I'm sorry you didn't know this, but americium is not really a big deal on the list of possible radioactive dangers. It emits mostly alpha particles which can be stopped in a few cm of air (or by your skin without penetrating it). The only way it could hurt you is if you breathed it in. If you own a smoke detector, you've already got americium in your house. Terorrist. I'll bet you've even got more than one smoke detector in your house. Building a dirty bomb, are you?
Beryllium is toxic but get real, building a dirty bomb out of it? You might as well build a bomb out of vinegar and baking soda, because it would probably do more damage.