ML20086D546
| ML20086D546 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 11/15/1991 |
| From: | Zeringue O TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20086D549 | List: |
| References | |
| NUDOCS 9111260143 | |
| Download: ML20086D546 (7) | |
Text
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vn e ne oem. a U.S. Nuclear Regulatory Commission ATTH: Document Control Desk Washington, D.C.
20555 Gentlement In the Matter of
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Docket Nos. 50-259 Tennessee Valley Authority
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50-260 50-296 BROWNS FERRY NUCLEAR PLANT (SFN) - IlEATING, VENTIl.ATION AND AIR CONDITIONING (IIVAC) SEISMIC DESIGN CRITERIA Rt.f e renc es :
- 1) HRC letter, dated July 26, 1988, Interim Operability Criteria for the Seismic Design Program for the Browns Ferry Nuclear Plant, Unit 2
- 2) NRC letter, dated January 23, 1991, NUREG 1232, Volume 3, Supplement 2, Safety Evaluation Report on Tennessee Valley Authority:
Browns Ferry Nuclear Performance Plan
- 4) TVA letter, dated July 10, 1991, Regulator) Framework for the Restart of Unita 1 and 3 This letter submits the BFN Class I llVAC duct and support seismic design criteria for staff review. The enclosed criteria is applicable to all three BFN Units. The seismic qualification of IIVAC is a BFN Nuclear Performance Plan special program. The qualification of Unit 2 and common i
IIVAC for one cycle of operation was performed either to an interim operability criteria, as approved by HRC in Reference 1, or to a previous revision of the enclosed design criteria. As documented in References 1 and 2, the staff took a post Unit 2 restart action item tn review TVA's seismic design criteria. TVA action to develop and submit !!VAC design criteria is considered complete based on this submittal.
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3-U.S. Nuclear Regulatory Commission 15 W As previously committed, the Unit 2 and common !!VAC, which met the interim operability criteria but did not meet the design criteria, will be reviewed and modified, as required, to meet the enclosed criteria prior to restarting from the next refueling outage. As stated in References 3 and 4, TVA vill implement the Units' I and 3 program for the seismic qualification of liVAC in accordance with the enclosed design criteria and the Unit 2 implementation precedent, prior to the restart of each unit,' to this letter provides background information for IIPN llVAC seismic qualification. Additionally, Unit 2 post restart open items and actions are summarized. Enclosure 2 provides a criteria comparison summary between the interim operebility criteria and the enclosed design j
criteria. > Enclosure 3 provides IIVAC design criteria for staff review.
I TVA requests the review of this criteria by January 15, 1992, in order to j
support the design and modifications which TVA committed to complete on Unit 2 prior to the restart from the next refueling outage. Upon completion of the staff review, TVA requests the issuance of a j
supplemental Safety Evaluation Report to document the closure of the post-restart action item identified in References 1 and 2.
There are no commitments contained in this letter.
If you have any questions contact Raul R. Ilaron, Site 1,1 censing Manager, at (205) 729-7566.
Sincerely,
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O. J'" Zeringtie Enclosures cc: See page 3 l
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3 U.S. Nuclear Regulatory Commission N0V 151931 cc (Enclosures):
NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637 Athens, Alabama 35611 Mr. Thierry M. Ross, Project Manager U.S. Nuclear Regulatory Commission 1
One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Project Chief U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Y
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l ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT (BMI)
MEATING, VENTILATION AND AIR CONDITIONING (!!VAC) s SEISMIC QUALIFICATION BAGEGRQ1!ED During initial plant construction, HVAC ducts and duct supports at BFN were fabricated to industry standards without consideration of seismic loads. The duct construction was based on the Sheet Metal and Air Conditioning National Association standards, with both the pocket lock and companion angle flan 6e transverse joint types used.
In 1970, the need for HVAC ducts to withstand earthquake loads was identified. HVAC seismic design criteria was issued in July 1970, and existing HVAC ducts and supports were modified accordingly.
Subsequent field evaluations by design engineers to review the installed supports against the design criteria resulted in additional modifications.
In January 1986, a Significant Condition Report (SCR) was written questioning the adequacy of liVAC support installation and qualification design criteria BFN-50-721.
In addition, field investigations identified discrepancies between the installed HVAC system configuration and the design criteria requirements.
As a result of the SCR, a HVAC seismic qualification program was initiated to eniure existing BFN Unit 2 and common Class 1 duct and associated supports were able to withstand seismic loads. Under the program, affected duct and supports were walked down to determine routing, configuration, and sizes of various duct and support features. The walkdown information was evaluated using the seinmic qualification acceptance requirements of the operability criteria BFN-50-C-7304 or the design criteria BFN-50-C-7104.
NRC review, documented in Inspection Report 50-260/89-29, section 3.12, determined that the design criteria BFN-50-C-7104 was more conservative than the interim operability criteria and, therefore, its use for restart qualification of IIVAC
~ duct and supports was acceptable.
The interim operability criteria for HVAC duct did not contain requirements to check duct buckling stresses. A study was performed and documented in a design calculation to demonstrate the duct was seismically qualified despite the lack of a buckling check in the operability criteria.
Results of the study were reviewed and accepted by NRC, and documented in Inspection Report 50-260/89-42.
Additionally, an impact assessment was performed to confirm that the duct i
systems, which were qualified using the El Centro response spectra, are in compliance with the artificial time history that closely fits the umooth llousner response spectra curve. The resulta of the assessment were reviewed and accepted by NRC as documented in Inspection Reports 50-260/89-32, 50-260/89-42, and NRC letter to 0. D. Kingsley dated August 22, 1990.
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,,,. Un[t 2 Post Restart _.Qntn_ Items The following BTN Unit 2 and common Class 1 IIVAC duct and supports post restart open items are documented in NUREG-1232, Volume 3, Supplement 21 1.
TVA should evaluate and identify the need for long-term modification of the approximate 11,830 feet of ductvork that met the ir.terim criteria.
2.
TVA should perform the long-term modification of the 509 existing supports that were qualified to the interim criteria.
3.
TVA should develop long-term criteria for IIVAC evaluation and perform long-term buckling evaluation for all ductvork qualified to the interim criteria.
TVA RESPONSE:
As previously committed, the BFN Unit 2 ITVAC, which met the interim operability criteria but did_not meet the design criteria, will be evaluated and modified as required to the enclosed criteria. This design criteria
-contains criteria for evaluation of !!VAC buckling, which is the same as previously reviewed by HRC for BFN Unit 2 restart.
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ENCLOSURE 2 BROWNS PERRY UllIT 2 IIVAC CRITERIA CO!4PARISON CHART (All allowables are for deadweight and DDE (SSE) seismic load combination)
TYPE OF bOAD OPERABILITY CRITERIA DESIGli CRITERIA pljingES DFli-5 0-C-7 3 04._Efev. 2 BFN-50-C-llqi_13pv. 5 Duct bending stress rectangular duct 12,000 psi 12,000 psi round duct 15,000 psi 15,000 pai Duct shear load or stress 4 le 4 Ig-rectangular duct V=5.5 w (6.4) w V=5.5 W (6.4) w-round duct 0.53Fy 0.53Fy
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Duct buckling not specified 90% critical stress buckling Fupport member stress tension and smaller of 1.2Fy 1.5 x AISC' bending and 0.7Fu shear smaller of 0.72Fy 1.5 x AISC' and 0.42Fu compression 90% critical
- 1. 5 x AISC's 90%
buckling critical buckling Bolt stress tension 1.0Fy or 0.7Fu 1.5 x AISC' shear smaller of 0.6Fy 1.5 x AISC' and 0.42Fu Wold stress increase factor smaller 1.5 x AISC' of 1.8 or 1.05 Fu/Fy j
(Fu & Fy for base metal)
Concrete expansion F.S.= 2 for evaluation GIP for evaluation shell anchors of existing anchors of existing anchors
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