ML050600298
| ML050600298 | |
| Person / Time | |
|---|---|
| Issue date: | 03/03/2005 |
| From: | Mayfield M Division of Engineering |
| To: | Heymer A Nuclear Energy Institute |
| Munson C, NRR/DE/EMEB, 415-2529 | |
| Shared Package | |
| ML050600284 | List: |
| References | |
| RG-1.165, TAC MC5403, Y20040253 | |
| Download: ML050600298 (3) | |
Text
March 3, 2005 Mr. Adrian Heymer Director, New Plant Development Nuclear Generating Division Nuclear Energy Institute 1776 I Street, NW Suite 400 Washington, D.C. 20006-3708
SUBJECT:
MODIFIED APPROACH TO REGULATORY GUIDE 1.165 TO DETERMINE SAFE SHUTDOWN EARTHQUAKE (SSE) SPECTRUM
Dear Mr. Heymer:
This letter transmits the Nuclear Regulatory Commission (NRC) staffs response to your letter dated November 30, 2004, which outlined your concerns with the initial use of Regulatory Guide 1.165 (RG 1.165), Identification and Characterization of Seismic Sources and Determination of Safe Shutdown Earthquake Ground Motion, to determine the SSE ground motion spectrum.
This letter also transmits the staffs response to the February 9, 2005, public meeting between the NRC staff and NEI to further discuss these concerns as well as other seismic issues related to the siting of new nuclear power plants.
The primary focus in both your letter to the staff and at our February 9, 2005, meeting is the long term stability of the hazard-based approach described in RG 1.165 to determine the appropriate SSE spectrum ground motion level. The staff is aware that developments in geology and seismology, such as new ground motion attenuation models or revised estimates of earthquake magnitude and recurrence, necessitate periodic updating of the reference probability level recommended by RG 1.165. Since the overall reference probability level is dependent on the individual reference probabilities of 29 nuclear power plant sites, the staff recognizes that updating the overall reference probability would require significant resources.
As a solution to this problem, your letter recommends the use of a new performance-based approach, which is described in ASCE Standard 43-05, Seismic Design Criteria for Structures, Systems, and Components in Nuclear Facilities and Commentary. The NRC staff is currently reviewing the performance-based approach since it is the approach selected by two of the three Early Site Permit (ESP) applicants.
At our February 9, 2005, meeting you also described your plans to address other seismic siting issues such as the treatment of large high frequency ground motions, a lower bound magnitude cutoff, and bounding ground motion (aleatory) uncertainty. Although the NRR staff may not be able to fully participate in the resolution of each of these issues due to limited resources, we are interested in monitoring their development and participating as much as possible.
A. Heymer The Office of Nuclear Regulatory Research has the agency lead for the revision of RG 1.165, and is the proper NRC organization to interface closely with NEI/EPRI in this regard. The NRC has formed an NRC Technical Advisory Group to examine these issues and their proposed resolution. Dr. Andrew Murphy is the chairman of the Seismic Issues Technical Advisory Group. Please contact Dr. Murphy at 301-415-6011 to further discuss these issues, as well as the schedule and resources for further staff participation.
Sincerely,
/RA/
Michael Mayfield, Director Division of Engineering Office of Nuclear Reactor Regulation
A. Heymer The Office of Nuclear Regulatory Research has the agency lead for the revision of RG 1.165, and is the proper NRC organization to interface closely with NEI/EPRI in this regard. The NRC has formed an NRC Technical Advisory Group to examine these issues and their proposed resolution. Dr. Andrew Murphy is the chairman of the Seismic Issues Technical Advisory Group. Please contact Dr. Murphy at 301-415-6011 to further discuss these issues, as well as the schedule and resources for further staff participation.
Sincerely, Michael E. Mayfield, Director Division of Engineering Office of Nuclear Reactor Regulation DISTRIBUTION:
EMEB RF CGrimes GBagchi YLi AMurphy THsia RBarrett SAli HGraves VThomas JBirmingham RidsNRRWPCMail: Y020040253 Package ML050600284 Incoming ML043510389 Memo ML050600298 OFFICE EMEB:DE EMEB:DE EMEB:DE ERAB:DET:RES DE:D NAME CMunson KManoly EImbro MEvans MMayfield DATE 2/ 29 /2005 2/25 /2005 2/25/2005 2/28/2005 3/ 03 /2005