Physico–statistical models based on the residual defectiveness of structural materials - Probabilistic Safety Assessment for Optimum Nuclear Power Plant Life Management (PLiM) - page 144

5.24 Trepan of defect No. 8. Result of radiographic inspection
(for Fig. 5.23).

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5.25 Macrograph of defect No. 9 (for Fig. 5.23)

the results were obtained are presented in Fig. 5.28. The samples contained
both intergranular stress corrosion (ISC) cracks, fatigue cracks and also the
cracks produced by the electrospark method. The data presented in Fig. 5.26
and 5.27 show that that the ISC cracks are more difficult to detect than
other cracks. Even for the cracks that make up 50-70% of wall thickness
the probability of non-detection is very high.
Information on the detectability of defects, obtained in studies in
direction 3, is shown in the diagrams in Fig. 5.27 and 5.28.

5.1.6 Reasons for non-detection of defects

The detectability of defects is affected by a large number of factors,