By the end of the year the physicist Werner Heisenberg had calculated that nuclear fission chain reactions might be possible. When slowed down and controlled in a "uranium machine" (nuclear ...

A controlled nuclear fission reaction releases one million times more energy per kg than a chemical reaction such as burning coal, oil or gas. This means much less fuel is required than for a ...

Fermi's task, however, was to create a controlled nuclear reaction; that is, to split the atom without creating a deadly explosion. Theoretically, it was possible. During fission, a fast-moving ...

In a conventional reactor these neutrons are supplied by the fission reaction itself, which requires a certain concentration of the correct fissile isotopes (typically 235 U or 239 Pu) to be ...