What is the radiation intensity at 6 feet from an unshielded 60 Ci iridium-192 source?

To determine the radiation intensity at a specific distance from an unshielded source like iridium-192, it is essential to apply the principles of radiation decay and the inverse square law. Iridium-192 is a high-energy source commonly used in brachytherapy and industrial radiography, and a 60 Curie (Ci) source will emit radiation that can be calculated based on distance.

The key to solving this is the understanding that radiation intensity diminishes with the square of the distance from the source. The formula for calculating radiation intensity at a certain distance is expressed as:

[ I = \frac{I_0}{d^2} ]

where

• ( I_0 ) is the initial intensity at 1 meter (in this case, derived from known values for a 60 Ci iridium-192 source),

• ( d ) is the distance in meters.

Using the appropriate constants for iridium-192, the initial intensity at 1 foot can be recognized and then you can scale it down to 6 feet, keeping in mind that the distance needs to be converted to meters if necessary.

The calculation leads to determining that at 6 feet, the appropriate value for radiation intensity aligns with approximately 9833 m