ML20235H996

Requests That 860630 Application for Amend to License NPF-3, Revising Tech Spec 3.4.1.2 Re Subcooling Margin Adequacy in Response to NRC 850603 Request,Be Withdrawn.Decision Based on Reassessment of Request & Subsequent Telcon Discussions

ML20235H996
Person / Time
Site:	Davis Besse
Issue date:	07/06/1987
From:	Shelton D TOLEDO EDISON CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
TAC-61937, NUDOCS 8707150348
Download: ML20235H996 (2)

Text

'

e TOLEDO-

%mm EDISON 4 i

i Docket No. 50-346 DONALD C. SHELTON Vce Presulent-Nuclear

]

i (419]249-2399 l License No. NPF-3  !

Serial-No. 1373 July 6, 1987 United States Nuclear Regulatory Commission '

l Document Control Desk Washington, D. C. 20555 Gentlemen:

Subject:

Subcooling Margin Adequacy (TAC No. 61937)

In accordance with the NRC's' letter of June 3,1985 (Log No. 1758), Toledo Edison evaluated the adequacy of the subcooling margin specified in the.

Davis-Besse Nuclear Power Station, Unit No. 1, Appendix A, Technical Specifications. Pursuant to the NRC's request, Toledo Edison submitted a 1 License Amendment Request under a cover letter (Serial No. 1268) dated June 30, 1986, which requested that the subcooling margin be revised in .

Technical Specification 3.4.1.2. I Subsequent telephone discussions with the NRC and Toledo Edison's reassessment of the NRC's request of June 3, 1985, have led Toledo Edison to the conclusion that the License Amendment Request (Serial No 1268) should be withdrawn. The basis for this conclusion is discussed below.

i' The NRC's letter of June 3, 1985, stated that the Standard Technical Specification may be nonconservative with regards to the required sub-coolint; margin (10*F) that must be established when reactor coolant pumps are to be secured in Modes 3, 4, and 5. Specifically, when instrument uncertainties and elevation head effects are taken into account, this subcooling margin may not be sufficient to prevent flashing in the higher elevation of the hot legs and steam accumulation at the top of the. hot leg U-bends, with consequent interruption of natural circulation. This was  ;

the very condition the subcooling margin was designed to prevent.. The NRC '

requested that Toledo Edison ensure that sufficient margin exists such  !

that void formation is precluded when instrument error and elevation effects are accounted for.

i Technical Specification 3.4.1.2a requires at least two of the following loops to be operable while in Modes 3 (Hot Standby), 4 (Hot Shutdown) or 5 j (Cold Shutdown): Reactor Coolant Loop 1 and its steam generator, Reactor 'l Coolant Loop 2 and its steam generator, Decay Heat Removal Loop 1, or  !

Decay Heat Removal Loop 2. Specification 3.4.1.2b requires that at.least' '

)

one of these coolant loops be'in operation while in the above modes of THE TOLEDO EDISON COMPANY

~

EDISON PLAZA 300 MADISON AVENUE TOLEDO, OHIO 43652 '

8707150348 B70706 PDR- ADOCKiO5000346 P ppg

i

= i Docket No. 50-346 i License No. NPF-3 Serial No. 1373 j Page 2 l i

operation. The footnote to this latter requirement provides that the decay heat removal pumps may be de-energized for up to an hour if (1) no ,

operations are permitted that would cause dilution of the reactor coolant i system boron concentration, and (2) core outlet temperature is maintained I at least 10*F below saturation temperature. l I

Toledo Edison believes that the core outlet temperature of 10*F below l saturation temperature (subcooled margin) as stated in Technical Specifi-cation 3.4.1.2 is a " safety margin" which should not include elevation head effects and instrument uncertainties. Therefore, the Technical Specification subcooling margin value should remain at 10*F and the head i effects and instrument uncertainties accounted for in Plant Procedure j PP 1102.10, Plant Shutdown and Cooldown. Not incorporating head effects and instrumentation errors in the Technical Specification will eliminate the need for future Technical Specification License Amendment Requests should the instrument uncertainty change (e.g., replacement of instrumen-tation with that containing different error values). Rather, the plant procedure would be revised to reflect the change.

Therefore, Toledo Edison requests that its License Amendment application (Serial No. 1268) dated June 30, 1986 be withdrawn from the NRC.

Very tru , yours, i

DCS:DRW:plf cc: DB-1 NRC Resident Inspector A. W. DeAgazio, NRC/NRR Davis-Besse Project Manager A. B. Davis, Regional Administrator (2 copies)

_ - _ - - _ - _ _ -