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Knowledge Base for Post-Fire Safe-Shutdown Analysis, Availability of Draft NUREG 1778

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Nuclear Regulatory Commission.

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Notice of availability for public comment.


The Nuclear Regulatory Commission is announcing the completion and availability of Draft NUREG-1778, “Knowledge Base for Post-Fire Safe-Shutdown Analysis,” January, 2004. The NRC is seeking comment from interested parties on the clarity and utility of the draft NUREG. The NRC will consider comments received in its final issue of NUREG-1778.


Comment period expires March 29, 2004. Comments submitted after this date will be considered if it is practical to do so, but assurance of consideration cannot be given except for comments received on or before this date.


Draft NUREG-1778 is available for inspection and copying for a fee at the NRC Public Document Room, 11555 Rockville Pike, Rockville, Maryland. As of January 30, 2004, you may also electronically access NUREG-series publications and other NRC records at NRC's Public Electronic reading Room at​reading-rm.html.

Submit written comments to the Chief, Rules Review and Directive Branch, Mail Stop: T6-D59 U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.

A free single copy of Draft NUREG-1778, to the extent of supply, may be requested by writing to Office of the Chief Information Officer, Reproduction and Distribution Services Section, U.S. Nuclear Regulatory Commission, Printing and Graphics Branch, Washington, DC 20555-0001 facsimile: 301-415-2289; e-mail:

Some publications in NUREG-series that are posted at NRC's Web site address​NRC/​NUREGS/​indexnum.html are updated regularly and may differ from the last printed version.

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Mark H. Salley, Office of Nuclear Reactor Regulation, Mail Stop O11 A11, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001. E-mail Telephone: 301-415-2840 FAX: 301-415-2300.

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As a result of a major fire that occurred at the Browns Ferry Nuclear Power Plant in 1975, the U.S. Nuclear Regulatory Commission (NRC) significantly revised its regulatory framework to enhance fire protection programs (FPPs) at operating nuclear power plants (NPPs). The revised criteria used in this framework had three main objectives to (1) prevent significant fires, (2) ensure the capability to shutdown the reactor and maintain it in a safe-shutdown condition, and (3) minimize radioactive releases to the environment in the event of a significant fire.

Recent Sandia National Laboratories (SNL) studies have shown that the revised criteria are beneficial to safety. Plant design changes required by the new regulatory framework have been effective in preventing a recurrence of a fire event of the severity experienced at Browns Ferry. In addition, according to a 1989 study performed by SNL plant modifications made in response to the new requirements have reduced the core damage frequencies (CDFs) at some plants by a factor of 10.

The NRC's regulatory framework provides several options for ensuring that structures, systems, and components (SSCs) important to safe shutdown are adequately protected from the effects of fire. Because of the potentially unacceptable consequences that an unmitigated fire may have on plant safety, each operating plant must perform a documented evaluation to demonstrate that, in the event a fire were to initiate and continue to burn (in spite of prevention and mitigation features), the performance of essential shutdown functions will be preserved and radioactive releases to the environment will be minimized. The document that describes this evaluation process and its results is commonly referred to as a “safe-shutdown analysis” (SSA).

Fire protection for NPPs is a complex subject. The purpose of this document is to facilitate understanding of the regulatory framework of the Fire Protection Program by compiling the related knowledge into a single document. This document assumes that the reader has had little or no involvement in the development and/or implementation of fire protection criteria, post-fire safe-shutdown analysis, or any of its related engineering disciplines. The criteria and assumptions described in this document are based on the NRC's regulatory framework for fire protection, as it was in place at the time of this writing. This document only clarifies existing criteria. This document does not contain any new or different staff positions and does not impose any new requirements. The knowledge base documented in this NUREG-series report must be used within the context of the licensing basis of each individual plant and with due consideration for the NRC's Backfit rule, as specified in Title 10, Section 50.109, Code of Federal Regulations (10 CFR 50.109).

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Date at Rockville, Maryland, this 20 day of January, 2004.

For the Nuclear Regulatory Commission.

John N. Hannon,

Chief, Plant Systems Branch, Division of Systems Safety and Analysis, Office of Nuclear Reactor Regulation.

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[FR Doc. 04-1899 Filed 1-28-04; 8:45 am]