ML19270G111

LER 78-022/01T-0 on 780404:Fischer & Porter 10B2496 Transmitters for Coolant Low Flow Monitoring Had High Output Deviation During Seismic Test.Caused by Vibration of Mounting Plate.Design Change Initiated

ML19270G111
Person / Time
Site:	Salem
Issue date:	04/17/1978
From:	Spencer T Public Service Enterprise Group
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19270G108	List: ML19270G107 ML19270G111
References
LER-78-022-01T, LER-78-22-1T, NUDOCS 7906040277
Download: ML19270G111 (3)

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~. . t Report Number: 78-22/0lT Report Date: h/17/78 Occurrence Date: 4/4/78 Facility: Salem Generating Station Public Service Electric & Gas Company Hancocks Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE:

Reactor Coolant Low Flow Protection seismic Qualification Deficiency CONDITIONS PRIOR TO OCCURRENCE:

N/A DESCRIPTION OF OCCURRENCE:

During a review of seismic test data for NEMA 12 panel enclosures, it was found that a transmitter manufactured by Fischer and Porter, Model No. 10B2496, was used in a NEMA 12 enclosure for monitoring reactor coolant flow. This transmitter had a high output deviation during the seismic test which exceeded acceptable tolerances. This transmitter in the noted application provides a low flow signal to the soiid state protection system for reactor trip. The transmitters' high output deviation during a seismic event could prevent it from performing its required function. This is only applicable if the reactor coolant low flow condition occurs in coincidence with a seismic event. Test reports indicate that the transmitter output returns to normal following the seismic disturbance.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

The Fischer and Porter 10B2496 transmitter experienced the high out-put deviation during the seismic test due to vibratory motion of the instrument mounting plate within the NEMA 12 enclosure. The sub-panel mounting plate was not stiff enough to adequately support the heavy 10B2496 transmitter. As a result, this transmitter was subjected to high vibration levels which caused its output to be offset in the upscale direction during the test. Subsequent inspection and cali-bration checks showed no damage or significant shift in transmitter accuracy.

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' UIR 78-22/0lT  !

ANALYSIS OF OCCURRENCE:

Sufficient diversity exists for protection against loss of reactor coolant flow transients to overcome the failure of one protection system parameter. However, if the cause of a loss in reactor coolant flow is not electrical in nature, the reactor coolant low flow transmitters are especially important. With the previously described condition existing, the low reactor coolant flow reactor trip may not have been initiated during a seismic event if needed within the time limitations imposed by the Technical Specifications. Eventually, the overtemperature AT reactor trip and/or the low reactor coolant flow reactor trip (when the seismic disturbance had subsided) would be initiated.

CORRECTIVE ACTION:

The installation of a unistrut to stiffen the sub-panel mounting plate in the NEMA 12 panel and enlarging the instrument mounting bracket will correct the output deviation of the transmitter to within acceptable tolerances during a seismic event. Confirmatory seismic tests have been performed demonstrating this design. This change will be incorporated in accordance with DCR ED-0357. Panel modifications will be completed prior to the unit returning to service from the present outage. ,

FAILURE _ DATA:

N/A

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Prepared by T. L. Spencer / ,

Manager Salem Generating Statior SORC Meeting No. 22-78 2237 249

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NAME OF PREPARER T. L. SOenCer PHCN E:

(6091365-7000 Sale, M .!

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