ML19256A958

LER 78-096/03L-0 on 781211:loss of Normal Power to Bus E-1 Caused by a 1/2 Scram & a 1/2 Group No 1 Isolation.Cause Unknown,But Suspected to Be Const Activities Associated W/ Fire Protection Mods

ML19256A958
Person / Time
Site:	Brunswick
Issue date:	01/11/1979
From:	Tollison A CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19256A954	List: ML19256A953 ML19256A958
References
LER-78-096-03L, LER-78-96-3L, NUDOCS 7901170196
Download: ML19256A958 (2)

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74 75 REPORT D ATE do EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h o 2 lAt 1120 hours0.013 days <br />0.311 hours <br />0.00185 weeks <br />4.2616e-4 months <br /> a loss of nomal power to bus E-1 caused a scram and a h group one 1 o 3 l Isolation due to loss of the "A" RPS MG set which is fed from E-1. Upon loss of normal o 4 l power, diesel generator #1 started and loaded. Both the "A" and "B" reactor recircula-1 lo]si tion pumps were running at 627. speed. When the loss of normal power to E-1 was l o 6 texperienced, the "A" reactor recirculation pump ran back to minimum speed and tripped.1 o 7 lThe recirculation loop was considered inoperable until the oumo was restarted (withoutl o a Idifficulty), 15 minutes after it tripped. (Technical Specification 3.4.1.1) l i 9 9 80 SYSTEM CAUSE CAUSE COMP VALVE CODE CODE SUSCODE COMPONENT CODE SU8 CODE SU8 CODE z z z J@ tz_1 @

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS FlTl l Af ter the RPS MG set was restarted, the h group one and h scram were reset. Normal l t i I power was restored to E-1 and the #1 diesel generator was secured. The cause for theI i - [ E-1 bus tripping was thoroughly investigated. Numerous construction activities assocjate liIll with fire protection modifications were taking place in the area of E-1. However, not i 4 I reason for the trip could be determined from conversations with construction personnel 7 8 9 80 ST S  % POWER oTHER STATUS OIS O RY DISCOVERY DESCRIPTION li 151 (ydh I o 8 l o lhl NA l l B lhl operator observation I

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Cause Description and Cattective Action in the E-1 area. Plant maintenance activities were also investigated and no activities related to E-1 were taking place. The reason for the recirculation pump runback and trip with a loss of E-1 was investigated and no cause could be determined. The possibility of a recirculation pump MG set D.C. control voltage transient was reviewed, but no reason for a transient was found. This event appears to be an isolated case and no further investigations are planned. This event is not expected to occur again.