B11587, Forwards Rev 3 to Safety-Related Piping Seismic Qualification Program, Per SEP Topic III.6.Changes to Damping Values,Peak Shifting & Independent Support Motion Described

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Forwards Rev 3 to Safety-Related Piping Seismic Qualification Program, Per SEP Topic III.6.Changes to Damping Values,Peak Shifting & Independent Support Motion Described
ML20128K033
Person / Time
Site: Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date: 06/27/1985
From: Opeka J
CONNECTICUT YANKEE ATOMIC POWER CO.
To: Zwolinski J
Office of Nuclear Reactor Regulation
Shared Package
ML20128K037 List:
References
TASK-03-06, TASK-3-6, TASK-RR B11587, NUDOCS 8507100465
Download: ML20128K033 (3)


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CONNECTICUT YANKEE ATOMIC POWER COMPANY B E R L I N. CONNECTICUT P o BOX 270 HARTFORD, CONNECTICUT 06141-0270 TELEPHONE 203-ess-s June 27,1985 Docket No. 50-213 B11587 Director of Nuclear Reactor Regulation Attn: Mr. John A. Zwolinski, Chief Operating Reactors Branch #5 U. S. Nuclear Regulatory Commission Washington, D. C. 20555

References:

(1) W. G. Counsil letter to D. M. Crutchfield, dated January 19, 1984.

Gentlemen:

Haddam Neck Plant SEP Topic III-6, Seismic Design Considerations In Reference (1). Connecticut Yankee Atomic Power Company (CYAPCO) submitted the criteria which were being utilized for the safety-related piping qualification program being undertaken to satisfy SEP Topic III-6. The purpose of this letter is to inform the Staff of changes that have been incorporated into' the criteria document. These changes are described in more detail below. A copy of Revision 3 to the criteria document is included as Attachment 1.

o Damping Values The Haddam Neck seismic reevaluation program is committed to the use of damping values per Regulatory Guide 1.61. Revision 3 of the criteria document proposes adoption of the Pressure Vessels Research Committee (PVRC) damping carve as described in the Welding Research Council (WRC)

Bulletin-300. This curve has previously been accepted by the NRC for use on Millstone Unit No. 3, Bellefonte, San Onofre Unit 1, and on BWR recirculation loop piping replacements. Additionally, the ASME Boiler and Pressure Vessel Code has incorporated the PVRC damping curve into Section 111, Appendix N (Code Case N-411).

In developing new building acceleration response spectra (ARS), the peak broadening and smoothing techniques provided in Regulatory Guide 1.122 will be utilized.

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t o Peak Shifting The floor response spectra generated for the SEP seismic reevaluation have been peak broadened by +15% to account for uncertainty in the calculation of structural frequency. This significantly increases the total seismic energy input to the piping system. The peak shifting methodology recognizes the fact that, for a piping system having multiple modes within the broadened range, only one mode can respond with the magnitude associated with the peak spectral value.

, The revised criteria document adopts the PVRC technical position on response spectra broadening as published in WRC Bulletin-300, requiring the enveloping of the results of shifted spectra. The detailed procedures

for implementation of peak shif ting have been incorporated into the ASME l Boiler and Pressure Code,Section III, Appendix N (Code Case N-397), and l have been approved by the NRC for use at San Onofre Unit 1.

o Independent Support Motion Where piping is located in more than one building or supported at more than one building elevation, the existing criteria specify the use of an envelope of applicable floor spectra. The proposed alternate approach is to utilize Independent Support Motion (ISM), wherein each pipe support is l driven by its applicable floor spectra rather than by the envelope spectra.

The ISM response spectra technique has been in the ASME Code, Appendix l N since 1978 and has been used extensively on BWR plants. Additionally, NUREG-1061 (Volume 4, Section 2.4) recommends that the ISM response spectrum method be allowed as an option in calculating the response of multiple-support piping with independent inputs.

In summary, the PVRC recommendations and ASME code approved methodologies described above are proposed to be utilized by CYAPCO in the area of piping system backfits, new piping systems, or support optimization.

No response to this letter is requested, unless the Staff disagrees with the changes indicated herein. If you have any questions on this, please contact us.

Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPANY L&GAL

3. F.Qka Senior Vice President L__

f Docket No. 50-213 Attachment i Haddam Neck Plant SEP Topic 111-6, Seismic Design Considerations l

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June,1985 r

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