Amount of hydrogen and loss of ductility in welded joints of Zircaloy-4

The analysis, study and characterization of weldments of nuclear materials assumes fundamental importance in the safety of nuclear reactors. Zircaloy-4 is used in different structural parts of nuclear reactors, mainly under severe environmental conditions. As a consequence, many different factors affect mechanical properties, specifically hydrides formed by absorbed hydrogen generated from radiolysis of water, causing loss of ductility, the most undesirable observed consequence. It is also known that the welding process facilitate the presence of hydrogen. In a previous work, we presented the results of measurements of hardness and hydrogen concentration as a function of the distance from the union for two specimens, obtained by TIG welding, applying similar standards adopted in the welding process of low chimney, utilized in MPR reactor but under two different environments: a) Under air exposure; and b) In a closed and controlled chamber under argon atmosphere. While higher hydrogen concentration were found in samples obtained by the first technique, there were not difference in the microhardness. In this work following these remarks, supplementary testing of Zircaloy-4 plates is given. Tensile test in specimens with controlled charges of hydrogen by cathodic techniques are presented. (author)