ML20085M514

RO 50-267/75/20:on 751024,reactor Plant Supply Fan 1B Developed Fault,Causing Reactor Plant MCC 3 Essential Bus to Be Out of Svc During Repair of Fan 1A.Caused by Loose Electrical Connection.Bus & Motor Meggered & Verified

ML20085M514
Person / Time
Site:	Fort Saint Vrain
Issue date:	11/18/1975
From:	Swart F PUBLIC SERVICE CO. OF COLORADO
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
P-75006, RO-50-267-75-20, NUDOCS 8311080615
Download: ML20085M514 (5)

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public service company. *e cenerade P. O. Box 361, Platteville, Colorado 80651

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November 18, 1975

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,' Fort St. Vrain Unit No. 1

• P-75006 s

Mr. E. Morris Howard,-Director @PP Nuclear Regulatory Commission Region IV Office of Inspection and Enforcement Suite 1000 Arlington, Texas 76012 REF: Facility Operating License No. DPR-34 Docket No. 50-267

Dear Mr. Howard:

Enclosed please find a copy of Unusual Event Report No. 50-267/75/20, Final, submitted per the requirements of the Technical Specifications.

Very truly yours, m f. -

E. 9 Frederic E. Swart Superintendent, Nuclear Production Fort St. Vrain Nuclear Generating Station FES/alk l cc: Mr. Roger S. Boyd

. 4LN6se 8311080615 751118 PDR ADOCK 05000267 Ir/Y/

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~w , COPY SENT REGION _

o o REPORT DATE: November 18 , 1975 UNUSUAL EVENT 75/20*

Page 1 of 3 OCCURRENCE DATE: October 24, 197,5_

FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT No. 50-267/75/20 Final IDENTIFICATION OF OCCURRENCE:

Reactor plant supply fan IB breaker developed a fault which caused the reactor plant MCC #3 essential bus to be out of service during repairs. This is identi-fled as an unusual event per Scction 7.6, Non-Routine Reports, Part C, Paragraph 3 of the Fort St. Vrain Technical Specifigations.

CONDITIONS PRIOR TO OCCURRENCE: Steady State Power Routine Shutdown' Hot Shutdown , Routine Load Change X Cold Shutdown Other (specify)

Refueling Shutdown Routine Startup The major plant parameters at the time of the event were as follows:

Power RTR 0 MWth 3

ELECT O MWe .

Secondary Coolant Pressure (1) psig Tc:aperaturen (1) *F.

'l ow 100,000 f/hr.

Primary Coolant Presnure O pain

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Temperature _ 100 *F' Core inlet

• 100-

• F Core Out l et:

Flow 1 ci rculeit or at 4,000 1;PH (J) Of no consequence.

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UNUSUAL EVENT 75/20 Page 2 of 3 4 .

DESCRIPTION OF -

OCCURRENCE: -

1B reactor plant supply fan w'as being returned to service to permit removing 1A supply fan from service. The assistant reactor operator attempted to start IB fan with the hand switch when the reactor plant, MCC #3, essential bus, breaker tripped.

APPARENT CAUSE OF OCCURRENCE: Design Unusual Service Cond.

. Including Environ.

Manufacture Component Failure Installation /Const. X Other (specify)

Operator Loose electrical connection.

Procedure The pparent cause of this occurrence was a loose electrical connection on the bus side of the supply fan breaker.

r ANALYSIS OF DCCURRENCE:

The incident occurred when an attempt was made to start the fan. The starting current and the apparent loose connection caused a phase-to-phase fault on the supply side of the fan breaker. The resulting phase-to-phase fault caused the i reactor plant essential bus #3 feed breaker trip and temporary loss of the bus.

CORRECTIVE ACTION:

i The bus and motor were meggered and verified to be normdl. The bus was repaired and the supply fan breaker was replaced with a spare breaker. The fan was started and run with no problems. There was no permanent-loss of Lhe essential bus and no danger to company personnel or the public. No further corrective action is required at this tine.

FAILUHR DATA /SIMILAR REPORTED OCCURitEN_C_ES,:

None

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l_ PROGI:AMot\ TIC 1MPAf,T: .

None CODE IMPACT:

None c . t

1 o o UNUSUAL EVENT 75/20  !

Page 3 of 3 tr Submitted By: _ . . .._,y

• Harvey W. tillyard, Jr.

Technical Services Supervisor Reviewed By:

. Francis M. Mathie Supe rint ender.t , Maintenance Approved By: f a

'rederic E. Swart Superintendent, Nuclear Production e

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LWUSUAL EVENTS AND ABNO10 tat. OCCURRENCE REPORTS DISTRIF.ttf10NS_

Wumber of Conf es San Francisco Operations Office .

ERDA -

1333Rroaduay Cakland, California 94612 2**

Attnt Manager 1*

California Patent Group Division of Reactor Research and De~elopment EltDA Washington, D.C. 20545 1*

Attn: Director 2*

Asst. Dir. for Cas Cooled Reactor Projects is Asst. Dir. for Engrg. and Technology 1*

Asst. Dir. for Reactor Safety 1*

EltDA-SCRPO-SD .

P. O. Box 81325 San Diego, Califotnia 92138 1*

Project Engineer ERDA - SCP10 P. O. Box 1446 Canoga Park, California 91304 1

Address +++ Director - .

Letter ERDA - SCRPO To, P. O. Bar. 1446

'Canoga Park, California 91304

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. Technical Information Centir ERDA .

P. O. Box 62 Osk Ridge. Tennessee 37830 10*

Address +++ John R. Zanot. Project Manager TFLC Ceneral Atomic Company

• To P. O. Box 81608

• San Diego, California 92138

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Address +++ Mr. E. Morris llovard, Director .

Letter Region IV.

To Office of Inspection & Enforcement

- Nuclear Regulatory Commission 611 Ryan Plaza Drive Suite 1000 Ar11ogton, Texas 76012

• 1 Director of Nuclear Reactor Regulation Attn: Mr. Roger S. Boyd, Acting Director Division of Reactor Licer.ning U. S. Nuc] car Regulatory Cor.nisslan itashington, D.C. 20555 1

Secretary, NTSC, Belleview 1 Vice Prenldcut ,1:nnin* cring & Planning, 3'ith Avenue Innineerine, 1

M.inatcr of Production (Ch:iirman, NFSO), Ec11cvieu 1 Director. Qu.elity Ae.surance 1

Technical Servicen Supervisor 1

Superintendent, Nuclear huduct lon 1 Superint endent , operations- 1.

• Training Coun dinatur 1 l'oi:C Conimit s ee 1-Techulcal Seiviren Filen 1 Traf ulng 1:evlev' .

81ndicat en a >erox cog f of the let t er t o t he -Isis s riot , i.' llA - fEITo , i s swot wif b 191 rnplen ni the s epos t .

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