Studies on the separation of Am(III) from trivalent lanthanides in high-level waste solution using modifier-free solvents and aqueous soluble bis-1,2,4-triazines

Abstract

The selective partitioning of trivalent actinides (An(III)) from high-level liquid waste (HLLW) is considered as an essential step in the management of spent nuclear fuel. The i-SANEX process for the separation of An(III) from the co-existing lanthanides (Ln(III)) in 4 M nitric acid solution and simulated HLLW was studied using a couple of symmetrical diglycolamides (TODGA and TDDGA) and an unsymmetrical diglycolamide (D3DODGA) in n-dodecane as the extraction phase. The selective stripping of Am(III) from the loaded organic phase containing trivalent Ln(III) was investigated using aqueous soluble bis-1,2,4-triazine derivatives such as SO3-Ph-BTP, SO3-Ph-BTBP and SO3-Ph-BTPhen in dilute nitric acid solution. The results revealed that the SF of Eu(III) over Am(III) decreased with increase in the concentration of nitric acid in all cases and SF decreased in the order SO3-Ph-BTP > SO3-Ph-BTBP > SO3-Ph-BTPhen. The co-stripping of lighter lanthanides (La, Ce, Pr, Nd) was also observed during the recovery of Am(III).