Scattering and image contrast simulation for double wall radiography of pipes

Radiographic image quality, which is quantified by radiographic sensitivity measurements, is significantly influenced by parameters such as scattering, effective attenuation coefficient and image contrast. In the present work, the Monte Carlo method has been utilized to simulate Gamma ray scattering and image contrast for double wall radiography of pipes and some experiments have been designed to determine the radiographic sensitivity and measure the effective attenuation coefficient. Wire type image quality indicators were simulated as artificial defects and the threshold contrast and minimum optical density difference for viewing each wire were investigated. It was found that the maximum allowable source to film distance for double wall exposure and single wall viewing technique was 1.4 times the outside diameter of the pipe and the image contrast and radiographic sensitivity were higher for this technique in comparison with the double wall viewing technique. The double wall exposure and double wall viewing technique is proposed to be used when the minimum source to film distance is higher than 1.4 times the outside diameter.