ML19261B198

LER 79-001/03L-0 on 790107:high Steam Line Flow Alarm & Automatic Isolation of Reactor Core Isolation Cooling Steam Supply Line Occurred.Caused by Failure of Micro Switch Inside Steam Line High Flow Differential Pressure Switch

ML19261B198
Person / Time
Site:	Quad Cities
Issue date:	01/18/1979
From:	Reed M COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19261B197	List: ML19261B196 ML19261B198
References
LER-79-001-03L-02, NUDOCS 7902140157
Download: ML19261B198 (2)

Text

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80 EVENT DESCHIPTION AND PRCB ABLE CONSEQUENCES 10121 l On January 7, 1979, at 5:55 a.m., the Unit One operator received a high steam line l g 3  ;

flow alarm and auto isolation of the RCIC steam supply line. Valves M0-1-1301-16 [

and M0-1-1301-17 closed as designed. A check of the RCIC system revealed that l

[o l4 ; g gg there was a problem with RCIC steam line high flow differential pressure switch [

g g g DPIS 1-1360-1A. In accordance with Technical Specification 3.5'.E.2., the HPCI l g , g system was started and proven operable. l

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(.y_jh 42 Wh 43 lBl0 44 8 0lh 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS i o l The cause of this occurrence was conoonent failurn Onn nf t ton micen ctaitchoc incido l j,,,9l steam line high flow differential pressure switch DPIS-1-1360-1A had failed. The [

, g micro switch was replaced and the high flow differential switch was recalibrated. j RCIC was returned to service and proven operable at 12:40 p.m. the same day. [

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I. LER NUMBER: LER/R0 79-01/03L-0

11. LICENSE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station Ill. FACILITY NAME: Unit One IV. DOCKET NUMBER: 050-254 V. EVENT DESCRIPTION:

On January 7, 1979 Unit One was operating at steady state with a thermal power of 1333 MWt and with an electrical load of 397 MWe. At 5:55 AM the unit operator received a high steam line flow alarm on the Reactor Core isolation Cooling System (RCIC),

which automatically closed valves M0-1-1301-16 and M0-1-1301-17, thus isolating the steam supply line. Af ter operations thoroughly checked the RCIC System, the unit operator tried to reset the alarm and open the M0-1-1301-16 and M0-1-1301-17 steam line valves. The alarm would not clear, and the valves would not open. A problem with a high steam line flow dif-ferential pressure switch was suspected. In accordance with Technical Specification 3.5.E.2. , the High Pressure Coolant injection System (HPCI) was proven operable at 8:05 AM.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE:

Since the HPCI System was tested and proven operable, safe plant operation was maintained. in addition, the RCIC System was returned to service and demonstrated operable in less than seven hours after the DP siwtch had malfunctioned.

Vll. CAUSE:

The cause of this occurrence was component failure. One of two micro switches inside the steam line high flow differential pressure switch, DPIS-1-1360-1A, had failed. Switch number I-1360-1A is an elbow-tap di f ferential pressure switch, manufac-tured by the Barton Instrument Co. as part number 0288.0025.B.

Vill. CORRECTIVE ACTION The immediate corrective action taken was to prove the HPCI System operable in accordance with Technical Specification 3 5.E.2. Work request 94-79 was issued to make the appropriate repairs.

The failed micro switch was replaced and the high flow dif-ferential pressure switch was recalibrated. The RCIC System was tested and proven operable at 12: 40 PM on January 7, 1979