Dalton Seminar Series: Interfacial Kinetic Studies of Advanced Spent Nuclear Fuel Recycle Processes
|Starts:||13:00 12 Oct 2016|
|Ends:||14:00 12 Oct 2016|
|What is it:||Seminar|
|Organiser:||Dalton Nuclear Institute|
|Who is it for:||University staff, Adults, Current University students|
|Speaker:||Professor Colin Boxall,|
Nuclear power is of great importance to the future of low carbon energy production and the ability to separate and recover the actinide elements from spent fuel is a key requirement for a sustainable nuclear fuel cycle. While the extraction of U and Pu for the fabrication of new fuel is well established with the PUREX process, recovery of the actinides, and their separation from the chemically similar lanthanides, remains challenging.
A range of new organic extractant molecules, such as N,N,N’,N’’ tetraoctyl diglycolamide (TODGA), have been developed for the recovery of trivalent actinides through solvent extraction processes in the context of advanced spent nuclear fuel recycle processes such as the GANEX and i-SANEX processes. For safe implementation at industrial scale, it is important that the ligands and their resultant f-block element complexes be well characterised with new understanding required for the associated chemical extraction mechanisms and kinetics.
Consequently, a study of the interfacial and mass transport kinetics of cerium extraction by TODGA has been conducted using a rotating diffusion cell (RDC) apparatus. The RDC comprises two solution phases which are separated by a defined area membrane interface and subjected constant rotation. This rotation establishes controlled hydrodynamic flow and well characterised boundary / diffusion layer conditions within each solution phase, facilitating the study of both diffusion and kinetic contributions to the rate of mass-transfer and the interrogation of the mechanism of extraction.
Studies to date have revealed significant insights into the Ce(III) / TODGA extraction system, indicating an interesting dependency on local hydrodynamics at the solution phase boundary with the key complexation reaction occurring in the aqueous phase. The extraction rate of Ce(III) has been shown to correlate with aqueous Ce(III) while the simultaneous extraction of HNO3 by TODGA is also demonstrated. The use of HNO3-pre-contacted TODGA indicates that the extraction of the acid may be inhibitive towards the continued extraction of metal ions and warrants further investigation.
A theoretical description of the Ce(III) / TODGA RDC system has been developed and combined with spectrometric quantification of the interfacial flux allowing for the determination of several key rate parameters including both the forward / complexation and back / decomplexation reaction rates, the aqueous decomplexation length and the interfacial rate constant.
Professor Colin Boxall
Role: The Lloyd’s Register Foundation Centre for the Safety of Nuclear Energy
Organisation: Lancaster University
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