ML20147D914
| ML20147D914 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/02/1988 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8803040201 | |
| Download: ML20147D914 (4) | |
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0 i TENNESSEE VALLEY AUTHORITY CHATTANOOGA, TENNESSEE 374ot SN 157B Lookout Place i
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MAR 2 ' 988 P
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 centlemen:
In the Matter of
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Dockat Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - RESOLUTION OF OPEN INSPECTION ISSUES l
During the NRC inspection in Knoxville, Tennessee, the week of February 15, 1988, a number of miscellaneous issues were reviewed. One of the issues identified was the effect of Square Root of the Sum of the Squares (SRSS) versus Absolute Sums (ABS) on the directional combination of recults of basic seismic load cases. This confirmatory letter documents resolution of this issue.
If you have any questions, please call D. L. Williams at (615) 632-7170.
Very truly yours TENNESSEE VALLEY AUTHORITY R. Grid y,Direckr Nuclear Licensing and Regulatory Affairs Enclosure cc:
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8803040201 880302 F'DR ADOCK 05000327 O
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An Equal Opportensty Employer
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Enclosure cc (Enclosure):
Mr. X. P. Barr, Acting Assistant Director for Inspection Programs L
TVA Projects Division l
U.S. Nuclear Regulatory Coenission Region II 101 Marietta Street, WW, Suite 2900 j
Atlanta, Georgia 30323 1
i Mr. G. G. Zech, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike I
Rockville, Maryland 20852 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Isou Ferry Road j
Soddy Daisy Tennessee 37379 4
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ENCLOSURE SEQUOYAH NUCLEAR PLANT SRSS VS. ABS COMBINATION 1.
Introduction Square Root of the Sum of the Squares (SRSS) was used for the piping system seismic directional combination mothod on SQN while the SQN SER issued by the NRC described it as Absolute' Sum (ABS). This study investigated the impact of the difference on the SQN piping design.
2.
Scope This evaluation assesses the differences when combining piping seismic results from the two directional responses by the SRSS method versus ABS combination.
3.
Approach Five piping analyses were selected to evaluate the impact of ABS vs. SRSS on the existing SQN design. Three of the five analyses were selected from a previous study addressing the vertical earthquake issue in response to TVA Problem Identification Report PIRSQNCEB8652. The fourth analysis was selected to assess the effect of the auxiliary building spectra and the fif th one assesses the effect of the interior concrete structure spectra.
All critical results, including pipe stress, penetration loads, aozzle loads, valve accelerations, and support loads, were evaluated.
Detailed evaluations of all supports designed to interim design criteria CEB-CI-21.89 were made. Other supports were also evaluated to determine that the percent incresse would not affect their qualification. The response increases for the faulted loading combination due to ABS vs. SRSS effects are as shown in the attached tabic.
4.
Conclusions Five piping systems were evalur ed to study the impact of SRSS vs ABS as the directional combination method.
The difference is around 10 percent when compared to the faulted load case, and the increased loads, stresses, and accelerations are all within allowables.
Based on this review, TVA concludes that the use of ABS directional combination for piping systems in lieu of the SRSS approach described in the SON FSAR does not represent a significant challenge to the design of SQN piping systems. As such, j
this issue is considered resolved for SQN unit 2 restart.
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ATTACHMENT SRSS VERSUS ABS COMPARISON l
Stress l
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l l Problems l
l ICS l
AB l
AB l
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lN2-14-lR l0600154-07-03lN2-64-2A lN2-3-10A, IIA, l N2-64-3R l
Attributes 12A l
l3%to13%in-l l
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l lPipeStress lcreasemax.EQN]2% increase l2%increasel3%increasemax.l0.5% increase l
l l9Fstressir, l max.
l max.
l l max.
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lacceptable I
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l l Penetration l l
l1.3% nux. l10% max.
l0.4% max.
l l Loads lNone lNone l Increase jincrease' l increase l
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l Nozzle lNonozzles l<4% Max.
l4.9% max. l<10% max.
l No nozzles l
l Loads l
l increase l increase l Increase; nozzles l l
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jarequallfled l
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lAllvalvesmeetl l
l0.2%maxincreasel l Valve lNovalves 12G/3Glimit.
l<3.5%
lAllvalvesmeet lfor5 valves.
l l Accelerations l l Increase <12%l increase l2G/3Glimit.
l6%increasefor l l
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l1valvewhichis]
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l lqualifiedper l
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1 l CFB 87-10C l
i l Supports l
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lqualifiedtol1% increase-lNoneare l3%
l10% increase-l0.1% increase-l lCEB-CI-21.89lwithin lqualifiedto l increase-lwithinallowablel within l
l l allowable lCEB-CI-21.89 lwithin l
l allowable l
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l I allowable l l
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