noun
fast neutron
Technical term in nuclear physics for a neutron with kinetic energy above a certain threshold, typically around 1 MeV.
高速中性子は原子炉の設計で重要な役割を果たす。
Fast neutrons play an important role in nuclear reactor design.
Thermal neutrons have much lower energy and are in thermal equilibrium with the surrounding medium, unlike fast neutrons.
Compound of 高速 (high speed) and 中性子 (neutron), a calque from English 'fast neutron'.