PNO-V-90-033, on 900726,observed Crack in Charging Pump Suction Header Piping Caused by Boric Acid Crystals on Elbow of Pump.Licensee Considers Piping Operable & to Be Repaired W/O Plant Shut Down.Inspector Monitoring Plant

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PNO-V-90-033:on 900726,observed Crack in Charging Pump Suction Header Piping Caused by Boric Acid Crystals on Elbow of Pump.Licensee Considers Piping Operable & to Be Repaired W/O Plant Shut Down.Inspector Monitoring Plant
ML20055J078
Person / Time
Site: Diablo Canyon Pacific Gas & Electric icon.png
Issue date: 07/27/1990
From: Morrill P, Narbut P
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
References
PNO-V-90-033, PNO-V-90-33, NUDOCS 9008010041
Download: ML20055J078 (2)


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" PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-V-9P.33 Date July 27, 1990 This preliminary notification constitutes EARLY noti e of events of POSSIBLE safety or public interest significance. The information presented is as initially received without verification or evaluation and is basically all that is known by Region V staff on this date.

FACILITY: PACIFIC GAS & ELECTRIC COMPANY Emergency Classification DIABLO CANYON UNIT 1 Notification of Unusual Event DOCKEi NO.50-27b Alert SAN LUIS OBISP0 COUNTY, CA Site Area Emergency General Emergency

,_X_ Not Applicable

SUBJECT:

CRACK IN CE.RGING PUMP SUCTION HEADER PIPING On July 26, 1990, at approximately 11:00 a.m. (PDT), the Senior Resident Inspector observed boric acid crystals en an elbow in the Unit 1, 4-inch diameter, suction piping to the positive displacement charging pump (PDP). The crystals were adjacent to a 3/4 inch socket connection to the elbow for a pressure gauge. During subsequent investigation by the licensee, it was determined that the crystals were due to a through wall crack in the piping. The crack 6ppears to be approximately 1-5/8" long.

The leakage is sufficient to cause a buildup of boric acid crystals, but not enough to drip. The suction piping is 4-inch, schedule 10, stainless steel and is normally at 30 to 40 psig pressure. The crack is in the common suction header and is not isolable from the suctions of the PDP or the safety-related centrifugal charging pumps.

The licensee considers tb t the piping is operabic and can be repaired without plant shutdown. The licensee has conducted analyses to show that the cracked pipe will not fail during design basis events and that the expected leakage from the crack does not cause unacceptable consequences. Region V and NRR have contacted the licensee several times since 5:30 p.m. (pDT), July 26, and are continuing to evaluate the licensee's position.

The plant is currently at 100% power and the PDP (which may have caused the crack due to vibration) is administretively shutdown by the facility.

The Senior Resident Inspector is monitoring the plant. NRR, Region V, and the licensee management are discussing the situation to determine; (1) operability of the charging system, and, (2) what type of repair is appropriate.

This informction is current as of 10:00 a.m. (PDT), July 27, 1990.

CONTACT: P. Morrill, RV P. Narbut FTS 463-3740 805-595-2354 3 ?.

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