ML20084F437

AO 250-75-7:on 750924,high Pressure Comparator in Pressurizer Protection Sys Channel III Malfunctioned.Caused by Two Failed Capacitors in Dc Power Supply.Comparator PC-3-457A Replaced

ML20084F437
Person / Time
Site:	Turkey Point
Issue date:	10/03/1975
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
AO-250-75-7, NUDOCS 8304210131
Download: ML20084F437 (2)

Text

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FLontDA POWER & LIGHT CU.*.*PAMf . _

October 3, 1975 -

1 Mi. Norman C. Moseley, Director, Region II

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. Office of Inspection and Enforcement. s .

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,U.S. Nuclear Regulatory Commission

.230 Peachtree Street, N.W., Suite 818 i 'A 1

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Atlanta, Georgia 30303

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De'ar Mr. Moseley:

. ABNOINAL OCCURRENCE 250-75-7 ., ,

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, .IURKEY POINT UNIT 3 ~

.' DATE OF OCCURRENCE:'SEPTDIBER 24, 1975 .

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. 1%LFUNCTION OF HIGH PRESSURE' CGIPARATOR IN .

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• PRESSURIZER PRESSURE PROTECTION SYST91 CHANNEL III A.. CONDITIONS PRIOR TO OCCURRENCE ., .

'Ihe reactor was in steady state power operation at 99% rated power. .

Pressurizer Pressure Protection System Channel III was in the tripped

• mode and a functional test of that channel was being perfomed per <.

Operating Procedure 14004.4 entitled " PRESSURIZER PRESSURE AND WATER '

. LEVEL PROTECTION CHANNELS Periodic Test."

B. DESCRI1/rION'0F OCCURRENCE .,.

l The periodic test was initiated at about 2:40 A\1 on September 24,'1975.

At about 3:30 N1, the test signal input did not trip the Channel III high pressurizer pressure comparator PC-3-457A at the required setpoint. -

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.C . DESIGNATION OF APPARENT CAUSE OF OCCURRENCE . ..

. Tests of the comparator revealed two failed capacitors in the d.c. power .

supply._: Failure.of these capacitors permitted an a.c. signal to be -

superimposed on the d.c. signal.in the comparator. This caused the .

ccT.parator trip.setpoint_.to bc.raisecl...above the required value.

D. ANALYSIS OF OCCURRENCC e '

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There are three channels of high pressurizer pressure protection.

Pressurizer Pressure Protection System logic requires that two of the -

three channels be in the trip mode in order to produce a reactor trip signal. During this periodic test, Channels I and II were verified operabic. Had an actual high pressurizer pressure occurred, a reactor trip signal would have been generated at the proper setpoint, there-

fore, the health and safety of the public were not.affected by this i

1 occurrence. .

8304210131 751003 . . -

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.. s g O i hir. Norman C. bloseley October 3, 1975

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Page Two E. CORRECTIVE ACTION Comparator PC-3-457A was replaced with a' spare comparator. The PRESSURIZER PRESSURE A\.I) NATER LEVEL PROTECTION CHANNELS Periodic Test was then satisfactorily completed at about 4:25 Ah! on September 24,.

1975.

Correspondence with the vendor has been initiated to further evaluate the malfunction. .

F. FAILURE DATA The faulty PC-3-457A comparator was >!odel No. 4111082-001, S/N A0 564, manufactured by the Hagan/ Computer Systems Division of Westinghouse.

htalfunction of this Stodel No. comparator occurred on one other occasion.

It was described in Abnormal Occurrence Report 251-75-3. .

A. D. INfkt Vice President .

Power Resources ,

h!AS/ jar cc: Jack R. Newman, Esquire - -

ice of >!anagement Infomation and Pro Director, Director, gice of Inspection and Enforcement (40 am Control (3) t 4

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