A fast neutron is a free neutron with a kinetic energy level close to 1 MeV (10 TJ/kg), hence a speed of 14,000 km/s. They are named fast neutrons to distinguish them from lower-energy thermal neutrons, and high-energy neutrons produced in cosmic showers or accelerators. Fast neutrons are produced by nuclear processes such as nuclear fission.

Fast neutrons can be made into thermal neutrons via a process called moderation. This is done with a neutron moderator. In reactors, typically heavy water, light water, or graphite are used to moderate neutrons.

See also

• Fast neutron reactor
• List of particles

Neutron

高速中性子 | Быстрые нейтроны