The comprehensive industrial safety standards and codes that exist today have evolved from lessons learned through past experience, research results, and improvements in technological capabilities. The current requirements for fire safety features of commercial nuclear power stations operated in the US are a notable example of this practice. Although fire protection has always been an important design requirement, from the aftermath of a serious fire that occurred in 1975 at the Browns Ferry plant, it was learned that the life safety and property protection concerns of the major fire insurance underwriters may not sufficiently encompass nuclear safety issues, particularly with regard to the potential for fire damage to result in the common mode failure of redundant trains of systems, and components important to the safe shutdown of the reactor. Following its investigations into the Browns Ferry fire, the Nuclear Regulatory Commission (NRC) promulgated guidance documents, which ultimately developed into mandatory regulations, necessary to assure the implementation of a fire protection program that would address nuclear safety concerns. The new criteria that evolved, contain prescriptive design features, as well as personnel and administrative requirements the Commission determined to be necessary to provide a defense-in-depth level of protection against the hazards of fire and its associated effects on safety related equipment. These criteria are primarily contained in Appendix R of Title 10 to the Code of Federal Regulations (10 CFR 50). Since 1983, various members of the Department of Nuclear Energy (DNE) at Brookhaven National Laboratory (BNL) have provided technical assistance to the Nuclear Regulatory Commission (NRC) in support of its evaluations of fire protection features implemented at commercial nuclear power stations operated in the US. This paper presents a discussion of the insights gained by the author during his active participation in this area.

After a 1975 fire at the Browns Ferry nuclear plant in Alabama threatened the unit¿s ability to shut down safely, the Nuclear Regulatory Comm. (NRC) issued prescriptive fire safety rules for commercial nuclear units. However, nuclear units with different designs and different ages have had difficulty meeting these rules and have sought exemptions to them. In 2004, NRC began to encourage the nation¿s 104 nuclear units to transition to a less prescriptive, risk-informed approach that will analyze the fire risks of individual nuclear units. This report examines: (1) the number and causes of fire incidents at nuclear units since 1995; (2) compliance with NRC fire safety regulations; and (3) the transition to the new approach. Includes recommendations. Illustrations.

In response to the 1975 Browns Ferry Nuclear Power Plant fire, the U.S. Nuclear Regulatory Commission (NRC) issued Appendix R to Title 10 of the Code of Federal Regulations Part 50. To support fire protection defense-in-depth 1- or 3-hour electric raceway fire barrier systems (ERFBS) were permitted for use as an acceptable method to protect electrical cables essential to fire protection safe shutdown capability. However, ERFBS were a new approach to fire barrier applications and as the initial installation of the ERFBS began, there was uncertainty regarding the ERFBS performance and definitive test standards for ERFBS qualification. Following review and research efforts, NRC resolved many concerns with ERFBS, including the fire resistance, ampacity derating, and seismic position retention. This report documents the history of various ERFBS and how U.S. commercial nuclear power plants use ERFBS for compliance. This report also documents the current state of the use of ERFBS and evaluates the effectiveness of these barriers in achieving adequate protection for nuclear power plants.

Concern over the risk of fire in commercial nuclear power plants increased after a fire at the Browns Ferry nuclear plant in Alabama in 1975. The fire damaged a relatively small area but adversely affected the functioning of one of the plant's safety systems and the operator's ability to monitor the status of the plant As a result of that fire, the Nuclear Regulatory Commission (NRC) and the nuclear utility industry have taken various actions to help ensure that nuclear plants are safe from the threat of fires and that utilities can safely shut these plants down should a fire occur. NRC's fire protection regulations are intended to (1) prevent fires from starting; (2) rapidly detect, control, and extinguish fires that do occur; and (3) protect a nuclear power plant's structures, systems, and components so that a fire that is not promptly extinguished will not prevent its safe shutdown. According to NRC's regulations, these activities are designed to provide reasonable assurance that any deficiencies occurring in one activity will be backed up by another system so there is no undue risk to public health and safety.

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 shut down 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.

Concern over the risk of fire in commercial nuclear power plants increased after a fire at the Browns Ferry nuclear plant in Alabama in 1975. The fire damaged a relatively small area but adversely affected the functioning of one of the plant's safety systems and the operator's ability to monitor the status of the plant As a result of that fire, the Nuclear Regulatory Commission (NRC) and the nuclear utility industry have taken various actions to help ensure that nuclear plants are safe from the threat of fires and that utilities can safely shut these plants down should a fire occur. NRC's fire protection regulations are intended to (1) prevent fires from starting; (2) rapidly detect, control, and extinguish fires that do occur; and (3) protect a nuclear power plant's structures, systems, and components so that a fire that is not promptly extinguished will not prevent its safe shutdown. According to NRC's regulations, these activities are designed to provide reasonable assurance that any deficiencies occurring in one activity will be backed up by another system so there is no undue risk to public health and safety.