PNO-II-85-078, crack Identified on Weld of 3/4-inch Sample Line Running Off RCS Letdown Line.Weld Crack in Identical Location to One Found on 850729.Weld Repaired.Pipe Supports Being Installed

PNO-II-85-078:crack Identified on Weld of 3/4-inch Sample Line Running Off RCS Letdown Line.Weld Crack in Identical Location to One Found on 850729.Weld Repaired.Pipe Supports Being Installed

ML20137G093
Person / Time
Site:	Sequoyah
Issue date:	08/14/1985
From:	Ignatonis A, Weise S NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
References
PNO-II-85-078, PNO-II-85-78, NUDOCS 8508270171
Download: ML20137G093 (2)

r fa August 14, 1985 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-II-85-78 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verifi-cation or evaluation, and is basically all that is known by the Region II staff on this date.

FACILITY: Tennessee Valley Authority Licensee Emergency Classification:

Sequoyah Unit 1 Notification of Unusual Event Docket No. 50-327 Alert Soddy-Daisy, Tennessee Site Area Emergency General Emergency X Not Applicable

SUBJECT:

LEAKING PRIMARY COOLANT SAMPLE LINE The licensee has reported that a routine walkthrough by an auxiliary operator identified a crack through the weld area of a 3/4-inch sample line which runs off the reactor coolant system letdown line. The weld crack is almost identical in location to one identified on July 29, 1985 on Unit 2. (PNO-II-85-74).

The leak of 0.4 gallons per minute was immediately isolated by a manual isolation valve.

There was no detectable airborne radioactivity and no hazard to plant personnel or the general public.

In both instances, both units were operating at 100 percent power and continued operations uninterrupted.

The licensee has completed weld repairs on both units, and pipe supports are being designed and installed on both branch lines, neither of which contained supports prior to detection of the leaks. The licensee has completed walkdowns of letdown lines in both units, except high radiation areas in containment, and found no other unsupported branch lines.

Region II is closely monitoring licensee actions aimed at determining whether or not the two sample lines required pipe supports in the original plant design.

Mata11urgical analysis of the Unit 2 crack indicated that the failure mechanism was low stress, high-cycle fatigue originating on the pipe outer diameter at a surface discontinuity. Similar analysis of the Unit I crack is now taking place.

Vibration analysis of both lines has not identified the source of any vibration which may have occurred.

Region II will continue to closely monitor the progress of the licensee's analyses and corrective actions. Region II has notified appropriate officials of the Office of Nuclear R: actor Regulation and the Office of Inspection and Enforcement.

Extensive local media interest has occurred. The licensee placed announcements of both ovsnts on the TVA automated, media call-in telephone service. Both the NRC and the licensee have responded to media inquiries.

The State of Tennessee has been informed.

This information is current as of 12 noon on August 14.

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Contact:

A. Ignatonis, 242-5563 S. Weise, 242-5535 DISTRIBUTION:

H. Street 3 30 ~MNBB$pPhillipsYg4 4 Will ste $'pMAIL:

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Licensee: L4;%4 (Reactor Licensees)

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