Nuclear Chain Reaction
A self-sustaining sequence of fissions in which neutrons released by one event trigger further events.
Formula / equation
k = neutrons produced / neutrons lost
Unit
Dimensionless
In depth
The multiplication factor k determines the outcome: below one the reaction dies out, exactly one gives steady power, and above one gives exponential growth. Reactors are held precisely at criticality by adjusting neutron absorption.
Examples in the real world
Fermi's Chicago Pile-1 achieving the first controlled chain reaction in December 1942.