Study on the corrosion local degradation of the isotopic change columns in the heavy-water fabrication plant

Romania decided to build a plant, in Romania, at Turnu Severin, on the Danube in order to produce the necessary heavy water for the five nuclear reactors planned. The separation process was chosen on the base of the isotopic change H2O-H2S. The complexity of the plant and the high degree of risk caused by the hydrogen sulphide toxicity impose periodical inspection on the resistance of the plant's structure. The inspections made at two years consist of checking the column wall thickness, non-destructive examination on the interior using penetrant liquids and magnetic powders and the replicas metallographic analysis, respectively. The mentioned examinations are performed especially in the maximum risk zones, namely in the places where the stressed corrosion processes are concentrated. During the revision that was made in May 2000 the 1304A Column was also examined, all the cracks were eliminated by polishing, and the microcracks were emphasised by replicas and non-destructive examinations. The highly corroded zones and those repaired are monitored with a view to follow there in time evolution. (orig.)