Controlled Potential Coulometry for the accurate determination of plutonium in the presence of uranium: The role of sulfate complexation

TALANTA

卷:222

Article

Canciani, Giacomo¹  Davrain, Ygor¹  Crozet, Marielle¹  Roudil, Daniele¹  Picart, Sebastien¹ 

[1] Univ Montpellier, CEA, DES, ISEC,DMRC,CETAMA, Marcoule, France

关键词: Controlled-potential coulometry;    Plutonium;    Sulfate;    Uranium;    Complexation;    Speciation;   

DOI  :  10.1016/j.talanta.2020.121490

来源: Elsevier

【 摘 要 】

Controlled Potential Coulometry (CPC) is generally regarded as one of the most accurate analytical methods available for the quantification of plutonium (Pu) in acidic aqueous solutions. With a growing use of mixed oxide nuclear fuel, there has been an interest in the technique's applicability to the analysis of Pu in the presence of uranium (U). Expanding on previous studies, the work presented herein demonstrates the highly accurate CPC analysis of Pu in mixed solutions (Pu + U) containing large quantities of U (U:Pu up to 100:1) as well as establishing the role played by sulfate anions during the analyses. By combining experimental results with speciation simulations, it is shown that the introduction of U in mixed Pu + U solutions is accompanied by increases in sulfate ions in the nitric acid medium which complex unequally with the different Pu cations in solution. The anions' stronger affinity of for Pu(IV) rather than Pu(III) causes a decrease in the formal potential of the Pu(IV)/Pu(III) redox couple, directly affecting the degree of completion of the electrochemical reactions performed during CPC. A correction factor, f, is applied to account for the degree of completion of the analysis' electrochemical steps and compensate for the effects of complexation. Thereby, a level of accuracy comparable to that achieved during the analysis of pure Pu solutions, is attained. Ultimately, a series of recommendations are put forward such that it becomes possible to maintain CPC's good analytical performance for the measurement of Pu content in mixed Pu + U solutions.

【 授权许可】

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