Few events altered nuclear power regulation as much as the Browns Ferry Unit 1 fire. In March 1975, thousands of electrical cables burned for about seven and a half hours, disabling all of Unit 1’s and many of Unit 2’s emergency core cooling systems. Only creative action by plant operators prevented reactor damage, and only a resort to water hoses rather than portable CO2 fire extinguishers quenched the flames.
The NRC was just two months old when the fire started, and it enacted sweeping reforms to enhance reactor safety from fires, including fire detection, prevention and suppression.
Browns Ferry was so momentous that any discussion of fire history before it often receives little attention and is mistakenly dismissed in a few sentences: The NRC’s predecessor, the Atomic Energy Commission, didn’t consider fire a nuclear safety issue. It erred in deferring to non-nuclear standards set by property insurance companies and engineering associations. Such deference was inadequate because insurance standards were designed to limit property damage rather than prevent a reactor accident.
In fact, the fire can’t be so easily blamed on AEC inattention. The agency did believe fire was a reactor safety issue, and it insisted on special fire protection designs that proved inadequate at Browns Ferry. Its key error, then, wasn’t in deferring to non-nuclear fire insurance experts; it sometimes didn’t defer enough. Most egregiously, nuclear regulators rejected expert recommendations on fire suppression systems believing that nuclear safety considerations demanded alternative designs.
By the late 1960s, fire protection experts favored water as a fire suppressant. Tests and experience showed water was the most desirable fire suppressant even in areas with electrical equipment because of its ability to rapidly smother and cool a growing fire. Businesses used water suppression in diverse applications such as computer factories and electric cable rooms in steel mills. Even AEC weapons plants added water to supplement their CO2-based systems. Fire insurance associations recommended water-based fire suppression systems for civilian nuclear power plants.
AEC regulators and the industry disagreed. Having limited nuclear-specific data on fires, they operated from the perspective that electricity and water didn’t mix. They feared water would cause short circuits and disable backup reactor safety systems. With AEC encouragement, new plants commonly installed fixed CO2 fire extinguishing systems in electrical areas, as was done in Browns Ferry’s damaged cable spreading room. In addition, the cable spreading room was not equipped with fire hoses and water supply piping called standpipes.
David Notley, the NRC’s first fire safety expert, noted the ironic result of the AEC’s ignorance on fire suppression. Believing that nuclear power was a special exception to standard industrial practice, regulators dismissed non-nuclear experience that might have improved reactor safety. Had water been used early in the 1975 fire, the duration of the fire, the damage to the plant and the challenge to safely shutting down the plant would have been significantly reduced.
The AEC did treat fire as a reactor safety threat, but it pursued ill-informed solutions. Chastened by Browns Ferry, the NRC expanded its fire regulations and a launched a fire research program that have measurably improved plant safety.
U.S. NRC Blog 
It makes no sense? Hmm, actually there are some places that water has been the source of electricity – it’s very good conductor so i think this is the reason why also that it shouldn’t be mix together if it is not necessary.
Mike — I was around then too, in my very first days at NRC. You are absolutely right. The local fire department wanted to use water, but the plant was resisting. As far as they knew, you didn’t put water on an electrical fire. The local Athens, Alabama fire chief finally said that he didn’t care what the plant thought, he was going in alone with a fire hose. At that point the plant gave in and started using water, and the fire was soon out. The chief was the hero of the day. He saved the place. I wonder if he ever got the recognition he deserved. If I knew his name at the time, I’ve forgotten.
By the way, some readers may not know the origin of the fire: that a worker was using a candle to test the adequacy of the seals around the cables going between the cable spreading room and the reactor building. There was, intentionally, negative pressure, so he was looking for any movement of the flame to see if there was air flow, which would indicate leakage. The air flow was strong enough that the negative pressure sucked in the candle flame, and the resulting fire burned through control cables.
It’s been 38+ years, so if my memory is faulty, someone please correct me.
— Peter Crane, NRC retiree
I’m glad the agency and plants responded to the evolution in fire suppression. What I don’t seem to see are considerations for realistic amounts of flood or pooled water that may result from, among other things, fire suppression activities. Electrical switchgear in nuclear plants seem fairly vulnerable (my observation). The most recent example being the Arkansas Nuclear One accident where I understand switchgear was lost to a broken fire main.
Are most nuclear plants’ switchgear on the lower level(s) for a particular reason – like seismic – or is that just ‘the way they do it’? I can’t imagine drains and sumps alone would be adequate for keeping switching equipment above water for any length of time. The easy answer would seem to be ‘put the switches on the second floor somewhere’. Maybe I’m missing something.
Thanks for your interest, Mike. You are right about the role of the fire department in extinguishing the blaze. The operators, however, were very creative in finding alternative ways of keeping the reactor core covered with water, even though the emergency core cooling system for Unit 1 was disabled.
Tom Wellock
I was around then, and my memory is that it wasn’t “creative action by plant operators ” that worked. The local fire department had wanted to do that from the time they arrived on the scene, but the plant (following thier regulations) resisted it until it was clear that they were losing the battle. Once water spray was authorized, the fire was out in a matter of minutes. But it was the local fire department, not plant operators, who had the successful plan. And it wasn’t creative, it was the way the fire department training directed for fighting large cable fires. I could be wrong, but that is the way I remember it.
If electricity and water didn’t mix: But Countries make electricity with water, what is the reason?