05000341/LER-1985-001, :on 850328 & 31,reactor Protection Sys Div 1 Power Loss Occurred,Resulting in Reactor Scram.Caused by Ground Fault at Breaker A6.Breaker Replaced & Duct Leak Repaired W/Temporary Seal

:on 850328 & 31,reactor Protection Sys Div 1 Power Loss Occurred,Resulting in Reactor Scram.Caused by Ground Fault at Breaker A6.Breaker Replaced & Duct Leak Repaired W/Temporary Seal

ML20116L757
Person / Time
Site:	Fermi
Issue date:	04/26/1985
From:	Lenart R, Wegele A DETROIT EDISON CO.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
LER-85-001, LER-85-1, NP-85-392, NUDOCS 8505030726
Download: ML20116L757 (3)

LER-1985-001, on 850328 & 31,reactor Protection Sys Div 1 Power Loss Occurred,Resulting in Reactor Scram.Caused by Ground Fault at Breaker A6.Breaker Replaced & Duct Leak Repaired W/Temporary Seal

Event date:
Report date:
3411985001R00 - NRC Website

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At 2345. hours on 03/28/85 while initial fuel loading was in progress, breaker posi-tion D on Bus # 11 automatically opened interrupting the 13.8 KV feed to System Service Transformer # 64 which supplies power to Division I.

Reactor Protection System Division I power was lost which resulted in a full scram because the neutron monitoring instrumentation RPS shorting links were removed.

Emergency Diesel Generator # 12 started automatically to supply power to Division I.

After offsite power was restored to Division I using tie breakers, EDG # 12 was unloaded and secured.

Subsequent trouble shooting did not reveal the cause of the problem. A similar event occurred on 03/31/85 after the transformer was reenergized.

Investigations conducted following the second occurrence revealed that water had entered the switchgear cabinet housing breaker position A6 and caused a ground fault at the A6 breaker which is an alternate feed to transformer # 64. A heavy rainstorm with strong winds preceded each occurrence.

It was concluded that the first event was caused by a ground fault at the same location.

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m.cr msn m While performing initial fuel loading at 2345 hours0.0271 days <br />0.651 hours <br />0.00388 weeks <br />8.922725e-4 months <br /> on 03/28/85, breaker D on Bus

1. 11 automatically opened interrupting 13.8 KV power to System Service Transformer

1. 64 (SS 64).

SS 64 supplies power to Division I.

A full scram signal was received because power to Division I of the Reactor Protection System (RPS) was lost and the RPS shorting links were removed per procedure during core alterations thus establishing non-coincident logic.

Emergency Diesel Generator # 12 automati-cally started (EDG # 11 was unavailable because of maintenance), Division I Battery chargers tripped, Division I Standby Gas Treatment System initiated, Division I Control Center HVAC switched to recirculation mode, Division I Emergency Equipment Cooling Water System and Emergency Equipment Service Water System automatically initiated, Division I Control Air Compressor initiated and Reactor Water Cleanup System, Drywell Sumps and Primary Pneumatic Supply Systems automatically isolated (isolation valve groups 10, 11, 13, and 18).

After power was restored to the refueling bridge, the fuel bundle which was being transferred when the event occurred was inserted into the core and core altera-tions were halted.

Division I offsite power was then restored by using tie breakers and EDG # 12 was. unloaded and secured. Throughout the event Division II systems were unaffected and thus available to perform their intended function.

All protection and safety systems functioned as designed throughout the event.

Extensive trouble shooting failed to reveal why breaker D opened and thus SS 64 was reenergized at 2210 hours0.0256 days <br />0.614 hours <br />0.00365 weeks <br />8.40905e-4 months <br /> on 03/30/85. At 062S hours on 03/31/85 breaker D again automatically opened. While attempting to place caution tags on breaker A6 (an alternate feed to SS 64) water was observed inside the switchgear cabinet. There was also extensive evidence of arcing on the breaker components.

Further observa-tion revealed a defective seal on the duct (directly above the switchgear cabinet) which houses the power feeds from CTG # 11 transforaer.

Since there was a heavy rainstorm with strong winds prior to each event, it is believed that water entered the cabinet during these storms causing a ground fault at the A6 breaker which resulted in breaker D opening.

The A6 breaker was replaced and the duct leak was repaired with a temporary seal.

During a future outage of Division I, the duct and switchgear will be thoroughly inspected and necessary repairs made to ensure a permanent seal.

Other switch-yard equipment will be inspected and repaired as necessary. A periodic mainte-nance schedule will be established to identify and correct equipment degradation.

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Ddron Edison !!difAFe"22e April 26, 1985 NP-85-392 U.S. Nuclear Regulatory Commission Attention:

Document Control Desk Washington, D.C.

20555 Gentlemen:

Reference:

Fermi 2 NRC Operating License No. NPF-33

Subject:

Transmittal of Licensee Event Report No.85-001 Please find enclosed LER No. 85-001-00, dated 04/26/85, for a report-able event which occurred on 03/28/85.

As indicated below, a copy of this LER is being sent to the Region III office.

If you have any questions, please contact us.

Sincerely,

'l

.R.S. Lenart Superintendent Nuclear Production Enclosure: NRC Forms 366, 366A cc:

Regional Administrator USNRC Region III 799 Roosevelt Road Glen Ellyn, IL 60137 Mr. P.M. Byron 2

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