ML19319C008
| ML19319C008 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/27/1977 |
| From: | Roe L TOLEDO EDISON CO. |
| To: | Rusche B Office of Nuclear Reactor Regulation |
| References | |
| 196, NUDOCS 8001300742 | |
| Download: ML19319C008 (3) | |
Text
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NRC r Dr.M 195 u.S. NUCLE AR REGULATORY F* MISSION DOCKET NUMi ER
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DATE F CUMENT TO:,Mr B'C Ruscjte Toledo Edison g 1-27-77 Toledo, Ohio p-L E roe
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ATE RECEIVED 1-31-77 M ffiER O NOTORIZ E D PROP INPUT FORM NUMBER OF COPIES RECEsVED BUNC LASSIFIE D
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DESCRIPTION ENCLOSU R E Ltr re ACRS ler dtd 1-14-77.....trans the Report Of Seismic Design Reviiv....ded 1-27-7 1 following:
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Davis Besse #1 ACKNOWLEDGED SAFETY FOR ACTION /INFORMATION ryt1 Tun 2-1-77 Guf ASSIGNED AD:
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TOLEDO January 27, 1977
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Mr. Bernard C. Rusche, Director Office of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D. C.
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Dear Mr. Rusche:
By letter dated January 14, 1977, the Advisory Committee on Reactor Safeguards ( ACRS) reported the results of their review at its 201st meeting, of the application by The Toledo Edison Company and The Cleveland Electric Illuminating Company for a license to operate the Davis-Besse Nuclear Power Station, Unit 1.
In this letter, the ACRS commented on the seismic design bases of the Davis-Besse, Unit 1, with the following wording:
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"The stru:tures and components of Davis-Besse, Unit 1,
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s were desigced for a Safe Shutdown Earthquake (SSE) g 0
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acceleration of 0.15g at the foundation level. Because
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seismic design bases, the Committee believes that an H
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acceleration of 0.20g would be more appropriate for j
the SSE acceleration at a site such as this in the Cen-tral Stable Region. The Applicant presented the results TJ x/
of preliminary calculations concerning the safety margins k
'e of the plant for an SSE acceleration of 0.20g.
The Committee recommends that the NRC Staf f review this aspect of the design in detail and assure itself that signifi-cant margins exist in all systems required to accomplish safe shutdown of the reactor and continued shutdown heat removal, in the event of an SSE at this higher level.
The Committee believes that such an evaluation need not delay the start of operation of Davis-Besse, Unit 1.
The Committee wishes to be kept informed."
During the course of the 201st ACRS meeting, the NRC staf f presented lengthy discussion concerning their current thinking on the appropriate SSE seismic criteria for a site such as the Davis-Besse Station site in the Central Stable Region and stated that the staff position now tends to consider an SSE acceleration value of 0.20g at the ground surface in free field as the appropriate conservative design criteria, continued...
THE TOLEDO EDISON COMPANY EDISON PLAZA 3CO MADISDN AVENUE TOLEDO. OHIO 43652
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, We feel that the seismic design criteria for the Davis-Besse No. 1 unit, which is presented in detail in the Final Safety Analysis Report (FSAR) and which includes an SSE acceleration of 0.15g at the foundation level, a modified Helena earthquake time history and other factors, is appropriate and conservative. However, in view of the NRC staff discussion at the 201st ACRS meeting and the comments in the ACRS letter of January 14, 1977, we have conducted a detailed analysis of the effect, of applying an acceleration of 0.20g at the Davis-Besse site ground surface in free field, on the structures and components of the Davis-Besse Station, Unit 1.
This detailed analysis has used the deconvolution analysis proce-dures, response spectra, damping values and other factors and pro-cedures contained in the current NRC Regulatory Guides and Standard Review Plans.
The report of this detailed analysis is attached for your use in reviewing this matter and shows that in every area of design for structures, systems and components of the Davis-Besse Unit 1, the seismic design criteria presented in the FSAR results in a design that is conservative and is in most cases more conservative than if an acceleration of 0.20g had been used under current NRC Regu-latory Guides.
As a result, we conclude that significant margin exists in all systems required to accomplish safe shutdown of the reactor and continued shutdown heat removal, in the event of an SSE of 0.20g.
Yours very truly, f
1 dJ Lowell E. Roe Vice President Facilities Development Attachment