Reply To: Animated nuclear reaction.

[Brian H]

Fission reactors are not necessary for fission. A radioactive element is one in which the atoms fission spontaneously at a particular rate, measured as “half-life”, meaning the length of time about half of a given sample of atoms will split. They do not have to be bombarded with the stray products (like neutrons) from other fission events. A reactor puts these atoms close together so that the collisions do occur, and then they fission at a much accelerated rate. A chain reaction means that enough are (held and constrained) close enough to cause a runaway series of fissions, an A-bomb. The half-life of an A-bomb is very short, for that reason! So is the whole life.

But scattered U238 and P239 atoms will decay at their predicted rates, more or less, and release heat wherever they are, and however isolated they are.