ASNT Industrial Radiography Radiation Safety Practice Test

To reduce exposure to one-half when using lead shielding for Ir-192, what thickness is required?

1. 0.1 in.

2. 0.5 in.

3. 0.2 in.

4. 0.4 in.

The correct answer is: 0.2 in.

To effectively reduce exposure to gamma radiation from Iridium-192 (Ir-192) by half, the concept of half-value layer (HVL) is essential. The HVL refers to the thickness of a material needed to attenuate the intensity of the radiation by 50%. For Ir-192, the half-value layer is approximately 0.2 inches of lead. When designing shielding to protect workers from the significant exposure levels typically associated with Ir-192, using the correct HVL ensures that the radiation dose is minimized. A lead thickness of 0.2 inches is sufficient to achieve this goal, effectively achieving the desired reduction in exposure. This concept is crucial in radiation safety practices, as using the correct shielding thickness directly impacts the safety and health of personnel who work around radioactive materials. Knowing the precise HVL allows for better planning and implementation of safety measures in industrial radiography settings.