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Re: Radioactive SparkPlugs



I just purchased (3) 0.1 microCurie sources. Even these sources must be
tagged and tracked by the university under federal law. Any man-made
source falls under this while naturally occoring sources don't (ex. a
piece of granite from Utah).

Sam


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Sam Sampere
Syracuse University
Department of Physics
Syracuse (Where all the snow is..), NY 13244



On Fri, 30 Jan 1998, Tim Sullivan x5830 wrote:


Pete Lohstreter wrote:

The above reminds me that I have in my Radiation Demonstration kit a
device that I rescued from a sidewalk sale. I don't have the details,
but, I seem to recall that the device was labled a "Spark Gap" for some
type of short wave radio (I think) It is about 1.5 cm in length and
maybe 3-4 mm in diameter. Both ends were gold and the body was
apparently a ceramic material. The box indicated that the device
contained Cesium-137. When I got it back to the lab, I Pegged the
needle on the gieger counter. I finally got an estimate of 100-400
microCuries. ( I really need better equipment)

I write:

I hope you are treating that source with some respect. While I don't claim to
be a Health Physicist, a reference book lets me calculate that a 400 microCi
source of Cs-137 produces a dose of about 0.16 mrem/hr at 1 meter (from gammas
alone.) That means that if you store the source a meter from your desk and you
spend 2000 hours per year at your desk, you are exposing yourself to an
additional dose per year equal to the average dose people in the US receive
each year from all sources. Dose from gammas goes up as R^2, so the time to
receive a significant dose goes down fast as you start handling it up close.

If it was designed to ionize air, that is more effectively accomplished with
betas. That raises the possiblity that the source may be unsealed which
increases the risk of spreading the material around, or ingesting it. Also,
that means that the total dose will increase much faster than R^2 as you get
close to handle it.

You are also getting close to the range where you may need a license. We need a
state license for a 1 mCi source of Co-57 in Ohio, for example.

Tim Sullivan
sullivan@kenyon.edu