Counter-Current Extraction of Neptunium from Simulated Pressurized Heavy Water Reactor High Level Waste Using N,N,N',N'-Tetraoctyl Diglycolamide

Abstract

The extraction behavior of neptunium was investigated from Pressurized Heavy Water Reactor Simulated High Level Waste (PHWR-SHLW) using 0.05 M N,N,N',N'-tetraoctyl diglycolamide (TODGA) + 5% iso-decanol dissolved in n-dodecane as the extractant. Batch extraction data revealed that the extraction of Np(IV) was a magnitude of order higher than that of the Np(VI). The stoichiometry of the extracted species was investigated by slope analysis and was found to be 2:1 (Ligand : Metal) for Np(IV) and 1:1 for Np(VI). The distribution data suggested that the neptunium in SHLW was predominantly converted into Np(VI) and its extraction decreased. Counter-current extraction studies employing 12 stages of mixer settler suggested that ∼97% extraction of Np was possible from PHWR-SHLW at organic-to-aqueous phase ratio (O/A) of 1. However, stripping was efficient and > 99.9% of Np could be back extracted in 8 stages from the loaded organic phase.

Keywords:

• Neptunium
• TODGA
• diglycolamide
• counter-current
• extraction
• waste management

ACKNOWLEDGMENT

The authors thank Dr. A. Goswami, Head, Radiochemistry Division, for his keen interest in this work.