[chimera]

Americium and Californium are currently used as alpha sources in smoke detectors.

Californium in smoke detectors? Gawd, I hope not. 252-Cf is one helluva neutron source. You don't want neuts in a smoke detector. Besides that, its tough to make (you're talking about something like a 14n-capture reaction in uranium, and thus is bloody expensive. Last I heard, ORNL was selling it for something like $50 per microgram. And since the neutron emission rate is about 2.8 million n/sec for a microgram, I don't think we want that in smoke detectors. Americium is the material of choice in that application, I think.

[B-Chan]

The cool thing about californium is that it emits neutrons much more profusely than do most radioactive atoms. As a result, its critical-mass requirement is quite small -- a few grams. Herman Kahn's book On Thermonuclear War describes a hypothetical nuclear weapon utilizing californium fuel: an "atomic six-gun" the size of a regular revolver shooting hollow-point californium-tipped bullets. Upon impact, the kinetic energy of the bullet crushes the hollow-point tip into a critical mass and boom -- a nuclear explosion in the sub-kiloton range, one per bullet.