ML20235U303

Responds to 870918 Request for Addl Info Re Proposed Reduction of Auxiliary Feedwater Flow Requirement.Util Determined That 600 Gpm Adequate to Ensure Smooth Transition to Natural Circulation Cooling

ML20235U303
Person / Time
Site:	Davis Besse
Issue date:	10/02/1987
From:	Shelton D TOLEDO EDISON CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
1426, TAC-65068, NUDOCS 8710140025
Download: ML20235U303 (2)

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TOLEDO

%mmEDISON DONALD C. SHELTON Vu;e Premders-par,iear

{419}249 2399 Docket No. 50-346 License No. NPF-3 Serial No. 1426 October 2, 1987 I

United States Nuclear Regulatory Commission Document Control Desk Washington, D. C.

20555

Subject:

Response to Request for Additional Information Regarding Toledo Edison's Proposed Reduction of the Auxiliary Feedwater Flow Requirement (TAC No. 65068)

Gentlemen:

This submittal responds to a request from Mr. A. W. DeAgazio. NRC Project Manager for Davis-Besse Unit No. 1. for additional information regarding Toledo Edison's letter dated March 23, 1987 (Serial No. 1360) that l

proposed a change to the Auxiliary Feedwater (AFW) flow requirement. This i

additional information was requested during a telephone conference call i

between the NRC staff and Toledo Edison representatives on September 18, 1987. Toledo Edison's proposed change involves Bases Section 3/4.7.1.2, Auxiliary Feedwater Systems, of the Davis-Besse Nuclear Power Station, Unit No. 1 Operating License, Appendix A, Technical Specifications.

The proposed Bases change was submitted in accordance with Toledo Edison's commitment to the NRC (Serial No. 1322, dated November 17, 1986) to propose a request to reduce the AFW flow requirement from 800 gpm to 600 gpm. The following additional information related to the quench tank rupture disk and natural circulation cooling is provided in support of the proposed change and in response to the NRC staff's request.

Although the Davis-Besse Updated Safety Analysis Report (USAR), page 15.2-34, states, in part, that 800 gpm AFW flow is required to prevent rupturing of the pressurizer quench tank rupture disk, the rupture of the quench tank rupture disk is not a safety evaluation criterion for any of the Chapter 15 accidents and, consequently, was not reviewed as part of Toledo Edison's re-analysis. Rupturing of the quench tank rupture disk is an operational concern due to the contamination of containment and resultant clean-up operations required. This operational concern was more significant with the original plant design than with the present plant configuration.

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Ig THE TOLEDO EDISON COMPANY EDISON PLAZA 300 MADISON AVENUE TOLEDO, OHIO 43652

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Dockst No. 50-346 TLicense No. NPF-3 Serial'No. 1426 October 2, 1987 Page 2 In the original plant design, the pilot operated relief valve (PORV) setpoint was below the Reactor Protection System (RPS) high pressure trip setpoint. Consequently, PORV actuations were potentially more frequent than they are now since the PORV setpoint is presently set above the RPS l

high pressure trip setpoint. Additionally, the Reactor Coolant System (RCS) pressurizer code safety valve discharge piping was originally routed to the quench tank.

However, the present configuration provides for the discharge directly to the containment atmosphere. Therefore, the present PORV setpoint and the pressurizer code safety valve discharge configuration.

t in combination with 600 gpm AFW flow, is less likely to rupture the quench tank rupture disk.

Following NRC approval'of this change, the USAR will

' be revised at the next update to delete the statement concerning the quench tank rupture disk from the Chapter 15 analysis as this rupture disk is not a safety criterion.

In response to the NRC staff's question regarding the capability to provide a smooth transition to natural circulation, Toledo Edison has reviewed the Babcock & Wilcox Loss of Feedwater analysis (B&W Document No. 32-1159090-01) and has determined that 600 gpm AFW flow is adequate to ensure a smooth transition to natural circulation cooling.

The conclusions of the proposed change in Serial No. 1360 to the Technical Specification Bases remain unchanged based on the above discussion.

Toledo Edison requests this change to the Bases be issued expeditiously for implementation.

Very tr yyours, RMC: bah cc: DB-1 NRC Resident Inspector A. W. DeAgazdo, Davis-Besse Project Manager State of Ohio

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