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

Effects of radiation of 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 with 60Co 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 the increase of Df and a decrease of the separation factor. The DEHPA - DTPA - lactic acid system is concluded to sustain absorption of radiation at an absorbed dose up to 200 Whxl-1 in the partitioning of transplutonium elements in HLW. (author)