The practical aim of the modular optimization and validation is to provide a testing system including a validated procedure which fulfills the requirements of the client in an optimum manner with minimum effort to guarantee the safe operation of a plant. In this way, a clear definition of the clients requirements is the starting point of the investigation. For the optimization the signal transfer chain of the testing system needs to be described in detail. The chain is then cut into modules e.g. experimental conditions for radiographic imaging and film image evaluation procedures. The strength of the influence of each module on the accuracy of the result is investigated. The parameters of the main influencing modules are optimized in a scientific way where both the results of modeling calculations and sets of experiments are exploited. The validation of the optimized testing system occurs also in a modular approach: The intrinsic capability of the physical method is confirmed by computer modeling and the reliability of the remaining factors from the industrial application including the human factor are determined quantitatively by statistical evaluation of blind trials e.g. by the ROC method.

The strategy will be applied to problems of radiographic testing in the fields of nuclear power generation and chemical plant safety. The specific examples will be the testing of ferritic tube welds containing thermally induced stress cracks and the problem of wall thickness determination of isolated non-empty tubes. In both cases the performance of image interpretation by human inspectors will be compared to the capability of automated systems including neural networks.