Improvement of Inspecting Heat-exchanging Tubes of Steam Generators at VVER NPPs in Ukraine
Y. Grebenyuk, M. Zaritsky, V. Kovyrshin, SSTC NRS, Ukraine
ABSTRACT
Several studies have found differences in how well operators detect cracks, even though the operators have been using similar equipment and following a similar procedure. These differences prompted the Swedish Nuclear Inspectorate (SKI) to initiate a research project, the results from which this report is based on. It is the ambition that this project can help improve training and education in NDT, and help ensure a high quality on NDT qualifications and testing. Even though the operators perform the testing according to similar (sometimes identical) procedures, the operators can use different sub-strategies to assimilate and assess information. In the studies presented here the operators performed manual ultrasonic testing on test pieces and completed questionnaires concerning how important certain information was when making assessments on the integrity of the test pieces. The first study revealed that the operators who had hit-rate above average used more time than the other operators did. The above-average performing operators also considered more information in the detection phase and less information in the characterisation phase than the operators performing below average did. It is concluded that it is important to consider much information in order to make a correct assessment in the detection phase, whereas much information in the characterisation phase reduces performance. The second study studied the effect of a stress condition on the performance of manual UT. The operators worked one day in no-stress condition and one day in stress condition (noise and time pressure) to simulate working conditions. Again, the operators performed manual UT on blind test pieces with manufactured flaws. The results showed operators to perform better under stress than no-stress. It is concluded that the operators felt challenged by the noise and time pressure, thereby becoming more focused and motivated than under the no-stress condition. The conflicting results of the two studies is explained by manual UT being a complex task which results in performance to some degree be depending on the operator and the situation.
Publication Source: 3nd International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components, November 14-16, 2001, Seville Spain. Publisher: Tecnatom s.a. - [Homepage]
