Fission products separation by ionic chromatography for elementary and isotopic analysis by mass spectrometry

The elementary and isotopic analysis of irradiated fuels is necessary to validate neutronic calculation codes and to improve the safety of reactors. In particular, the determination of isotope content and concentration in fission products resulting from nuclear reactions are performed using thermo-ionization mass spectroscopy (TIMS) and inductively coupled plasma mass spectroscopy (ICPMS). Even if mass spectroscopy is a precise and sensitive technique, a preliminary chromatographic separation is necessary to avoid isobaric interferences in the spectrum of fission products such as 90Sr-90Y-90Zr, 104Ru-104Pd, 137Cs-137Ba, 142Ce-142Nd, 150Sm-150Nd etc.. Also, the thermal ionization phenomenon is disturbed by the presence of other elements on the filament such as the easily ionizable elements. Chromatographic separations allow to eliminate these matrix effects. The HPLC systems which are presented use the ionic chromatography methods to separate the alkali and alkaline-earths, the transition metals and rare earths. Weakly acid cation exchangers (WCX) and strongly acid cation exchangers (SCX) are studied and compared. The influence of complexing acids addition such as hydroxy-isobutyric, oxalic, di-picolinic, di-glycolic etc.. was studied in order to control the selectivity and to reduce the interaction of triple-charged cations with the stationary phase. The concentration of these acids must be as low as possible to avoid the disturbance of thermal ionization in TIMS. Different types of detection were applied: indirect UV, visible after post-column derivation, and conductometry. The direct coupling of ionic chromatography with ICPMS was evaluated too