05000366/LER-1978-054-01, /01T-0:on 781017,differential Pressure Between Drywell & Torus Could Not Be Established W/O High Leakage Rate.Caused by Improper Setting of Drywell Vacuum Breaker Valves.Valves Repaired

/01T-0:on 781017,differential Pressure Between Drywell & Torus Could Not Be Established W/O High Leakage Rate.Caused by Improper Setting of Drywell Vacuum Breaker Valves.Valves Repaired

ML20148B255
Person / Time
Site:	Hatch
Issue date:	10/24/1978
From:	Nix R GEORGIA POWER CO.
To:
Shared Package
ML20148B254	List: 05000366/LER-1978-054, Forwards LER 78-054/01T-0 05000366/LER-1978-054-01, /01T-0:on 781017,differential Pressure Between Drywell & Torus Could Not Be Established W/O High Leakage Rate.Caused by Improper Setting of Drywell Vacuum Breaker Valves.Valves Repaired
References
LER-78-054-01T, LER-78-54-1T, NUDOCS 7810310154
Download: ML20148B255 (2)

LER-1978-054, /01T-0:on 781017,differential Pressure Between Drywell & Torus Could Not Be Established W/O High Leakage Rate.Caused by Improper Setting of Drywell Vacuum Breaker Valves.Valves Repaired

Event date:
Report date:
3661978054R01 - NRC Website

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in MURATIVE REPORT LER 50-366/1978-54 On October 17, 1978, while performing Test and Experiment Report 78-09, a differential pressure between the drywell and torus could not be established without a high leakage rate. The Unit was shutdown (Technical Specification.

3.6.4.1.d.) to investigate the cause of the leakage.

.Drywell vacuum breakers 2T48-F323A thru 2T48-F323L were found to be leaking past the seats. The leakage was caused by the retaining magnets, that are used for the setpoint adjustment, being extended too far. Procedure HNP-2-3958, Suppression to Drywell Vacuum Creaker Delta P Test, fails to specify the need for a slight gap between the. magnet and magnet plate to insure the pallet seal is seated properly onto the plate.

The valves were repaired and procedure H"P-2-3957, Suppression Chamber to Drywell Vacuum Breaker System Operability, performed and found satisf actory.

A Procedure Change Request is being sutxnitted to the Plant Review Board to incorporate the verification of a gap between the magnet and magnet plate when performing procedure HNP-2-3958.

There were no probable. consequences because the Torus Spray and Standby Gas Systems were available to create a differential pressure that wuld assist i

the vacuum.breaFer pallet seals in sealing against the plate. The ability of the drywell vacuum breakers to relieve a drywell vacuum was not impeded and public health and safety were not affected by this occurrence.

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