ML20136F833
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NUCLEAR REGULATORY COMMISSION o
h WASHINGTON, D. C. 20655 MAR 5 1985 MEMORANDUM FOR: Elinor Adensam, Chief.
Licensing Branch # 4 Division of Licensing FROM:
Frank C. Cherny, Acting Chief Mechanical Engineering Branch Division of Engineering
SUBJECT:
PIPING DESIGN CRITERIA V0GTLE NUCLEAR PLANTS UNITS 1 AND 2'(DOCKET NO. 50-424,50-425)
Reference:
Letter from D. O. Foster Grace, George Power to E. G. Adensam, NRC, dated Jan. 4, 1985 with enclosures
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In the referenced letter, the applicant requested NRC approval to use ASME Code Case N-411 damping values in the response spectrum seismic analyses for l
the Vogtle plant piping. These damping values will be used for pipe stress l
verification and for pipe support optimization. When the values are used for support optimization, the applicant will as::ertain that increased pipe deflections due to greater piping flexibility will not violate the Vogtle plant separation criteria.
The applicant does not. intend to mix the criteria of Regulatory Guide 1.61 with the criteria of Code Case N-411 for a given piping analyses. Further..as part of the. applicant's integrated piping analyses /as-built reconciliation program, the applicant will assure that increased piping displacements and clearances are acceptable.
In an effort to investigate the overall effects of the proposed damping values, a number of independent studies are cited by the applicant for typical piping systems which assess the potential benefits resulting from use of the frequency-dependent damping values for the seismic analysis of piping. The over,all conclusions of these studies are that the use of the Code Case N-411 frequency-dependency damping values results in reduced piping responses snd a reduction in the number of rigid supports and snubbers.
Independent studies perfomed by Westinghouse also support this conclusion.
The recomended application of these damping values to systems where design is not complete will pemit optimization of the systems, keep the number of snubbers to a minimum, and cause the design of the systems to better satisfy nonnal operating conditions. For systems that are past the design phase, the use of'these damping values in the as-built reconciliation phase will limit the number of changes in the design.
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Elinor Adensam Since the above commitments are documented in the referenced lettery the staff finds the applicant's request to use ASME Code Case N-411 to be acceptable.
The applicant's use of Code Case N-411 should be documented in a future amendment to the FSAR.
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Frank C. Cherny, Acting Chief Mechanical Engineering Branch Division of Engineering cc:
J. Knight R. Bosnak M. Miller H. Brammer R. Kirkwood R. Pichumani J. Rajan
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