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Why doesn't the U.S. Nuclear Regulatory Commission (NRC) enforce its fire protection regulations, instead of giving out hundreds of exemptions?
The NRC enforces all of its regulations, including those related to fire protection. However, the NRC issued a new fire protection rule in 1981, after about 50 percent of the nation's nuclear power plants had been constructed (or were nearing completion). As a result, the new rule created situations in which licensees were required to modify their already-constructed plants with negligible safety gains. In such situations, after thorough review, the NRC granted exemptions from the fire protection rule, in accordance with the requirements of Title 10, Section 50.12, of the Code of Federal Regulations (10 CFR 50.12), "Specific Exemptions."
Why doesn't the NRC force nuclear power plant licensees to make real long-term changes to their plants in order to provide fire protection, instead of allowing them to use "interim" compensatory measures that seem to be accepted as permanent changes?
In general, the NRC does expect licensees to make real changes to their plants in a timely manner, instead of using "interim" compensatory measures that seem to be permanent. However, in the area of fire safety, the NRC has a unique challenge. This is because licensees' put interim (or temporary) compensatory measures in place because of questions regarding their interpretations of the agency's regulations (rather than because of degraded or failed safety structures, systems, or components). Nonetheless, since that time, the NRC has been performing the necessary research to further clarify and substantiate our regulatory expectations, and has issued a number of related letters to licensees. Consequently, licensees have been taking actions to make real long-term changes to their plants and remove these temporary compensatory measures.
Has there ever been a fire that caused a serious accident at a nuclear power plant?
Since the inception of commercial nuclear power about four decades ago, U.S. nuclear plants have not experienced any accidents caused by fire, which resulted in either a release of radioactivity to the environment or damage to the reactor core. However, in 1975, a fire occurred at the Browns Ferry Nuclear Power Plant. That fire was very serious, because it damaged many systems required to keep the plant safe. In response, in 1981, the NRC issued a new fire protection rule, which imposed stringent fire safety requirements. As a result, since the Browns Ferry fire, the U.S. nuclear industry has not experienced any accidents or serious events attributable to fire. Moreover, since 1995, most (approximately 70 percent) of the fires that have occurred in nuclear power plants have been in the non-safety-related turbine buildings.
How is fire protection provided in nuclear power plants?
Fire protection is provided by three layers of defense, commonly referred to collectively as defense-in-depth. First, plants maintain fire safety by taking measures to minimize the likelihood that fires might occur. Second, plants establish fire protection systems (sprinklers, fire water systems, etc.) to extinguish (and minimize the consequences of) any fires that do occur. Finally, plants rely on redundant safety systems (e.g., installing fire barriers) that are unlikely to be damaged by a single fire.
Why does it take the NRC so long to make licensees change their plants, once an issue (such as the failure of Hemyc fire barriers) has been identified?
The NRC expects licensees to make changes to their plants, in a timely manner, to ensure compliance with the agency's regulations. In imposing time frames within which licensees must modify their plants, the NRC considers the impact of the issues on public safety. With respect to issues like the failure of Hemyc fire barriers, the NRC allowed significant time because the agency needed additional time to research several outstanding questions regarding the capability of the Hemyc barrier. Nonetheless, the NRC determined that fire safety was maintained in the interim by other defenses (e.g., fire suppression systems, fire prevention mechanisms, and redundant safety systems) while the agency continued its research.
Why doesn't the NRC test fire barriers, instead of relying on the word of licensees?
A cornerstone of the NRC's regulatory oversight principle is the expectation that licensees, as opposed to the NRC, bear the responsibility to take all necessary measures to safely operate their plants. Testing the capability of fire barriers is one of a large number of such licensee responsibilities.
Nonetheless, the NRC does not rely on the word of licensees to determine the adequacy of fire barriers. Rather, the NRC reviews the detailed procedures and results of tests performed by licensees, to determine the adequacy of fire barriers. Additionally, on an as needed basis, the NRC may choose to perform confirmatory research to determine the adequacy of research performed by the licensees. The NRC has also commissioned its own fire barrier tests in several instances. In addition, the NRC continues to use advances in the state-of-the-art (e.g., new test methods) to further refine its assessment and understanding of the adequacy of these barriers.
How has the NRC research program supported fire barrier activities?
The NRC's Office of Nuclear Regulatory Research (RES) has supported the agency's fire barrier activities by testing electrical raceway fire barrier systems (ERFBSs). During 2005, RES sponsored confirmatory fire endurance testing at Omega Point Laboratories (OPL) of typical Hemyc 1-hour rated ERFBSs. Sixteen tests were performed on conduits, cable trays, junction boxes, airdrops, and supports protected with Hemyc 1-hour rated ERFBSs. RES has also witnessed several industry-sponsored tests of ERFBSs.
Page Last Reviewed/Updated Monday, June 08, 2020