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Notice of Availability and Draft Report for Comment, “Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986-2003”

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Nuclear Regulatory Commission (NRC).


Notice of availability of the Office of Nuclear Regulatory Research draft report entitled, “Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986-2003,” and request for public comment.


The Nuclear Regulatory Commission (NRC) is announcing the availability of the Office of Nuclear Regulatory Research draft report entitled, “Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986-2003.”


Comments on this document should be submitted by January 31, 2005. Comments received after that date will be considered to the extent practicable. To ensure efficient and complete comment resolution, comments should include references to the section, page, and line numbers of the document to which the comment applies, if possible.


Members of the public are invited and encouraged to submit written comments to Michael Lesar, Chief Rules and Directives Branch, Office of Administration, Mail Stop T-6D59, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001. Hand-deliver comments attention to Michael Lesar, 11545 Rockville Pike, Rockville, Maryland, between 7:30 a.m. and 4:15 p.m. on Federal workdays. Comments may also be sent electronically

This document is available at the Agencywide Documents Access and Management System (ADAMS) Public Electronic Reading Room on the Internet at the NRC Web site at​reading-rm/​adams.html under Accession No. ML043380322, and at the NRC Public Document Room, 11555 Rockville Pike, Rockville, MD. Please note that on October 25, 2004, the NRC terminated public access to ADAMS and initiated an additional security review of publicly available documents to ensure that potentially sensitive information is removed from the ADAMS database accessible through the NRC's Web site. Interested members of the public may obtain copies of the referenced documents for review and/or copying by contacting the Public Document Room pending resumption of public access to ADAMS. The NRC Public Documents Room is located at NRC Headquarters in Rockville, MD, and can be contacted at (800) 397-4209, (301) 415-4737 or by e-mail to

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Dale Rasmuson, Operating Experience Risk Analysis Branch, Office of Nuclear Regulatory Research, telephone (301) 415-7571, e-mail

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Draft Report Entitled, “Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986-2003”

This report is an update of two previous reports analyzing loss of offsite power (LOOP) events at U.S. commercial nuclear power plants. LOOP data over the period 1986-2003 were collected and analyzed. Frequency and duration estimates for critical and shutdown operations were generated for five categories of LOOPs: plant centered, switchyard centered, grid related, severe weather related, and extreme weather related. Overall, LOOP frequencies during critical operation have decreased significantly in recent years, while LOOP durations have increased. Various additional topics of interest were also addressed. These topics include potential effects of deregulation, seasonal impacts on LOOP frequencies, consequential LOOPs and others. Finally, additional engineering analyses of the LOOP data were presented. This information is needed in probabilistic risk assessment models of U.S. commercial nuclear power plants to accurately model current risk from LOOP and associated station blackout scenarios.

The NRC is seeking public comment in order to receive feedback from the widest range of parties and to ensure that all information relevant to developing this document is available to the NRC staff. This document is issued for comment only and is not intended for interim use. The NRC will review Start Printed Page 75571public comments received on the document, incorporate suggested changes as necessary, and issue the final report for use.

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Dated at Rockville, Maryland, this 13th day of December, 2004.

For the Nuclear Regulatory Commission.

Charles E. Ader,

Director, Division of Risk Analysis and Applications, Office of Nuclear Regulatory Research.

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[FR Doc. 04-27613 Filed 12-16-04; 8:45 am]