PNO-V-85-062B, on 850919,reactor Tripped Due to Failure of Steam Reheater Dump Valve to Actuate Resulting in Main Turbine Overspeed.Caused by Lack of Lubricating Oil in Bearing Sumps & Failure of Pressure Switch & Relay: Difference between revisions

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PNO-V-85-062B:on 850919,reactor Tripped Due to Failure of Steam Reheater Dump Valve to Actuate Resulting in Main Turbine Overspeed.Caused by Lack of Lubricating Oil in Bearing Sumps & Failure of Pressure Switch & Relay
ML20132F217
Person / Time
Site: San Onofre Southern California Edison icon.png
Issue date: 09/23/1985
From: Huey R, Johnson P
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
References
PNO-V-85-062B, PNO-V-85-62B, NUDOCS 8510010270
Download: ML20132F217 (1)


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PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE-PNO-V-85-62B Date: 09/23/85 This preliminary notification constitutes EARLY notice 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: Southern California' Edison Company Emergency Classification ,

San Onofre Unit 1 Notification of Unusual Event Docket No. 50-206 Alert Site Area Emergency .

General Emergency XX Not Applicable

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SUBJECT:

SECOND UPDATE - REACTOR TRIP INVOLVING INOPERABLE TURBINE-DRIVEN ,

AUXILIARY FEED PUMP AND MAIN TURBINE OVERSPEED San Onofre Unit 1, t' ripped at 1905 on September 19, 1985. The turbine-driven auxiliary feedwater-(AFW) pump started but tripped after a brief run. The AFP trip was initially  :

believed to be due to overspeed, b"ut was. subsequently determined by the licensee to have resulted from insufficient lubricating oil in the bearing sumps.

Following the main turbine trip, one steam reheater dump valve did not actuate as required, resulting in a main turbine overspeed to'126% of normal speed (1800 rpm). The licensee has determined that.this was caused by failure of a pressure switch and a relay, both of which were replaced (this is not a nuclear' safety related system).

Following the event, both turbine bearing sumps on the turbine-driven AFW pump were found to have-low oil level. The sight glass on the inboard bearing (pump end of turbine) was correctly indicating a low level, but the sight glass on the outboard end was incorrectly indicating a normal level due to blockage by a portion of a protective ear plug.

In interviews with maintenance personnel subsequent to the event, licensee management-determined that a maintenance person had improperly used a portion of an ear plug as a gasket to repair a leaking sight glass. The licensee believes the loss of oil from the inboard sump resulted from wear on'a shaft. oil seal, plus some sight glass leakage. The  ;

turbine-driven AFP has been repaired and successfully tested.

The' unit is expected to restart today (9/23/85) following completion of minor repairs unrelated to this' event.

This informatio is current as of 10:00 am on September 23, 1985.

CONTACT: P ha on R. Huey FT 4DL3745 (714) 492-2641

. DISTRIBUTION H St. 3' E MNBBDPhillips E/W Willste Air Rights I Mail:

Chairman Pallidino EDO- NRR IE NMSS ADM:DMB Comm. Zech PA '01A .RES g DOT:Trans Only Comm. Bernthal MPA AEOD Comm. Roberts ELD Comm. Asselstine Regions :[f-T 2h d-J

  • D j M- 7'Vd SECT' INPO 7:YV NSAC 7: Y.2-ACRS Licensee: S* 2 '7 CA '(Reactor Licensees) REC 10N V: FORM 211 PDR Resident Inspector f.'/ > (Revised 3/14/83)- 1 h00 0WW PNO-V-85-062B PDR

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