The Influence of the Crack Opening in the UT Inspection Qualification

The character of cracks is an important parameter in manufacturing of test pieces for UT qualification. In these studies we (Trueflaw and Fortum Nuclear Services) have manufactured 22 cracks by different production methods. Opening of cracks have been manipulated for different values. Sizing of the true dimensions of cracks has been made by destructive tests. These values are the basis for the evaluation of the accuracy of different NTE techniques. This presentation will focus on NDT aspect. The purpose of these studies is to find dependency in test results and opening of cracks. We also try to find out differences in accuracy between various techniques. The test pieces have been inspected by nine inspectors from Finnish NDT vendors (Polartest, Inspecta, VTT). Inspectors used different techniques and procedures for flaw size evaluation. Three inspectors made sizing (size defining) by traditional manual method. They used different techniques and probes. Two inspectors used manual phase array technique and four inspectors made sizing (size defining) by mechanizesd phase array technique. All inspections were blind tests. In the evaluation of the results it has been concentrated in the used techniques and procedures. Influences of human elements has not been studied.