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This paper gives an introduction to the field of human factors with the focus on their influence on the reliability of NDT in the nuclear energy production (in-service inspections) and final storage of highly radioactive nuclear waste. A set of methodological tools has been developed in the scope of three projects, namely: 1) a theoretical model describing potential human factors influencing manual ultrasonic inspection performance during inservice inspections in nuclear power plants; 2) a method for identifying potential human errors during acquisition and evaluation of data gathered with mechanized ultrasonic, radiographic and eddy-current systems, as well as visual testing with a remote camera (Failure Modes and Effects Analysis, FMEA); and 3) use of eye tracking methodology to optimize existing procedures and practices. The experimental results have shown that time pressure, mental workload and experience influence the quality of the inspection performance. Noticeable were influences from the organization of the working schedule, communication, procedures, supervision and demonstration task. Implementing human redundancy in critical tasks, such as defect identification, as well as using an automated aid (software) to help operators in decision making about the existence and size of defects, could lead to other kinds of problems, namely social loafing (excerpting less effort when working on tasks collectively as compared to working alone) and automation bias (uncritical reliance on the proper function of an automated system without recognizing its limitations and the possibilities of automation failure) that might affect the reliability of NDT in an undesired manner.
The human factors approach relies on understanding the properties of human capability and limitations under various conditions and the application of that knowledge in designing and developing safe systems. Following the principles of the MTO (Man Technology Organisation) approach, emphasis should be given to the way people interact with technical as well as organisational systems.
A model describing human factor influences in relation to the performance shaping factors and their effect on manual ultrasonic inspection performance had been built and a part of it empirically tested. The experimental task involved repeated inspection of 18 defects according to the standard procedure under no, middle and high time pressure. Stress coping strategies, the mental workload of the task, stress reaction and organisational factors have been measured. The results have shown that time pressure, mental workload and experience influence the quality of the inspection performance. Organisational factors and their influence on the inspection results were rated as important by the operators. However, further research is necessary into the effects of stress.