Before revision: The basic requirements are To start with a subcritical system To create a super prompt critical system To make the change between these two states in a length of time (insertion time) which is shorter than the time between the random appearance of a neutron in the fissile material through spontaneous fission or by other random processes.
After revision: :The basic requirements are To start with a subcritical system To create a super prompt critical system To make the change between these two states in a length of time (insertion time) which is shorter than the time between the random appearance of a neutron in the fissile material through spontaneous fission or by other random processes.