ML20140B799

Safety Evaluation Supporting Subcompartment Pressure Analysis & Proposed Valve Room Design,Per Low Stress Superpipe Requirements of Branch Technical Position Meb 3-1 Re Protection Against Main Steam or Feedwater Line Breaks

ML20140B799
Person / Time
Site:	South Texas
Issue date:	06/06/1977
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20140B735	List: ML20140B760 ML20140B799 ST-HL-AE-1582, Clarifies 851024 Response to NRC Request for Study of Jet Impingement Effects in Break Exclusion Area of Main Steam & Feedwater Piping.Encl NRC & Safety Evaluation Cited to Support Claim That Study Lacks Justification
References
ST-HL-AE-1582, NUDOCS 8601270134
Download: ML20140B799 (2)

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ATTACHMENT ST HL AE. I St A PAGE a OF3 SAFETY EVALUATION OF THE DYNMilt EFFECTS OF p0STULATED PIPE FAILURES OUTSIDE CONTAINMENT - SOUTH TEXAS PROJECT UNITS 1 AND 2 l

I' In response to our concern of routing the steam lines near safety systems."

6 the applicant submitted the report " Dynamic Effects of Postulated Pipe S

Failures Outside Containment - South Texas Project Units 1 and 2" for our

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review.

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I Our review covered the protective features provided for individual systems and a review of preliminary piping layout drawings. The applicant's original 9,

design of the main steam and feedwater piping systens proposed a break

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exclusion area for the piping in the main steam and feedwater valve rooms.

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This was based on meeting the low stress. "superpipe" requirements of e,

Branch Technical position MEB 3-1.

However, the report showed that I.,

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all four auxiliary feedwater pumps for the South Texas Project will be located below these valve ronms. For safety, in addition to the low stress piping, pr.

we. required the applicant to design the valve rooms to withstand the environ-

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mental effects of a main steam or feedwater line break equivalent to the p

flow area of a single ended pipe rupture.

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As a result, the applicant proposed to redesign his main steam and feedwater valve rooms with a vent area capable of venting the release of larger than one equivalent single ended pipe break and provided a subcompartment pressure

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ana. lysis to show that the rooms would withstand the environmental effects of N. :

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a break in this area.

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PAGE 30F 3 I

We have reviewed the results of the applicant's subcompartment pressure analysis and have also performed our own independent analysis of their if:-

new valve room design and find that the proposed design is now in I

ace:rdance with our Branch Technical Position APCSB 3-1 and therefore acceptable.

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