ML20207N866
| ML20207N866 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 10/13/1988 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| TAC-00023, TAC-23, NUDOCS 8810190427 | |
| Download: ML20207N866 (5) | |
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA TENNESSEE 374ol SN 157B Lookout Place OST 131988 U.S. Nuclear Regulatory Commission ATTN Document Control Desk Washington, D.C.
20555 Centlement In the Matter of
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Docket Nos. 50-259 Tennessee Valley Authority
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50-260.
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50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - SEISMIC PROGRAM INTERIM OPERABILITY CRITERIA - RESOLUTION OF SAFETY EVALUATION OPEN ITEMS Referencet TVA's letter to ycu dated September 21, 1988. "BFN Seismic Program Interim Operability Criteria - Safety Evaluation Open Items and Conument s" The referenced letter documented commitments made between TVA and NRC (T. Cheng) to resolve outstanding oper items on the BFN Seismic Program Interim Operability Criteria Safety Evaluation (SE). Four actions remain to be completed by TVA before this program can be approved by NRC. Thore actions are:
Item 1 - Electrical conduit and conduit supports - Use of (2.0 x Fy)/(0.75 x 2.3) interim allowable stress criteria. Original justification provided by TVA for use of this higher allowable stress criteria was inadequate.
TVA agreed to provide further discussion and justification for this higher allowable stress value.
Item 2 - Electrical conduit and e anduit supports - buckling criteria for aluminum conduits. While it is understood that buckling may not be a critical failure mode for aluminum conduit. NRC would like a calculation justifying aluminum conduit resistance to buckling.
TVA agreed to generate this calculation and make available for NRC review and inspection.
Item 3 - HVAC ductwork and supports. While buckling of HVAC ductwork might not have been an original design requirement. NRC would like justification that either buckling with HVAC cracking will not occur at BFN. or if cracking does occur, that leakage will not impact plant operation.
TVA agreed to provide such justification and make available for htC review and inspection' O
SG10190427 881013 1
PDR ADOCK 011000259 P
PDC l
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An Equal Opportunity Employer
06 13 m U.S. Nuclear Revilatory Commission Item 4 - Prywell access steel platforms - use of absolute sumation for irterim operability and phasing for long term. TVA wording of response in the referenced letter implied not that TVA can use phasing where justified f or long term evaluation, but that it will utilize phasing.
IVA witi "evise and resubmit this response to clarify that use of phasing in the long term is an acceptable analysis option where properly justifled.
Items 1 and 4 are addressed in the enclosure to this letter.
Items 2 and 3 will bw available for NRC inspection on October 31, 1988, as previously comitted in the referenced submittal.
No new comitments are contained in this submittal.
If any questions remain relative tc the above, please contact Patrick P. Carier at (205) 729-3570.
Very truly yours.
TENNESSEE VALLEY,AUTil0RITY
.g R. Cr diey, Man er Nuclear Licensi"ng and Reguiatory Affairs Enclosure cc:
See page 3 i
f)hl[ j } jggg U.S. Nuci. ear Regulatory Commission cc (Enclosure):
Ms. S. C. Black Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. F. R. McCoy, Assistant Director for Inspection Programs TVA Projects Division U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Seite 2900 Atlanta, Georgia ?O323 Browns Ferry Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 617 Athens. Alabama 35611
e ENCLOSURE Item 1 - Electrical Conduit and Conduit Supports TVA has determined that the use of (2.0 x Fy)/(0.75 x 2.3) is an acceptable stress level for the purposes of restart., where Fy is the allowable stress level at yield. This is based upon testing performed at Wyle Laboratories, Test Report No. 17743-1.
This report was transmitted to NRC on April 8, 1987.
The following is a comparison between the desi n allowable stress and E
calculated stress based upon strain gauge measurements of aluminum conduit t
from the Wyle test lab report.
l SMNARY OF CONDUIT STRESS RATIOS Test Series Run No.
Max Stress Max Stress / Design Allowable
[
(ASI) l 1
9 8.8 1.1 1
10 9.9 1.3 3
1 1
11 12.3 1.6 1
12 15,6 2.1 1
13 13.6 1.8 4
25 10.6 1.4 4
26 13.2 1.8 l
4 27 16.2 2.2 5
62 10.5 1.4 i
5 63 17.6 2.3 6
76 12.1 1.6 6
77 15.4 2.1 9
35 9.9 1.3 9
36 14.5 1.9 9
37 27.5 3.1 10 89 9.9 1.3 l
Other test results were not tabulated because those series were performed without strain gauges, or the stress levels observed at the 2 x BFN design l
basis earthquake input level (table limitation), were still within tha long term stress allowables.
l-l As observed from these test results, aluminum conduit specimens repeatedly experienced stress levels greater than the basic design allowable of i
Fy/(0.75 x 2.3) and beyond the proposed operability criteria level of (2.0 x Fy)/(0.75 x 2.3).
Furthermore, as noted in the test report, thero was no obser<ed damage of conduit or the cables inside the conduit at these etress levels.
l This test inforuution demonstrates that conduit can withstand stress levels j
well in excess of the basic design allowable without impairing the structural integrity of the conduit.
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2 Item 4 - Revised Respotase to Drywell Access Steel Platforms Issue Safety Evaluation Report subparagraph 2.1.d states "During the May 18, 1988 meeting, TVA committed to combine these dynamic reactions on an absolute sum basis, regardless of their phase relati7nship."
TVA Comment i
1 As committed to in the meeting, TVA will re/ise tha operability criteria to i
reflect that the absolute summation of loads was utilized for the restart evaluation of the drywell access steel platforms. However, for post-restart, T5A may use, as an option, phasing of the seismic loads for its long-term evaluation of the drywell platforms and would reflect its use in tue long-term criteria.
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