ML20214N356
| ML20214N356 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 11/18/1986 |
| From: | Bailey J GEORGIA POWER CO. |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| GN-1186, NUDOCS 8612030612 | |
| Download: ML20214N356 (4) | |
Text
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Georgia Pbwer Company Fast Offics Box 282 Waynesboro, Georgia 30830 Telephone 404 554-9961 404 724 8114 Southern Company Services, Inc Pbst Office Eax 2625 Birmingham, Alabama 35202 Telephone 205 870-6011 VOgtle Project November 18, 1986 Director of Nuclear Reactor Regulation File: X7BC35 Attention:
Mr. B. J. Youngblood Log:
GN-1186 PWR Project Directorate #4 Division of PWR Licensing A U. S. Nuclear Regulatory Commission Washington, D.C.
20555 NRC DOCYEI NUMBERS 50-424 AND 50-425 CONSTRUCTION PERMIT NUMBERS CPPR-108 AND CPPR-109 V0GTLE ELECTRIC GENERATING PIANT - UNITS 1 AND 2 REQUEST FOR ADDITIONAL INFORMATION:
STATIC LOAD ANALYSIS
Dear Mr. Denton:
Members of your staff have requested additional information on the development of a 1.7 static load factor used in the analysis of piping systems which have significant responses at several vibrational frequencies. Attachment A lists the questions asked by your staff along with the GPC response. Attachment B provides the proposed FSAR change which addresses this issue.
If your staff requires any additional information, please do not hesitate to contact me.
Sincerely,
-h,
(
l J. A. Bailey Project Licensing Manager JAB /caa Attachment xc:
R. E. Conway NRC Regional Administrator R. A. Thomas NRC Resident Inspector l
J. E. Joiner, Esquire D. Feig B. W. Churchill, Esquire R. W. McManus M. A. Miller (2)
L. T. Gucwa B. Jones, Esquire Vogtle Project File G. Bockhold, Jr.
8612030612 861118 05 PDR ADOCK 05000424 A
PDR-
Attachment A (Continued)
Page 2 of 2 floor response spectra broadened so that the peak was flat from 2.2 HZ to 20 HZ for two piping systems, and from 2 5 HZ to 33 HZ for the third.
A statistical study was performed of the ratio (dynamic response / static response).
This study was performed for member moments, node displacements, and support forces for each piping system.
The following items smmnarize the steps performed for each piping system.
(1) Member moments at the 20 highest stress locations, the 20 highest node displacements, and all support forces (for both static and dynamic analyses) were selected to be included in the statistical study.
(2) The ratio dynamic / static response was calculated at each node point selected.
(3) The sum, mean, and standard deviation was calculated for each category; moments, node displacements, and support forces.
(4) A static load coefficient was calculated for each category equal to the mean plus one standard deviation.
The static load coefficient of 1 7 was a maximum of all the individual coefficients from each category and from each piping system.
Question 2:
Where would Westinghouse use the 1 7 factor vs. the 1 5 factor?
Response
The 1 7 factor would be used for static analysis of complex piping systems where frequencies are not easily calculated.
An example would be complex B31.1 piping systems. The 1 5 factor would still be used for simple piping systems such as vents and drains.
Although not discussed, GPC also plans to use the 1 7 factor for equivalent static load analysis of complex ASKE piping systems.
Question 3:
Would the peak acceleration of the applicable response spectra be applied to the 1 7 factor?
Response
The equivalent static load method of analysis will be used in the design of complex piping systems with significant responses at several vibrational frequencies. In these cases, the static load factor of 1 7 will be applied to the peak acceleration of the applicable floor response spectra.
The FSAR change request will be changed to clarify this.
i 192/CAC
ATTACHMENT A Members of the U.S. Nuclear Regulatory Commission ~ Staff requested additional information on the development of a static load factor of 1 7, which is being added to paragraph 3 7.B.3 5 of the Vogtle FSAR.
This load factor is for equivalent static analysis of complex piping systems, which have significant responses at several vibrational frequencies.
The following questions were asked, with responses af ter each question:
Question 1:
How did GPC come by the 1 7 factor and what does it consider?
Response
There are two accepted methods to perform Seismic Analysis of Category 1 structures, systems and components per (SRP 3 7.2), (1) Dynamic response spectrum or time history analysis and (2) Equivalent static load method. To perform seismic analysis of piping systems, using the equivalent static load method, a factor of 1 5 is applied to the peak acceleration of the applicable floor response spectra.
However, the system must be represented by a simple model for the 1 5 factor to apply.
In order to analyze complex piping systems using the static load method, it was necessary to determine an acceptable static load factor. A study has been performed to determine what factor could be used to conservatively account for behavior of complex piping systems.
Three piping systems were selected for the study, two were Vogtle analysis lines and the third was an NRC benchmark problem (323A).
Three static analyses were performed for each piping system with a 1-0 acceleration applied along each coordinate axis.
Each unidirectional 1-G analysis was multiplied by the peak acceleration of the applicable Vogtle floor response spectra, and then the response in the three orthogonal directions were l
combined using the square root sum of the squares method.
A dynamic response spectrum analysis was also performed for each piping system.
The dynamic analysis was performed in accordance with the following criteria:
(1) 3-D shock with directions combined by square root sum of the squares method (Reg. Guide 1 92).
(2) Broadened floor responses spectrum (Reg. Guide 1.122).
(3) Closely spaced modes contributions (reg. Guide 1 92).
(4) Full ZPA method (NUREG-1061).
The peaks of the applicable floor response spectra were broadened an additional amount to ensure that the significant modes of the piping system would fall on j
the peak of the spectra.
The peak acceleration for the vertical and horizontal i
192/CAC
r ATTACHMENT B VEGP FSAR Section 3.7.B.3.5 - Use of Equivalent Static Load Method of Analysis Change last paragraph as follows:
The above equivalent static load method of analysis is used for design of platforms, electrical cable trays and supports, conduits and supports, HVAC ducts and supports, simple piping systems and other substructures.
The equivalent static load method of analysis can also be used for design of complex piping systems, with significant responses at several vibrational frequencies. In this case, the static load factor of 1.7 shall be applied to the peak accelerations of the applicable floor response spectra.
In lieu of the equivalent static load method, the method stated in BP-TOP-1, Section 2.3.2 and Appendix D (2) may be used for piping.
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