ASNT Industrial Radiography Radiation Safety Practice Test

If 0.50 in. of steel is considered 1 half-value layer for Ir-192, how many half-value layers does 1.5 in. of steel represent?

1. 1.0

2. 2.0

3. 3.0

4. 4.0

The correct answer is: 3.0

To determine how many half-value layers are represented by 1.5 inches of steel when 0.50 inches is defined as 1 half-value layer for Ir-192, you start by recognizing that each half-value layer reduces the radiation intensity by half. Since one half-value layer corresponds to 0.50 inches of steel, you can calculate the number of half-value layers in 1.5 inches by dividing the total thickness by the thickness of one half-value layer: 1.5 inches (total thickness) divided by 0.50 inches (thickness of one half-value layer) equals 3. This means that 1.5 inches of steel represents three times the thickness defined for one half-value layer. Therefore, it corresponds to 3 half-value layers. Understanding half-value layers is crucial in radiation safety practices as it helps in estimating the amount of shielding needed to protect individuals from radiation exposure effectively.