Many of the features of the reactor are designed to control the speed of the reaction and the temperature inside the shielding. An uncontrolled fission reaction is the basis of an atomic bomb.

Yet despite improvements in the design of nuclear-fission reactors ... need only be a value of about 2, as compared with over 50 for a reactor that generates electricity from fusion alone.

Although to most the term ‘fission reactor’ brings to mind something close to the commonly operated light-water reactors (LWRs) which operate using plain water (H 2 O) as coolant and with ...