Review of scientific activity at Saraf in 2014-2015 and prospects for the future

As part of the IRR2 reactor preventive maintenance, an ultrasonic scanning system was developed for inspection of the reactor tank wall. The first ultrasonic inspection was carried out in 2007. Indications found on the second inspection in 2015 were evaluated and compared those found on 2007. While, the ultrasonic inspection provides various types of data, much of it had to be evaluated exclusively by human inspectors with aid of computed imaging. Special types of thickness variations, defined in computer algorithms were regarded as flaws. Designated algorithms successfully managed to locate and define the flaws without human assistance. Each flaw was evaluated by a set of measurements and required parameters. Consequently quantitatively compared to the results of the first scan, which is essential for the monitoring of the tank's state A few types of measurements errors and saturation of the ultrasonic signals introduced inaccuracies to the evaluation of the flaws. Correction technics successfully applied to correct the mentioned and additional inaccuracies. The total scanned area is tens of square meters. Total number of indications is over 44,000, of which over 1,500 were defined as flaws, significant enough for evaluation and comparison. This large number of flaws represents rigorous approach, aimed to find all the imperfections, rather than problematic findings. Apart from the evaluation of thickness variation, quantitative approach was followed in the measurement of the tank shape. While the tank is nominally a round cylinder, deviations from roundness do exist. These deviations were accurately determined and minute changes between the previous scan and the present were detected. This task is challenging since the ultrasonic transducer is located the tip of a folding arm on a few meters long manipulator, inserted into the tank through a central diameter hole of a few millimeters