ML20093A372
| ML20093A372 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 06/27/1984 |
| From: | Hunter D VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| FVY-84-67, IEB-79-02, IEB-79-14, IEB-79-2, NUDOCS 8407100399 | |
| Download: ML20093A372 (3) | |
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VERMONT YANKEE NUCLEAR POWER CORPORATION RD 5, Box 169, Ferry Road, Brattleboro, VT 05301
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'k June 27, 1984 ENGINEERING OFFICE 1671 WORCESTER ROAD FVY 84-67 FRAMINGHAM, MASSACHUSETTS 01701 TELEPHONE 611-872-8100 United States Nuclear Regulatory Commission Office of Inspection and Enforcement Region 1 631 Park Avenuo King of Prussia, PA 19406 Attention:
Dr. Thomas E. Murley, Regional Administrator
References:
(a) Licence No. DPR-28 (Docket No. 50-271)
(b) Letter, VYNPC to USNRC, WVY 80-106, dated July 25, 1980 (c) Letter, VYNPC to USNRC, FVY 83-16, dated March 1, 1983 (d) Letter, USNRC to All Licensees, T&E Bulletin 79-02, dated March 8, 1979 (e) Letter, USNRC to A'.1 Licensees, T&E Bull %in 79-14, dated July 2, 1979
Subject:
Seismic Piping Reanalysis Program
Dear Sir:
By letter, dated March 1, 1983 [ Reference (c)], we informed you of the status of the Vermont Yankee Seismic Piping Reanalysis Program.
This program was initiated by us in response to the concerns expressed in I&E Bulletins 79-02 and 79-14 [ References (d) and (e)]. The purpose of this letter is to update you with respect to the status of our program.
BACKGROUND This Seismic Piping Roanalysis Program was outlined to you by letter, dated July 25, 1980 [Raference (b and has been underway since then. Our Bulletin 79-02 ef fort began by testing concrete expansion anchor installations on supports designated seirmic by the original A/E, Ebasco. This led to the replacement of all existing Phillips Self-Drilling Anchors on these *,upports with Hilti-Kwik Bolts. This was completed in early 1980 and provided a partial resolution of the Bulletin. A temporary resolution to address the flexibility effects on base plate and anchor bolt design stresses was made by demonstrating that a factor of safety of at least two existed. The Bulletin 79-14 offort was started in late 1979, nd discrepancies between the Ebasco piping model and the fleid conditions were evaluated and resolved within the context of the original design methodologies. This work was completed *n the Spring of 1980, and the Bulletin requirements waro considered to be completely resolved at that time. 8407100399 840627 PDR ADOCK 05000271 /\\\\ G PDR y\\ 0
D United States Nuclear Regulatory Commission June 27, 1984 Attention: Dr. Thomas E. Murley Page 2 As part of the reanalysis effort, the original soismic design was reviewed and upgraded to current regulatory requirements. The original maximum hypothetical earthquake (SSg) zero period accaleration of 0.14 g has been retained, however, the ground response spectrum has been revised to conform to Regulatory Guide 1.60. SSE floor response spectra have been generated in conformance with Regulatory Guides 1.61 and 1.122, using new building models which have been verified against as-built data. These enhancements add conservatism to the original ground response spectrum for the following reasons: 1. The Regulatory Guide 1.60 response spectra shape has a broader frequency content and higher peak acceleration. 2. Explicit consideration of building vertical amplification is included. (The original design assumed that vertical acceleration was constant at 2/3 of the horizontal ground acceleration values.) We have evaluated these changes to the piping and pipe support design requirements and have concluded that they will produce a noce conservativo result than would be obtained from the original ground response spectra. Since there were differonces in the modeling and analysis methodologies used - in the original design and current-day practice, it was also decided to upgrade design calculations in parallel with the evaluation of base plate finxibility undertaken to address Bulletin 79-02. Dynamic analysis for piping is performed using the response spectrum method, and the approximations obtained from the so-called Robinson Fix are no longer employed. The upgraded analysis will result in enhancements to the seismic piping design for the following reasons: 1. As-built branch piping has been incorporated into the main line model where required to produce more accurate results; 2. Seismic qualification of branch line piping included in Item 1 will be verified; and, j; 3. Piping model response includes consideration of supports which were [' originally designed for dead weight forces only. i The scope of the seismic piping list is identified in the Vermont Yankee Final Safety Analysis Report (FSAR). i Minor changes have been made to the list to include additions based on Regulatory Guide 1.29 requirements and changes in seismic boundaries based on l system functionality consistent with the FSAR. However, since the FSAR is our licensed design basis, the seismic piping list is consistent with it and not necessarily with Regulatory Guide 1.29 in its entirety. Dynamic piping analyses are being performed using developed response spectra and evaluated to the B31.1 Power Piping Code, using SSE allowable stresses as required by the FSAR. l l ~ _ _.. _ _ _, -. _ _. _. _, _ _ _. -. _. _
i United States Uuclear Regulatory Commission June 27, 1984 Attention: Dr. Thomas E. Murley Page 3 Pipe support analyses are based on current engineering approaches, including consideration of base plate flexibility and effects caused by friction-induced loadings. Pipe support acceptance criteria are as specified in the FSAR. In summation, we feel that this modified program, using modern analysis methods, will resolve I&E Bulletin 79-02 and provides an enhancement to the base design of safety-related seismic piping. SCHEDULE The engineering activities for the Seismic Piping Reanalysis Program are scheduled such that all piping analyses and pipe support designs related to the original seismic supports with base plates will be completed by the end of 1984. The remaining pipe support design and analysis to close out our Seismic Piping Reanalysis Program will be completed during 1985. We are installing some hardware modifications on Bulletin 79-02 scope base plates in areas which are inaccessible while operating, during our present refueling outage. We will be working on base plate modifications for other supports during operation as designs are completed in 1984 and 1985. We expect to complete all hardware modifications prior to startup from the recirculation pipe replacement outage, which is scheduled to begin in September 1985. We trust that the scope and schedule for these activities are deemed acceptable; however, should you have any questions regarding this ratter, please contact us. Very truly yours. VERM0 YANKEE NUCLEAR POWER CORPORATION tsb onald Hunter Vice President RO/ gad ,}}