ML17272A457

Deficiency Rept:Defective Steel Plate Used in Supporting Structure for Pipe Whip Restraints in Main Steam Tunnel. Cracking Attributed to Overheating SA-537 Class II Steel. Defective A-537 Matl Rejected

ML17272A457
Person / Time
Site:	Columbia
Issue date:	05/31/1979
From:	WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:
Shared Package
ML17272A456	List: ML17272A455 ML17272A457
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 7906080305
Download: ML17272A457 (2)

Text

Attachment G02-79-111 SS NUCLEAR PROJECT NO. 2 REPORTABL DEFICIENCY AND CORRECTIVE ACTION FOR DEFECTIVE STEEL PLATE USED IN SUPPORTING STRUCTURE FOR PIPE WHIP RESTRAINTS IN tlAIN STEAtl TUNNEL WASHINGTON PUBLIC POWER SUPPLY SYSTEH DOCKET NO. 50-397 LICENSE NO. CPPR-93 Nature of Deficieno ASHE SA-537 Class II steel from U, S. Steel Co. heat W74206 used in the main steam tunnel pipe whip restraint support structure was found to have extensive internal cracking as revealed by ultrasonic examination of an installed component. Examination of the SA-537 Class II steel in the installed component was undertaken after cracking of material from the same heat was observed during fabrication, and subsequent examination of samples from material still in the fabrication shop indicated exten-sive cracking was present. The cracking was attributed to overheating during the rolling or heat treatment process, and was concluded not to be laminations or lamellar tearing. The cracking is considered to be an injurious defect, and as such this deficiency was concluded to con-stitute a failure to meet ASt1E SA-20 performance specifications.

In addition, extensive cracking was observed on the edges of a second heat (T68042) of SA-537 Class II steel plate manufactured by U. S. Steel Co., upon receipt at the fabricator's shop. This material was rejected and was not used in fabrication.

Safet Im lications If the SA-537 material remained as installed in the main steam tunnel pipe whip restraint supporting structure, and was subjected to pipe whip impact loads, resulting from a pipe break in a reactor feedwater line, the com-ponent could fail and prevent the pipe whip'estraint structure 'from re-straining the motion of the ruptured pipe. This could result in loss of containment integrity through damage to the reactor feedwater isolation valve or feedwater piping upstream of the isolation valve.

Corrective Action Taken All SA-537 material from the heat found to have internal cracking was rejected. This includes the single component installed in the main steam tunnel, other components shipped to the site'ut not installed, components in fabrication, and raw material in the fabricator's shop.

Replacement SA-537 Class II steel plate has been ordered.

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