In the present work, we extracted Mo-Tc-RuPd-Rh-Te alloy particles from spent fuel by a non-oxidative selective leaching of the fuel matrix, characterized them and studied their leaching behavior under different redox conditions. After selecting the optimal experimental conditions by using a synthetic alloy, the radioactive alloy particles were extracted from spent fuel and characterized by using SEM (scanning electron microscopy)-WDS (wavelength dispersive spectra). Micrometer sized alloy particles display very similar compositions, on average (wt. %): 32.7% Mo, 40.5% Ru, 7% Tc, 4.4% Rh, 12.2% Pd and 3.8% Te. The alloy particles were leached in 10 mM NaCl and 2 mM NaHCO 3 solutions, purged with two kinds of gas mixtures. It was observed that, under purging with Ar + 0.03% CO 2 , the leaching rates of 99 Tc and 100 Mo were similar, about 1.5 ppb/day. The results obtained under purging with 89.97% Ar + 0.03% CO 2 + 10% H 2 indicate that the 4d alloy particles are very effective catalysts for reduction caused by hydrogen: the concentrations of 99 Tc and 100 Mo dropped to levels below 1 ppb. No significant leaching of Ru, Rh, Pd and Te was observed during purging with both gas mixtures.

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