Which radiation is found only in or near an operation reactor?

• A. Neutron
• B. Beta
• C. Gamma
• D. Rem (millirem)

Answer: (A)

Neutrons are produced in a reactor when fissile nuclei split during fission. This makes them a defining feature of an operating reactor, since the core itself is the source of most neutron radiation. Outside the reactor, neutron flux drops quickly and is highly dependent on shielding and distance, whereas other radiation types arise from radioactive decay of fission fragments and activation products and can be detected around the facility even when the reactor isn’t actively producing power. Rem is a unit used to measure dose, not a type of radiation, so it isn’t the radiation itself. Because neutrons come from the fission process inside the reactor core, they are the radiation most closely associated with being found in or near an operating reactor.