The reliability of radiography of thick section welds

Munns, I. J.; Schneider, C. R. A.
May 2000
AIP Conference Proceedings;2000, Vol. 509 Issue 1, p2151
Academic Journal
This paper describes the experimental validation of a simple model of radiography, first published by Pollitt in 1962, which treats flaws as smooth, parallel-sided slots. Six thick-section specimens were manufactured to represent welds in Magnox pressure vessels (now operated by BNFL Magnox Generation). The welds contain 16 large, realistic, planar defects. They were radiographed under various exposure conditions and evaluated by two interpreters. The specimens were then sectioned to determine defect size, orientation, gape and roughness. The experimental data show variations in detectability that are strongly correlated with theoretical predictions. In almost all cases, Pollitt theory is either accurate or pessimistic. We have used the experimental data to derive statistical models for the reliability of radiography. Such models can be used to estimate the probability of detecting a defect (with associated confidence limits), from knowledge of its size, orientation and other relevant parameters. In addition, work has been carried out to assess the human aspects of radiographic inspection. Encouragingly, this work showed little variation in the ability of different interpreters to discern large planar flaws. © 2000 American Institute of Physics.


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