ML19256F352

Final Deficiency Rept Re Deficient Weld in Steam Generator Lower Lateral Support.In June 1979,pinhole Discovered in Weld Preparation Area.Reinsp Showed Three Addl Rejectable Indications.Part Returned for Repair

ML19256F352
Person / Time
Site:	Catawba
Issue date:	12/13/1979
From:	DUKE POWER CO.
To:
Shared Package
ML19256F350	List: ML19256F349 ML19256F352
References
NUDOCS 7912180593
Download: ML19256F352 (5)

Text

DUKE POWER CC'MPANY CATAWBA NUCLEAR STATION FINAL REPORT ON DEFICIENT WELD IN THE STEAM GENERATOR LO'.4ER LATERAL SUPPORT ATTACHMENTS: DUKE POWER COM?ANY DRAWI"G CN-1070-12 1608 251 791216v573

1.0 Introduction This final report is being filed as required by ICCFR 50.55(e) to present informa-tion and conclusions concerning Duke Power's investigation into the deficient welds discovered on the Steam Generator Lower Lateral Support. This report covers the events and investigative activity which has taken place subsequent to the discovery of the weld deficiencies on July 2,1979. NRC Region II was notified by telecon on November 13, 1979 that the Steam Generatre Lower Lateral Supports fabricated by Lance Industries, Inc. and delivered to the Catawba Nu-clear Station were found to contain deficient welds which required analysis by Duke Design Engineering and weld repair by Lamco Industries.

2.0 Description The Steam Generator Lower Lateral (SGLL) Suppcrts for the Catawca Nuclear Sta-tion were designed by Duke Power Design Engineering. Duke contracted the fabri-Cation of these compenent supports to Lanco Industries, Inc. of El Cajon, Cali-fo rn i a . Tnese supports consist of welded beam members, the gener;.i details of which are shown on the a ttached Drawing No. CN-1070-12. Each support consists of two (2) major parts, that when welded together at the construction site form a scuare ring that surrounds the Steam Generator. This ring is succorted by welded attachments to embedments contained in the structural concrete walls.

Beginning in June of 1979, the first of the Unit 2 SGLL supports was prepared for installation by the Duke Construction Department. During the site preping and cleaning of one part (69t8-6), a pinhole (slag pocket) of apprcxinc tely 1/16" diareter was discovered in the veld preparation area. Since the pinhole consti-tuted a rejected defect in the weld, Duke Design Engineering was notifieo on July 2,1979 by Duke Construction utilizing Nonconfomance Item Report (NCI)

No. 5C56. Duke Design Engineering requested that Duke Construction attempt to remove the pinhale by grinding to a aximum cepth of one-half (1) inch (in the 3

resolution to NCI 6066 on July 13,1979). If the pinhole could not be removed, the i. eld was to be inspected using ultrasenic examina tion with the results sent to Duke Design Engineering for review. On July 31, 1979, Duke Construction notified Duke Design Engineering that the pinhole had not been removed when ground to a depth of one-half (b) inch and a ccoy of the ultrasonic inspection report for the weld was transmitted to Duke Design Engineering. The ultrasonic inspection report indicated that a rejectable indication extended for a distance of an additional one and one-half (lb) incnes into the weld (parallel to the long axis Jf the weld). As the size and length of the indication exceeded the ac-ceptance criteria of the Duke Cesign Engineering fabrication specification, Larco was contacted and requested to cerform re-inspection of all eight parts of the SGLL supports. Further work on these supports was placed on hold at the construction site. Cn October 5, 6, 3, and 9,1979, Laaco Industries ultra-sonically re-examined all full penetraticn welds at the four corners of toe SGLL supports under the review of the Duke Construction Cuality Assurance De-partment. A copy of this ultrasonic inspection was forwarded to Duke Design Engineering a'y Lanco Industries cn October Za, 1979. The re-inspection shcwed three additional rejectable indications in welds of part 6948-6 atjacent to and on the same side as the weld with the original defect. The re.maining seven 1608 252

of the eight parts were found to contain no rejectable indications. The exact location of the four rejectable indications was verified by Duke Construction in flCI 7025 issued November 9, 1979. Design Engineering reviewed the design calculations of the supports and the Quality Assurance records associated with the fabrication of this part. A review of the QA records fer the part indicated that all required ultrasonic inspection was completed by Lamco Industrics prior to shipment, with no rejectable indications found. On Nove-ber 12, 1979, Duke Design Engineering informed the Duke Quality Assurance Department that while the supports contained adequate strength to perform their intended functions (see Safety Implications), the part did not conforn to the fabricatien specifi-cations and represented an apparent breakdown in a portion of the Quality As-surance program. On t!ovember 13, 1979, this fact was reported to flRC Region II.

A review by Lamco Industries of the fabrication of this part indicates that during the /inal ultrasonic examination of the welds, the part was non-conformed due to a mis-alignment of the gussets, and placed en hold. The ultrasonic ex-amination was apparently not completed in the area of the deficient weld, even after Duke Design Engineering sent Lanco Industries a disposition on the non-conformance, and the hold removed from the part. A check list of the welds to be inspected appears to have been signed off when only part of the welds were examined.

The part with the deficient v; elds was returned to Lamco en ?!ovember 16, 1979 and weld repaired to restore the part to the specified condition. Final in-spection of the weld repaired area was completed satisfactorily and the part returned to Duke Power Company.

3.0 Safety Imolications The Steam Generator Lowera L- teral Supports provide support and restraint to the Stean Generator for earthquake loadings and prinary reactor coolant 1c00 pipe ruptures. The welds in questicn were specified to be full penetration welds, with final ultrasonic examination required to verify this condition. Lanco Industries chose to make the welds by utilizing a single bevel weld preparation.

In addition, a one-cuarter (1/4) inch fillet weld was added to the back side of the weld. This additional fillet weld was added by Lamco to avoid problems with possible undercut of final weld profiles that could reduce the effective area of the weld or result in rejectable indications during the visual and ultrasonic examination of the welds, and to inprove the " cosmetic" appearance of the single bevel welds. This fillet weld represents additional seia metal to that specified by Duke Cesign Ingineering. When the size of the pinhole is taken into consideration and that portion of the weld is considered to be in-effective in carrying any loading, the remaining weld size is greater than the ninimum weld metal size specified by Cuke Design Engineering. Therefore, this part of the SGLL support would have been able to perform its function as de-signed. Hence, public safety would not have been jeopardized, a.0 Corrective ;ction The part with the daficient welds was returned to Lrco Industries to recair the deficient welds to the specified configuraticn. This was cone to assure

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uniformity of the ultimate capacity of all of the supports. Duke Pcwer Con-pany is reviewing the procedures utilized by Lanco. Lanco Industries has in-dicated that it will modify the checklist used when the part configuration has multiple joints to be examined.

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