Which isotopes are commonly used as gamma sources in industrial radiography?

In industrial radiography, the most commonly used gamma sources are Iridium-192 and Cobalt-60. These isotopes emit gamma radiation that is utilized for non-destructive testing of materials and structures, allowing inspectors to examine the integrity of welds, joints, and overall component structure without causing any damage.

Iridium-192 is favored because it has a relatively short half-life of about 73 days, which allows for less long-term radioactive waste and makes it suitable for many applications in both industrial and medical settings. Cobalt-60, with a longer half-life of around 5.27 years, provides a strong gamma source that is essential for applications requiring deeper penetration, such as thick steel parts in heavy industry.

The other isotopes listed in the choices have applications in other areas, but they are not typically used in industrial radiography. For example, Cesium-137 is used in various measurement devices, while Iodine-131 and Technetium-99 are primarily utilized in medical diagnostics and treatment. Thus, the combination of Iridium-192 and Cobalt-60 stands out as the standard in industrial radiography due to their effective gamma radiation properties and practical utility in safety inspections.