ML20127D996

Submits Addl Info in Response to IE Bulletin 79-02 Re Deadweight Pipe Supports,Per 850508 & Subsequent Telcons. Confirmatory Factor of Safety Study Performed for Anchor Bolts.Installation of Mods to Upgrade Sys in Progress

ML20127D996
Person / Time
Site:	Vermont Yankee
Issue date:	05/14/1985
From:	Oliver R YANKEE ATOMIC ELECTRIC CO.
To:	Varela A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
FVY-85-44, IEB-79-02, IEB-79-2, VYM-123-85, NUDOCS 8506240392
Download: ML20127D996 (9)

Text

Tc'epho"c(6 ")*' 8'oo ATOMIC ELECTRIC COMPANY TWX 710 380 7619  :

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s 1671 Worcester Road Framingham, Massachusetts 01701 n1I v

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May 14, 1985 l FVY 85-44 VYM 123/85 --

United States Nuclear Regulatory Commission Region I 631 Park Avenue -

King of Prussia, PA 19406 "

i r Attention: Mr. A. Varella

Dear Mr. Varella:

Pursuant to our telephone conversation on May 8, 1985, we have performed I a confirmatory _ factor _of_ safety _ study for anchor bolts on deadweight pipe supports. However, subsequent telephone conversations both between ourselves and Mr. J. Dure of the NRC and Dr. A. Kadak of Vermont Yankee indicated that there were other areas of concern regarding I&E Bulletin 79-02 requirements. 2 To ensure there is no misunderstanding concerning the status of Vermont 3 Yankee's response to Bulletin 79-02 regarding deadweight supports, the following information is provided. -

I&E Bulletin 79-02 requires that all pipe supports which uso drilled-in anchor bolts on Seismic Class 1 Systems be evaluated to their licensed [FSAR -'

requirements) loads for: 1) adequate installation; and 2) an adequate factor  ;

of safety in the design of these bolts.

Vermont Yankee's FSAR states that the design of Seismic Class 1 piping systems be as follows: _

1) All deadweight (gravity and spring) supports shall be designe.1 to --

limit pipe stresses to 1.5 kai. (The only load that these supports 5

are designed to car:y is deadweight and thermal piping loads, i.e., M no seismic loads.)  ;

2) All seismic supports are designed to resist seismic loads and are h located to limit pipe stresses in an earthquake to code allowables. -

No further discussion of seismic pipe supports will be continued here as _

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they have all been adequately addressed to the NRC's satisfaction during the l April inspection. -

m Responses to NRC auditors regarding the adequate installation of -

deadweight supports at Vermont Yankee included the following:  ;

8506240392 0505142 3 PDR ADOCh 050 -

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Unit'ed States Nuclear Regulatory Commission May 14, 1985 Attention: Mr. Varella Page 2 - VYM 123/85

1) While resolving the IRB 79-14 requirements, all pipe supports were inspected (including deadweight supports) and as-built sketches were provided.

2) If any deadweight support was in need of repair, a Nonconformance Report (NCR) was prepared. (This information, together with NCRs, Work Orders and Close-Out Reports, was available at the plant during the audit and was reviewed.)

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3) Vemont Yankee has an In-Service Inspection (ISI) Program which includes the inspection of. pipe supports (deadweight and seismic) during every outage. Any. discrepancies / deviations would obviously be repaired according to established procedures.

4) Finally, testing of gravity supports is performed every day at Vemont Yankee since they suecassfully fulfill .their (FSAR) design function. (Reference NRC IRB 79-02, Revisi'on 2 "the preferred test method to demonstrate ... is using direct pull'(tension test) equal to or greater than design load".)

This final observation, that gravity supports are continuously performing their design function (deadweight support), was the rationale used to obviate the need for a formal testing / inspection program even though those supports are located on seismic lines. (See July 6, 1979 letter to NBC, WVY 79-76, page 2.)

YAEC has conducted a confirmatory Factor of Safety (FOS) study of

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deadweight supports to ensure complianMfth thei~ design ~re@sfr~ements of.IRB 79-02. The results of this study are attached for your infomation, and the complete study is documented in VY Calculation Number VYC-340. The FOS from our study ranged from 2.03 to 195, with only three supports having a FOS. less

- than 4. This study evaluated 89. randomly selected deadweight supports out of a total of 318, providing an approximately 28% sample. ~This sample, performed on a system basis, provides a 95% statistical confidence level.

As part of the overall 79-02 response, Vermont Yankee decided to voluntarily upgrade the seismic Class 1 piping systems to confom to the -

requirements of Regulatory Guide 1.60/1.61 developed ARS. This Seismic i Roanalysis Program (SRP) has been well documented in correspondence to the NRC and all design engineering work is completed. " Deadweight" supports were modeled in our SRP piping analyses, ~such that any seismic effects wou,ld be

- included in the total load for pipejsupport evaluation.

Wo.are now proceeding to install these modifications to the upgraded

spectrum and analysis. Modification work on accessible supports.will be perfomed during operation. At'. this time,- wo are confident that the completion of'all modifications can be accomplished prior to restart from our.

six month pipe replacement outage scheduled to commence in mid-September 1985.

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United States Nuclear Regulatory Consission May 14, 1985

- Attention: Mr. Varella Page 3 - VYM 123/85 We feel that this letter and attachment. provide all the information necessary to demonstrate that VY has met all the requirements of IEB 79-02; however, should you have any further questions, please do not hesitate to call.

Sincerely,

%&PGa Robert P. Oliver Lecd Mechanical Engineer RP0/sb ,

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