Sparking New Conversations on Reactor Fire Safety

Scott Burnell
Public Affairs Officer
 

ocoThis week, the NRC took enforcement action against Duke Energy Carolinas LLC for failing to meet an important deadline in improving its fire safety program at the Oconee nuclear plant in South Carolina. In a Confirmatory Order, the agency set a new timeline for Duke to make the necessary changes, including interim milestones that will each result in safety enhancements as Oconee completes the process.

Fire safety is an important and evergreen topic when discussing the safety of U.S. nuclear power plants. NRC regulations include two approaches to fire protection and the issue is easily misunderstood or misrepresented, so it benefits from a refresher on everything that fits under the “fire protection” umbrella.

Let’s start with the bottom line — every U.S. nuclear power plant meets the relevant NRC requirements for protecting its reactor from fire hazards. Even if a plant has an “exemption” from a part of the NRC’s least-flexible fire protection approach, called Appendix R, that plant can still shut down safely in case of a fire.

Appendix R is effectively a one-size-fits-all approach for plants that are in fact custom-built projects. Newer plants tend to be built closer to Appendix R requirements, while older plants are more likely to have difficulty meeting specific mandates.

When it was issued, the NRC knew that the appendix wouldn’t apply to every part of every plant, so plants would apply for exemptions where Appendix R didn’t make sense. The NRC has a well-established process for reviewing exemption requests, which must have solid technical support in order to be approved. When the federal court covering southern New York upheld the agency’s process, the ruling even noted the NRC rejects exemption requests if they’re not justified.

You can see an everyday example of exemptions when you take an eye exam to get a driver’s license. Since not everyone’s vision falls in the acceptable range, regulations allow people to wear glasses or contacts. This can be considered an “exemption” from uncorrected vision requirements that’s still acceptable and compliant with the law.

Even if a plant has Appendix R exemptions, the NRC inspects the plant’s overall fire protection program to ensure it maintains safety.

Exemptions are sometimes confused with separate “compensatory measures” plants will put in place for specific issues until permanent solutions are in place. Exemptions are permanent in any case, and as we noted, plants must justify their requests with solid data. Compensatory measures, while they can be acceptable for extended periods of time, are not a basis for exemptions. As with exemptions, however, the NRC only accepts compensatory measures if they will provide acceptable fire protection capabilities.

Compensatory measures also have an everyday example on the roads — when a traffic light is malfunctioning, a police officer normally directs traffic at the intersection. Instead of the city closing the intersection until the traffic lights are fixed, officials compensate for the degraded traffic light in an acceptable way.

Bottom line: The NRC will not accept any fix for an exemption or a compensatory measure unless it’s safe.

Oconee is switching to the second approach, an updated fire protection standard called NFPA 805. You can think of this standard as a way for plants to customize their fire protection based on risk information. For example, the risk of fire in an otherwise empty room with concrete walls with electrical cable trays is less than for the same room with a barrel of lubricating oil stored in a corner. Under this new standard, plants use advanced fire analysis tools to determine where their fire protection resources are most needed. Oconee was one of two plants testing the transition as pilot projects.

julydropquoteThe NRC is currently evaluating applications from several plants to switch to the NFPA 805 standard. When plants transition to NFPA 805, their analyses can uncover new fire protection issues, and the NRC ensures those issues are appropriately handled as they’re identified. All new issues are accounted for with compensatory measures, and will either be fixed by a change to the plant or evaluated as part of the transition to NFPA 805. Since switching to the new standard is optional, the NRC uses its “enforcement discretion” in deciding whether to take action against plants that find new issues during the switch. That decision is made after the issues are identified and compensatory measures are put in place.

There is no question that a fire at a nuclear plant can be serious business. The NRC takes it very seriously. In reading stories about the NRC’s fire safety program, it is important to remember that not all fires carry the same risk, and the risk depends on the size and location of a fire. Also, each plant has its own fire department and trained local firefighters to call on for additional help.

The NRC’s work on fire protection, as with all its efforts in overseeing U.S. nuclear power plants, is meeting its goal — ensuring the public remains safe.

Before the Browns Ferry Fire: Antiquated Notions That Electricity and Water Didn’t Mix

Tom Wellock
NRC Historian
 
Browns Ferry Fire: Historial Photo
Browns Ferry Fire: Historical Photo

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.

firemanDavid 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.

%d bloggers like this: