Many have asked me if it is possible to build a nuclear bomb from smoke-detectors. Some media exaggerates my whole thing, and wrote "He was trying to building an atomic bomb from smoke-detectors"!
But the answer is, Yes! It is possible. But you will need about 323 076 920 377 smoke-detektors if I had calculated it right. A smoke-detektor contains about 0,26 µg Americium-241. And the critical mass for Am-241 is about 84 kilograms. This is the bare critical mass. Then it could be reduced to about "only" 23 kilograms, with some reflection shields and so.
So, start collecting! Over 323 billions of smoke-detectors!
It is also possible to build a nuclear bomb from the far more expensive Californium. 1998 was the price $56 per microgram of Californium-252. The critical mass for Cf-252 is 2,73 kilograms, then a critical mass would cost about $153 billions.