Neutron flux is a vital scalar quantity utilized within the disciplines of nuclear physics and reactor engineering. It represents the total distance traveled by all free neutrons within a specific volume over a defined period of time. This metric is essential for characterizing the intensity of a neutron field inside a reactor.
Mathematically, the flux can also be defined by observing the number of neutrons passing through a small sphere of a given radius, normalized by the sphere's maximal cross section and the duration of the observation. The standard unit for neutron flux is cm⁻²s⁻¹, reflecting its dimension of inverse area multiplied by inverse time.