fast neutrons

Fast neutrons are high-energy particles that are released during certain nuclear reactions, such as fission in a nuclear reactor. Unlike slow (thermal) neutrons, fast neutrons move at very high speeds and have more energy. They can effectively initiate further reactions if they collide with other atomic nuclei, which makes them important for sustaining nuclear chain reactions. Because of their high speed and energy, fast neutrons require specialized moderation—slowing down—for safer handling and controlled reactions in reactors or medical applications.