[no-s]

It would take a warehouse full (hundreds of thousands to millions) of smoke detectors to make anything substantially dangerous. For one thing, the radiation emitted by the smoke detector can be stopped by a sheet of paper. I supposed you could extract enough from a few hundred to feed to someone and poison them or give them cancer maybe, especially if you can get it stuck inside a person.

OTOH you can use the material to make sensitive instruments, like neutron diffractometers & scintillators & such. This is actually quite fun. But don't do it where you live. Get a lab with a fume hood and other safety gear because you're going to need some strong acid to do it right and accidents with strong acids are unpleasant for the unprepared.

[wrench]

It doesn’t take thousands. A little of this and a little of that and you have a dirty device.

http://www.dangerouslaboratories.org/radscout.html