ML20137D911

Responds to Parr 780327 Request for Addl Info Re Calculation of Seismic Design Margins.Info Requested Unavailable & Response Could Not Be Provided Before Nov 1978.Effort of Scope Requested Believed Unwarranted

ML20137D911
Person / Time
Site:	North Anna, 05000000
Issue date:	05/05/1978
From:	Brown S VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Case E, Parr O Office of Nuclear Reactor Regulation
Shared Package
ML20136A555	List: IA-85-363, Submits Topics for Discussion at Commission 830708 Meeting W/Acrs.Topics Include Seismic Design Margins ML20136A550 ML20136E176 ML20136E418 ML20136E423 ML20136E621 ML20136E929 ML20136F618 ML20137D336 ML20137D440 ML20137D455 ML20137D472 ML20137D477 ML20137D494 ML20137D511 ML20137D540 ML20137D551 ML20137D557 ML20137D562 ML20137D570 ML20137D576 ML20137D583 ML20137D588 ML20137D598 ML20137D601 ML20137D609 ML20137D616 ML20137D621 ML20137D627 ML20137D635 ML20137D641 ML20137D646 ML20137D652 ML20137D659 ML20137D665 ML20137D670 ML20137D849 ML20137D867 ML20137D881 ML20137D911 ML20137D924 ML20137D951 ML20137D978 ML20137E016 ML20137E026 ML20137E044 ML20137E056 ML20137E075 ML20137E098 ML20137E113 ... further results
References
FOIA-85-363 188-032778, 188-32778, NUDOCS 8508230086
Download: ML20137D911 (2)

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i RICHEOND, Vl AGINI A 23261 VIRGINI A ELECTRIC AND FOWER ColdPA.

1 May 5, 1978 l i

T Mr. Edson G. Case, Acting Director Serial No. 188/032778 Office of Nuclear Reactor Regulation LQA/ESG:jdt

- Attn: Mr. O. D. Parr, Chief Light Water Reactors Branch No. 3 Docket Nos. 50-338 Division of Project Management 50-339 U. S. Nuclear Regulatory Commission Washington, D. C. 20555 C; ca

Dear Mr. Case:

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We have received and carefully reviewed Mr. Parr's;htter oft March 27,1978, which forwarded Staff Coments 3.76, 3.77, 3 dif_and 3.79. b These comments requested extensive additional information cori2phing Die M calculation of seismic design margins at the North Anna Power Sation, A.5 Units 1 and 2. g m

As we indicated to the Staff during their site visit on February 24, 1978, and in subsequent telephone conversations, the informa-

! tion sought in these requests is not presently available. Based on our review of the scope of the work required, we estimate that responding to these requests would require over 2000 man-hours of effort expended over a six month period. We would therefore not be able to provide you with our response any earlier than November,1978.

Most of the required time would be needed for developing stress profiles to indicate the five highest stress points and the five most highly stressed ~ pipe supports for the piping systems identified in Comment 3.78.

In order to determine the highest stress points on a piping system, a complete review of all the available detailed pipe stress analyses is re-quired. Some piping systems consist of more than one type of piping material, and include different operating conditions. Consequently, different portions of a system may have different pipe stress allowables.

In addition, the highest combined stress point may not have the highest seismic stress. Thus, the ratio of seismic stress to allowable stress for combined loading may not be highest at the point with the highest combined stress. The five most highly stressed points in a particular piping system will therefore not be necessarily indicative of the points with the smallest seismic margin.

Each system has a large number of pipe supports, and the effort required to determine the five most highly stressed system supports may be even more involved than that of selecting the five most highly stressed hg82

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Mr. Edson G. Case SHEET NO. 2 VIRGINIA ELECTRIC AND POWER COMPANY TO points in the piping. A pipe support consists of several different elements, e.g. frame members, base plates and anchor bolts, which would require review along with the pipe / support interface. It would therefore be an extremely lengthy task to detemine the pipe supports with the highest stress within a system, considering the number of supports involved. For example, in the Chemical and Volume Control System alone, there are on the order of 3000 pipe supports.

A similar problem would exist in attempting to respond to the Staff's other requests. For example, in order to determine the HVAC ductwork support components which have the lowest seismic marg' ins, as requested in Comment 3.76, an extensive review of a large number of duct supports would be required. There are about 400 seismic duct supports in the auxiliary building, for example.

The manhour estimate and discussion above does not include consideration of piping which was analyzed by the simplified analysis method defined in Section 3.7.3.1.3.7 of the FSAR. This piping includes

• large portions of the auxiliary feedwater, component cooling water, chemical and volume control, and instrument air systems. In these cases, the detailed stress analyses required by the Staff comments were not previously perfomed, in accordance with ASME code requirements.

All Seismic . Class I components at the North Anna Power Station are verified to have stresses within the allowables specified by the appropriate codes, by methods described in the FSAR, and considering the specified seismic design bases for the site. A new effort of the scope requested, in order to quantify seismic margins, does not appear to be warranted. Development of this information would require an extremely large expenditure of time and engineering effort, the extent of which may not have been anticipated by the Staff. Accordingly, we ask that the expected useful-ness of the requested infomation be re-evaluated, in light of the schedule and costs involved. In the interim, we have not authorized our architect-engf-neer to proceed with the review effort described above.

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g- 1 San C'.' Brown, Jr.

Vice President-Power Station Engineering and Construction l

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