Technetium metal and pyrometallurgically formed sediments: study and speciation by Tc NMR and EXAFS/XANES

摘要

EXAFS and NMR are being developed with respect to study and speciation of technetium-99 during pyrometallurgical reprocessing of spent nuclear fuel. Based on the set of standards including technetium metal, different technetium halogenides, oxohalogenides, oxides and pyrometallurgically formed sediments, Tc hemical forms responsible for Tc accumulation i fused salts, deposits or gas-off depending on the applied reprocessing conditions are studied by means of NMR and EXAFS. NMR spectrum of Tc metal powder obtained by FT of a free induction decay accumulated after excitation of the spin system by a sequence of high frequency pulses (0.8 μs) with a dead time of 5.4 μs and a repetition time of 1 μs, provided with Knight shift K(ppm) = 7 305 - 1.52 * T; v_Q(~(99)Tc) = 230 kHz at 293 K, C_Q(~(99)Tc) = 5.52 MHz. EXAF spectra provided with excellent evidence for Tc(IV) halogenides, but need further development for lower oxidation states of technetium.