ML20247F224
| ML20247F224 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/30/1989 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8904030367 | |
| Download: ML20247F224 (4) | |
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4 TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 37401 SN 157B Lookout Place MAR 301989 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Hashington, D.C.
20555 Gentlemen:
In the 'atter of
)
Docket Nos. 50-327 M
Tennessee Valley Authority
)
50-328 SEQUOYAH NUCLEAR PLANT (SQN) UNITS 1 AND 2 - NRC INSPECTION REPORT NOS.
50-327/88-12 AND 50-328/88 RESPONSE TO UNRESOLVED ITEM (URI) 88-12-03 Enclosed is TVA's response to URI 88-12-03, "DBA ZPA Effects," which was transmitted by Steven D. Richardson's June 24, 1988 letter to S. A. White.
The information provided in this response is supplemental to TVA's response provided in my March 2, 1988 letter to NRC on open inspection issues.
If you have any questions, please telephone E. T. Knuettel at (615) 843-7215.
Very truly yours, TENNESSEE VALLEY AUTHORITY t
R.
ridley, M nager Nuclear Lice sing and Regulatory Affairs Enclosure cc: See page 2 1
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8904030367 890330 i DR ADOCK 050 7-O
'l I An Equal opportunity Employer L-
U.S. Nuclear Regulatory Commission Enclosure cc (Enclosure):
Ms. S. C. Black, Assistant Director for Projects j
TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Ms. L. J. Watson, Acting Assistant Director for Inspection Programs
- TVA Projects Division
- U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta Georgia, 30323 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379
ENCLOSURE UNRESOLVED ITEM (URI) 88-12-03 TITLE: DBA ZPA EFFECTS ITEM DESCRIPTION:
"The staff review of Employee Concerns Element Report 221.2(B) identified that TVA had not followed the recommendations in civil engineering report CEB 80-58 for evaluating ZPA effects on the piping for the containment DBA analysis.
TVA addressed this concern for restart by evaluating a sample of five piping systems attached to the containment to demonstrate that restart design criteria were not exceeded.
TVA should complete the evaluation of the remaining systems attached to the containment to demonstrate these systems meet the FSAR allowable limits."
RESPONSE
It is TVA's position that the Bechtel North American Power Corporation design basis accident (DBA)/zero period acceleration (ZPA) study informally reviewed by NRC during the February 1988 inspection demonstrates the acceptability of the remaining systems attached to the steel containment vessel (SCV), and no further evaluations are required.
This position is based on the fact that the sample of five piping analysis problems selected for the study represents a worst-case sample that bounds the problem.
The selection of four of the five piping analysis problems for investigation was based on:
- Piping analyses subjected to higher ZPA accelerations
- Piping analyses with representative configurations of piping systems both inside and outside the SCV
- Piping analyses that encompass a variety of restraint configurat. ions near the SCV, which is the influence zone of DBA inertia effects The maximum ZPA values were identified by reviewing the north-south and east-west DBA response spectra curvet.
Because of the relatively small vertical ZPA component values, the vertical directional effects were assumed negligible in the selection process.
The piping isometrics for those analysis problems that are subjected to the larger ZPA values were then reviewed. A variety of piping layout and support configurations (tied back to the SCV), representing piping both inside and outside the SCV, was selected to represent a wide range of boundary conditions and piping layout.
The fifth piping analysis problem that was selected was a piping analysis problem that was previously selected and reviewec' by Gilbert Commonwealth, Incorporated, as part of the SQN unit 2 Rigorous Analysis Review Program.
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- 6 The Bechte.1 study demonstrates that the piping, supports, and SCV penetrations included itithin the selected problems are still acceptable when the DBA/ZPA effects are considered.
Furthermore, because the problems selected in the sample contained " worst-case attributes," there is a high degree'of confidence l
that the other piping systems not included in the sample would likewise be acceptable. TVA considers this evaluation to be representative of the remaining systems attached to the SCV, and no further evaluations are required j
or scheduled.
TVA is currently required to evaluate / analyze DBA/ZPA effects by DC-SQN-V-13.3, which states, "any subsequent reanalysis of the entire problem shall include the missing mass effects."
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