ML20080E106

Informs That Term Mechanically Intact Redefined to Mean That Lower Portion of Torus Shell Up to Normal Operating Water Level Has No Openings & Capable of Holding Water

ML20080E106
Person / Time
Site:	Oyster Creek
Issue date:	02/03/1984
From:	Fiedler P GENERAL PUBLIC UTILITIES CORP.
To:	Crutchfield D Office of Nuclear Reactor Regulation
References
NUDOCS 8402090341
Download: ML20080E106 (2)

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GPU Nuclear Corporation Nuclear

=== 388 Forked River, New Jersey 08731-0388 609 971-4000 Writer's Direct Dial Number:

February 3, 1984 Mr. Dennis M. Crutchfield, Chief Operating Reactors Branch 15 Division of Licensing U.S. Nuclear Regulatory Commission Washington, D. C.

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Subject:

Oyster Creek Nuclear Generating Station Docket No. 50-219

'lbrus Modifications Concurrent With Reactor Refueling Present outage conditions require that some torus modification work be performed concurrently with refueling. Existing Technical Specification 3.5.A.2.d requires that the torus be " mechanically intact." A safety evaluation submitted with Technical Specification Change Request No. 53 dated January ll, 1977 defined " mechanically intact" to include the ability to flood the containment to provide long-term emergency core cooling within several hours. For the purpose of completing the present work scope on the torus we have redefined " mechanically intact" for this outage project only. By

" mechanically intact" it is meant that the lower portion of the torus shell, up to the normal operating water level, has no openings and is capable of holding water.

We consider this definition to be appropriate for the given circumstances because:

a) The core is at such a reduced decay heat rate, cooling requirements are minimal. In addition, an evaluation on the basis of adiabatic heatup of the present fuel in its proposed configuration indicates that the core may be dry and without forced cooling for up to ten hours before exceeding the cladding temperature limit of 2200 degrees F.

b) No control rod drive maintenance / replacement will be performed during refueling. 'Ibe safety evaluation that accompanied Technical Specification Change Request No. 53 stated that the largest postulated leak during refueling is 1300 gpm resulting from the complete removal of or failure to backseat a control rod. As this maintenance will not be performed during refueling or while fuel is in the vessel, the potential for loss of coolant due to this largest

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postulated leak need not be considered for the period of time in question.

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c) No movements of heavy loads, those greater than 800 pounds, will take place in the drywell during the time of concurrent torus work and refueling or while fuel is in the vessel. 'Ihis will virtually eliminate the possibility of small diameter pipe breaks during the period in question.

d) No work will be permitted that could result in draining the reactor vessel below the safety limit of 4'8" above the top of the active fuel.

e) In the very unlikely event of a leak, plant conditions, core heatup time, and the leakage flow rate would allow the following steps to be taken before core damage could occur:

1) stop or reduce the leak and/or,

2) off-load the core to the fuel pool, f) The probability of leaks during this period is extremely low based on:

1) not allowing control rod drive maintenance,

2) not allowing maintenance that can result in draining reactor vessel water level below 4'8" above the top of the active fuel, and

3) not allowing heavy lifts greater than 800 pounds to be performed in the drywell.

Nevertheless, a 50 gym leak that might occur from valve packing or pump seals has been postulated. Under these conditions, a core spray pump can take suction frcan the condensate storage tank alone and still be able to provide makeup for 5 days based solely on that tank's capacity.

In the event that any comments or questions arise, please contact Mr.

James Knubel of af staff at (201) 299-2264.

Very truly yours, Y

Peter B. Fiedler Vice President and Director Oyster Creek 1r/0117e cc: Dr. Thomas E. Murley, Administrator Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406 NRC Resident Inspector Oyster Creek Nuclear Generating Station Forked River, NJ 08731

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