I'm still working on getting a fireman to come out to the school to demonstrate a radioactive detector. No luck so far. This is for a project on Marie Curie.

Any other suggestions would be greatly appreciated.

2 answers

I assume you have talked to the chief of the RADHAZ team.

Marie Curie discovered Radioactivity, that is the essence of her greatness. I guess you could make a poster on that failing the fun demo.
Do really you need a fireman to demonstrate one? Most smoke detectors contain a radioactive Americium-241 source. The only problem might be coming up with a smoke source to test it. Cigarettes are banned from public buildings now. You might consider blowing talcum power at it.

There is a good article about how they work at
http://www.world-nuclear.org/info/inf57.htm

What do you want the fireman to demonstrate: the detection of smoke or the radioactivity of the Americium source?