The radiolytic behaviour of a CyMe4BTBP-based solvent for actinide/lanthanide separation: insights into the degradation products

The radiolytic degradation of bipyridine derivative CyMe4-BTBP dissolved in 1-octanol, solvent intended for the separation of actinides from lanthanides in spent nuclear fuel, was investigated, as the solvent performances in the extraction process may be modified by radiolysis. Ligand solutions were exposed to doses up to 150 kGy in different experimental conditions with a dose rate ranging from 20 Gy/h to 2.5 kGy/h. Identification of the degradation products was performed by means of electrospray ionization mass spectrometry (ESI-MS) combined with nuclear magnetic resonance spectroscopy (1H-NMR). It is evident that the CyMe4-BTBP content decreases with increasing the total absorbed dose and that the dose rate affects the yield of degradation products but not their type. Different hypotheses on the structure of the degradation products are proposed from their mass spectra fragmentation (MSn spectra).