05000278/LER-1986-001, :on 860203,Group III Outboard Isolation Occurred & half-scram Signal Generated.Caused by Lowered Voltage When Recirculation Pump 2B Started.Alternate Feed to New Static Inverter May Be Changed

:on 860203,Group III Outboard Isolation Occurred & half-scram Signal Generated.Caused by Lowered Voltage When Recirculation Pump 2B Started.Alternate Feed to New Static Inverter May Be Changed

ML20207T586
Person / Time
Site:	Peach Bottom
Issue date:	03/09/1987
From:	Birely W, Logue R PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-86-001, LER-86-1, NUDOCS 8703240157
Download: ML20207T586 (4)

LER-1986-001, on 860203,Group III Outboard Isolation Occurred & half-scram Signal Generated.Caused by Lowered Voltage When Recirculation Pump 2B Started.Alternate Feed to New Static Inverter May Be Changed

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
2781986001R00 - NRC Website

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Abstract:

3-86-01, Rev. 1 On February 3, 1986, at 1535 hours0.0178 days <br />0.426 hours <br />0.00254 weeks <br />5.840675e-4 months <br />, a Primary Containment l Additionally, the Roactor Protection System (RPS) generated a Isolation System (PCIS) Croup III outboard isolation occurred.

half-scram signal.

These actions occurred when the 2D recirculation pump was started.

Starting this pump lowered the voltage on the #3 startup nource which caunod an undervoltage condition on the E-13 emergency bus.

At the time of thin event the 3D RPS logic and the outboard PCIS logic were being supplied by their alternate source, E-134-W-A.

Sinco E-134-W-A in supplied by E-13 bus, the low voltago condition caused an undervoltage trip of the alternate courco breaker thereby removing power to the 3D RPS and outboard PCIS logica.

Loan of power to theno logien resulted in de-onergization of RPS channel

'B' relays thereby generating a half-scram signal, and do-onorgization of PCIS outboard logic relays thoroby causing a l Group III outboard isolation.

Changing the alternate feed from E-134-W-A to a new static inverter in being pursued.

The RPS/PCIS logica would not be nunceptible to emergency bun voltage transients becauno the inverter would be supplied by the ntation batteries.

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" ?E'a" 7f.U Prach Bottom Atomic Power Station 0 l6 l0 l0 l0 l2 l7 p 8l6 O l 0; I 0l1 0 l2 0 l3 op rent u we e maremn Unit Conditions Prior to Event Unit 3 at zero percent power Description of the Event:

l On February 3,1986, at 1535 hours0.0178 days <br />0.426 hours <br />0.00254 weeks <br />5.840675e-4 months <br />, a Primary ContainmentIsolation System (PCIS)

Additionally, the Reactor Protection System (RPS) generated a half-scram signal.

These actions occurred when the 2B recirculation pump was started.

Starting this pump lowered the voltage on the #3 startup source which caused an undervoltage condition on the E-13 emergency bus.

At the time of this event the 3B RPS logic and the outboard PCIS logic were being supplied by their alternate source, E-134-W-A.

Since E-134-W-A is supplied by E-13 bus, the low voltage conditicn caused an undervoltage trip of the alternate source breaker thereby removing power to the 3B RPS and outboard PCIS logica.

Loss of power to these logics resulted in de-energization of RPS channel

'B' relays thereby generating a half-scram signal, and de-lenergizationofPCISoutboardlogicrelayswhichcausedaGroup III outboard isolation.

It should be noted that, by design, no control rod movement occurs when a half-scram signal is generated.

Consequencen of the Event:

The RPS and PCIS functioned properly during the voltage transient.

There were no adverno consequences of this event.

Cauan of the Event:

Cause of the event was starting a large pump motor on the #3 startup nource while the 3D RPS motor-generator (M/G) not was out of service.

The 3D RPS M/G not in the primary cource of power for these RPS/PCIS logica and was out of servlce at the time.

Normally, the inertia of the M/G set flywheel annuron a constant voltage to the RPS/PCIS relaya during bus voltage dips.

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.ac n mas.mn alternate source for the RPS/PCIS logics does not have such capability.

Corrective Actions

Changing the alternate feed from E-134-W-A to a new static inverter is being pursued.

The RPS/PCIS logics would not be susceptible to emergency bus voltage transients because the inverter would be supplied by the station batteries.

In the interim, a 4-second time delay has been added to the undervoltage trip circuit of the alternate source breakers.

This time delay will allow the alternate source to remain in service for most motor starts and other transients which affect startup source and emergency bus voltages.

Previous similar occurrences:

Peach Bottom LERs 2-86-04 and 2-86-06.

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t PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHl A. PA.1910 4

March 9, 1987 12151841 4000 Docket No. 50-278 U.S. Nuclear Regulatory Commission ATTN:

Document Control Desk j

Washington, DC 20555

SUBJECT:

Licensee Event Report I

Peach Bottom Atomic Power Station - Unit 3 This revised LER concerns a Primary Containment Isolation System Group III outboard isolation caused by starting the 2B l

recirculation pump, and is being submitted because Revision 0 had erroneously reported that a Group II outboard isolation had also occurred during this event.

Reference:

Docket No. 50-278 Revised Report Number:

3-86-01 Revision Number:

01 Event Date:

February 3, 1986 l

Revised Report Date:

March 9, 1987 Facility:

Peach Bottom Atoric Power Station RD 1, Box 208, Delta, PA 17314 l

.This revised LER is being submitted pursuant to the l

requirements of 10 CFR 50.73(a)(2)(iv).

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Very truly yours, 42/Erdr~

R. H. Logue Assistant to the Manager Nuclear Support Department cca Dr. Thomas E. Murley, Administrator, Region I, USNRC l

T. P. Johnson, NRC Resident Inspector l

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