A CONTROLLED POTENTIAL COULOMETER FOR HIGH-PRECISION URANIUM AND PLUTONIUM ANALYSIS .2. APPLICATION AND PERFORMANCE

Controlled potential coulometry is considered to be a reliable method for the determination of the uranium and/or plutonium content of candi date reference materials. Although base materials selected for that pu rpose have a high purity, they nevertheless contain traces of metallic impurities such as copper, iron and molybdenum which interfere in the electrochemical processes involved. A study of the behaviour of these elements during the pre-electrolysis and electrolysis of uranium solu tions has been performed. Their influence must be accounted for in ord er to obtain accurate results. The performance of a home-made coulomet er designed for high precision analysis has been tested under various conditions and for various materials. The ultimate precisions obtainab le with the instrument lie in the order of 0.01 to 0.05% relative as o verall uncertainties, depending mainly on the analyte (U or Pu), and o n its purity.