ML20238D884
| ML20238D884 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/29/1987 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8801040495 | |
| Download: ML20238D884 (3) | |
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9-TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 37401 -
SN 157B Lookout Place 1
l O!!8 291987 i
l U.S. Nuclear Regulatory Commission ATTN: Document Control Desk i
Washington, D.C.
20555
.j Gentlemen:
In the Matter of
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Docket Nos. 50-327
'i Tennessee Valley Authority
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50-328
'SEQUOYAH NUCLEAR PLANT (SQN) - USE OF AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) CODE CASE N-411 i
References:
1.
NRC letter to TVA dated December 2, 1985, "Use of ASME Code Cases N-397 and N-411 for the Sequoyah Nuclear Plant Units 1 and 2" 2.
TVA letter to NRC dated February 12, 1986 3.
TVA letter to NRC dated September 29, 1987 l
This transmittal supersedes a previocs TVA submittal on use of ASME Code i
Case N-411 at SQN units 1 and 2, reference 3.
It incorporates comments received from your organization.
Code Case N-411 concerns the use.of alternati.ve damping values for seismic analysis of piping, section III, revision 1, class 1, 2, and 3 construction.
In reference 1, NRC conditionally approved the use of ASME Code Case N-411 for SQN subject to TVA's commitment to impose the following two conditions:
" Commit to use the case for piping systems analyzed by response spectrum methods and not those using time-history analysis methods."
"When the alternate damping criteria of.this code case are used, they will be used in their entirety in a given analy' sis and shall not be a mixture of Regulatory Guide 1.61 criteria and the alternated criteria of this code case."
TVA's commitment to meet these conditions was transmitted to NRC by reference 2.
TVA also documented this in amendment 3 of the updated Final Safety Analysis Report (FSAR) in table 3.7.1-3.
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l U.S. Nuclear Regulatory Commission bbbbblbO7 Code Case N-411 is being applied to analysis of piping attached to two structures:
Seismic analysis of piping in the additional diesel generator building (ADGB).
It should be noted that the work on the fifth diesel generator addition (i.e., ADGB) has been temporarily put on hold due to higher priority work.
When the ADGB is reactivated, N-411 damping will not be used without NRC approval.
Design Basis Accident (DBA) analysis of piping attached to the steel containment vessel (SCV).
DBA vibratory motions of the SCV are caused by a loss of coolant accident (LOCA).
The response spectrum method was used in all analyses. For the seismic analysis of the piping, all the conditions stipulated by NRC were met.
The piping attached to the SCV was analyzed for the DBA vibratory motion, applying response spectra only to the SCV attachment points'using the independent support motion method.
The remainder of the pipe supports (i.e., supports not attached to the SCV) have a zero DBA spectrum applied to them for this analysis.
The analysis was performed this way because only the supports connected to the SCV experience vibratory motion for the DBA loading condition.
Also, Code Case N-411 damping has been used for the following cases, and the conditions of reference I were met:
Code Case N-411 damping has been used as the basis for not performing reanalysis of piping in the essential raw cooling water (ERCW) pipe tunnel.
TVA has generated preliminary design' basis response spectra for the ERCH pipe tunnel using techniques that are consistent with our FSAR commitments.
The new preliminary response spectra are the same or lower than the spectra used in the original analysis. Therefore, it is expected that the final design basis response spectra will be lower also.
Code Case N-411 damping has been used to recalculate pipe movements at support points on ERCH piping in the annulus area. The increased. damping was used to predict imore realistic pipe movements to demonstrate that the support clearances would accommodate the pipe movements.
The current program for regeneration of support calculations on rigorously analyzed piping has recalculated pipe movements that are consistent with our FSAR commitments.
In those cases where insufficient gap exists, a modification will be prepared and a prerestart and postrestart determination made in accordance with the restart criteria.
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- U.S. Nuclear Regulatory Commission hhh2,91907 Code Case N-411 damping has been used to analyze portions of the seismic category I(L) fire protection system piping.
The report containing the analysis of the fire protection piping is
-currently being revised to delete N-411 damping as a basis for acceptance.
In summary, SQN has utilized the damping provisions of Code Case N-411 only for those cases described above.
In most instances, subsequent actions have been performed by TVA that supersede the design decisions dependent on usage l
of this code case. All future uses of Code Case N-411 damping will only be approved with the concurrence of your staff.
If you have any questions or comments, please telephone M. R. Harding at (615) 870-6422.
Very truly yours, TENNESSEE VA LEY AUTHORITY R.
ridley, D ector Nuclear Licensing and Regulatory Affairs cc: Mr. K. P. Barr, Acting Assistant Director for Inspection Programs TVA Projects Division Office of Special Projects U.S. Nuclear Regulatory Commission Region II 101 Marietta Streat, NW, Suite 2900 Atlanta,. Georgia 30323 Mr. G. G. Zech, Assistant Director for Projects TVA Projects Division Office of Special Projects U.S. Nuclear Regulatory Commission Mail Stop 7E23 l
7920 Norfolk Avenue Bethesda, Maryland 20814 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379
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