ML20214S328

Forwards Revised Response to Question Q410.15-1 Re Pipe Break Critera for Flooding Analyses.Changes Simplify Plant Design & Const & Improves Plant Maintainability by Reducing Number of Supports

ML20214S328
Person / Time
Site:	Vogtle
Issue date:	06/01/1987
From:	Bailey J SOUTHERN COMPANY SERVICES, INC.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
GN-1375, NUDOCS 8706090230
Download: ML20214S328 (3)

Text

r-Southem Company Services. Inc.'

Post OMco Box 282 Waynesboro. Georgia s0830

• • • " "* % EZ Vogtle Project June 1, 1987 U. S. Nuclear Regulatory Commission File: X7BC35 Attn: Document Control Desk Log: GN-1375 Washington, D.C. 20555 NRC DOCKET NUMBER 50-425 CONSTRUCTION PERMIT NUMBER CPPR-109 V0GTLE ELECTRIC GENERATING PLANT - UNIT 2 PIPE BREAK CRITERIA FOR FLOODING ANALYSES Gentlemen:

In response to VEGP FSAR Question 410.15, the VEPG Project indicated that the flooding analysis was done in accordance with the Standard Review Plan guidelines which require cracks to be postulated in moderate energy piping designed to non-seismic Category 1 standards. In addition, the response stated that as further assurance that the failure would be a crack rather than a rupture, non-seismic Category 1 piping is supported to withstand SSE loads and to maintain the pipe stresses within faulted allowables, with the exception of six categories of piping. It is being proposed for Unit 2 to add moderate energy, non-seismic Category 1 piping, 2 inches and smaller to the list of exceptions where the faulted allowables are not considered.

The Project will continue to maintain the pipe stresses within the faulted allowables for the high energy piping, the seismic Category 1 piping, and the non-seismic Category 1 piping larger than 2 inches nominal diameter. However, on Unit 2, the Project proposes to discontinue the practice of limiting the pipe wall stresses to faulted allowables for the moderate energy non-seismic Category 1 piping 2 inches and smaller, but will continue to provide support designs that will withstand SSE loads. This change dc,es not affect plant safety, and it does not change the protection of safety-related equipment. It does simplify plant design and construction and improves plant maintainability by reducing the number of supports. The revised response to Question Q410.15-1 is attached.

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g U. S. Nuclear Regulatory Commission June 1, 1987 Pipe Break Criteria for Flooding Analyses Page Two File: X7BC35 Log: GN-1375 The flooding analysis will continue to postulate through wall leakage cracks in these pipes. The justification for postulating cracks in these pipes is that it satisfies the requirements of Standard Review Plan 3.6.1 and Branch Technical Position MEB 3-1. MEB 3-1 paragraph B.2.C.2 states, "Through wall leakage cracks should be postulated in fluid system piping designed to non-seismic standards...", and paragraph B.3.C states ". . .through wall leakage cracks should be postulated in moderate energy fluid system piping...".

It is requested that any comments with respect to our revised position be provided by June 15, 1987.

Sincerely, J. A. Bailey Project Licensing Manager JAB:jc Attachment xc: R. E. Conway J. P. O'Reilly P. D. Rice L. T. Gucwa R. A. Thomas J. E. Joiner B. W. Churchill M. A. Miller (2)

G. Bockhold, Jr.

NRC Regional Administrator NRC Resident Inspector R. Goddard R. W. McManus D. Feig NORMS

. .s VEGP-FSAR-Q Question 410.15 In FSAR subsections 3F.2.2 and 3F.2.4 regarding pipe break and flooding assumptions, you state your analysis includes the effect of flooding from the worst case pipe crack in each room or general area. Staff position normally requires that for flooding analysis purposes, the complete failure of non-Seismic Category 1 moderate energy piping systems should be considered in lieu of cracks in determining the worst case flooding condition. Revise your analysis and FSAR as necessary to include the worst case flooding condition for each room or area in the event of a complete failure of the most limiting non-Seismic Category 1 moderate energy line, or provide justification.

Response

The flooding analysis has been performed in accordance with the guidelines stated in the Standard Review Plan. Standard Review Plan 3.4.1, Flood Protection, states that the effects of piping failures are to be analyzed following guidelines in Standard Review Plan 3.6.1. Standard Review Plan 3.6.1 refers to Branch Technical Position MEB 3-1 for determination of pipe break type and location. Paragraph B.2.C(2) of Branch Technical Positions MEB 3-1 states that through-wall leakage cracks are to be postulated in moderate energy piping designed to nonseismic standards. Full ruptures are postulated in non-Seismic Category I high energy piping.

As a further assurance that the failure mode of non-Seismic Category 1 piping will be a critical crack rather than double-ended rupture, non-Seismic Category 1 piping in safety-related structures has been supported to withstand safe shutdown earthquake loads. The pipe support loads are determined by analyzing the piping system. For SSE loading, with the exception of the piping listed below, pipe stresses are also 4 calculated to consider that they are maintained within faulted (

allowables (2.4 S h)8 e 14 Duriron lines e Copper lines e ASTM A-120 galvanized lines e Air service lines e Process tubing 5 3/8 in.(instrument tu %bing) s -

e dAocke.ro.k eaarg e - widWc b or3 I p*p h

2. hchc5 oAct enador m LIAd 2, on 3 Amend. 9 8/84 Q410.15-1 Amend. 14 2/85

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