ML20023C595

Discusses Results of Analysis Performed to Determine Probability of Postulated Tornado Generated Missile Contacting Gratings Covering Ventilation Openings. Probability Acceptably Small.Condition Not RO

ML20023C595
Person / Time
Site:	Davis Besse
Issue date:	04/29/1983
From:	Crouse R TOLEDO EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
1-353, NUDOCS 8305170462
Download: ML20023C595 (2)

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% EDISON Docket No. 50-346 RCHue P. CRaSE Vce Prewent Nxtw License No. NPF-3 wisie>ssaat Serial No.-1-353 April 29, 1983 Mr. James G. Keppler Regional Administrator, Region III Office of Inspection and Enforcement

U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr. Keppler:

On March 18, 1983, Toledo Edison personnel at the Davis-Besse Nuclear

, Power Station discovered cut-out sections in three steel gratings covering ventilation openings in the concrete wall between the Service Water Pump Room and the Traveling Screen Room in the Intake Structure. These gratings act as barriers for tornado generated missiles. One of the three gratings affected measured approximately 3'-1" by I'-4" with ten small conduits (maximum size 4"-0) passing through the area. The total cut-out area is approximately 30% of the grating. The cut-out sections in the remaining two gratings constitute approxiamtely 7% of the grating area of each, however, conduits substantially fill the cut-out sections.

t Following the discovery of the present condition of these gratings, an analysis was performed by Toledo Edison to determine the probability of a postulated tornado generated missile contacting these gratings. It was determined that the probability of a tornado missile contacting these gratings during the remainder of the year that the wall openings behind the gratings are open is acceptably small (1.05 x 10-8).

The present condition of these gratings does not constitute a reportable occurrence as defined by Technical Specifications 6.9.1.8 or 6.9.1.9.

This information is being submitted to make you aware of the present condition of these gratings and Toledo Edison's actions to rectify the situation.

1 8305170462 830429 l PDR ADOCK 05000346 P PDR THE TOLEGO EOISON COMPANY EDISON PLAZA 300 MADISON AVENUE TOLEDO, OHIO 43652 ffol MAY 1 1 G63

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Docket No. 50-346 License No. NPF-3 Serial No. 1-353 April 29, 1983 Page 2 The ventilation wall openings behind these gratings are scheduled to be closed with reinforced concrete under Facility Change Request 81-054.

This change will eliminate the need for the steel gratings for tornado missile protection. It is expected that this modification will be com-pleted by August 1, 1983.

Please do not hesitate to contact me if you have any further questions.

Very truly yours, R P Cme /pm ,

RPC:RAL:LER:1j k cc: DB-1 NRC Resident Inspector I

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