What type of radiation is most dangerous to personnel?

• A. Gamma
• B. Alpha
• C. Beta
• D. Neutron

Answer: (A)

Penetration and shielding determine how dangerous radiation is to personnel. Gamma rays are highly penetrating electromagnetic radiation, so they can pass through the body and lots of shielding, making external exposure hard to shield against and capable of reaching vital organs. This means a person can receive a significant whole‑body dose from external sources without obvious, localized clues, increasing potential harm.

Alpha particles, while extremely ionizing, have very low penetration and are stopped by skin or a sheet of paper; they’re most dangerous if inhaled or ingested, when they can cause intense local damage. Beta particles penetrate more than alpha but still don’t reach as deeply as gamma, so their external hazard is less than gamma, though they can cause skin burns or internal damage if they enter the body. Neutrons are also very penetrating and can cause substantial biological damage, but their damage depends on energy and the materials around them; in many general safety scenarios, gamma radiation presents the greater external threat due to its ability to reach and affect internal tissues more readily.