Plutonium analysis from controlled-potential coulometry for the certification of the MP3 standard material

Coulometry is an assay method in which the quantity of the element analyzed is determined by measuring a quantity of electricity. For contributing to the certification of the new metal plutonium reference material (MP3), controlled-potential coulometry (CPC) has many advantages: it is a high accuracy absolute chemical analysis technique. Many studies are now conducted on plutonium solutions, to improve the operating conditions and the current apparatus, for mass determination with a precision of 0.1%. The different experimental preliminary results are discussed and the apparatus described. The coulometry cell assembly comprises a motor connected to a stirrer designed to prevent splashing, an inlet tube for inert gas, three electrodes, and a thermocouple for measuring the temperature. The measuring system includes a potentiostat, a CPU, a calibrated current generator, a temperature indicator and a voltmeter, all maintained at a constant temperature. Current integration is made by electronic components, introduced in the potentiostat and the CPU. (authors)