ML20094G022
| ML20094G022 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 08/01/1984 |
| From: | Tucker H DUKE POWER CO. |
| To: | Adensam E, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-1061 TAC-55566, TAC-55567, NUDOCS 8408130169 | |
| Download: ML20094G022 (3) | |
Text
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August 1, 1984
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Mr. linrold R. Donton, Director Office of Nuclear Ronctor Regulation U. S. Nuctant Roguintory Commission Washington, D. C.
20555 Attention:
Ms. E. G. Adensam, Chief Licensing Branch No. 4
Subject:
McGuiro Nuclonr Station Docket Nos. 50-369 and 50-370 piping Soismic Analysis Changen Dont Mr. Dantons planno find attached a description and justification for proposed piping seismic analysia changen for the McGuiro Nucient Station to adopt damping values and specten shif tina methods for piping systems recommended by the tank group of the pressuro Vessel Roscarch Committoo (pVRC) of the Wolding Research Council. The proposed changes reduce the excessive conservatism in current notamic design requirements and would allow use of fewer anubborn and other noismic rentrainta on modified piping at McGuire and would allow removal of some existing snubbers and seismic ragtrainto to reduce inservice inspection, maintenance, and access /interforence problems.
Although the proposed changen do not involvo a chango in the technical specifications or an unroviewed *:nfoty question and therefore are permitted pursuant to 10 CFR 50.59, it is requestod that the NRC reviou ar.d approve those changos prior to imptomontation.
Similar changes have previounty boon submitted and approved by the NRC nu avidenced by your February 8, 1984 letter to Southern Californin 1:dison containing n anfoty cynluation report on the San Onofro Unit 1 Goimmic Scovaluation program.
In addition, tho NRC is 6miliar with and genernity icupports those changen through participation in the pVR0 Technical Committoa, and forthcoming recommendationn in the committon's draft f4nr.0-1061 indicato NRC support for the channon.
It is requented that the review /npproval be proccamed in a Limaly manner,in order that elimination of unneconsary supports on existing or modifiod piping nyntoma can be performed an varioun modifications are proconned, and in view of the attendant lond time noconsary for engineering nupport work to tako advantage of the upcoming refueling outages on Units 1 and 2 (currently scheduled for March 24, 1985 and Janunty 10, 1985 renpoetively). Onco approved, those channon will be incorporated into the next applicable annuni updata to the HeCuiro FftAR.
If there nra eny questions concerning thin requent, planno advino.
Very truly yourn.
yl
-Q). &L I k it. Tucker 0
I l
Mr. Harold R. Denton. Direct:r August 1, 1984 Page 2 PBN/rha J
Attachment cci Mr. J. P. O'Reilly. Regional Administrator U. S. Nuclear Regulatory Commission Region 11 101 Mariotta Street. NW. Suite 2900 Atlanta. Coorgia 30323 Mr. Ralph Birkel Division of Project Management i
Office of Nuclear Reactor Regulation U. S. Niitlear Regulatory Commission Washington, D. C.
20555 Mr. W. T.Ordern Santor Resident Innpoctor McGuire Nucicar Station i
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DUKE POWER COMPANY MCGUIRE NUCLEAR STATION, UNITS 1 AND 2 PROPOSED PIPING SEISMIC ANALYSIS CHANGES Ddmping Values for Dynamic Analysis of Piping As an option.to the damping values currently given in FSAR Section 3.7.1.3, damping may be taken.as _5% for frequencies below 10 hz, linearly decreasing to 2% at 20 hz and 2% for frequencies above 20 hz. These values for damping apply to all pipe sizes for both Safe Shutdown Earthquake (SSE) and Operating Basis Earthquake (0BE) loadings.
Justification:
These damping values have been recommended by the PVRC Task Group on Damping Values based on extensive review of available data. There is still conservatism included due to the use of response spectra instead of time history analysis which can be considered as additional justification for use of increased damp-ing values._ Use of the increased damping values for time history analysis will be justified.on a case-by-case basis. These damping values reduce excessive conservatism in current requirements and will result in significant reduction in predicted pipe response..This will allow elimination of snubbers on exist-ing piping and use of fewer snubbers and other seismic supports on piping added or modified by plant modifications. This will result in reduced cost and radiation exposure-for Inservice Inspection of snubbers and increased overall reliability of the piping due to reduced probability of' snubber fai?ure and reduced thermal stress in new and modified piping due to fewer seismic supports- (Ref. NUREG/
CR3718).
Respcnse Spectra Shifting As an alternative to the method of spectra broadening described in FSAR Section 3./.2.8 for piping analysis, an envelop of the response of the piping system to shifted floor response spectra may be used. The method to be used is de-scribed in the' Code Case N-397 and the Summer 1984 addendum to Section III, Appendix N of the ASME Boiler and Pressure Vessel Code.
Justification:
The floor response spectra for McGuire structures are characterized by a single dominant peak; therefore, the application of this method is straight forward.
The proposed change reduces the excessive conservatism in the current response spectra analysis and will result in fewer snubbers and other seismic supports.
The response of the piping using this method has been compared with the response calculated using time history analysis for typical piping models by both Duke Power and Lawrence Livermore National Lab (reference NUREG/CR-3428). Both studies conclude that the proposed method is conservative compared to time history analysis but reduces the conservatism of the current spectra broadening method.
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