ML20114B572

Provides Updated Status of Seismic Reanalysis Program & Results of Recent Evaluation of Support Loads on Structural members.Safety-related Piping Dynamically Analyzed Using Amplified Response Spectre Curves,Per Reg Guide 1.60

ML20114B572
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	01/23/1985
From:	Capstick R VERMONT YANKEE NUCLEAR POWER CORP.
To:	Vassallo D Office of Nuclear Reactor Regulation
References
RTR-REGGD-01.060, RTR-REGGD-1.060 NUDOCS 8501290332
Download: ML20114B572 (3)

Text

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VERMONT YANKEE NUCLEAR POWER CORPORATION w

. RD 5, Box 169, Ferry Road Brattleboro, VT 05301 REPLY TO:

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y ENGINEERING OFFICE 1671 WORCESTER RO AD

• FRAMINGHAM, MASSACHUSETTS 01701

{ TELEPHONE 6t 7-872 4100 5 *

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w i January 23, 1985 F

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E United States Nuclear Regulatory Commission P washington, D. C. 20555 5

g Attention: Office of Nuclear Reactor Regulation

- Mr. Domenic B. Vassallo, Chief k Operating Reactors Branch No. 2 pg Division of Licensing 4

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References:

(a) License No. DPR-28 (Docket No. 50-271) m (b) Letter, VYNPC to USNRC, FVY 84-67, dated June 27, 1984 .

Subject:

Vermont Yankee Seismic Reanalysis Program - Status and Results g of Evaluation of Support Loads on Structural Members g

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Dear Sir:

The purpose of this letter is to provide an updated status of our Seismic y Reanalysis Program (SRP) and the results of our recent evaluation of support P loads on structural members. As part of the Seismic Reanrslysis Program, our P safety-related piping was dynamically analyzed using amplified response

spectra curves generated from Regulatory Guide 1.60. As we informed you in L

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our letter of June 27, 1984 [ Reference (b)], it was expected that the SRP g' would produce more conservative results than those obtained from the original FSAR ground response spectra.

• We have completed the pipe stress analysis and as a result have y determined that additional supports would be required to accommodate the higher loads. In addition, we are currently completing the evaluation of the

[ existing supports and have determined that modifications would also be p

required. We are also designing supports to the upgraded condition, consistent with the schedule outlined in Reference (b).

I As part of the design process, an evaluation of support loads on structural members (embedded base plates and building structural steel) was also made. During this check, we determined that several of the structural members were overstressed to the new loads generated by the Regulatory Guide 1.60 amplified spectra. In checking further, we determined that the original loads used by the plant designor (Ebasco) were in some cases actually higher than the SRP loads. Ebasco was then asked to document how they evaluated the original pipe support loads on structural members.

7 8501290332 850123 PDR ADOCK 05000271 t) O p PDR

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United States Nuclear Regulatory Commission January 23, 1985 g Attention: Mr. Domenic B. Vassallo Page 2 xd i

The original design of the plant was based on a pseudo-static seismic L analysis of the safety-related piping to obtain pipe stresses and pipe support '.

loads. However, piping resonance and building amplification were not -

, initially considered, but prior to obtaining the operating license, Ebasco 3 applied very conservative static " bump factors", the so-called " Robinson Fix" j factors, to pipe support loads. Supports were modified and extra supports were added to compensate for the " Robinson Fix" loads. j In our recent review, no records could be founo showing an evaluation by -

Ebasco of the structural members for " Robinson Fix" loads (although the -

l " Robinson Fix" loads on pipe supports were evaluated). As a result, Vermont -

y Yankee initiated an investigation which included a plant walkdown and a review

[ of existing loading conditions. Three " worst" cases involving five support d i loads and associated structural members were chosen for detailed 3

[ investigation. These supports and structural components are: i E 2 Pipe Support Structure q r J E RSW - H168 W10x21 Steel Beam =

[ RSW - H167. H171, H173 W10x21 Steel Beam j

F RSW - H224 Embedded Plate -

i P During several working sessions between YAEC and Ebasco engineets, it was -

r agreed that the investigation would use the as-built conditio.cc, the pipe d E operating and Safe Shutdown Earthquake reaction loads and criteriu consistent g trith VYNP FSAR, including the " Robinson Fix" loads.

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b The identified building structural components were first analyzad under ,

the effect of the " Robinson Fix" pipe support loads. Under the static '

E application of these very conservative loads, several points of building structures associated with two of the three supports were overstressed. A 7 further evaluation was then performed by Ebasco to determine the ability of

$ the structural members to withstand the reaction loads determined by a dynamic r piping analysis using the as-built piping and pipe support configuration and s 7 the Amplified Response Spectra of the Vermont Yankee FSAR. This evaluation 1 found that building structural members comply with the acceptance criteria of .

L Vermont Yankee FSAR Section 12.2.1. Vermont Yankee subsequently evaluated an  ?

additional four structural members to Regulatory Guide 1.60 loads and j F

determined them to be adequate. Thus our evaluation, which encompassed 20% of .

structural beams and 25% of embedded base plates that have pipe supports T attached, confirmed their structural adequacy. _

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Based on the results of these evaluations, we concluded that the structural members meet FSAR criteria. Moreover, as part of our Reanalysis s Program, Vermont Yankee intends to continue to upgrade the piping systems and associated supports and structures to the amplified Regulatory Guide 1.60

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- United States Nuclscr R:gulctcry Comicsicn Jtnunry 23, 1985 Attention: Mr. Domenic B. Vassallo Page 3 spectra consistent with current design practices. Should you have any questions or require additional information in this matter, please contact us.

Very trtly yours, VERMONT YANKEE NUCLEAR POWER CORPORATICM Robert W. Capstick Licensing Engineer RWC/aja A