ML18037A509

Forwards Response to 930319 Ltr Requesting Addl Info Re Evaluation of Seismic Adequacy of Flexible Conduit Units 1, 2 & 3,per Generic Ltr 87-02,Suppl 1

ML18037A509
Person / Time
Site:	Browns Ferry
Issue date:	10/15/1993
From:	Salas P TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR GL-87-02, GL-87-2, NUDOCS 9310250005
Download: ML18037A509 (13)

Text

ACCEI ERAT DOCUMENT DIST UTION SYSTEM REGULAT INFORMATION DISTRIBUTION STEM (RIDS)

ACCESSION NBR:9310250005 DOC.DATE: 93/10/15 NOTARIZED: NO DOCKET FACIL:50;.259 Browns Ferry Nuclear Power Station, Unit 1, Tennessee 05000259 56-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 50-296 Browns Ferry Nuclear Power Station, Unit 3, Tennessee 05000296 A NAME AUTHOR AFFILIATION SAL Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Forwards response to 930319 ltr requesting addi info re D evaluation of seismic adequacy of flexible conduit units 1, 2 6 3,per Generic Ltr 87-02,Suppl l.

DISTRIBUTION CODE: R025D COPIES RECEIVED:LTR / ENCL SIZE:

TITLE: Seismic Qualification of Equipment in Operating lants A-46 NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL D OGC/HDS3 1 1 NRR/PD11-2 1 1 PD2-4-PD 1 1 TRIMBLE,D 1 1 D WILLIAMS,J. 1 1 INTERNAL: ACRS 6 6 NRR/DE 1 1 NRR/DE/ECGB 2 2 NRR/DE/EELB 1 1 NRR/DE/EMEB 4 4 NRR/DRCH/HICB 1 1 NRR/DRPE/PDl-3 1 1 NRR DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 EG 01 1 1 EXTERNAL: NRC PDR 1 1 D

NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTEl CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISIS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 25 ENCL 25

Tennessee Valley Authority. Post Office Box 2OOO, Decatur, Atabama 35609 OCT I5 IQ93 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

In the Matter of ) Docket Nos. 50-259 Tennessee Valley Authority ) 50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - GENERIC LETTER (GL) 1i VERIFICATION OF SEISMIC ADEQUACY OF MECHANICAL 87-02'UPPLEMENT AND ELECTRICAL EQUIPMENT IN OPERATING REACTORS'NRESOLVED SAFETY ISSUE (USZ) A-46 - RESPONSE TO REQUEST FOR ADDZTZONAL INFORMATION REGARDING THE EVALUATION OF THE SEISMIC ADEQUACY OF FLEXIBLE CONDUIT - UNITS 1~ 2g AND 3 This letter provides TVA's response to the staff's request for additional information, which was transmitted by letter from F. J. Hebdon to M. O. Medford, dated March 19, 1993. In this letter, NRC documented the completion of its review of TVA's response to GL 87-02, Supplement 1, and identified two separate requests for information regarding flexible conduit.

Enclosure 1 to this letter provides background information related to BFN flexible conduit, a summary of the staff's requests and the corresponding TVA responses. Enclosure 2 to this letter provides a listing of commitments.

The due date of this letter was extended from September 30, 1993 to October 15, 1993, based on a conversation with NRC's Project Manager.

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U.S. Nuclear Regulatory Commission Page 2 N

GCT 15 1993 S If you 729-2636.

have any questions, please telephone me at (205)

Sincerely, Pedro Salas Manager of Site Licensing Enclosures cc (Enclosures):

Mr. R. V. Crlenjak, Project Chief U.S. Nuclear Regulatory Commission Region 101 II Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637 Athens, Alabama 35611 Mr. J. F. Williams, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. D. C. Trimble, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852

ENCLOSURE 1 Tennessee Valley Authority Browns Ferry Nuclear Plant (BFN)

Units 1, 2, and 3 Generic Letter 87-02, Supplement 1 Additional Information Re ardin Flexible Conduit Back round BFN was initially constructed using General Construction Specification G-3, "Installing Electrical Conduit Systems and Fabricated Conduit Boxes." This specification required that flexible conduit be provided for electrical connections to equipment (such as motors, valves, lighting fixtures), but contained no specific requirement for minimum lengths for seismic and thermal movements. TVA subsequently recognized the need for flexible conduit length requirements to ensure adequate thermal movements and revised General Construction Specification G-40, "Installing Electrical Conduit Systems and Conduit Boxes," in October of 1980. However, G-40 was not made applicable to BFN until January 15, 1986.

The overall program that resolved the flexible conduit issue for BFN Unit 2 was described in Volume 3 of TVA's Nuclear Performance Plan (NPP)(Reference 1). Programmatic details were provided in References 2 and 3. For the restart of Unit 2, TVA committed to inspect all flexible conduits attached to electrical equipment covered by 10 CFR 50.49. These inspections verified that the lengths of the flexible conduits were adequate to accommodate thermal and seismic movement. Those flexible conduits not meeting the requirements of G-40 were reworked, replaced, or technically justified on a case by case basis. TVA also committed to evaluate other flexible conduit attached to safety related equipment (other than 10 CFR 50.49 electrical equipment) within the scope of BFN's program to address Unresolved Safety Issue (USI) A-46. NRC acceptance of this program was included as part of Reference 4. In Reference 5, TVA stated that the flexible conduit program would be implemented on Units 1 and 3 in accordance with the Unit 2 precedent.

A summary of the two staff requests for additional information contained in Reference 6 and TVA's responses are provided below:

TVA is requested to provide a description of the general approach, including the procedure and acceptance criteria, which it will use to evaluate the seismic adequacy of flexible conduit attached to electrical equipment not covered by,10 CFR 50.49.

TVA Res onse BFN will use the criteria contained in TVA's General Engineering Specification G-40 (formerly General Construction Specification G-40) to evaluate the seismic adequacy of flexible conduit attached to safety related electrical equipment not covered by 10 CFR 50.49 (i.e.,

important to safety but in a mild environment) and within the scope of (USI) A-46 for Units 1, 2, and 3. This criteria was previously used to evaluate flexible conduit attached to electrical equipment covered by 10 CFR 50.49 (harsh environment). The acceptance criteria for the inspected conduits requires the exposed conduit be calculated using the equation and criteria below:

FL = SD + K Where, FL Minimum exposed flexible conduit length between flexible fittings SD Field Measured straight line distance between flexible conduit fittings (When an obstacle prevents a straight line measurement of SD, the proposed flexible conduit route shall be determined, and that distance shall be used)

I K 1 inch or 4 inches (1 inch flexible conduit length is the maximum combined seismic/thermal movement in any direction for floor mounted equipment, 4 inch flexible conduit length is the maximum combined seismic/thermal movement in any direction for pipe mounted devices) 2 ~ NRC Re est TVA is requested to submit its long term criteria for staff review and approval, or alternatively, provide a justification why the interim criteria used for Unit 2 restart is adequate for long term application for Units 1, 2, and 3.

TVA Res onse TVA considers the inspection and evaluation criteria utilized for flexible conduit attached to electrical equipment covered by 10 CFR 50.49 to be long term rather than interim criteria. TVA's commitments in Volume 3 of the NPP established permanent resolutions regarding flexible conduit, which terminates at 10 CFR 50.49 equipment. The subject criteria was developed based on the maximum worst case seismic/thermal movements. The criteria was submitted for NRC review in Reference 2 and accepted by NRC in Reference 4. The evaluations for flexible conduit, attached to 10 CFR 50.49 devices, were completed prior to the restart of Unit 2.

TVA interpreted the staff's reference to BFN's use of interim criteria in Reference 4 to apply only to the evaluation of flexible conduit within the scope of USI A-46 and not attached to electrical equipment covered by 10 CFR 50.49. The Generic Implementation Procedure (GIP) for Seismic Verification of Nuclear Plant Equipment did not (at the time of Unit 2 restart or as issued in February 1992) specifically address flexible conduit. As a result, the staff noted in Reference 4 that the BFN flexible conduit program was acceptable pending NRC's resolution of USI A-46.

Since the GIP does not provide specific criteria for the evaluation of flexible conduit, TVA plans to continue to utilize the criteria provided in G-40 for attachments to 10 CFR 50.49 equipment. Additionally, as stated above, TVA will utilize the criteria for theA-46.

evaluation of flexible conduit within the scope of USI

conclusion For BFN Units 1, 2, and 3, TVA plans to utilize the criteria in General Engineering Specification G-40 for the evaluation of flexible conduit for electrical equipment within the scope of 10 CFR 50.49 and USI A-46. This approach will provide a consistent methodology for the evaluation of flexible conduit that envelopes the worst case seismic displacements and thermal movements.

References 1~ TVA letter to NRC, dated October 24, 1988, Browns Ferry Nuclear Plant Nuclear Performance Plan, Revision 2 2 ~ TVA letter to NRC, dated August 18, 1989, Unit 2 Flexible Conduit Browns Ferry Nuclear Plant Program Plan (TAC 62260) 3 ~ TVA letter to NRC, dated March 2, 1990, Browns Ferry Nuclear Plant Unit 2 Response to Request for Additional Information Flexible Conduit Letter Dated December 19, 1989 (TAC 62260) 4 ~ NRC letter to TVA, dated January 23, 1991, NUREG-1232, Volume 3, Supplement 2-Browns Ferry, Unit 2.

5. TVA letter to NRC, dated July 10, 1991, Browns Ferry Nuclear Plant Regulatory Framework for the Restart of Units 1 and 3 NRC letter to TVA, dated March 19, 1993, Generic Letter 87-02, Supplement 1 Response Browns Ferry Nuclear Plant (TAC NOS. M69430, M69431, and M69432)

ENCLOSURE 2 Tennessee Valley Authority Browns Ferry Nuclear Plant (BFN)

Units 1, 2, and 3 Generic Letter 87-02, Supplement l.

Additional Information Regarding Flexible Conduit Summar of Commitment TVA will evaluate the seismic adequacy of flexible conduit for electrical equipment within the scope of Unresolved Safety Issue (USI) A-46 for BFN Units 1, 2, and 3 utilizing the criteria in TVA's General Engineering Specification G-40.

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