05000277/LER-1985-015-01, :on 850822,full Scram & Primary Containment Isolation Sys Groups II & III Initiated Due to Reactor Low Level Signal.Caused by Pressure Transmitter PT-53 Block Valve Leak.Block Valve Replaced

:on 850822,full Scram & Primary Containment Isolation Sys Groups II & III Initiated Due to Reactor Low Level Signal.Caused by Pressure Transmitter PT-53 Block Valve Leak.Block Valve Replaced

ML20132G800
Person / Time
Site:	Peach Bottom
Issue date:	09/20/1985
From:	Birely W PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:
Shared Package
ML20132G754	List: 05000277/LER-1985-015-01, :on 850822,full Scram & Primary Containment Isolation Sys Groups II & III Initiated Due to Reactor Low Level Signal.Caused by Pressure Transmitter PT-53 Block Valve Leak.Block Valve Replaced 05000277/LER-1985-016-02, :on 850826,full Scram & Primary Containment Isolation Sys Groups II & III Initiated Due to Reactor Low Level Signal.Caused by Failure to Ensure That Pressure Transmitter Returned to Svc from 850822 Event ML20132G751
References
2-85-15, LER-85-015-01, LER-85-15-1, NUDOCS 8510010629
Download: ML20132G800 (3)

LER-1985-015, on 850822,full Scram & Primary Containment Isolation Sys Groups II & III Initiated Due to Reactor Low Level Signal.Caused by Pressure Transmitter PT-53 Block Valve Leak.Block Valve Replaced

Event date:
Report date:
2771985015R01 - NRC Website

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Abstract:

2-85-15 On August 22, 1985, with Unit 2 in cold shutdown, the reactor protection system initiated a full scram due to an inadvertent reactor low level signal.

Additionally, the primary containment e

isolation system initiated Group II and Group III isolations due to the same reactor low level signal.

Because Unit 2 was in the cold shutdown condition, no control, rod mov'ement occurred.

The event occurred when a reactor pressure transmitter was being surveillance tested.

The scram and Group II and Group III isolations were reset and the affected systems restored to normal.

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-..c i-ma n 's Description of the Event:

On August 22, 1985, at 10:11 a.m.,

while Unit 2 was in cold shutdown,.a full scram was initiated by the reactor protection system.(RPS) due to an inadvertent reactor low level signal.

Additionally, the Primary Containment Isolation System (PCIS) initiated Group II and Group III isolations due to the same reactor low level signal.

Because Unit 2 was in the cold shutdown condition, no control rod movement occurred..RPS and PCIS responded properly.

The inadvertent signal was generated when reactor pressure transmitter PT-2-6-53B was being surveillance tested.

The scram and Group II and Group III isolations were reset and all 'af fected systems were returned to normal.

Consequences of the Event:

There were no adverse consequences, because the event did not jeopardize the capability to maintain the reactor in the cold shutdown condition.

Cause of the Event

The reactor pressure transmitter PT-2-6-53B was being surveillance tested.

PT-2-6-53B shares a sensing line with reactor level transmitters LT-2-2-3-101C and LT-2-2-3-101D.

These.two level transmitters actuate the RPS and PCIS systems during a reactor low level condition.

During the surveillance test, the PT-53B block valve is placed in the closed position.

A high pressure is then applied to the volume between the transmitter and the block valve.

Due to a leak through the block valve, a small pressure spike occurred in the common. sensing line when the test pressure was applied.

This spike caused LT-101C and LT-101D, which respond to pressures of the magnitude of inches of water, to generate low level trip signals.

Simultaneous low level signals from LT-101C and LT-101D initiate j

a full scram and Group II and Group III isolations.

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Corrective Actions

The leaking block valve was replaced on August 24, 1985.

Previous Similar Occurrences:

LER 2-85-04 concerned an instrument rack pressure spike resulting in a full scram and Group II and Group III isolations.

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