What type of radiation is considered to be non-penetrating and not considered an external hazard?

• A. Alpha radiation
• B. Beta radiation
• C. Gamma radiation
• D. X-ray radiation

Answer: (A)

Alpha radiation is the type that has very low penetrating ability. These particles are heavy helium nuclei that travel only a short distance in air and can be stopped by a sheet of paper or by the outer layer of skin. Because they don’t travel far, they pose little external hazard; their danger comes mainly if the radioactive material is inside the body (inhaled or ingested). In contrast, beta radiation can penetrate skin to some extent and gamma rays and X-rays are highly penetrating and pose external hazards, requiring shielding. So alpha radiation is the non-penetrating type and not considered an external hazard.