ML13309A256
| ML13309A256 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/25/1992 |
| From: | Rosenblum R SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TASK-03-02, TASK-03-04.A, TASK-3-2, TASK-3-4.A, TASK-RR NUDOCS 9206290252 | |
| Download: ML13309A256 (2) | |
Text
Southern Calfornia Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 R. M. ROSENBLUM June 25, 1992 TELEPHONE MANAGER OF (714) 454-4505 NUCLEAR REGULATORY AFFAIRS U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
SUBJECT:
Docket No. 50-206 SEP Topics:
111-2, Wind and Tornado Loadings III-4.A, Tornado Missiles Modifications to 480V Room San Onofre Nuclear Generation Station, Unit 1 (SONGS 1)
REFERENCES:
- 1. Letter, M. 0. Medford, SCE to G. E. Lear, NRC, "SEP Topics 111-2, Wind and Tornado Loadings; III-4.A, Tornado Missiles, San Onofre Nuclear Generating Station Unit 1," October 10, 1986
- 2. Letter, F. R. Nandy, SCE to NRC, "SEP Topics 111-2, Wind and Tornado Loadings; III-4.A, Tornado Missiles, San Onofre Nuclear Generating Station Unit 1," August 31, 1990 This letter provides the cost estimate to upgrade the 480V room masonry walls at SONGS 1 to meet tornado hazard criteria. The potential failure of the walls was found to be the major tornado risk contributor to the core damage frequency at SONGS 1. We committed to provide this estimate to the NRC during a site visit by the NRC staff on December 18 and 19, 1991.
The cost estimates to resolve the tornado issue had been submitted initially to the NRC by letter dated October 10, 1986 (Reference 1), and were subsequently revised by letter dated August 31, 1990 (Reference 2).
- However, the estimated $10-$53 million cost was based on a deterministic evaluation, and could not be directly related to the Tornado Probabilistic Risk Assessment.
The total costs for the SONGS 1 480V room tornado modification are estimated to be approximately $1.1 million. The modification is intended to prevent the failure of the 480V room south and west reinforced masonry walls due to tornado wind loading. The design change will consist of additional steel framing to support electric raceways independently of the 480V room walls, and steel plates to shield the walls from the high tornado winds.
9206290252 920625 PDR ADOCK 05000206 P
Document Control Desk
-2 As noted earlier, the purpose of this transmittal is to satisfy our commitment to the NRC to provide cost estimates for the 480V room modifications. As the NRC is aware, SONGS 1 is expected to be permanently shutdown following Cycle 11 operation. Accordingly, this transmittal is considered to complete our action for the Cycle 12 Full-Term Operating License Item No. 2, "Tornado Modifications," as identified in the NRC's January 2, 1990 Order. The NRC safety review of this item and issuance of a safety evaluation will close out the tornado hazard issue for SONGS 1.
If you have any question regarding this matter, or desire additional information, please contact me.
Very truly yours, cc:
J. B. Martin, Regional Administrator, NRC Region V George Kalman, NRC Senior Project Manager, San Onofre Unit 1 J. 0. Bradfute, NRC Project Manager, San Onofre Unit 1 C. W. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2&3