What is "neutron flux"

n. (context physics English) The number of neutrons passing through one square centimeter of a given target in one second.

n. the rate of flow of neutrons; the number of neutrons passing through a unit area in unit time

The neutron flux is a quantity used in nuclear reactor physics corresponding to the total length travelled by all neutrons per unit time and volume, or nearly equivalently number of neutrons travelling through a unit area in unit time. The neutron fluence is defined as the neutron flux integrated over a certain time period.