Radiation effects on the separation of lanthanides and transplutonides by the TALSPEAK-type extraction

Abstract

Effects of radiation on the extraction system composed of DEHPA extractant and DTPA aqueous solution containing nitrate were studied by measuring distribution ratios of Am(III) and Nd(III) with the extractant and DTPA solution either one of which was irradiated with⁶⁰Co γ-rays or the organic—aqueous mixed phase irradiated under continuous stirring. The irradiation causes an increase of Df and a decrease of the Nd/Am separation factor β, to an especially large extent in the mixed phase system. These effects are due firstly to the radiolytic decomposition of DTPA and secondarily to the formation of MEHPA. The replacement of nitrate with lactate stops the degradation of DTPA and DEHPA resulting in the retardation of increase of Df and a decrease of separation factor. The DEHPA-DTPA-lactic acid system is concluded to sustain absorption of radiation at an absorbed dose up to 200 Wh·I⁻¹ in the partitioning of transplutonium elements in HLW.