ML20215D794
| ML20215D794 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 10/06/1986 |
| From: | Bailey J GEORGIA POWER CO. |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| GN-1101, NUDOCS 8610140299 | |
| Download: ML20215D794 (4) | |
Text
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Georgia Pbwer Company -
Fbst Office Box 282 Yt,.
^ -o, Georgi 2 30630 Telephone 404 554-9961 404 724-8114 Southem Company Services,Inc. -
Fbst Office Box 2625 Birmingham, Alabama 35202 Vogtle Project t
October 6,.1986 Director of Nuclear Reactor Regulation-File: X7BC35 Attention:
Mr. B. J. Youngblood Log:
GN-1101 PWR Project Directorate #4 Division of PWR Licensing A U. S. Nuclear Regulatory Commission Washington, D.C.
20555 NRC DOCKET NUMBERS 50-424 AND 50-425 CONSTRUCTION PERMIT NUMBERS CPPR-108 AND CPPR-109 j.
V0GTLE ELECTRIC GENERATING PIANT - UNITS 1 AND 2 PIPING ANALYSIS - EQUIVALENT STATIC LOAD
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Dear Mr. Denton:
The Vogtle FSAR currently identifies two methods of' seismic analysis of non-NSSS piping systems (3.7.B.3).
The Vogtle project is. identifying a third method, the equivalent status load (ESL) method.
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The ESL method is currently used for platform, conduit and cable tray, and HVAC supports. To determine seismic response, an acceleration value is-
- established based on the dynamic characteristics of the structure. This acceleration is imposed as a static load. For multidegree-of-freedom structures, the applied acceleration is set at 1.5 times the peak acceleration.
f The Vogtle project has prepared a study to evaluate the applicability of the ESL method to piping systems. This study ccmpares dynamic analysis results from the response spectra method to results from the ESL method. This study demonstrates that the ESL method conservatively approximates dynamic analysis results. The Vogtle project has determined that a factor of 1.7 (in lieu of the current FSAR factor of 1.5) can be shown to bound the effect of multiple modes of response for piping systems.
. The Vogtle project therefore is revising FSAR 3.7.B.3.5 (attached) to show the use of the ESL method, with the 1.7 factor, for piping systems seismic analysis.
f li 8610140299 861006 PDR ADOCK 05000424 PDR A
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Director of Nuclear Reactor Regulation File: X7BC35 October 6,1986 Log:
GN-1101 Page 2 If your staff requires any additional information, please do not hesitate to
-contact me.
- scerely, J. A. Bailey Project Licensing Manager JAB /sm Attachment xc:
R. E. Conway R. A. Thomas J. E. Joiner, Esquire B. W. Churchill, Esquire M. A. Miller (2)
B. Jones, Esquire G. Bockhold, Jr.
NRC Regional Administrator NRC Resident Inspector D. Feig R. A. McManus-L. T. Gucwa Vogtle Project File 0765V l
VEGP-FSAR-3
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3.7.B.3.4 Basis for Selection of Frequencies Piping system frequencies are calculated and dynamic inter-actions with support structures are accounted for in accordance with section 2 of BP-TOP-1.828 I
i 3.7.B.3.5 Use of Equivalent Static Load Method of Analysis' The equivalent static load method involves equivalent hor-izontal and vertical static forces applied at the-center of
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gravity of various masses.
The equivalent force at a mass location is computed as the product of the mass and the seismic acceleration value applicable to that mass location.
The magnitude of the seismic. acceleration is established on the basis of the dynamic response characteristics of the component.
Components which can be adequately characterized as a single-degree-of-freedom system are designed for accelerations asso-ciated with their natural frequency.
Seismic acceleration values used for design of multidegree-of-freedom systems, which may be in the resonance region of the amplified response spectra enrves, are the peak acceleration values multiplied by a factor of 1.5 unless a lower factor is justified.
In lieu of I
using the peak acceleration value, the actual frequency may be calculated and the corresponding acceleration value may be used.
In this case, the calculated frequency must be higher than that frequency related to the peak acceleration; other-wise, the peak acceleration value is used in design.
For systems and components which have fundamental frequencies of 33 Hz or greater, the zero period acceleration is taken as th'e j
seismic acceleration value.
The equivalent static load method of analysis is used for design of platforms, electrical cable trays and supports, conduits and supports, HVAC ducts and supports,.and other BP-MP-1, ret tim _ 2_3.2 see, abhed substructures.
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3.7.8.3.6 Three Components of Earthquake Motion Section 5.1 of BP-TOP-1 provides the criteria used to combine the results of horizontal and vertical seismic responses for
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piping systems.ca:
For the structures, systems, and equipment qualified by analysis, the three component earthquake effects are combined using the square root of the sum of the squares method, as described in paragraph 3.7.B.2.6, or an equivalent method y
yielding essentially the same results.
For equipment qualified t
3.7.B.3-4
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Insert to Paragraph 3.7.B.3.'5 The complexity of typical piping systems can result in significant responses at several vibration frequencies. The factor of 1.5, which is used for less complex systems, is increased to 1.7 for piping system analysis to envelope the combined responses of multiple modes of vibration. In lieu of the-equivalent sta ig load method, the method stated in BP-TOP-1, section 2.3.2 andAppendixDg21, may be used.
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