About the blog: What Things Are Made Of


The United States relies on imports for dozens of commodities in everyday use. Often enough, that reliance is 100%. In this book I aim to provide awareness of the hidden geology and mineralogy behind common things, and to develop an appreciation for the global resource distribution that underpins our society. While concerns about oil import reliance are in the news every day, our needs for other minerals are comparable and are typically unknown even to technologically aware Americans.

Monday, April 5, 2010

Pandemonium rules

If you’re like many Americans, you probably think your home and life represent marginally controlled pandemonium, sometimes verging on delirium. But if you operate a safe home, you may well have some useful pandemonium and not even know it.

Pandemonium and delirium were the working names for radioactive Elements 95 and 96, synthesized in 1944 by Glenn Seaborg, Albert Ghiorso, and Ralph A. James during the Manhattan Project to unleash the power of the atom. Radioactive plutonium decays by emitting beta particles to form Element 95 – now called americium – and Element 96, curium. 

Americium, named for the Americas, occupies a tiny wafer in ionization-type smoke detectors.  A fraction of a gram of radioactive americium metal, rolled with gold to form a thin foil, is sandwiched in a silver-palladium pellet.  Alpha particles emitted by the americium are big and can’t travel very far. They ionize the air in a small chamber, and the ions set up a small current between two plates connected to a battery or electrical source.  When smoke enters the chamber, the ions are attracted to smoke particles rather than the electrical terminals, so the current measured is less than normal.  Once the current falls beneath a pre-set threshold, the smoke alarm goes off, and pandemonium follows.

Most americium production comes from nuclear facilities, where it is a by-product of plutonium reactions. One such facility, Los Alamos National Lab, recently put out a call for commercial partners to work with them in marketing and distributing the element.

Radioactivity in your smoke detector is not dangerous. As noted above, the particles can’t travel beyond the chamber in which they form. It would not be a good idea to eat your smoke detector, however.

Smoke detectors have been suggested by the paranoid as targets for terrorists who would use the americium to make nuclear explosives. There’s only about 0.00000029 gram in each smoke detector, and it takes around 80 kilograms to attain critical mass to explode, so it would take a LOT of smoke detectors – likely, most of those in existence, or more – to make an explosive. Don’t lose any sleep over it.

The photo via Wikipedia is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license

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