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REFRESH: Do Not Fear Your Smoke Detector – It Could Save Your Life

Maureen Conley
Public Affairs Officer

refresh leafWe sometimes get calls from people worried about radiation from smoke detectors in their homes. There are many reasons why the public need not fear these products.

Ionization chamber smoke detectors contain very small amounts of nuclear material. They might use americium-241, radium-226 or nickel-63. These products detect fires early and can save lives. [We explained how smoke detectors work in greater detail in an earlier blog post.]

The Atomic Energy Commission granted the first license to distribute smoke detectors in 1963. These early models were used mainly in factories, public buildings and warehouses. In 1969, the AEC allowed homeowners to use smoke detectors without the need for a license. Their use in homes expanded in the early 1970s. The NRC took over from the AEC in 1975.

Makers and distributors of smoke detectors must get a license from the NRC. They must show that the smoke detector meets our health, safety and labeling requirements.

smokedetectornewMost smoke detectors sold today use 1 microcurie or less of Am-241. They are very safe. A 2001 study found people living in a home with two of these units receive less than 0.002 millirems of radiation dose each year. That is about the dose from space and the earth that an East Coast resident receives in 12 hours. Denver residents receive that dose in about three hours. These doses are part of what is known as “background radiation.”

The radioactive source in the smoke detector is between two layers of metal and sealed inside the ionization chamber. The seal can only be broken by the deliberate use of force, which obviously we discourage. Still, even then it would result in only a small radiation dose. The foil does not break down over time. In a fire, the source would release less than 0.1 percent of its radioactivity. It’s important to understand that none of the sources used in smoke detectors can make anything else radioactive.

What about disposing of smoke detectors? A 1979 analysis looked at the annual dose from normal use and disposal of Am-241 smoke detectors. The study used actual data and assumptions that would overstate the risk. It allowed the NRC to conclude that 10 million unwanted smoke detectors each year can be safely put in the trash.

The 2001 study looked at doses from misuse. It found that a teacher who removed an americium source from a smoke detector and stored it in the classroom could receive 0.009 millirems per year. If the teacher used the source in classroom demonstrations, handling it for 10 hours each year would give less than a 0.001 mrem dose. A person who swallowed the source would receive a 600 mrem dose while it was passing through the body.

I hope this information allays concerns. Unless you remove and swallow the source, your dose from a smoke detector could not be distinguished from what you get throughout your day. And that smoke detector could save your life.

 REFRESH is an occasional series during which we revisit previous blog posts. This originally ran on June 11, 2013. We are rerunning now in honor of Fire Prevention Week. According to the National Fire Protection Association, the week was established to commemorate the Great Chicago Fire, which killed more than 250 people, left 100,000 homeless, destroyed more than 17,400 structures and burned more than 2,000 acres. This year’s theme is Smoke Alarms Save Lives: Test Yours Every Month.

 

Bringing Fire Protection Into Focus

Daniel Frumkin
Senior Fire Protection Engineer
 

The NRC’s fire protection staff and graphic artists have worked together to create a new introduction to our website’s fire protection pages. The illustrations for the “Prevention,” “Suppression” and “Safe Shutdown” tabs highlight the details in each area of fire protection.

Fire Protection infographic_r11Prevention is a combination of training, NRC inspections and procedures to keep potential fire starters such as welding under control. U.S. reactors have improved their prevention efforts over time. In 1985 they reported 22 significant fires. By the late 1990s, even though more reactors were running, the annual reporting numbers had fallen by more than half. In 2011 U.S. plants reported only six significant fires – less than one fire for every 10 operating reactors.

The next layer of protection involves fighting fires if they occur at or near a reactor. Plants’ fire detection systems are a lot like the smoke detectors in your house. When these detectors go off, however, trained firefighters show up with extinguishers and fire hoses. Many key plant areas also have automatic sprinkler systems. Plants also have plenty of firefighting water available and can get that water onto a fire using onsite staff and equipment or fire engines from nearby communities.

Even with all these measures, U.S. plants must still be able to safely shut down if a fire breaks out. The fire protection approach puts barriers between each reactor’s multiple sets of shutdown equipment, so a fire can’t disable all the equipment at once. The power and control cables are separated to make sure that those systems are available to shut the plant down.

Plants also have alternate control stations if fires disrupt the control room’s ability to manage the situation. The plants have emergency power sources, both installed large diesel generators and portable equipment the NRC required after 9/11. These sources help ensure fires outside the reactor can’t deprive systems of the electricity they need.

Check out the new graphics and fire protection web pages. We hope this information makes the topic easier to understand and gives you a better sense of how layers of protection help ensure nuclear plants remain safe from fires.

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.

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