • e


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, , WELDING PROJECT

! EMPLOYEE CONCERN EVALUATION _ REPORT l

SURFACE GRINDING OF WELDS AT BROWNS FERRY

NUCLEAR PLANT PREPARED BY / '

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Report Number WP-11-BFN Revision 0 Date 4 4 - N'7 l

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11670

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WP-11-BFN  !

, Revision 0 EMPLOYEE CONCERN

SUMMARY

SHEET SURFACE GRINDING OF WELDS AT BROWNS FERRY NUCLEAR PLANT I. SCOPE OF EVALUATION

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This report addresses two employee concerns-dealing with grinding of weld surfaces and shrinkage of stainless steel butt weld joints. These concerns were limited to two issues to aid in the evaluation effort.

A. Grinding of weld surfaces may mask weld surface defects and remove "excess" metal.

B. Stainless steel butt weld joints exhibit excessive shrinkage at the joint.

Text of the two concerns is provided in the technical report WP-11-BFN under Attachment 1.

II. ANALYSIS OF ISSUES ADDRESSED BY CONCERNS The issues addressed by this evaluation evolved from Watts Bar concerns that were applied to Browns Ferry for evaluation for generic implication.

A. One issue implies inspectors require weld surfaces to be ground to a smooth finish that may mask surface defects and excess metal seems to have been removed. Grinding of weld surfaces is not in violation of construction codes, standards, or Browns Ferry Construction Procedures. In contrast, in many cases codes, standards, and construction procedures require grinding to obtain suitable weld profiles for nondestructive testing and to eliminate or reduce surface defects.

This issue is discussed in WP-11-BFN, Paragraph III A.

B. One issue stated there was excessive shrinkage at stainless stoel butt weld joints. Construction codes, standards, and specifications do not offer established critorion for acceptance or rejection of shrinkage.

This issue is discussed in WP-11-BFN, Paragraph III B.

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11670 Page 1 of 2 l

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(- WP-11-BFN Revision 0 III. COLLECTIVE SIGNIFICANCE No collective significant effect on hardware or the TVA welding program at Browns Ferry was identified.

IV. ROOT CAUSE(S)

The root cause of the employee concerns in this area is the TVA decision to apply Watts Bar employee concerns to other nuclear sites for evaluation for generic implications.

V. CORRECTIVE ACTION No corrective action is indicated.

VI. REINSPECTION REQUIRED No.

VII. ISSUE CLOSURE Closed.

VIII. ATTACHMENTS

1. Evaluation Report WP-11-BFN.

11570 Page 2 of 2

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, WP-11-BFN Revision 0 WELDING PROJECT EMPLOYEE __ CONCERN EVALUATION REPORT SURFACE GRINDING CF. WELDS AT BROWNS FERRY WUCLEAR PLANT I. SCOPE OF EVALUATION This report addresses two employee concerns. Text of the concerns is provided under Attachment 1.

The subject concerns originated at Watts Bar Nucluse Plant, and were generically applied to Browns Ferry Nuclear Plant (BFN). This evaluation is based on review of the BFN Welding Phase 1 Report, current and superseded process specifiestions and implementing procedures, and the Weld Project Reports WP-11-SQN and WP-19-SQN. Alsv reviewed were the BFN Corrective Action Reports, Discrepancy Reports, Nonconformance Reports, and the AEC/USNRC Inspection Reports for 1970 through 1985. The American Society of Mechanical Engineers (ASME)

Boiler and Pressure Vessel Code Section III, The USA Standard for Pressure Piping B31.1.0, American Institute of Steel Construction's (AISC) Eighth Edition of the Manual of Steel Construction, and the Amarican Society For Metals (ASM) Metals Handbook Volume 1 were reviewed and compared with the text of the concerns. The findings presented herein are based upon review of the above noted documents and interviews with cognizant TVA personnel.

II. ISSUES ADDRESSED BY CONCERhS A. Surface grinding of welds may mask surface defects and remove "excess" metal.

B. Excessive shrinkage at stainless steel butt joints.

III. ANALYSIS OF ISSUES ADDRESSED BY CONCERNS

4. One concern stated that TVA inspectors required pipe welds to be surface ground to a smooth finish and that the finish may mask a surface defect. The other concern stated that stainless steel butt weld joints seem to have "excess" metal removed.

ASME Section III Subsections NB, NC, ND 4424 require in part that the surface of welds shall be sufficiently free from coarse ripples, grooves, overlaps, and abrupt ridges and valleys for proper interpretation of radiographic and other required nondestructive examinations (NDE) of the welds.

11740 Page 1 of 3

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WP-11-BFN Revision 0 Additionally, when surface defects have been detected, NB, NC, ND 4452 states in part, "weld metal surface defects may be removed by grinding or machining."

ASME Section V Article 2. T-222.2, requires that weld ripples or weld surface irregularities be removed by any suitable process to such a degree that the resulting radiographic image due to any irtegularities cannot mask or be confused with the image of any discontinuity.

USA Standard B31.1.0 at 127.4.2 requires in part that the finished -

surface of the weld shall merge smoothly into the component surface at the weld toe.

Nucicar Power Operations Procedure PHP 1502.07 Procedure No. N-VT-3 requires in part that after welding all welds shall be examined for compliance with the applicable welding specification for at least weld defects, contour and finish of outside surface of welds, reinforcement and suitability to perform other nondestructiva tests.

Browns Ferry Construction procedure BF-15 requires in part all welded joints to be examined by radiography shall have excessive weld ripples or weld surface irregularities removed by grinding.

A review of the BFN Discrepancy Reports, Nonconformance Reports, Corrective Action Reports, and the AEC/USNRC Inspection Reports revealed no indication that the surface grinding of welds has created a hardware deficiency.

The above review shows no problem exists at BFN relative to surface preparation of wolds by grinding and that the construction codes, standards, and procedures not only recognize grinding as an acceptable means for surface preparation and defect removal or reduction but, in some cases require it.

Considering that portion of the concern relative to inspectors requiring surface grinding of welds, it is recognized that some inspectors require weld surface preparation which may exceed the minimum requirements. It is also widely recognized that as the visual inspector gains experience in the various NDE surface preparation requirements, he/she is less likely to ask for cosmetic preparation beyond that required for propec interpretation of the specified NDE.

B. One concern states that stainless steel butt weld joints exhibit excessive shrinkage.

Austenitic stainless steels exhibit variable amounts of distortation and warping when heat is applied. The ASM Metals llandbook section on stainless stools, austenitic grades, ' states in part, "their high coefficient of thermal expancion - over half again as great as that for ordinary ctcel or 400 serias alloys -

demand careful attention to control of distortation ond warping."

11740 Page 2 of 3

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( (' WP-ll-DFN Revision 0 The AISC Manual of Steel Construction, in part 6 Miscellaneous Data and Mathematical Tables, states in part, "Application of heat by welding produces residual stresses, which are generally accompanied by distortion of various amounts. Both the stresses and distortions are minimized by controlled welding procedures and fabrication methods.

BFN detailed weld procedures GT-SM-88-0-1, GT-SM-88-0-1A, GT-SM-88-01-1B, and GT-SM88-0-lc for welding stainless steel specify the amperage ranges, based on filler material size, that may be used and establishes a maximum allowable interpass -

temperature.

Further review of the BFN Corrective Action Reports, Discrepancy Reports, Nonconformance Reports, and the AEC/USNRC Inspection Reports did not reveal indication that a problem exists with the distortion and warpage (hoop shrinkage) in the stainless steel butt weld joints at BFN.

The above review did not reveal any established criterion to base acceptance or rejection of shrinkage of stainless steel butt weld joints. The review did establish; however, thac various amounts of distortion and warpage will occur when welding stainless steel.

Also, detailed welding procedures have been implemented at BFN to minimize distortion and warping when welding stainless steel.

IV. COLLECTIVE SIGNIFICANCE This evaluation revealed no adverse effect on hardware or the TVA welding program.

V. ROOT CAUSE(S)

The reason for the employee concerns relating to surface grinding of welds and shrinkage of stainless steel butt weld joints is the application of Watts Bar concerns to other TVA nuclear sites for evaluation for generic implications.

VI. CORRECTIVE ACTION No corrective action is indicated.

VII. ATTACHMENTS

1. Employeo Concerns 11740 page 3 of 3

( (- WP-11-BFN Revision 0 WELDING PROJECT EMPLOYEE CONCERN EVALUATION REPORT l

1 ATTACHMENT 1 I TEXT OF EMPLOYEE CONCERNS Evaluation Report WP-11-BFN addresses two employee concerns. The text of the concerns is shown on the following pages. ..

IN-85-282-002 IN-85-299-003 l

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R EFERE!1CE - ECPS132J-ECPS132C! TEN!!ESSEE VALLEY AUTHORITY FP.EQU EllCY - REQUEST PAGE -

Or3P - 1553 - Rl!M OFFICE OF HUCLEAR P0HER RUN TIME - 11:5 EMPLOYEE CONCERil PROGRAtt SYSTEM (ECPS) rut! DATE - 03/le CATEGORY: IIE NOH QA/QC llELDIllG EMPLOYEE CONCERif ItiFORf1ATION BY CATEGORY / SUBCATEGORY llP - 11 SURFACE GRIllDING OF llELDS S

H 1 REPORT APPL SUB R PLT 2 SAF RELATED HISTORICAL CONCERN REF. SEC' C0rlCERN HUMBER CAT CAT D LOC BF BL SQ !!B CAT -

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REPORT ORIGIll CONCERN DESCRIPTION SUBCAT -

Ill 282-00202 HE 50711 N !!BN 1Y Y Y Y IN-85-282-002 QTC UllTIL RECENTLY, TVA I! ELD IllSPECTORS 150014 2 SR SR SR SR REQUIRED ALL PIPE HELDS 70 BE SURFAC E GROUND TO A SMOOTH FINISH. THE C0 flCERil IS THAT SMOOTH GRIllDING MAY AC TUALLY HASK A SURFACE DEFECT HHICH H OULD OTHERHISE BE DETECTABLE. NO FU RTHER DETAILS IIERE AVAILABLE. (SQN I SSUES ADDRESSED IN RPT HP-ll-SQN RI) 1 C0!!CERHS FOR CATEGORY HE HP - 11 ConCER!!S ARE GROUPED BY LAST 2 DIGITS OF SUBCATEGGRY HUMBER.

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I eREQUEllCY - REQUEST OFFICE OF !!UCLEAR Pot!ER RUN TIME - 11:56:4 o!!P - 1555 - R1!Il EMPLOYEE C0t!CERil PROGRAtt SYSTEM (ECP3) RU!I DATE - 03/16/8 EMPLO(EE C0tlCERil IliFORt1ATI0tl BY CATEGORY / SUBCATEGORY

.TEGORY: HE floti QA/QC HELDING llP - 34 UllSATISFACTORY HELD APPEARAtlCE S

H 1 REPORT APPL REF. SECTIO SUB R PLT 2 SAF RELATED HISTORICAL C0riCERN CAT - HE C0!!CERil flUMbER CAT CAT D LOC BF BL SQ IIB REPORT ORIGIll C0tlCERif DESCRIPTION SUBCAT - 34

!!! 299-00301 HE 50919 5 ll3N 1N tl Y N QTC SS HELDS SEEN TO HAVE EXCESS METAL R T50138 2 flA NA SR flA EMOVED AT BUTT HELD JOIllTS, ALSO THE llELDS EXHIBIT EXCESSIVE SHRINKAGE A 02 HE 50934 S HBN 1Y Y N Y T JOIllTS. THIS CONCERtl IS GENERIC B 2 SR SR NA SR UT HAVE EXAMPLES. THIS HAS BEEtt NOT ICED FOR THE PAST 6 YEARS IN BOTH UN

, ITS. DETAILS Kil0HN TO QTC, HITHHELD L , DUE TO CONFIDENTIALITY. C0tlSTRUCTIO v 11 DEPT CONCER. (5011 ISSUES ADDRESSED IN RPT HP-19-SQN Rl) 1 CarlCERilS FOR CATEGORY HE HP - 34 C0tlCERilS ARE GROUPED BY LAST 2 DIGITS OF SUBCATEGORY llUMBER.

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