ML20070R150

Forwards Seismic Qualification of Cable Trays & Conduit (Phase Ii,Design Baseline & Verification)

ML20070R150
Person / Time
Site:	Sequoyah
Issue date:	03/26/1991
From:	Wallace E TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-R00419, TAC-R00420, TAC-R419, TAC-R420, NUDOCS 9104010085
Download: ML20070R150 (4)

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knneuee Vaney Authonty 1101 Mamet street Chanawga$knence 9402

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hAAJ126 7391 U.S. Nuclear Regulatory Commission ATTN:

Document Control Desk Washington, D.C.

20555 Gentlemen:

In the Matter of

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Docket Nos 50-327 Tennescoe Valley Authority

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50-328 SEQUOYAll NUCLEAR PLANT (SQN) - SEISMIC QUALIFICATION OF CABLE TRAYS

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AND CONDUIT (PHASE 11, DESIGN BASELINE AND VERIFICATION, TAC NOS. R00419/R00420)

Reference:

NRC lotter to TVA dated January 18, 1991, on the above subject As requestud in the above reference, Enclosure 1 contains a discussion on the seismic qualification of cable trays and conduits at Sequoyah that carry safety-related cables. With respect to cable trays, the discussion presented in Enclosure 1 was derived from offorts to resolvo Employco Concern (EC) 238.03 SQN-04.

For conduits, Design Criteria SQN-DC-V-13.10 defines the requirements for seismic qualification.

The cable trays and conduits woro ovaluated before restart and woro determined to be acceptable for restart and operability.

For cable trays, EC 238.03 SQN-04 defined commitments to document the long-term criteria and ovaluate the trays to that critoria. The long-term critoria have been developed and are described in Enclosure 1.

Cable trays will be evaluated in accordanco with EC 238.03 SQN-04.

Conduits have boon evaluated and qualified to the design criteria.

As noted in the above reference, there is no clear discussion in the SQN Updated Final Safety Analysis Report (UFSAR) on the seismic qualification of cable trays and conduit. Accordingly, TVA agrees to provido a clarification to the UFSAR in next year's (1991) annual UFSAR update.

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. 7, U.Sr Nuclear Regulatory Comission -

MAR 261991

- Please direct questions concerning this issue to W. C. Ludwig at

_ (615) 843-7460.

- Very truly yours, TENNESSEE VALLEY' AUTHORITY hC

\\r W lt E.G.'

llace,' Manager Nuclen iconsing and

-Regulatory Affairs cc (Enclosures):

Ms. S. C.-Black,_ Deputy Director Project Directorate:11-4' U.S. Nuclear Regulatory Comission-One' White Flint, North.

11555 Rockville Pike Rockville,.Marylan

• ^h52 Mr. ; J. N. Donohew,.

t Manager EU.S. Nuclear Regulatw, Comission

'One White Flint, North

~11555 Rockville Pike

_Rockville, Maryland 20652 NRC'Rosident Inspector

-Sequoyah Nuclear-Plant 2600 Igou Ferry Road-Soddy-Daisy,-Tennessee 37379 Me'.

B.-A. Wilson, Project Chief

.U.S. Nuclear Regulatory Comission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia.30323-i y

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ENCLOSURE 1 Cable Trays The cable tray. criteria are derived from testing. A factor of safety of 1.25, against the tested capacity, is naintained for the vertical load for

'horisontal tray configurations. A maximum ductility factor of three (based on test data) is used to define an elastic-perfectly plastic curve that is used in the transverse direction (parallel to the rungs). These limits are used in an interaction equation to evaluate tray sections for the safe shutdown earthquake-(SSE) loading condition.

The trays will also be evaluated to

-ensure a minimum factor of safety of 1.25 against test capacity for actual dead loads.

Cable tray "X" and "T" fittings will be evaluated to ensure a minimum factor of safety of 1.25 against formation of a first hinge in the direction for normal vertical loadings. These fittings will not be evaluated in the horizontal direction since intersecting trays provide axial support in this direction.

Other cable tray components (i.e., bolts and connectors) will be evaluated using American Iron and Steel Institute or American Institute of Steel Construction allowables with a 0.9 Fy limit. Where test data is used to establish capacities, a factor of safety of 1.5 will be maintained against the ultimate _ test load for the SSE loading con?!'-lon.

l The cable trays are designed to carry a design load of 30 pounds per square foot (45 pounds per linear foot for 18-inch trays).

In cases where weights L

exceed these values (because of cable overfill and application of fire-retardant coating), the actual dead loads will be used. The trays will be qualified for dead load, construction load, design basis accident loada, and SSE loads.

Conduit SQN Design Criteria SQN-DC-V-13.10 requires that the deadweight plus SSE I

stress for conduit be limited to a maximum of 0.9 of the materini yield stress for safety-related conduit systems attached to. Category I buildings.

Since conduit systems contain threaded connections that may occur anywhere within the system, a stress intensification factor is applied to the yield L

stress of the conduit to obtain the allowable design stress (yield stress

/ (.75 x 2.3]).

This ensures that the maximum conduit stress based on the sectional properties of the conduit will not exceed the 0.9 Fy allowabic.

ENCLOSURE 2.

The information contained in Enclosure 1 of this response will be used to provide a revised SQN Updated Final Safety Analysis. Report (UFSAR) in the 1991 Annual UFSAR update that is scheduled to b~e submitted by April 15, 1992, 4

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