AWS Certified Welding Inspector — FundamentalsNondestructive Examination (NDE)Medium
During a radiographic testing (RT) inspection of a 1-inch thick steel weld, the CWI observes that the image quality indicator (IQI) wires are clearly visible, but there is excessive scatter radiation present, causing a hazy film. Which adjustment would be MOST effective in reducing the scatter radiation and improving image clarity without significantly compromising sensitivity?
- AIncreasing the exposure time.
- BUsing lead screens on both sides of the film.
- CDecreasing the kilovoltage (kV) setting.
- DIncreasing the source-to-film distance (SFD).
Show answer & explanationAnswer & explanation
Correct answer: B. Using lead screens on both sides of the film.
Lead screens placed on both sides of the film serve two primary purposes: the front screen absorbs low-energy scatter radiation before it reaches the film, and the back screen absorbs backscatter radiation. This significantly reduces scatter effects, leading to a clearer image with improved contrast without necessarily reducing sensitivity to detail.
Why the other options are wrong
- A. Increasing exposure time primarily affects film density, not scatter radiation. While it might make the IQI wires darker, it would also darken the scatter, maintaining the hazy appearance.
- C. Decreasing kV reduces the penetrating power and can reduce scatter, but it primarily affects contrast and may require a much longer exposure time, potentially hindering productivity.
- D. Increasing SFD reduces geometric unsharpness but has a limited effect on scatter radiation; it primarily impacts definition.
RT - Scatter Radiation Reduction
In Radiographic Testing (RT), scatter radiation can degrade image quality (cause haziness). Using lead screens is a primary method to absorb scatter and improve film clarity.
- Scatter radiation causes film haziness.
- Lead screens absorb scatter.
- Front screen reduces scatter entering film from object.
- Back screen reduces backscatter from objects behind film.
Memory trick: Contrast, Definition, Sensitivity: Controlled by kV, SFD, and Scatter.