Radiochemical investigations on corrosion of valve metals

In order to determine the applicability of valve metals of the Purex process, the corrosion behaviour of these elements was investigated under practical conditions. For these investigations a new technique, based upon the combined application of neutron activation analysis and normal electrochemical procedures, was developed and applied to questions of particular interest. This method had the advantage that it can distinguish between the amount of material directly dissolved due to corrosion from that due to incorporation in the oxide layer. It has been proved that not only isotopic but also non-isotopic radionuclides can be successfully used for this determination. Anodic potentiodynamic and potentiostatic measurements on Hf, Ti and Ta have shown that under the practical conditions employed in the Purex process, any metal removal can be neglected. A plutonium content of up to 2.2 g/l even stabilized the oxide layer towards corrosion by forming mixed oxides of Hf and Pu. The influence of F-ions on the stability of the oxide layer has been systematically investigated and techniques evolved for masking these corroding anions. (orig.)