ML20126J198

Requests Evaluation of Adequacy of Subcooling Margin Specified in Tech Spec 3.4.1.2 That Must Be Established for Natural Circulation Conditions.Revised Subcooling Margin Required No Later than 850715

ML20126J198
Person / Time
Site:	Davis Besse
Issue date:	06/03/1985
From:	Stolz J Office of Nuclear Reactor Regulation
To:	Crouse R TOLEDO EDISON CO.
References
TAC-61937, NUDOCS 8506180553
Download: ML20126J198 (2)

Text

r JUN 031985 b0/h Docket No. 50-346 DIST pBCFchet File JPartlow L PDR ACRS-10 NRC PDR RIngram Mr. Richard P. Crouse ORB #4 Rdg ADeAgazio Vice Presider,t, Nuclear HThompson Gray File Toledo Edison Company OELD EBrach Edison Plaza - Stop 712 EJordan H0rnstein 300 Madison Avenue BGrimes Toledo, Ohio 43652

SUBJECT:

SUBC00 LING MARGIN IN TECHNICAL SPECIFICATION As part of the staff's review of Multiplant Action (MPA) number B-57, dealing with technical specifications for decay heat removal, we identified a possible nonconservatism 'in the standard technical specifications regarding the required subcooling margin that must be established when reactor coolant pumps are to be secured in modes 3, 4 and 5. The required subcooling margin is stated to be 10 F. However, 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, the very condition the subcooling margin was designed to prevent.

You'are therefore requested to evaluate the adequacy of the subcooling margin specified in Technical Specification 3.4.1.2 that must be established for natural circulation conditions, and ensure that a sufficient margin exists such that void formation is precluded when instrument error and elevation effects are accounted for. If you conclude that the margin specified is inadequate, you should propose a revised subcooling margin which will ensure that void fannation does not occur when decay heat removal is through natural circulation only. Please confirm the adequacy of the specified subcooling margin or submit a proposed revision to your technical specifications no later than July 15, 1985.

Sincerely,

• onouus w - u a JCW F. Was4*

John F. Stolz, Chief Operating Reactors Branch #4 Division of Licensing cc: See next page ORB #4:0 ORB #4 ADeAgaztff;cr JStolk k 6/J/85 6/$85 8506180553 850603 PDR ADOCK 05000346 P PDR

7 ftr. R. P. Crouse Davis-Besse Nuclear Power Station, Unit No. 1 Toledo Edison Company cc:

Donald H. Hauser, Esq. Ohio Department of Health The Cleveland Electric ATTN: Radiological Health Illuminating Company Program Director P. O. Box 5000 P. O. Box 118 Cleveland, Ohio 44101 Columbus, Ohio 43216 Mr. Robert F. Peters Attorney General Manager, Nuclear Licensing Department of Attorney Toledo Edison Company General Edison Plaza 30 East Broad Street 300 Madison Avenue Columbus, Ohio 43215 Toledo, Ohio 43652 Gerald Charnoff, Esq. Mr. James W. Harris, Director (Addressee Only)

Shaw, Pittman, Potts Division of Power Generation and Trowbridge Ohio Department of Industrial Pelations 1800 M Street, N.W. 2323 West 5th Avenue Washington, D.C. 20036 P. O. Box 825 Columbus, Ohio 43216 Paul M. Smart, Esq. Mr. Harold Kahn, Staff Scientist Fuller & Henry Power Siting Commission 300 Madison Avenue 361 East Broad Street P. O. Box 2088 Columbus, Ohio 43216 Toledo, Ohio 43603 Mr. Robert B. Borsum President, Board of Babccck & Wilcox County Commissioners of Nuclear Power Generation Ottawa County Division Port Clinton, Ohio 43452 Suite 200, 7910 Woodmont Avenue Bethesda, Maryland 20814 U.S. Nuclear Regulatory Commission Resident Inspector's Office 5503 N. State Route 2 Oak Harbor, Ohio 43449 Mr. James G. Keppler, Regional Administrator U.S. Nuclear Regulatory Commission, Region III 799 Roosevelt Road Glen Elln, Illinois 60137