Decontamination of high level activity solutions from cesium and strontium by chromatography

International audienceThe high rate of irradiation of certain samples resulting from various programs carried out in ATALANTE facility is essentially due to the presence of $^{137}$+$^{134}$Cs and $^{90}$Sr. The elimination of these radionuclides would make it possible to handle these samples in glove boxes without having to carry out important dilution beforehand. It would allow to analyze these samples by techniques usually implemented in glove boxes (ICP, radiometry, ...) and to reach lower detection limits.Preliminary tests were carried out with real samples by using extraction chromatography as separative technique.The principle of the cations/Cs separation consists in adding on a 2 mL column filled with resin AM-PAN (ammonium molybdophosphate embedded in polyacrylnitrile), the sample adjusted before at a nitric acidity of 2M, then a washing solution ([HNO$_3$] = 2M). During these two steps, Cs$^+$ is expected to be retained by the resin while the other cations cross the column.This separation, tested on an aliquote of a solution of irradiated fuel dissolution, showed that contrary to the cesium, elements measured by ICP-AES (U and Pu) and by gamma spectrometry ($^{154}$+$^{155}$Eu, $^{244}$Ce, $^{241}$Am and $^{106}$Ru) are not retained during the feeding and washing steps. The decontamination factor of cesium is superior to 500.The principle of the cations / Sr separation consists in adding on a 2 mL column filled with a Sr resin ((1.0M 4,4 ' (5 ')-di-t-butylcyclohexano 18-crown-6 (crown ether) in 1-octanol (weighing 40%) / inert chromatographic support (weighing 60%)) the sample, adjusted before at the acidity [HNO$_3$] = 3M / [H$_2$C$_2$O$_4$] = 0.01M, then a washing solution ([HNO$_3$] = 3M / [H$_2$C$_2$O$_4$] = 0.01M). During these two steps, the strontium is expected to be retained by the resin whereas the other cations cross the column.This separation, tested on an aliquote of a solution of irradiated dissolution of fuel, showed that elements measured by ICP-AES (U, Fe, Mo, Zr, Pd, Zr, Pd, Ru, Tc) and by spectrometry gamma ($^{134}$+$^{137}$Cs, $^{154}$+$^{155}$Eu, $^{241}$Am, $^{106}$Ru) are not retained during the feeding and washing stages. The passage on the column of an elution solution ([HNO$_3$] = 0.01M) led to the total recovery of the initial strontium. The results of the cations / Cs and cations / Sr separations are very encouraging. Additional experiments on other high level radioactive samples are in progress to consolidate both tested methods. They consist in using a wider range of samples, studying the influence of fluorides and determining the behavior of a largest number of elements. These studies will be presented on the poster