PNO-V-85-072, on 851024,reactor Tripped from 80% Power During Scheduled Loss of Load Test.Cause Undetermined.Util Requested Assistance from C-E to Determine Cause of Trip & Cooldown of RCS

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PNO-V-85-072:on 851024,reactor Tripped from 80% Power During Scheduled Loss of Load Test.Cause Undetermined.Util Requested Assistance from C-E to Determine Cause of Trip & Cooldown of RCS
ML20133P975
Person / Time
Site: Palo Verde Arizona Public Service icon.png
Issue date: 10/25/1985
From: Miller L, Zimmerman R
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
References
PNO-V-85-072, PNO-V-85-72, NUDOCS 8511010288
Download: ML20133P975 (1)


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PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-V-85 -72 if a te: 10/25/85 Thic preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public intsrest significance. The information presented is as initially received without verification or cvaluation and is basically all that is known by Region V staff on this date.

FACILITY: Arizona Public Service Emergency Classification Palo Verde Unit 1 )( Notification of Unusual. Event Docket No. 50-528 Alert

_ Site Area Eme.gency

_ General Emergency

_Not Applicable

SUBJECT:

REACTOR TRIP WITH SAFETY INJECTION On October 24, 1985, at 10:10 am (MST) the Unit I reactor tripped from 80% power during a ccheduled loss of load test. Following the reactor trip, an automatic safety injection cystem actuation (SISA) and containment isolation system actuation (CISA) were received as a result of low pressurizer pressure. A main steam isolation system (MSIS) actuation also occurred. A Notification of Unusual Event was declared at 10:19 am as a result of the rs:ctor-trip and safety injection, in accordance with the site emergency plan. All cmergency safety features functioned normally.

Tha cause of the reactor trip appears to'itave been unexplained (possibly spurious)

" Low Steam Generator Levels" in both steam generators. Post trip data indicates that the trip signals lasted for approximately .3 seconds and then cleared. The initial cause of the safety features actuations was believed to have been from cooldown of the reactor coolant system (RCS) which resulted from the steam bypass control system overresponding.

Th2 utility has requested Combustion Ex.gineering to assist them with the determination of tha cause of the reactor trip and the cooldown'of the RCS. Region V is independently rzviewing this event. , . .,

The Notification of Unusual Event-(NOTE) was terminated at 10:45 am when plant conditions rsturned to normal hot standby conditions. The. licensee plans on being shutdown while ths cause of the reactor trip is investigated. During the shutdown, secondary plant maintenance will be performed; this is expected to last several days.

Tha licensee has notified"the local media of the reactor trip and NOUE.

This information is current as of 4:00 pm (PST) October 24, 1985 CONTACT: L. Miller R. Zimmerman FIS 463-3869 (602) 386-5260 DISTRIBUTION M IW Willste l:c oAir Rights&

H St. /.' o 2 MNBHQ:TlPhillir sla: E/W Mail:

Chairman Pallidino EDO NRR IE NMSS ADM:DMB Comm. Zech PA OIA RES DOT:Trans Only Ccmm. Bernthal MPA AEOD Comm. Roberts ELD 4 Comm. Asselstine SECY Regions: M - N M -/d ]

INPOf1: 22FSAC Wo/

-83 E-D 2 ACRS Licensee: g/ V 2 CA (Re.tctor Licensees) REGION V: FORM 211 PDR Resident InspectorgV 7 (Revised 3/14/83) 8511010288 851025

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