ML13330B352
| ML13330B352 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 07/15/1988 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| TAC-67952, NUDOCS 8807220045 | |
| Download: ML13330B352 (2) | |
Text
Southem California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M.O.MEDFORD TELEPHONE MANAGER OF NUCLEAR ENGINEERING (818) 302-1749 AND LICENSING July 15, 1988 U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Operating Basis Earthquake (TAC No. 67952)
San Onofre Nuclear Generating Station Unit 1 By letter dated May 4, 1987, SCE informed the NRC of our intentions related to seismic analyses for an Operating Basis Earthquake (OBE) at San Onofre Unit 1. In a letter dated May 23, 1988, the NRC Staff noted that the statement regarding our intention to perform seismic analyses for only the 0.67g modified Housner response spectrum was in apparent conflict with the design basis of some structures which were designed to the more conservative 0.67g modified Newmark response spectra. The purpose of this letter is to clarify this apparent discrepancy.
The purpose of our May 4, 1987 letter was to identify our intentions for future seismic analyses for those items which were part of the "seismic reviews performed within the context of the SEP."
This clarification was required because the SEP seismic evaluations did not include any reviews or evaluations performed for an OBE. The letter stated that it is our intention to perform seismic analyses for only the 0.67g modified Housner earthquake for all future design modifications which require seismic review. No OBE analyses will be performed.
As indicated in the NRC's May 23, 1988 letter, there were several structures at San Onofre Unit I which were designed to the higher seismic levels consistent with the criteria applied to Units 2 and 3; i.e., the 0.67g modified Newmark response spectra. Specifically, the Sphere Enclosure Building and the Diesel Generator Building were designed and built to these higher spectra. It is noted that these structures were also designed for an OBE.
The statement in our May 4, 1987 letter was only intended to apply to those items which were part of the "seismic reviews performed within the context of the SEP."
It is these SEP seismic evaluations which now establish the seismic design basis for these items.
The Sphere Enclosure Building and Diesel Generator Building (including the Seismic Category A diesel generator, switchgear, batteries, and supporting equipment located within this structure)
PO 72OO45 880715 7
P ADQCK 05000206 PNU
Document Control Desk July 15, 1988 were not part of the SEP seismic reviews and therefore their original seismic design analyses continue to be the seismic design bases for these structures.
This includes not only the modified Newmark response spectra but also the original OBE analyses.
If at any time in the future it becomes necessary or desirable to revise the seismic design bases for the Sphere Enclosure Building or Diesel Generator Building, NRC approval will be requested. At this time such action is not anticipated.
If you have any additional questions regarding this matter, please let me know.
Very truly yours, cc: J. B. Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3