Re: Where can I find some everyday items that are radioactive?

Patrick:

     There are a number of everyday items that should be radioactive 
enough to be detected by your school's Geiger Counter.  Keep in mind that 
some detectors are not very efficient at detecting gamma rays.

     I do use the lantern mantles containing thorium for field check 
sources for some of my instruments.  They work well, but you are correct - 
the Coleman mantles no longer contain thorium.  There are still a few 
foreign brands of lantern mantle that do contain thorium.  The best way to 
check would be to test them in the store with your Geiger Counter before 
purchasing them.

     Another easily obtainable radioactive item is the potassium chloride 
salt substitute (for sodium chloride) which can be obtained at almost any 
grocery store.  The potassium in the salt substitute contains a small 
percentage of the isotope K-40 whichemits a fairly high-energy gamma ray.  
However, because K-40 has a very long half-life, the number of K-40 decays 
per second is not extrememly large in a normal container of salt 
substitute.  If you have a fairly efficient Geiger Counter, you should be 
able to measure a doubling or tripling of background radioactivity with 
the instrument close to the KI salts.

     Another item that should cause a detectable response in your 
instrument is a smoke detector containing americium-241.  In the US, these 
usually contain about 1 microcurie of Am-241, and should give a pretty 
good response when the instrument is brought close to the surface of the 
detector.  It is probably not a good idea to attempt to disassemble the 
detector, since the 60 keV (60,000 electron volts of energy) gamma rays 
should be easily detected at the outer surface of the smoke detector.  
With a 400-year half-life, the Am-241 source should still be easily 
detected on any smoke detector, no matter how old, and will be for several 
hundred more years.

     Also usable to make a dramatic demonstration are the bright orange 
plates marketed under the brand of Fiesta Ware.  The orange coloring is 
actually uranium oxide, and your detector should be able to detect both 
gamma rays and beta particles.  The newer Fiesta plates are not as bright 
orange and do not contain uranium, but antique shops and flea markets 
frequently have these plates.

     Another possibiblty for your demonstration (and I would recommend 
that you try this out before actually making a demonstration) is to wipe 
the screen of a television set with a small piece of filter paper after 
the set has been on for several hours.  If the room has a moderate to high 
level of radon, you should be able to remove a fairly good amount of 
alpha, beta and gamma radioactivity which will decay on your filter paper 
with a relatively short half-life of about 30 minutes.  There are a lot of 
physical parameters that might affect the results of this "wipe test," so 
do not be surprised if the results are variable, but it can make a 
dramatic demo if you count the filter paper before and after wiping the 
screen of the television.

     I hope this helps.  Let me know how your project goes, and if there 
is anything else I can do, please feel free to email me at gelsg@aol.com.  
Good luck, Patrick.

Gerald L. Gels, CHP
gelsg@aol.com