Put this on your radar screens, at least for now

Put this on your radar screens, at least for now:

http://m.boiseweekly.com/boise/feds-still-measuring-radioactivity-in-boise-apartment/Content?oid=3328086

Will Davis / from my iPhone 4S

NS Savannah Association

American Nuclear Society

Fuel Cycle Week

Atomic Power Review

As readers of this list know, if the apartment dweller was breaking apart smoke detectors, the most  likely substance is a small amount of americium-241.  See below US EPA web page on smoke detectors and radiation safety.  If the user had uranium ore, the fissile component would be the usual proportion of U235 more or less, but hardly a dangerous source of radiation.  The dangers come from inhalation and/or ingestion of any heavy metal which confound the body's ability to excrete it.  

The news report does not identify the chemicals, but a guess would be, among others, hydrofluoric acid which can produce nasty skin burns on contact. http://emedicine.medscape.com/article/773304-overview 

Note that the ANS Idaho section has for years worked with Idaho fire departments to distribute smoke detectors for free to homes that need them as a fire prevention measure. 

Since the news report mentions the NRC's comment about licensed radioisotopes, it may be that the user also had a cesium-137 source which is used in nondestructive testing of materials including concrete on construction job sites. http://en.wikipedia.org/wiki/Industrial_radiography  Other possibilities are iridium-192 and cobalt-60.  If the user broke it apart, that could represent a more significant threat of exposure. The reference for accidents involving fatalities from uncontrolled radioisotope testing devices occured in Brazil in 1987 http://en.wikipedia.org/wiki/Goi%C3%A2nia_accident

How much radiation is in smoke detectors?

http://www.epa.gov/radiation/sources/smoke_alarm.html 

The radiation source in an ionization chamber detector is a very small disc, about 3 to 5 millimeters in diameter, weighing about 0.5 gram. It is a composite of americium-241 in a gold matrix. The average activity in a smoke detector source is about one microcurie, 1 millionth of a curie.

Americium emits alpha particles and low energy gamma rays. It has a half-life of about 432 years. The long half-life means that americium decays very slowly, emitting very little radiation. At the end of the 10 year useful life of the smoke detector, it retains essentially all its original activity.

How much radiation exposure will I get from a smoke detector?

As long as the radiation source stays in the detector, exposures would be negligible (less than about 1/100 of a millirem per year), since alpha particles cannot travel very far or penetrate even a single sheet of paper, and the gamma rays emitted by americium are relatively weak. If the source were removed, it would be very easy for a small child to swallow, but even then exposures would be very low because the source would pass through the body fairly rapidly (by contrast, the same amount of americium in a loose powdered form would give a significant dose if swallowed or inhaled). Still, its not a good idea to separate the source from the detector apparatus.

Dan Yurman
dan.yurman@outlook.com
Twitter: @djysrv Blog: NeutronBytes
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