PNO-V-86-042, on 860712,reactor Tripped from 100% Power on Low Steam Generator RCS Flow Channels a & B,Causing Turbine Generator Trip,Sys Voltage Fluctuation & Loss of Power.Cause Unknown.Plant Restored to Safe Shutdown Status

PNO-V-86-042:on 860712,reactor Tripped from 100% Power on Low Steam Generator RCS Flow Channels a & B,Causing Turbine Generator Trip,Sys Voltage Fluctuation & Loss of Power.Cause Unknown.Plant Restored to Safe Shutdown Status

ML20203C576
Person / Time
Site:	Palo Verde
Issue date:	07/14/1986
From:	Miller L, Zimmerman R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
References
PNO-V-86-042, PNO-V-86-42, NUDOCS 8607210027
Download: ML20203C576 (1)

PEELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-V-86-42 Date: 07/14/86 This preliminary notification constitutes EARLY notice 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: Arizona Nuclear Power Project Emergency Classification Palo Verde Unit 1 X Notification of Unusual Event Docket Nos. 50-528; ~-Alert Site Area Emergency General Emergency Not Applicable

SUBJECT:

SPURIOUS REACTOR TRIP AND SUBSEQUENT SAFETY INJECTION.

On July 12, 1986 at 10:45 AM, MST, the Unit I reactor tripped from 100% power on low Steam Generator reactor coolant system flow channels "A" and "B". The "A" channel trip cleared 113 msec after actuation and the "B" channel cleared within 254 msec. Following the reactor trip, the turbine generator trip caused a system voltage fluctuation that resulted in a partial loss of power to nonessential loads in the plant. The loss of power caused several normally cpen secondary motor operated control valves to fail "as is" resulting in a continuing flow path from the main steam header to the condenser producing a plant cooldown. At 10:49 AM, a Safety Injection and Containment Isolation Actuation occurred as a result of the plant cooldown to 545'F. Minimum RCS pressure was reached at 1770 psia. All systems apparently operated as designed, except as indicated below.

Steam generator sample line isolation valve failed to close upon Containment Isolation Action.

During the event the operators identified loss of charging due to the apparent lack of an adequate suction path. Upon restoration of an adequate path all three pumps were started, however, the E charging pump was found not to be pumping rated flow and was subsequently secured. The cause of the pump not operating correctly is also under investigation by the licensee.

At 10:52 AM, the cooldown was terminated at 519'F when low steam generator pressure caused a Main Steam 1 solation Actuation to shut the main steam and main feedwater isolation valves. A Notification of Unusual Event was declared at 11:10 AM based on the requirements of the site cmsrgency plan, and the event was terminated at appro:timately 12:40 PM af ter conditions had been restored to a normal shutdown status.

The plant is currently in Mode 3 while the licensee esolves the problems identified during the plant trip.

This information is current as of 1500 (MST) July 14, 1986.

CONTACT: L. Miller, Jr. R. Zimmerman FTS 463-3869 (602) 386-5260 860721002/ 860714 DISTRIBUTION PDR ISE PNO-V-86-042 PDN H St. M MNBB UN Phillips7l2( E/W Willste Air Rights Mail:

Chairman Palladino EDO NRR IE NMSS ADM:DMB Comm. Zech PA OIA RES DOT:Trans Only Comm. Bernthal MPA AEOD C

SECY A ine Regions: b ' D N N $ h / b '

INPO 7/ YJ~ NSAC 7! V6 ~

ACRS Licensee: 9/M CA REGION V: FORM 211 (Reactor Licensees)~

PDR Resident Inspector 7/ M (Revised 3/14/83) o I