ML19210E295

Forwards LER 79-041/03X-1

ML19210E295
Person / Time
Site:	Fort Saint Vrain
Issue date:	11/20/1979
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19210E296	List: ML19210E295 ML19210E297
References
P-79276, NUDOCS 7912040296
Download: ML19210E295 (3)

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\ public service company oe cdlendo j 16805 Weld County Road 19 1/2, Platteville, Colorado 80651 November 20, 1979 Fort St. Vrain Unit No. 1 P-79276 Mr. Karl V. Seyfrit, Director Nuclear Regulatory Commission Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012 REF: Facility Operating License No. DPR-34 Docket No. 50-267

Dear Mr. Seyfrit:

Enclosed please find a copy of Reportable Occurrence Report No. 50-267/

79-41/03-X-1, Supplement, submitted per tne requirements of Technical Specification AC 7.5.2(b)4.

Also, please find enclosed one copy of the Licensee Event Report for Reportable Occurrence Report No. 50-267/ 79-41/03-X-1.

Very truly yours,

$wwl%

Don Warembourg y Manager, Nuclear Production DW/cls cc: Director, MIPC

. 1.470 349 A*s

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REPORT DATE: November 19, 1979 _

REPORTABLE OCCURRENCE 79-41

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ISSUE 1 OCCURRENCE DATE: Octob er 26, 1979 Page 1 of 2 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO 16805 WELD COUNTY ROAD 19 1/2 PLAITEVILLE, COLORADO 80651 REPORT NO. 50-267/ 79-41/C; 1 Supplement IDENTIFICATION OF OCCURRENCE :

A malfunction of helium circulator 1C speed modifier caused loss of Plant Pro-tective System function of high speed trips. This resulted in operation under a degraded mode permitted by LCO 4.4.1 and is reportable per Fort St. Vrain Technical Specification AC 7.5.2(b)2.

EVENT DESCRIPTION:

On October 26, 1979, while operating at 30% thermal power and 76 MR electrical power, operations personnel observed that one of three channels for the 1C cir-culator speed protection tripped on low speed while the circulator was operating at approximately 4,500 rpm.

This resulted in loss of the speed signal and trip capability in one of the three associated high speed trip channels for the 1C circulator. Two redundant channels wore available and operable.

CAUSE DESCRIPTION:

Instrument calibration drif t due to bridge unbalance.

The balancing problem is caused iy a change in resistance between the two leads of the speed element and ground at the circulator connection end. The difference in resistance occurs over a period of time in the cable connectors as a result of the temperature and humidity of the ambient air.

CORRECTIVE ACTION:

Adjusting the IC circulator speed modifier restored overspeed protection to the affected channel.

As an interim measure, the adjustment of the speed modifiers is being checked on a weekly basia.

New connectors have been ordered and will be environmentally qualified for installation. The results will be reported in a future supplemental report.

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REPORTABLE OCCURRENCE 79-41 ISSUE 1 Page 2 of 2 Prepared by:

s , w.e A , . _ ._ ul- o Micqsci J. Ferris V Technical Services Engineer Reviewed by: v [/ t.hm J. W. Gahm Technical Services Supervisor e

Reviewed by:

Frank M. Mathie Operations Manager Approved by: -

<t ow _M Don Warembourg g Manager, Nuclear Production 1470 351

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