ML19262A922

LER 79-042/03L-0:on 791106,valve ERV Nr 108A Opened During Operation for No Reason.After Calibr,Valve Malfunctioned within 1-h.Caused by Component Failure.Pressure Switch Replaced

ML19262A922
Person / Time
Site:	Oyster Creek
Issue date:	12/06/1979
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19262A920	List: ML19262A919 ML19262A922
References
LER-79-042-03L, LER-79-42-3L, NUDOCS 7912110317
Download: ML19262A922 (3)

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83 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES O'o The j O 2 l During normal operation, ERV NR 108A opened for no apparent reason.

@ t3 1 operator manually closed the valve by placing the control switch in the l o 4 l "Off" position. Power was reduced to 1700 MWt. Readings indicated that l Wy; the valve had not fully seated so it was manually opened and closed, [

I c is 1 i at which time it seated. Testing revealed that the setpoint had drifted j oj;,; down to normal operating pressure. After recalibration the valve was placed l

,Oie l back in service. The ERV opened one hour later for no apparent reason. i EC 7 E S SYSTEM CAUSE CAUSE COMP. VALVE 00*E CO;E SUS 00;E COMPONEtJT OODE SUECOCE EUSCOOE ole 1 l S i H10 ] @ lE @ lE @ l! N S l T l R lU l@ l El@ l Z j @

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35 36 3_d 40 41 42 43 44 47 CAUSE DESCHIFTION AND CORRECTIVE ACTIONS 1 O l The cause of this event is attributed to component failure resulting l 3 #i from the use of a switch that was not preconditioned. The pressure switch I i ,7 l was replaced with a spare pressure sensor which had been conditioned to all  ;

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~~7 Madison Avenue at Punch Bowl Road Morristown. New Jersey 07960 (201)455-8200 OYSTER CREEK NUCLEAR GENERATING STATION Forked River, New Jersey 08731 Licensee Event Report Reportable Occur'ence No. 50-219/79-42/3L-0 Report Date December 6, 1979 Occurrence Date November 6, 1979 Identification of Occurrence One electromatic relief valve (NR 10bA) lifted during normal operation and was placed in the "Off" position. This event is considered to be a reportable occurrence as defined in the Technical Specifications, paragraph 6.9.2.b(2) .

_ Conditions Prior to Occurrence The plant was operating at steady state power. The major plant parameters at the tirae of the occurrence weie:

Power: Iteactor, 1862.25 MWt -

Generator 648 MWe Flow: Feedwater, 6.95 x 106 lb/hr 4

Recirculation, 15.2 x 10 gpm Stack Gas: 3.19 x 104 pti/sec Description of Occurrence On Sunday, November 6, 1979, electromatic relief valve (ERV) NR 108A opened for no apparer t reason during normal plant operation at steady state conditions.

The control roam operators manually closed the valve by placing the control switch in the "3ff" position. Reactor power was reduced to approximately 1700 MWt. Tempeieture readings indicated the valve had not fully seated and the valve was manu11y opened and closed in ;:n attempt to fully seat it. The attempt was successful and the temperature downstream of the valve decreased.

On Monday, November 7, 1979, a test and calibration surveillance was conducted on the pressure sensor for ERV "A". Tbc setpoint of the pressure sensor was found to have drifted down to normal reactor operating pressure. The pressure setpoint was recalibrated and checked. The control switch was returned to the " Auto" position. Reactor power was increased to return to full power.

1528 079 Jersey Central Power & Light Company is a Member of the General Pubhc Utihties System

Reportable 0 currence No. 50-219/79-42/3L-0 Page 2 December 6, 1979 Less than an hour after being recalibrated, ER7 "A" opened again. The control room operators manually closed the valve and redaced reactor power to approximately 1700 MWt.

On Tuesday, November 8, 1979, the pressure sensor for ERV "A" was replaced and calibrated. The control switch was returned to the " Auto" position.

Apparent Cause of Occurrence The pressure switch that experienced instrument drift was new and not pre-conditioned.

Analysis of Occurrence The relief valves are provided to remove sufficient energy from the primary system to prevent the safety valves from lifting during a transient. The limiting pressure transient is a turbine trip from rated design power with a failure of the bypass to function. Under these conditions, five (5) relief valves are required to operate in order to prevent reaching the lowest setpoint of the primary system safety valves. It should be noted that a 25 psig margin exists between the resulting peak pressure and the lowest safety valve setpoint as an assurance that the safety valves will not lift during a transient. With four (4) relief valves operable, core thermal power must be reduced to 1740 MWt to preserve the 25 psig margin between peak transient pressure and the lowest safety valve setpoint.

Corrective Action The pressure switch, when new, may have some deviation over stated accuracy because the bourdon tube has not been preconditioned to establish its return ,

to the same shape after pressure stressing. A vendor recommendation stated that all new bourdon type pressure switches should be specified to be pre-conditioned by the manufacturer. This preconditioning includes a temperature soak of the bourdon tube at -65*F. and 165*F. for two hours at each tempera-ture and then pressure cycle 2000 times between 0 and 1200 psig. On November 24, 1979, a new bourdon tebe pressure sensor for NR 108A was replaced by a spare pressure sensor that was preconditioned at the plant to plant parameters. All new switches that will be ordered henceforth will be specified to ';e pre-conditioned. Since this problem would only be found in new repiscement switches, instruments that are in service and show no signs of drift would not have to be replaced.

Failure Data Manufacturer: Barksdale Model: 825-H-1255 Reference Reportable Occurrence No. 50-219/79-33/3L-0. 1528 000