05000250/LER-1985-019, On 850721,reactor Protection Sys Actuated, Turbine Tripped & Auxiliary Feedwater Initiated Due to Spurious Low Pressure Signal.Probably Caused by Lightning. Periodic Operability Test Performed

On 850721,reactor Protection Sys Actuated, Turbine Tripped & Auxiliary Feedwater Initiated Due to Spurious Low Pressure Signal.Probably Caused by Lightning. Periodic Operability Test Performed

ML20134G691
Person / Time
Site:	Turkey Point
Issue date:	08/20/1985
From:	Teuteberg R, Williams J FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
L-85-325, LER-85-019, LER-85-19, NUDOCS 8508280031
Download: ML20134G691 (2)

LER-1985-019, On 850721,reactor Protection Sys Actuated, Turbine Tripped & Auxiliary Feedwater Initiated Due to Spurious Low Pressure Signal.Probably Caused by Lightning. Periodic Operability Test Performed

Event date:
Report date:
2501985019R00 - NRC Website

text

c' FLORIDA POWER & LIGHT COMPANY AUG 2 01985 L-85-325 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D. C.

20555 Gentlemen:

Re: Reportable Event 85-019 Turkey Point Unit 3 Date of Event: July 21,1985 Reactor Protection System Actuation - Reactor Trip and Auxillary Feedwater Initiation The attached Licensee Event Report is being submitted pursuant to the requirements of 10 CFR to provide notification of the subject event.

Very truly yours,

3. W. Williams, Jr.

Group Vice President Nuclear Energy Department 3WW/SAV:dkw Attachment cc:

Dr. 3. Nelson Grace, Region II, USNRC PNS-LI-85-293/1 ege2gggi gggggo [9

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Event:

On July 21,1985 at 11:41 p.m., Unit 3 experienced a reactor trip from 100% power due to a spurious low pressurizer pressure signal generated in the reactor protection system (RPS). The reactor trip logic in the RPS initiated a subsequent turbine trip. The reactor trip resulted in steam generator levels decreasing below the low-low setpoints,15% of the narrow range span, due to steam generator shrink. This initiated an automatic start of auxiliary feedwater pumps. Plant procedures were used to stabilize the unit in a hot standby condition.

Cause of Event

A heavy electrical and rain storm was in progress at the time of the event. The findings from a post-trip review indicated that the most probable cause was a lightning strike, which affected pressurizer pressure protection comparators generating a spurious pressurizer low pressure reactor trip.

Corrective Actions

The following corrective measures were taken:

1)To ensure that the pressurizer pressure and level protection channels were not damaged by the lightning strike, a periodic operability test was performed using Operating Procedure 14004.4.

These protection channels performed satisfactorily.

2) A review was conducted of the printouts of the Unit 3 480 VAC Load Center Voltage Analyzers and the Undervoltage Circuits Sequence o; Events Recorder. No abnormal indications were evident on these printouts.

3) A post-trip review was performed and no abnormal operating conditions associated with the trip were identified.

The health and safety of the pablic were not affected. Similar occurrences: None. NM# /

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