ML20084F397

AO 251-75-8:on 750525,diesel Generator Breaker 4A & Bus Stripping 4B Relay Malfunctioned During Engineered Safeguards & Emergency Power Sys Integrated Test. Intermittent Open Circuit Caused by Electrolytic Corrosion

ML20084F397
Person / Time
Site:	Turkey Point
Issue date:	10/13/1975
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20084F373	List: ML20084F397 ML20084F415
References
AO-251-75-8, NUDOCS 8304210121
Download: ML20084F397 (2)

Text

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FLCRIDA POWEP. la UGHT CC .%W o

'oOctober 13, 1975 5,

Mr. Norman C. Moseley, Director, Region II -

% g ' /,2 N Office of Inspection and Enforcement 9j U. S. Nuclear Regulatory Commission N 4 3h,/Jyj.ht 230 Peachtree Street, N.W., Suite 818 - P

,f,* bd ,;,pjj fV-j Atlanta, Georgia 30303 E 1

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Dear Mr. Moseley:

$ , D ABNORMAL OCCURRENCE 251-75-8 8 gig \[

TURKEY POINT UNIT 4 -

DATE OF OCCURRENCE: MAY 25, 1975 .

SUPPLEMENTARY REPORT NO. 1 MALFUNCTION OF 4A DIESEL GENERATOR BREAKER AND 4B BUS STRIPPING RELAY DURING ECGINEERED SAFEGUARDS AND EMERGENCY POWER SYSTEM INTEGRATED TEST -

A. BACKGROUND An Engineered Safeguards and Eme'gency r Power System Integrated Test was initiated on 'May 25, 1975. There .

w.ere two separate equipment malfunctions during the initial test. This report concerns the malfunction of the 4B bus stripping relay 127Z1/4AB1, Type HFA, manufactured by General Electric.

The subject bus stripping relay failed to cause the 4B turbine plant cooling water pump breaker, the 4B Load Center breaker, and the 4D Load Center breaker.to open.

. Therefore, the 4B Diesel Generator breaker could not close automatically because the 4B 4160 volt bus was not completely stripped of load. Complete load stripping of a 4160 volt bus is required as a permissive to allow a diesel generator breaker to automatically close in on the' bus.

B. INVESTIGATION ,

Following the occurrence, the relay was extensively bench tested at Turkey Point, but the malfunction could not be duplicated. The relay was then sent to the manufacturer for further investigation. The investigation of the relay coil revealed an intermittent 6 pen circuit which had apparently been caused by electrolytic corrosion. The' .

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, Mr. Norman C. im3nley \J '

October 13, 1975 s' Page Two *  ;

manufacturer has determined this to be a' recurring failure mechanism in HFA, HGA and HMA relays which are constructed with milky-white nylon coil spools. A heat stabilizing component of the nylon contains halogen ions which can be released from the nylon over a period of time. The halogen ions can then combine with moisture to form hydrochloric acid and copper salts which can eventually corrode the coil wire. Therefore, a relay with a nylon spool has the to highpotential humidity. for a shorter than normal life when subjected TheHFA, of manufacturer no longer uses nylon spools in the production HGA, and HMA relays. The spools are now made of Lexan which has the desired chemical, mechanical and electrical properties for use in spools.

problems associated with the useThere are no known corrosion of Lexan. '

C. CORRECTIVE ACTION

• Unit 4 electrical equipment has been inspected and all HFA )

and HGA relays with nylon spools have been identified. 'There were nylon approximately spools. 120 HFA relays and two HGA relays with All nylon spools will be replaced with Lexan spools before the end of the next Unit 4 refueling outage.

' Since equipment,HFA and HGA relays are also used in Unit 3 electrical will be developed a similarforspool thatinspection Unit. Alland replacement program.

nylon spools found in Unit 3 electrical equipment will be replaced with Lexan spools before the end of the next Unit 3 refueling outage.

~

. D. Schmidt Vice President Power Resources .

MAS / jar ~

cc: Jack R. Newman, Esquire I

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