ML20084M451

AO 3-72-7:on 721107,4,160-volt Switchgear Rooms Partially Flooded When Water Backed Up Through Floor Drains.Caused by Heavy Rains & Plugged Drainage Sys.Water Pumped Out & Drains Unplugged

ML20084M451
Person / Time
Site:	Turkey Point
Issue date:	11/17/1972
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084M439	List: ML20084M451 ML20084M514 ML20084M517
References
AO-3-72-7, NUDOCS 8306020172
Download: ML20084M451 (2)

Text

P.o. Box 3100 MIAMI. FLORIDA 33:01 1 "

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b J D, '."JJ2 FLORIDA POWER & UGHT COMPANY November 17, 1972 AY Mr. John F. O' Leary, Director <,,^~

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Division of Reactor Licensing M, . ., . .i,h fc U. S. Atomic Energy Commission fd_Id{*Lb h Washington, D. C.'20545 y _,

TURKEY POINT PLANT UNIT NO. 3 ' 5,"f 'M

/.7 DOCKET NOS. 50-250 AND 50-251

,. N ABNORMAL OCCURRENCE NO. 3-72-7 PARTIAL FLOODI!G OF SWITCHGEAR ROOMS

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Dear Mr. O' Leary:

In accordance with Technical Specification 6.6.2 a(1) and in amplification of the Company's telegram to the Director, Region II, Directorate of Regulatory Operations of November 8, 1972, this report is submitted.

At approximately noon on November 7, 1972, both of the Unit No. 3 4160 volt switch-gear rooms were partially flooded during a heavy rain v. hen water backed up through the floor drains. The rain began at about 11:30 a.m. and ceased at about 1:00 p.m.

1.22 inches rainfall was recorded at the plant site. The maximum water depth was estimated to be four inches at the west'end of the rooms, with an average depth throughout the rooms of one inch. The floor sloper downward to drains located at each end of the two rooms. The equipment in the switchgear rooms was not affected by the water. The unit was in a hot shutdown condition throughout the rain.

fSeveralfactorscontributedtocausetheAbnormalOccurrence. The unusually heavy rain was, of course, a primary cause. The switchgear rooms are located on the ground elevation below the outdoor turbine generator elevation. Floor drains from j the turbine ' elevation connect to a common drain system along with floor drains from

' the switchgear rooms and other adjacent areas. The common drain system empties into a yard drain catch basin which drains to the discharge canal. This drain to the

' discharge canal was later found to be almost completely plugged. The combination of

/the heavy rain and the numerous drains connected to a plugged system caused the flooding. Although most of the' water entered tne rooms by backing up through the floor drains, some water may have entered under the entrance doors.

Efforts to pump and drain the room were begun immediately upon discovering the condition. Sand bags were placed at the doors to keep the water out. Portable pumps were used to pump the water out of the rooms and the catch basin.

Investigation of the plugged drain line revealed that the outfall from the catch basin to discharge canal did not actually extend to the discharge canal. At some

• time following completion of the drain system, sand and rock fill were placed on the canal bank to support a temporary trailer and the outfall was covered at that time.

The sand and rock fill were removed and the drain line was extended to the edge /

of.the discharge canal. This will prevent recurrence of this event. ,

8306020172 72112e g # 4 PDR ADOCK 05000250 S

PDR COPY SElff REGION h~- "" '

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4 1-2 The flooding was an Abnormal Occurrence, under Section 1.13.8, Technical Specifications, because the flooding threatened the safe operation of the unit. Had the water risen to a depth of 6 to 8 inches in the center of the rooms, terminal blocks and relays of the switchgear and safeguards sequencers would have been in water and undesirable operation of the switchgear would have occurred.

Very truly yours, s

A. D. Schmidt Q P Director of Power Resources JRB mew cc: Mr. John Davis, Director Region II, Directorate of Regulatory Operation U. S. Atomic Energy Commission Suite 218, 230 Peachtree Street, N. W.

Atlanta, Georgia Dr. James Coughlin J. R. Bensen W. H. Rogers, Jr.

Documentary Files G. E. Liebler C.E.Branning/PlantFile D. W. Jones J. W. Williams, Jr.

Plant Nuclear Safety Committee

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