ML20236S859
| ML20236S859 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 11/23/1987 |
| From: | Papanic G YANKEE ATOMIC ELECTRIC CO. |
| To: | Fairtile M NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-CR-0098, RTR-NUREG-CR-98, TASK-03-06, TASK-3-6, TASK-RR FYR-87-118, NUDOCS 8711300144 | |
| Download: ML20236S859 (2) | |
Text
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t Telephone (617) 872-8100 TWX 710380 7619 YANKEE ATOMIC ELECTRIC COMPANY x y db 1671 Worcester Road, Framingham, Massachusetts 01701
- ~YAN KEE November 23, 1987 FYR 87-118 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Attention:
Mr. Morton Fairtile, Project Manager Project Directorate I-3 Division of Reactor Projects I/II
References:
(a) License No. DPR-3 (Docket No. 50-29)
(b) Letter, YAEC to USNRC, dated August 31, 1987, " Clarification of Staff Position, SEP Topic III-6, Safety Evaluation Report" (c) Document No. DC-1, " Seismic Reevaluation and Retrofit Criteria", submitted via Letter, YAEC to USNRC, dated April 30, 1987 (d) 'NUREG/CR-0098, " Development of criteria for Seismic Review of Selected Nuclear Power Plants" (e) Letter, USNRC to YAEC, dated July 16, 1987, "NUREG-0825, Section 4.11 Seismic Design Considerations"
Subject:
Seismic Evaluation of Piping - Seismic Anchor Motions
Dear Sir:
In Reference (b), YAEC requested your clarification on the use of seismic anchor motions (SAMs) in the evaluation of Safe Shutdown System (SSS) piping at Yankee Nuclear Power Station.
Based on our recent telephone conversations the following methodology for treating SAMs has been developed.
Upon receipt of your concurrence with this methodology, Yankee will revise the Seismic Reevaluation and Retrofit Criteria (DC-1) [ Reference (c)], and proceed with our piping evaluation commitments accordingly.
In the evaluation of SSS piping, 100% of the loads due to SAMs caused by the Yankee Composite Spectrum (YCS) will be used in combination with thermal expansion and thermal anchor motions in ANSI B31.1 equations 13 and 14.
Pipe stress for these equations will be limited to the allowables stated in Sections 8.3.l(c) and 8.3.l(d) of DC-1.
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SAMs due to building displacements will be developed using the damping ratios recommended by NUREG/CH-0098 [ Reference (d)]. A damping ratio of 3% will be used for the Vapor Container. The Vapor Container is a combination welded steel, bolted steel, and concrete structure. Stress levels in the Vapor Container due to YCS loads are. expected to be equal to or less than 1/2 yield stress. Therefore, 3% of critical damping is consistent with the recommendations of Reference (d). A damping ratio of 5% will'be used for the Reactor Support Structure. The Reactor Support Structure is a reinforced concrete structure and stress levels are expected to be over 1/2 yield stress under YCS loading. Therefore, a damping ratio of 5% is consistent with the recommendations of Reference (d).
Seismic e.nchor motions caused by piping movement will be developed using the appropriate damping ratios recommended in Reference (d).
All other aspects of the piping evaluation will be in accordance with the SEP Topic III-6 Safety Evaluation [ Reference (e)]. Likewise, all of our previously stated commitments to use the NRC site specific spectra for the remainder of these piping analyses remain in force.
We believe that the information contained herein is sufficient to resolve this issue.
It is our understanding that a letter will be forthcoming from the staff in response to this letter and to our clarification letter [ Reference (b)]. Your earliest attention to this matter will be appreciated. Please advise if we can be of further assistance.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY a _.d +
G. Pa nic, Jr Senior Project Engineer Licensing GF/gbc cc: USNRC - Region I USNRC Resident Inspector - YNPS
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