ML19309A505

Forwards Supplemental LER 78-005/03X-3

ML19309A505
Person / Time
Site:	Fort Saint Vrain
Issue date:	03/18/1980
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML19309A506	List: ML19309A505 ML19309A510
References
P-80055, NUDOCS 8003310373
Download: ML19309A505 (7)

Text

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] public service company oe cenende 16805 Weld County Road 191/2, Platteville, Colorado 80651 u- J March 18, 1980 Fort St. Vrain Unit No. 1 f-80055 Mr. Karl V. Seyfrit, Director Nuclear Regulatory Commission Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012

Reference:

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/

78-05, Final Supplement, submitted per the requirements of Technical Speci-fication AC 7.5.2(b)2.

Also, please find enclosed one copy of the Licensee Event Report for Reportable Occurrence Report No. 50-267/78-05 Very truly yours, Ww Don Warembour Manager, Nuclear Production DW/cis Enclosure cc: Director, MIPC l

5 8oossio sp.

REPORT DATE: March 18, 1980 REPORTABLE OCCURRENCE 78-05 January 11, 1978 ISSUE 3 OCCURRENCE DATE: (Determined March 13, 1978) Page 1 of 6  ;

FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO I 16805 WELD COUNTY ROAD 19 1/2 PLATIEVILLE, COLORADO 80651 REPORT NO. 50-267/ 78-05/03-X-3 1 FINAL SUPPLEMENT IDENTIFICATION OF OCCURRENCE:

A malfunction of helium circulator spaed modifiers caused loss of Plant Protective System function of high speed trips. This resulted in operation under a degraded mode permitted by LCO 4.4.1, Table 4.4-3, and is reportable  ;

per Fort St. Vrain Technical Specification AC 7.5.2(b)2. I This report is submitted as a Final Supplement to Reportable Occurrence j Report No. 50-267/78-05/03-L-0, Preliminary and Supplemental reports X-1  ;

and X-2.

I EVEMT DESCRIPTION:

See Figure 1. The speed measuring system (SM), @ , is designed to measure the rotational speed and alignment wobble of the helium circulator shaf t.

This is accomplished by the use of a reluctance type detector probe (SE),

@ , connected to a phase sensitive carrier type electronics system.

Precision machined slots in the rotating shaft of the helium circulator provide timing pulses whose frequency is proportional to shaf t rotational speed.

The electronic system which produces this signal operates on the principle of a balanced bridge connected to probes consisting of two identical coils.

In normal operation, the bridge is nulled for minimum zero phase shif t output with the rotating shaf t centered in the bearing.

Three separate channels monitor the speed of each helium circulator. The pulse si als are transmitted by the SM's, @ , to the speed transmitter (ST 's) , 3 , which produces a 0 to 10 volt output signal proportional to shaf t RPM for use in the summer modifiers and process tri modules.

The process trip modul s are the speed switches low (SSL), 4 , and speed switches high (SSH), 5 . If the circulator speed reaches either the high or low trip setting, the SSL's or SSH's initiate trip signals to the two of three solid state logic, @ , wh produces a circulator shutdown via the special control relays (XCR's), .

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REPORTABLE OCCURRENCE 78-05 ISSUE 3 l l

Page 2 of 6 l

l EVENT DESCRIPTION: (Cont' d)

Table 1 summarizes the failures experienced and reported in the previous three issues of this report.

TABLE 1 Speed PPS Approximate Indicated Reactor Da te Modifier Channel Circulator Speed Speed Power %

e 1-11-78 21161 A lA 2300 13 i M 1-11-78 21162 A 1C 2300 200 13 b1-11-78 21166 C 1C 2300 200 13 4-25-78 21164 B 1C 6300 55 5-7-78 21164 B 1C 4000 33 7-8-78 21170 B 1D 6000 5200 50

7 78 21164 B IC 6100 5000 50 7-8-78 21164 B 1C 6100 5000 IO

"*10-14-78 21172 C 1D 4300 2100 37 11-7-78 21161 A 1A 4300 55 11-12-78 21166 C 1C 5600 60 11-18-78 21164 B 1C 5600 60 12-11-78 21161 A 1A 5900 50 12-12-78 21161 A lA 7000 69 12-29-78 21161 A LA 6800 64 1- 1-79 21161 A LA 6800 64 1- 22 -79 21162 A 1C 4500 28 g1-23-79 21162 A 1C 6000 60 1-23-79 21172 C 1D 4600 33 1-28-79($)21172 C 1D 5200 42 1-30-79 21172 C 1D 5200 42 2-1-79 21172 C ID 4500 28

([) Three Failures As an interim measure, the adjustment of the speed modifiers was checked on a weekly basis.

REPORTABLE OCCURRDICE 78-05 ISSUE 3 Page 3 of 6 CAUSE DES CRIPTION:

Instrument calibration drif t due to bridge unbalance.

The balancing problem was caused by 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:

Table 2 summarizes the corrective actions for the failures reported in the previous three issues of this report.

TABLE 2 Speed Date Modifier Corrective Action o 1- 11-78 21161 Balanced speed modifier.

5 1-11-78 21162 Balanced speed modifier.

$! 1-11-78 21166 Connected spare cable / balanced speed modifier.

4 78 21164 Balanced speed modifier.

5-7-78 21164 Connected spare cable / balanced speed modifier.

7-8-78 21170 Balanced speed modifier.

-4 7-8-78 21164 Balanced speed modifier.

$ 7-8-78 vs 21164 Balanced speed modifier.

El 10-14-78 21172 Balanced speed modifier.

11-7-78 21161 Connected spare cable / balanced speed modifier.

11-12-78 21166 Balanced speed modifier.

11-18-78 21164 Connected spare cable / balanced speed modifier.

12-1~-78 21161 Balanced speed modifier.

12-12-78 21161 Balanced speed modifier.

l 12-29-78 21161 Balanced speed modifier.

1 79 21161 Connected spare cable / balanced speed modifier.

g 1- 22-79 21162 None - Change in temperature altered cable resistance.

] 1-23-79 21162 Balanced speed modifier.

1-23-79 21172 Connected spare cable / balanced speed modifier.

1-28-79 21172 Balanced speed modifier (three times) .

11-30-79 21172 Connected spare cable / balanced speed modifier.

2-1-79 21172 Connected spare cable / balanced speed modifier.

REPORTABLE OCCURRENCE 78-05 ISSUE 3 Page 4 of 6 CORRECTIVE ACTION: (Cont' d)

New cable connectors were certified to conform with the requirements and specifications of the purchase order.

The new cable connectors have been installed and tested.

No further corrective' action is anticipated or required.

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REPORTABLE OCCURRENCE 78-05 ISSUE 3 Page 6 of 6 Prepared By: . o Michael J. FerriBJ Technical Services Engineer

/

Reviewed By: / .

. u. < a echnical Services Supervisor Reviewed By:

Frank M. Mathie l

Operations Manager i

Approved By: 1 7m m[u Don Warembourg /

Manager, Nuclear Product' ion l

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