Investigation of the corrosion of valve metals and alloys under the influence of plutonium

In recent years valve metals (hafnium, titanium, zirconium and tantalum) being well-known for building self-protecting oxide layers against corrosion have become very important for the Purex process. Firstly as electrode materials for electrochemical separation of plutonium from uranium and secondly as heterogeneous inhibitors for preventing criticality, but their general acceptance could only be agreed to if corrosion phenomena were investigated under practical conditions, especially under the influence of plutonium. For this special purpose combined radiochemical and electrochemical methods were developed to determine simultaneously the amount of corrosive material directly penetrating into the solution compared with that quantity which was transferred to building the oxide layer. Using these methods the stability of the oxide layer against corrosion was investigated under the influence of plutonium and a variety of parameters (potential, time, temperature, chemical composition), the specific composition of the oxide layer and its plutonium content and structure being analysed by XPS. The third physical quantity simultaneously measured during the formation of the oxide layer in presence of plutonium was the dielectric constant obtained from impedance measurements. So under the influence of plutonium detailed information about the formation, composition and corrosion behaviour of characteristic oxide layers of valve metals are obtained by this new procedure which combines electrochemical and radiochemical methods. (orig.)