Development of a Selective Americium Separation Process Using H₄TPAEN as Water-Soluble Stripping Agent

ABSTRACT

Recycling americium from spent nuclear fuel is considered as an important option for a future sustainable nuclear fuel cycle. The PUREX solvent extraction process allows to separate uranium and plutonium from a solution of spent fuel dissolved in nitric acid. In a second step, it would be desirable to separate americium from fission products, and especially lanthanides, but also from curium in order to further transmute americium in future fast neutron reactors. For this purpose, we report the investigation of a new solvent extraction process based on the use of TODGA as an extractant in the organic phase and H₄TPAEN as a selective Am(III) stripping agent in the aqueous phase. With this promising system it is possible to co-extract Am, Cm and lanthanides at high acidity and then selectively strip americium from the loaded organic phase at pH around 1 with H₄TPAEN. Batch extraction data were acquired to evaluate best conditions to develop a liquid-liquid extraction flow sheet. The influence of several parameters like concentration of ligand, cations and temperature on Am(III)/Cm(III) and Am/lanthanides separation was evaluated. Especially, the ability of H₄TPAEN complexing agent to strip macro-concentrations of Am was demonstrated.

KEYWORDS:

• Americium
• curium
• H₄TPAEN
• liquid-liquid extraction

Nomenclature

An Actinides

DDistribution Ratio

DFDecontamination Factor

eqequilibrium

EXAmExtraction of Americium process

FPFission Products

H₄TPAEN N,N,N’,N’-tetrakis[(6-carboxypyridin-2-yl)methyl] -ethylenediamine

iniinitial

LnLanthanides

SFSeparation Factor

TEDGAN,N,N’,N’-tetraethyl diglycolamide

TODGAN,N,N’,N’-tetraoctyl diglycolamide

TPHHydrogenated TetraPropylene

V_aqVolume of aqueous phase

V_orgVolume of organic phase

Additional information

Funding

This work was funded by the European SACSESS Project (Contract No. FP7-Fission-2012-323-282) and results from a collaboration between SACSESS partners.