NL-13-084, Reassessment of the Seismic Core Damage Frequency

Reassessment of the Seismic Core Damage Frequency

ML13183A279
Person / Time
Site:	Indian Point
Issue date:	06/26/2013
From:	Ventosa J Entergy Nuclear Northeast
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-13-084
Download: ML13183A279 (3)

Text

Enteray Nuclear Northeast Indian Point Energy Center v-rEnte g 450 Broadway, GSB P.O. Box 249 Buchanan, NY 10511-0249 Tel 914 254 6700 John A. Ventosa Site Vice President Administration NL-13-084 June 26, 2013 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station O-P1-17 Washington, DC 20555-0001

Subject:

Indian Point Nuclear Power Plant Units 2 and 3 Reassessment of the Seismic Core Damage Frequency Docket No. 50-247 and 50-286 License No. DPR-26 and DPR-64

References:

1) New York Power Authority letter to the NRC (IPN-97-132), "Indian Point 3 Nuclear Power Plant - Individual Plant Examination of External Events (IPEEE)", dated September 26, 1997

2) NRC Generic Letter 88-20, Supplement 4, "Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities", dated June 28, 1991

3) NRC "Safety/Risk Assessment Results for Generic Issue (GI) 199, Implications of Updated Probabilistic Hazard Estimates in Central and Eastern United States on Existing Plants", dated September 2, 2010

4) EPRI, "Updated Seismic Hazard Results for Arkansas, Fitzpatrick, Grand Gulf, Indian Point, Pilgrim, River Bend, Vermont Yankee, and Waterford Nuclear Sites", dated August 2010

5) Consolidated Edison letter to the NRC, "Final Response to Generic Letter 88-20, Supplement 4: Submittal of Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities", dated December 6, 1995

Dear Sir or Madam:

Reference 1 provided the results of the Individual Plant Examination of External Events and fulfilled the requirements of Generic Letter (GL) 88-20, Supplement 4 (Reference 2) for Indian Point Unit 3 (IP3). A recent NRC Safety/Risk Assessment of US Nuclear Plant Seismic Core Damage Frequencies (SCDF) based on, among others, the 2008 US Geological Survey (USGS) hazard curves (Reference 3) identified IP3 as a plant with a large calculated SCDF. In this assessment the NRC used plant capacity estimates extracted from Reference 1. Although the NRC estimated SCDF was in the acceptable range, Entergy assembled a Seismic Review Team (SRT) to reassess key IP3 components.

NL-13-084 Docket Nos. 50-247 and 50-286 License Nos. DPR-26 and DPR-64 Page 2 of 3 The plant level High Confidence of a Low Probability of Failure (HCLPF) spectrum peak ground acceleration estimate provided in Reference 1 was calculated in a very conservative manner to be below the Safe Shutdown Earthquake (SSE) peak ground acceleration. When using the resulting capacity estimates in conjunction with the USGS seismic hazard curves, the NRC determined a very conservative SCDF estimate of 1.0E-04 per year, or 1 in 10,000 reactor-years for IP3. Using the improved plant capacities developed by the SRT, a reassessment of the SCDF estimate was performed (Enclosure 1). This resulted in a SCDF of 9.4E-06 per year, or 1 in 106,383 reactor-years using the same USGS hazard curves. With the use of the improved plant capacity and EPRI updated 2010 hazard curves (Reference 4); the SCDF estimate is further reduced to 7.1 E-06 per year (or 1 in 140,845 reactor-years) for IP3. In conclusion the SRT has demonstrated a larger plant-level seismic capacity than that used in the NRC assessment; this would move IP3 from the Continue to Excluded evaluation screening section of Reference 3.

As part of the Fukushima Near-Term Task Force (NTTF) considerations, Entergy reduced the height of the plant stack from Elev. 390 feet to Elevation 202 feet, a 188 feet height reduction, with the new stack configuration resulting in a stack median capacity and HCLPF in excess of the values established to screen out components. The plant stack was a high Indian Point Unit 2 (IP2) risk contributor. In the original IP2 IPEEE submittal (Reference 5), the stack failure contributed 46% to the top Seismic Damage States (SDSs), which in turn contributed 45% to the total seismic core damage frequency of 1.46E-5 per year (prior to upgrading the Component Cooling Water (CCW) Surge Tank hold down bolts). Thus, the stack failure contributed 1.46E-5 x .45 x .46 = 3E-6 per year to the IP2 SCDF. After upgrading the hold down bolts, the CCW contribution was essentially eliminated, giving a revised seismic CDF for IP2 of 1.1E-5 per year. Eliminating the stack as a significant seismic contributor would therefore reduce the seismic core damage frequency reported in the revised IPEEE results to 1.1 E-5 per year - 3E-6 per year = 8.3 x E-6 per year.

There are no new regulatory commitments in this submittal.

If you have any questions or require additional information, please contact Mr. Robert Walpole, Licensing Manager at 914-254-6710.

Sincerely, JAV/rw

Enclosures:

Enclosure 1: Entergy Nuclear Engineering Report No. IP-RPT-1 1-00012, "Reassessment of Indian Point 3 Seismic Core Damage Frequency",

dated April 2011

NL-13-084 Docket Nos. 50-247 and 50-286 License Nos. DPR-26 and DPR-64 Page 3 of 3 cc: NRC Resident Inspector's Office Mr. Douglas Pickett, Senior Project Manager, NRC NRR Mr. Martin Stutzke, Senior Level Advisor, NRC RES Ms. Lisa Regner, Senior Project Manager, NRC NRR Mr. William M. Dean, Regional Administrator, NRC Region 1 Mr. Francis J. Murray Jr., President and CEO, NYSERDA Ms. Bridget Frymire, New York State Dept. of Public Service