05000322/LER-1986-014

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LER 86-014-01:on 860305,full Reactor Trip Occurred Due to Momentary False Low Vessel Level Signal,Causing Hydraulic Pressure Spike in Ref Leg A.Bourton Tube Type Pressure Transmitter Replaced W/Rosemount Model 1153
ML20055C493
Person / Time
Site: Shoreham File:Long Island Lighting Company icon.png
Issue date: 05/16/1990
From: Schnaars G
LONG ISLAND LIGHTING CO.
To:
Shared Package
ML20055C491 List:
References
LER-86-014, LER-86-14, NUDOCS 9005240060
Download: ML20055C493 (3)
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LER-2086-014,
Event date:
Report date:
3222086014R00 - NRC Website
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NAME TE LEPMONE NUMSE R George Schnaars, Operational Compliance Engineer

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[ On March 5, 1986 at 1132 a full Reactor Trip occurred due to a momentary false low vessel level signal, while an I&C Technician was

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' valving in a pressure transmitter to the reference leg. The plant L was in Operational Condition 5 with the mode switch in Refuel and  ;

l all rods inserted in the core. Technicians had just completed l -instrument calibrations and were returning 1061*PT-006 (Remote

! Shutdown panel RPV pressure transmitter) to service. Due to probable air entrapment in the instrument (a Bourdon tube type, which cannot be vented), opening the isolation valve caused a hydraulic pressure spike in the "A" reference leg, resulting in a

' momentary false low level signal. A full Reactor Trip occurred.

The instrument was returned to service, and the performance of the procedure was suspended. The operators verified the signal as false and immediately reset the trip. Plant Management was notified of the event and the NRC was notified at 1350 per 10CFR50.72.

Corrective actions include a modification to replace the Bourdon

-Tube type pressure transmitter with a Rosemount Model 1153. This Supplemental Report is being submitted to inform the Commission of the status of the corrective actions.

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On March 5, 1986 at ll32 a full Reactor Trip occurred due to a momentary false low "essel level signal, while an Instrument and Controls (I&C) Teet ' tian was valving in a pressure transmitter to the reference leg. ne plant was in Operational Condition 5 (refuel) with the mode switch in Refuel and all rods inserted in the core.

Two I&C Technicians had just completed calibrations in accordance with plant procedure SP 44.133.03 (Remote Shutdown Instruments 18

Month Channel Calibrations) and were ready to return 1C61*PT-006 (Remote Shutdown panel RPV pressure transmitter) to service. Since this instrument is extremely sensitive and has caused a problem in o the past (Refer to LER 85-006), the technicians used extreme caution when opening the isolation valve. However, due to probable air

-entrapment in the instrument (a Bourdon tube type, which cannot be vented), opening the valve caused a hydraulic pressure spike in the "A" reference leg, resulting in a momentary false low level signal.

A full Reactor Trip occurred. The instrument was returned to service and the performance of the procedure was suspended. The operators verified the signal as false and immediately reset the

' trip. Plant Management was notified of the event and the NRC was notified at 1350 per 10CFR50.72.

There was no safety significance to the event. The Reactor Protection System functioned as designed. The operators carried out

all required actions. Had the event occurred under a more severe 3 set of conditions (5% power), the plant would have been capable of a safe shutdown.

To prevent recurrence, the following actions were taken:

l- 1) A modification-was prepared which would replace the Bailey E

Bourdon tube type pressure transmitter with~a Rosemount Model 1153 pressure transmitter (which is ventable and will eliminate l possible air entrapment). This modification also applies to a pressure transmitter (lC32-PT-004B) on the "B" Reference leg, as well. Implementation of this modification has been deferred L indefinitely due to the New York State - LILCO Shoreham Settlement Agreement.

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011 0l3 0F Ol3 TEXT (1mmo asses Ap rueveof, aos em NMC perm 3354 w (171 2)- Two other Bourdon tube pressure gauges are connected to the reference legs and could also present the same potential for '

causing reactor trips-(1B21-PI-025A on the "A" reference leg and 1B21-PI-025B on the "B" reference leg). The preventive maintenance'(PM) activities associated with these gauges were identified and the applicable PM Surveillance Activity Work i

Sheets (SAWS) were marked with precautionary statements to:

a. perform this work during shutdown only,'and b. consider inserting a full scram prior to valving the gauge back into service.
3) A report describing the incident in detail was read by all I&C Technicians, foremen and supervisors.

This. supplement report is being submitted to inform the Commission of the status of these corrective actions.

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ff.C Perm 305A (649)

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