ASNT Industrial Radiography Radiation Safety Practice Test

If a radiographer is at a crank assembly receiving 100 mR (1000 μSv), where would the "RADIATION AREA" sign be posted if the crank assembly is 25 ft in length?

1. 100 ft (30.48 m)

2. 85 ft (25.9 m)

3. 111.8 ft (34.08 m)

4. 50 ft (15.24 m)

The correct answer is: 111.8 ft (34.08 m)

In the context of radiography, the designation of a "RADIATION AREA" is based on establishing a boundary where individuals might receive a certain dose of radiation in a given time. According to established safety standards, a "RADIATION AREA" is typically defined as a location where an individual could receive a dose of 0.1 rem (100 mrem or 1000 μSv) in one hour. When considering the setup of a crank assembly that is 25 feet long, one must account for both the direct exposure from the radiation source and the distance at which the dose falls below this threshold. The selected answer of 111.8 feet establishes a safety margin that extends well beyond the length of the assembly itself, ensuring that the radiation does not exceed the allowable limits at a distance where individuals could potentially be present. This calculation often incorporates factors such as the radiation attenuation over distance as well as the expected exposure levels, which may dictate where the signs should be placed to warn individuals of potential radiation hazards. In this case, the placement of the sign at 111.8 feet from the source thus prioritizes safety by providing a buffer zone beyond the immediate vicinity of the assembly, ensuring that anyone approaching does not receive a dose that