ML13330B120
| ML13330B120 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/10/1986 |
| From: | Medford M Southern California Edison Co |
| To: | Lear G Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML13330B121 | List: |
| References | |
| TASK-03-02, TASK-03-04.A, TASK-3-2, TASK-3-4.A, TASK-RR NUDOCS 8610160167 | |
| Download: ML13330B120 (2) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M.O.MEDFORD TELEPHONE MANAGER OF NUCLEAR ENGINEERING October 10 1986 (818 302-1749 AND LICENSING Director, Office of Nuclear Reactor Regulation Attention: G. E. Lear, Director PWR Project Directorate No. 1 Division of PWR Licensing-A U. S. Nuclear Regulatory Commission Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-206 SEP Topics:
111-2 Wind and Tornado Loadings III-4.A Tornado Missiles San Onofre Nuclear Generating Station Unit 1 As part of the Systematic Evaluation Program, SCE committed to performing a site specific evaluation to identify the design basis tornado event. By letter dated September 17, 1984 the report, "Tornado Hazard Analysis Relating to SEP Topic 111-2 at San Onofre Unit 1," was transmitted to the NRC. This report identified the tornado hazard range of 59 mph to 183 mph with respective occurrence probabilities of 10-4 per year to 10-7 per year for San Onofre Unit 1. This information along with the scope of modifications required at each windspeed was used to determine the design basis tornado for San Onofre Unit 1 by a cost/safety benefit methodology. Provided as an enclosure to this letter is the report, "Tornado Resistance Design Review for San Onofre Nuclear Generating Station Unit 1," dated August 1986.
The enclosed report identifies the design basis tornado as the 103 mph windspeed with a probability of occurrence of 10-5 per year. The modifications associated with this windspeed total approximately $4.7 million dollars. It is indicated in the report that the next highest tornado windspeed with a probability of 10-per year would require modifications in the range of $19 million dollars. This substantial increase in cost did not include a corresponding increase in safety benefit. The modifications in the enclosed report, recommended for the 10-5 probability windspeed event, will be scheduled in accordance with the SONGS 1 ILS following NRC review and approval of the design basis tornado windspeed.
8610160167 861010 PDR ADOCK 05000206 P
PDR LiA
Mr. G. E. Lear 2 -
October 10, 1986 It should be noted that the modifications discussed in the enclosed report are of a preliminary nature. Consequently, the final design may result in some slight deviations from the identified modifications. However, a design basis capability corresponding to the 10-5 tornado will be maintained.
If you have any questions regarding this matter, please let me know.
Very truly yours, Enclosure cc:
R. Dudley, NRC/NRR San Onofre Unit 1 Project Manager F. R. Huey, NRC Senior Resident Inspector, Units 1, 2 and 3
- 3. B. Martin, NRC Region V, Regional Administrator