ML090330188
| ML090330188 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/08/2009 |
| From: | Sheron B Office of Nuclear Regulatory Research |
| To: | Leeds E Office of Nuclear Reactor Regulation |
| A. M. Kammerer, RES/DE, 301-251-7695 | |
| Shared Package | |
| ML090330278 | List: |
| References | |
| RIL 09-001 | |
| Download: ML090330188 (3) | |
Text
April 08, 2009 MEMORANDUM TO:
Eric J. Leeds, Director Office of Nuclear Reactor Regulation FROM:
Brian W. Sheron, Director /RA J. Lyons for/
Office of Nuclear Regulatory Research
SUBJECT:
RESEARCH INFORMATION LETTER 09-001: PRELIMINARY DETERMINISTIC ANALYSIS OF SEISMIC HAZARD AT DIABLO CANYON NPP FROM NEWLY IDENTIFIED SHORELINE FAULT On November 14, 2008, the Pacific Gas & Electric (PG&E) Company informed the U.S. Nuclear Regulatory Commission (NRC) that it had identified a zone of seismicity that may indicate a previously unknown fault located offshore of the Diablo Canyon Nuclear Power Plant (DCNPP).
The fault was identified as a result of a collaborative research program between PG&E and the United States Geologic Survey (USGS) that was focused on increasing understanding of the tectonics in the region of the DCNPP. Shortly after its notification to NRC, PG&E provided sets of initial scientific information related to the fault to NRC staff. In one of these documents, PG&E named the fault the Shoreline Fault. Based on the initial information provided by PG&E and the USGS, NRC staff in the Office of Nuclear Regulatory Research (RES) undertook a preliminary independent assessment of the possible implications of the Shoreline Fault to the DCNPP.
This review consists of two parts. First, using the new seismological and tectonic information provided by the USGS and PG&E, coupled with existing information as detailed in earlier reports, NRC staff undertook a preliminary deterministic seismic hazard assessment (enclosed). This assessment included both a best estimate analysis of the Shoreline Fault and a small parametric study. The purpose of the parametric study was to look at the impact of the uncertainty of the parameters and to inform future reviews by NRC staff as ongoing field work progresses. The resulting calculated seismic ground motions were compared to loading levels for which the plant has been previously analyzed, as detailed in the Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2 (NUREG-0675 Supplement No. 34). In the second part of this review, staff identified and discussed a series of ongoing or broader issues related to the seismicity of the DCNPP area that NRC staff may want to consider in the future.
CONTACT: Annie Kammerer, RES/DE 301-251-7695
E. Leeds The results of the preliminary assessment indicate that the best-estimate 84th percentile deterministic seismic loading levels predicted for a maximum magnitude earthquake on the Shoreline Fault are below those for which the plant was previously analyzed in the Diablo Canyon Long-Term Seismic Program (LTSP) for all frequencies of interest. The parametric study indicates that the ground motions at the highest end of the range of the most important parameters will be approximately at the design values for a range of frequencies of interest.
The shear wave velocity profile (a property of the DCNPP site) had the most significant impact.
As noted, this work is based on the limited preliminary information currently available to NRC staff. Additional information should be reviewed as it is obtained by the USGS and PG&E as a result of ongoing field work.
RES has coordinated this analysis with Michael Markley from the Plant Licensing Branch IV, Division of Operating Reactor Licensing.
Enclosure:
As stated
ML090330278 OFFICE RES/DE/SGSEB RES/DE/SGSEB Tech Editor SUNSI Review RES/DE/SGSEB D: RES/DE D: RES NAME A. Kammerer (J. Ake for)
J. Ake J. Zabel (via email)
A. Kammerer R. Hogan M. Case B. Sheron (J. Lyons for)
DATE 02/04/09 02/04/09 01/27/09 04/08/09 02/18/09 02/06/09 04/08/09