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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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

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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

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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

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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

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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.

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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.

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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.

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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

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Reviewed By: / .

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Frank M. Mathie l

Operations Manager

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

Manager, Nuclear Product' ion l

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