Coulometric analysis of Uranium in solution through Boron Doped Diamond
electrodes (BDD)

Controlled potential coulometry (CPC) is an analytical technique allowing for the accurate determination of an electroactive species in solution by measuring the amount of electricity used during its quantitative electrochemical oxidation or reduction. Connected only to physical standards, CPC is a primary analysis method which can attain uncertainties close to 0.1%. These uncertainties, as well as the small amount of analyte employed, have led to a resurgence in interest in CPC as a nuclear analysis technique in the field of metrology. In particular, the technique has been successfully employed for the determination of Pu amount content in reference materials. However, CPC is sensitive to the material of the working electrode used to perform the electrochemical reactions. Au electrodes –used for the analysis of Pu– display a narrow electrochemical window in acidic media, which excludes their use for the study of U by reduction. Historically performed using Hg – a material nowadays forbidden in the nuclear industry– the analysis of U by CPC remains a challenge in nuclear metrology. Amongst the modern electrode materials which could replace Hg, Boron Doped Diamond (BDD) possesses a good chemical stability and interesting electronic properties. In particular, its surface oxygen terminations inhibit the adsorption of molecules, leading to a low double layer capacitance as well as a large electrochemical window (-1.5 to +1.6 V/MSE in 0.5M H2SO4). These properties render BDD a promising alternative to Hg for the CPC analysis of U amount content in solutions. We present herein recent advances on the use of BDD for the determination of U amount content in sulphuric acid through CPC. Initially, the optimal experimental parameters for CPC analysis using BDD electrodes were determined through electrochemical studies. The applicability of BDD as an alternative to Hg was then studied through the CPC analysis of U standard solutions. As well as demonstrating its use in the CPC analysis of U, the results highlight the importance of BDD when compared to traditional working electrode materials. With its high versatility, BDD would allow to extend the technique to a large amount of analytes and, effectively, enhance its importance within the field of nuclear analysis.