Some more facts about neutrons...
- Outside the nucleus, neutrons only live for about 10 seconds before decaying as mentioned above.
- Free neutrons (as in the 'unchained' sense) are valuable. They are a lot harder to get a hold of than electrons, alpha particles or even gamma rays, so any process that generates a stream of these particles is prized. Nuclear reactors are a common source of neutrons.
- It is neutron bombardment which transmutes a nucleus of one element to another. Electrons don't do it, and alpha particles need to be travelling pretty fast to do it.
- Because of the above properties, it is neutrons that are the most dangerous radiation of any radioactive material, as they are the most efficient at rendering neighbouring materials radioactive.
- Neutron capture is what causes a U-235 nucleus to fission and release more neutrons, precipitating a chain reaction.
- Upon release, neutrons in nuclear reactors travel too fast to be captured by uranium nuclei. They need to be slowed down by collisions with atoms in moderator materials, such as heavy water, graphite, or cadmium. They are much more likely to be captured by U nuclei once they have been slowed down in such a way.