PNO-V-92-010, on 920331,plant Reactor Trip Breaker Failed to Open During Routine Surveillance Test.Licensee Has Unsuccessfully Attempted to Reproduce Failure,In Breaker Cubicle & on Test Stand in Electrical Shop

PNO-V-92-010:on 920331,plant Reactor Trip Breaker Failed to Open During Routine Surveillance Test.Licensee Has Unsuccessfully Attempted to Reproduce Failure,In Breaker Cubicle & on Test Stand in Electrical Shop

ML20203G047
Person / Time
Site:	Palo Verde
Issue date:	04/02/1992
From:	Richards S NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
References
PNO-V-92-010, PNO-V-92-10, NUDOCS 9712180020
Download: ML20203G047 (2)

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. NOI!TICATION OF EVENT OR

' UNUSUAL OCCURRENCE--PNO-V-9210 Date: 04/02/92 i

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< This preliminary' notification constitutes EARLY notice of events of P0.S$1BLE safety .

,e or public interest significance. The inforination presented is as initially received ' '

e withuut verification or evaluattun and is basically all that is known by Region V

• staff on this date. ,

FACILITY: ARIZONA PUBLIC SERVICE COMPANY Emergency Clas'sification PALO VERDE UNIT 3 Notification of Unusual Event DOCKET NO. 50 530 Alert ,

WINTERSBURG, AZ. Site Area Emergency General Emergency i TNot Applicable

SUBJECT:

REACTOR TRIP BREAKER FAILURE TO OPEN

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1jOnMarch 31,19927 at approximately 11:18 pm (MST) the Palo Ver e Unit 3The 'C' n reactor trip breaker failed to open durin a routine surveillance test.

n conducting the test, operator 4 had

' f) breaker is ,a Westinghouse 'model t/S-206.sttempted to trip the , breaker usin

• After cushing the trip button, the operators observed conflicting control room

> indications for the breaker. The closed indicator light went out, but the open ~

O indicator light did not illuminate. Additionally, although the alarm printer i~indicatedthatthebreakerhadopened,thw>wasindicationofcurrentstill 4 passing through the brehker. An Auiiliary Operator was dispatched to the breaker -

i and icported that the poyition flag indicated on intermediate po;ition. An '

2 . attempt tn open the breaker again both frc" the control room and locally f ailed.

..The operators then tripped open'the 'A' r uctor trip brea.ker, which is in series

,' w{th~the 'C' breaker. The unit remained at 100% power throughout the event with

• power to the control' element drive mechanisms provided via the parallel Dath 'B'

, jnd 'O' reactor trip?breakens.

1 'After discussicn with maintenance, the licensee elected to charge the breaker closing springs manually and then press the closing button. ,By breaker design, lthis resulted in'the,, breaker opening.

$ .TM licensee has unsNebsfully' attempted to repro' duce the,f ailure, both in the , ,

.bceaker cubicle and on a test stand in the electri. cal shoo. There are .40 readily

,1 visible signs of any damage to the t.reaker. _

. '1$e licensee has replaced the breaker with a spare breaker and has returncd the -

) 'r~eactor trip switchgearito a ncrmal condition. The breaker is presently

, ,ciuarantined. The licensee' intends to gain the assistance of Westinghouse in 1 disassembling the breaker in an attempt to determine the root cause of f ailure.

> Theireaker has been previously tested month y and had no known history of It

, failures, although thegt.icenseo was still conducting a review in this area. -

' .is thought that the breaker'han been in service since initial plant -

construction. The breaker cyqle counter indicated about 900 cycles on the f breaker. The licensee is alsc conducting a review of industry history with this

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model breaker.

9712180020 920402 PDR IbE 11 s!>/-

PNO-V-92-010 PDR (t

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A conference call with the licensee was held at 1:00 pm (PST) on Aprt) 2. 1992, '

. with OEDO, NRR, and Region V participating, during which the event and future actions were reviewed. 'A Region V inspector with circuit breaker experience has ,

been dispatched to the s.ite.. ,

This information has been discussed with the licensee and is current as of 1:30 pm (PST) on April 2,1992.

The licensee does not olen a press release.

CONTACT: S. Richards' FTS 448-0287

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