Explain the concept of dose equivalent and the units used for occupational radiation exposure.

• A. Dose equivalent accounts for radiation type and biological effect; units are sievert (Sv) or rem; 1 Sv = 100 rem.
• B. Dose equivalent is the same as absorbed dose; units gray.
• C. Dose equivalent measures shielding thickness; units HVL.
• D. Dose equivalent is energy per photon; units joules.

Answer: (A)

Dose equivalent is the measure used in occupational radiation exposure to account for the fact that different types of radiation cause different biological effects for the same energy deposited. It starts with the absorbed dose, which is the energy deposited per unit mass (gray). This is multiplied by a radiation weighting factor that reflects the relative biological damaging potential of the radiation type. For X-rays, gamma rays, and beta radiation, the weighting factor is about 1, while for alpha particles it's much larger (20), so alpha exposure is more harmful for the same energy deposition. The resulting dose equivalent is expressed in sieverts, or in the older unit rem, with the relationship 1 sievert equals 100 rem. This framework lets a worker's exposure be compared across different radiation types and linked to risk. For example, 0.1 Gy of alpha radiation gives 0.1 × 20 = 2 Sv of dose equivalent, illustrating how type matters even when the energy deposition is the same. The units reflect the need to quantify risk rather than just energy deposition. The other options either describe absorbed dose in gray, shielding thickness measures, or energy per photon, which do not capture the protective concept of dose equivalent.