ML18114A784
| ML18114A784 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 05/01/1979 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Colman M VIRGINIA, COMMONWEALTH OF |
| Shared Package | |
| ML18114A786 | List: |
| References | |
| NUDOCS 7907120408 | |
| Download: ML18114A784 (2) | |
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May 1, 1979 The i4onorable Marshall Coleman Attorney G;:meral Commonweal th of Virginia Supr~me Court Building 1101 *E;ast qroad Street Richll]Ond, Virg-inia 23219
Dear Mr. Attorney General:
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>~ 7 t-652--i Your letter of March 20, 1979 to Chairman Hendrie of the Nuclear Regulatory" Commission has been referred to me for response.
In your letter you requested that the pipe stress reanalyses for Surry Power Station receive a separate and expeditious_ review by our staff.
We have already taken certain steps toward this end *.
Following the Nuclear Regulatory Commission order of March 13, 1979 to shut down the five nuclear* power plants,, including the two-unit Surry Power Station, independent review teams for each affected power plant were established within the staff of the Office of Nuclear Reactor-Regulation.
In particular, the staff review team for the Surry facility is dedicated to prompt review and analysis of submittals by the Virginia Electric and Power Company (VEPCO) in support of lifting the Surry shutdown order. The Surry review team has met with the licensee at the site of the Surry facility and has travelled to the Stone and Webster offices in Boston to re-view the preliminary reanalysis results. The Surry review team shares no members with review teams for the other affected power p 1 ants and remains ready_ to promptly review VEPCO I s reana lyses.
It should be pointed out that at this time VEPCO is reanalyzing the impacted piping systems of Surry Unit No. 1 only. Surry Unit No. 2 has been shutdown*for steam generator replacement and.stress analyses of the Unit No. 2 piping systems will follow the current reanalysis effort for Unit No. 1. The staff review team for the Surry Power Station will remain available for prompt review of the *vEPCO sub-mittals for both Unit No. land Unit No. 2.
In response to your concerns regarding site-specific considerations for seismic events at the Surry Power Station, I offer the following comments.
As you noted, the foundation conditions at the Surry and Beaver Valley sites do differ. The Beaver Valley facility is fou!1ded on about 50 feet of sands and gravel which overlay rock.
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e Mr. Marshall Coleman May 1~ 1979 Surry facility is founded on about 1300 feet of sediments which overlay rock. These conditions, including the characteristics of overburden damping and amplification of vibrations from bedrock to the surface, were taken into account in establi~hing the seismic
- design basis for each of the plants. _
Insofar as local seismicity is concerned, the 1300 feet of over-burden at Surry site masks the basement rock so that faulting cannot be identified in the area. This is true for most of the eastern United States.- Since the tectonic structures which give rise to earthquakes cannot be identified and localized, our practice is to assume that earthquakes at least as severe as regional historical earthquak~s could occur anywhere in the region.
In addition, in establishing the seismic design bases for a'nucl~ar power plant, we take into account the impacts on that. plant of more distant earthquakes. For example, the Charleston, South Carolina earthquake of 1886 was felt in the region of the Surry site.
VEPCO is considering us.ing an advanced-analysis method which takes into account soil-structure interactions to determine Surry plant response motion due to seismic events. This method was used by VEPCO for the design of the now-cancelled Surry Units Nos. 3 and 4.
However, it was not used in the original design analysis for Surry Unit Nos. l and 2.
We have maintained continuing dialogue with VEPCO regarding the use of this technique for Unit Nos. land 2, and VEPCO is aware of our requirements.in this matter.
While we continue to meet with VEPCO and Stone and Webster represent-atives to discuss preliminary results of their reanalyses, we are at this time awaiting submittal of these results by VEPCO for staff evaluation.
Following the staff evaluation of the VEPCO submittals for each reactor unit, we will be in a position to reconsider whether continued suspension of operations at that unit remains necessary or appropriate.
The staff's
. recommendation concerning possible resumption of operation wi 11 be considered by the Corrunission before a final decision is made.
If you have any additional questions, please contact my office.
ELDoih'X'.
.s.' tf L.eW 4-;J.b-79 Sincerely, Qtginal Signed By
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) fk>ger S. Boyd.
/ "fvHarold R. Denton, Director
- i/ Office of Nuclear Reactor Regulation
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