ML20204F149

Forwards Addl Info Re Pipe Whip Restraint Design,In Response to 860516 Request

ML20204F149
Person / Time
Site:	Davis Besse
Issue date:	07/28/1986
From:	Williams J TOLEDO EDISON CO.
To:	Stolz J Office of Nuclear Reactor Regulation
References
1288, TAC-40076, NUDOCS 8608040106
Download: ML20204F149 (3)

Text

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TOLEDO EDISON JOE WILUAMS. JR Serwr We Prescent - th-(419}249 2300

[419}249 S223 Docket No. 50-346 License No. NFP-3 Serial No. 1288 July 28, 1986 Mr. John F. Stolz, Director PWR Project Directorate No. 6 Division of PWR Licensing - B United States Nuclear Regulatory Commission Washington, D.C. 20555

Dear Mr. Stolz:

In your May 16, 1986 letter (Log No. 1988) you requested additional information concerning the pipe whip restraint design at the Davis-Besse Nuclear Power Station Unit ho. 1. The additional information you have requested is provided in Attachment 1 to this letter.

Very truly yours, h W$ P := ,

TJB:CLM:dem attachment cc: DB-1 NRC Resident Inspector 8608040106 860728 PDR ADOCK 05000346 P PDR g\

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EDISON PLAZA 300 MADISON AVENUE TOLEDO, OHIO 43652 THE TOLEDO ED: SON COMPANY

Dock 3t No. 50-346 License No. NFP-3 Serial No. 1288 July 28, 1986 ATTACHMENT 1 Response to request for additional information concerning pipe whip restraint design.

Request No. 1 Describe the load combinations that were used in the design and analysis of reactor coolant hot leg whip restraints. Specifically, indicate if

, the load combinations included the consideration of

a. Ioads from jet impingement and compartment pressurization of the secondary shield wall,

b. seismically induced displacement of the secondary shield wall.

Response

The reactor coolant pipe whip restraints were designed primarily for LOCA loads as a result of postulated guillotine pipe breaks. Pipe break thrust forcing functions were calculated in accordance with BN-TOP-2, Revision 2, " Design for Pipe Break Effects", approved for use by NRC letter dated June 17, 1974. The energy input from the pipe break thrust force is balanced by the resistance of the piping and pipe whip restraints to determine the maximum displacements and loads to the pipe whip restraints.

An evaluation of the reactor coolant hot leg pipe whip restraints was performed in accordance with Procedure No. 7749-C-101, " Criteria for Verification of Pipe Whip Restraints for the Reactor Coolant System for the Toledo Edison Company Davis-Besse Nuclear Power Station Unit 1",

Revision 1, January, 1980. This evaluation is documented in a report titled " Davis-Besse Nuclear Power Station Unit i Verification Study of Pipe Whip Restraints on the Reactor Coolant System" and was previously transmitted to the Office of Inspection and Enforcement, Region III, on March 7, 1980 (Serial No. 1-118).

Although jet impingement forces are postulated to occur for a slot break and are considered in the design, the maximum load to the restraint results from a guillotine break. Compartment pressurization loads do not affect the whip restraint design. Seismically induced displacements of the secondary shield wall were considered by assuring that the seismically induced displacements of the pipe and shield wall will not cause contact between the pipe and the restraint. (Reference Section II, Subsection 2.0, of the above cited report.)

.s Dockst No. 50-346 License No. NFP-3 Serial No. 1288 July 28, 1986 The secondary shield walls were designed to sustain operating, thermal, seismic loads and loss of coolant accident loads. The loss of coolant accident loads considered for the design of the secondary shield wall are as follows:

Thrust loads from pipe break Pipe whipping Compartment pressurization Rapid temperature rise Jet impingement forces Internal missiles All of the above considered loadings are combined in accordance with load combinations as listed in the Davis-Besse Unit 1 USAR, Section 3.8.

Request No. 2 Describe how the spring rates of connections of pipe whip restraints to secondary shield wall were computed.

Response

The connections of pipe whip restraints to the secondary shield wall are designed such that all stresses within the connecting components remain within the elastic stress range for the specific materials used.

(Reference Section II, Subsection 2.0, of the previously cited report.)

Spring rates for the connecting materials were not computed as the elastic deflections which result from the applied loads are insignificant.

Request No. 3 Describe the allowable stress or strain used in your design.

Response

Allowable stresses for structural members in which the behavior was required to remain in the elastic range were limited to the following values:

F "

• t y E = 0.9 F b

Fv =F/k3 y

in which, F = allowable tensile stress F = material yield stress F7 = allowable bending stress F = allowable shear stress For structural steel members in which plastic deformation was predicted, the allowabic strain was limited to fifty percent of the strain at the ultimate stress.