If a cobalt source of 73 Ci is exposed through a 3 half-value collimator, what is the restricted area on the cold or collimated side?

To determine the restricted area on the cold or collimated side of a cobalt source with a specific activity of 73 Curie (Ci) and using a collimator with 3 half-values, it is essential to understand how half-value layers function in radiation shielding.

Each half-value layer (HVL) reduces the intensity of radiation by half. When multiple half-values are applied, the remaining intensity can be calculated by taking the initial intensity and applying the reduction factor for the number of layers. In this case, with three half-value layers, the intensity of radiation on the cold side can be estimated.

The specific calculations for the remaining intensity after three half-value layers would use the formula:

Remaining Intensity = Initial Intensity × (1/2)^n,

where n is the number of half-value layers. For three half-value layers, this becomes:

Remaining Intensity = Initial Intensity × (1/2)^3 = Initial Intensity × 1/8.

After determining the intensity, you can calculate the area that corresponds to the restricted zone, which is necessary to ensure safety and compliance with radiation exposure limits. The calculations would align with locating the restricted area according to the safety standards set for radiation exposure.

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