What are the minimum thicknesses recommended for both IR 192 and CO 60?

What are the minimum thicknesses recommended for both IR 192 and CO 60?

• A. IR 192 - 1/2" (12 mm); CO 60 - 1 1/2" (38 mm)
• B. IR 192 - 1/4" (6 mm); CO 60 - 1" (25 mm)
• C. IR 192 - 3/4" (19 mm); CO 60 - 2" (50 mm)
• D. IR 192 - 1" (25 mm); CO 60 - 1" (25 mm)

Answer: (A)

Understanding how gamma-ray source energy affects penetration helps decide which radiography source to use for welding inspections. Ir-192 emits gamma rays with lower energy, so it yields good image quality on thinner sections but doesn’t penetrate much thicker material. A practical minimum thickness for using Ir-192 is about 1/2 inch (12 mm). Co-60 emits higher-energy gamma rays, allowing deeper penetration, so it’s appropriate for thicker sections; a practical minimum thickness for Co-60 is about 1 1/2 inches (38 mm). So the recommended minimums reflect using Ir-192 for thinner welds and Co-60 for thicker ones. If the material is thinner than these values, another approach or source would typically be needed to obtain a reliable radiograph.

Understanding how gamma-ray source energy affects penetration helps decide which radiography source to use for welding inspections. Ir-192 emits gamma rays with lower energy, so it yields good image quality on thinner sections but doesn’t penetrate much thicker material. A practical minimum thickness for using Ir-192 is about 1/2 inch (12 mm). Co-60 emits higher-energy gamma rays, allowing deeper penetration, so it’s appropriate for thicker sections; a practical minimum thickness for Co-60 is about 1 1/2 inches (38 mm). So the recommended minimums reflect using Ir-192 for thinner welds and Co-60 for thicker ones. If the material is thinner than these values, another approach or source would typically be needed to obtain a reliable radiograph.