Gamma radiation is used to detect structural flaws in materials through a technique called gamma radiography, which works much like medical X-rays but with higher penetration power.
Here’s how it works:
- Radiation Source – A radioactive isotope such as cobalt-60 or iridium-192 emits gamma rays.
- Placement of Object – The material or structure to be tested (e.g., metal welds, pipelines, aircraft components) is placed between the gamma source and a detector or photographic film.
- Penetration – Gamma rays pass through the material. Areas with different densities or thicknesses (caused by cracks, voids, corrosion, or inclusions) absorb gamma rays differently.
- Detection – The rays that pass through strike a radiation-sensitive film or digital detector on the opposite side, creating an image (radiograph).
- Flaw Identification – On the radiograph, flaws appear as variations in darkness:
- Lighter areas = denser regions that absorbed more radiation
- Darker areas = less dense regions, possibly indicating cracks, voids, or defects
Advantages:
- Can detect internal defects without damaging the material (non-destructive testing)
- Works on thick or dense materials where X-rays may not penetrate effectively
Applications:
- Inspecting welded joints in pipelines
- Checking airplane parts for fatigue cracks
- Ensuring integrity of critical infrastructure like bridges or pressure vessels