ML20154S069

Responds to Questions Re Seismic Amplified Response Spectra Generation (IE Bulletin 79-14) & Pipe & Pipe Support Seismic Calculation Methods (IE Bulletin 79-02)

ML20154S069
Person / Time
Site:	Browns Ferry
Issue date:	09/28/1988
From:	Gridley R TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
IEB-79-02, IEB-79-14, IEB-79-2, TAC-00015, TAC-00016, TAC-00017, TAC-15, TAC-16, TAC-17, NUDOCS 8810040429
Download: ML20154S069 (4)

Text

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'. TENNESSEE VALLEY AUTHORITY CH ATTANOOSA. Tf!NNESSEE 37401 SN 1578 Lookout Place SEP 281988 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

L In the Matter of ) Docket Nos. 50-259 Tennessee Valley Authority ) 50-260

) 50-296 BR0HNS FERRY NUCLEAR PLANT (BFN) - SEISMIC AMPLIFIED RESPONSE SPECTRA AND OFFICE OF INSPECTION AND ENFORCEHENT BULLETIN (IEB) 79-14 AND 79-02 PIPE AND PIPE SUPPORTS SEISMIC CALCULATION METHODS The purpose of this letter is to respond to questions expressed by the staff relative to seismic amplified response spectra (ARS) generation and IEB 79-14 and 79-02 pipe and pipe support calculation methods.

The enclosure contains TVA's response to these questions and reflects TVA's understanding of the conclusions reached during the meeting between TVA and NRC on September 8 and 9, 1988.

ARS questions were initially raised during an August 15 to 19, 1988 NRC audit of BFN seismic spectra. 79-14/02 questions were noted in a June 30, 1988 meeting between TVA and NRC.

Discussion of programmatir. 79-14/02 milestones, commitments, and schedules will be addressed in a separate submittal.

If you have any questions, please telephone Patrick Carter, BFN, at (205) 729-2689.

Very truly yours,

TENNESSEE VALLEY AUTHORITY U I'M R. Gridley, Managerr'k, V

l Nuclear I-icensing and Regulatory Affairs l

Enclosure cc: See page 2 (l es10040429 000?28 DR ADOCK0500g9 ((

l An Equal opportenity Employer L

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, U.S. Nuclear Regulatory Commission SEP18 E88 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, Suite 2900 Atlanta, Georgia 30323 Browns Ferry Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637 Athens, Alabama 35611 1

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..- BROHNS FERRY NUCLEAR PLANT SEISMIC AMPLIFIED RESPONSE SPECTRA AND 79-14/02 PIPE AND PIPE SUPPORT SEISMIC CALCULATION METHODS Garing an August M to 19, 1988 audit of BFN seismic spectra generation, the NRC staff questioned the original structural dynamic model and some of the u s w ptioni, used to gen'erate the horizontal and vertical seismic amplified response (ARS) for the reactor building. In a June 30, 1988 meeting between TVA and NRC, the NRC staff als9 questioned the pipe and pipe support soismic calculation methods being used for Browns Ferry Inspection and Enforcement Bulletin (IEB) 79-14/02 program. The following is TVA's response to the staff's questions related to seismic ARS items and nine items of piping seismic design methodology (from the above referenced meeting).

A. Seismic Amplified Response Spectra

1. TVA has developed a new artificial ground time history whose spectra closely enveloped the viginal licensed ground design spectra for all damping values required for the building and subsystem analyses. This artificial ground motion time history is in compilance with the NRC safety evaluation dated January 29, 1988, "Alternate Input for Seismic System Analysis -

Artificial Time ht story," and is consistent with Standard Review Plan (SRP) 3.7.1, Enveloping Requirements.

2. New horizontal ARS will be geneiated b& sed on the new time history and existing building structural models except where model refinement is required to address the staff's questions.

For example, a multistick model will be used to generate new spectra inside the drywell in lieu of the one stick model used

previously.

3. New vertical ARS will be generated for each Class I building using two-thirds of the new artificial ground time history and a model similar to the existing horizontal seismic model unless the building can be shown to be rigid (greater than 20 Hertz) in the vertical direction.

4. The new ARS will be broadened 2 10 percent for rock-founded structures and i 15 percent for soil-founded structures.

5. The design basis ARS will be compared to the new ARS.

l Differences between the design basis ARS and new ARS will be evaluated and action taken if required.

6. The design basis ARS as justified by the evaluation process l described in item A.5 or the new ARS may be used for new work.

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B. 79-14/02 Pipe and pipe Support Seismic Calculation Methods

1. Vertical Seismic Input - vertical ARS w111 be used (See A.3 above).

J. Seismic Damping Value - 1/2 percent critical damping will be used for the OBE case and the OBE (SSE) case.

3. Peak Broadening of the Seismic spectra - the new broadened ARS will be used (see item A.4 above). The peak shifting method may be used in lieu of the broadened spectra.

4. Seismic Anchor Motions - seismic anchor motions will be considered.

5. Elevation of ARS Input - either enveloped spectra or independent support motion will be used.

6. Zero Period Acceleration (ZPA) Effects - ZPA effects wlil be ,

considered.

7. Combination of Modes - the square root of the sem of squares method will be used for the combination of modes except that closely spaced modes will be combined by the absolute summation <

method (10 percent grouping method).

8. Combination of Directions - the spatial combination of the effects of one horizontal (X or Z direction) and the vertical (Y direction) will be combined by the absolute summation method. The maximum results of the two by absolute summation; either (X, Y) or (Y, Z) will be used.

9. Rigid Range o 20 Hertz is considered to be the lower bound of the rigid range.

As an alternative, the time history method may be used in lieu of the response spectrum method. When the time history method is used, it will be applied in a manner consistent with the commitments above.

The methodologies presented for seismic ampilfied response spectra generation and 79-14/02 pipe and pipe support seismic analyses are consistent with the Browns Ferry Final Safety Analysis Report (FSAR).

This enclosure more specifically defines the FSAR analysis methods.

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