NDT Radiographic Testing Safety 5

Question 1

What is the purpose of a 'source activity decay chart' kept on an Ir-192 camera?

Accepted Answer

To calculate current source activity for proper exposure times

Answer

Because Ir-192 decays continuously, the decay chart lets radiographers calculate current activity so they can set correct exposure times and maintain image quality.

Question 2

Which area classification applies to a location where dose rate could exceed 0.02 mSv (2 mrem) in any one hour but is unrestricted to the public?

Accepted Answer

Unrestricted area

Answer

An unrestricted area under 10 CFR Part 20 is one where individual doses stay below 0.02 mSv (2 mrem) per hour and access is not controlled for radiation protection.

Question 3

A 'two-man rule' in radiographic testing requires that:

Accepted Answer

At least two qualified individuals must be present during source exposure operations

Answer

The two-man rule ensures that at least two qualified radiographers are present during any exposure, providing a safety check and emergency response capability.

Question 4

Se-75 is preferred over Ir-192 for imaging thin materials primarily because:

Accepted Answer

Se-75 emits lower-energy gamma rays that provide better contrast in thin sections

Answer

Se-75's lower energy gamma rays (~66–401 keV) are better suited for thin materials and small-diameter pipe welds, providing superior contrast compared to Ir-192.

Question 5

After completing a radiographic exposure, a radiographer must perform a 'post-exposure survey' to verify:

Accepted Answer

The source has returned to its fully shielded position in the camera

Answer

A post-exposure survey with a calibrated radiation survey meter confirms the source is fully retracted and dose rates have returned to background levels.

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Practice Test

NDT Radiographic Testing Safety 5