Separations of neutron poisons Sm, Nd, Ru, Rh, and Pd from spent nuclear fuel by NH3/HCl gas mixture treatment coupled with liquid Sn extraction

The selective removal of neutron-absorbing fission products from spent nuclear fuel is critical for enhancing neutron economy and enabling efficient recycling. In this work, we present a novel two-step dry reprocessing strategy that integrates NH 3 /HCl gas mixture treatment with liquid Sn extraction to achieve phase-selective separation of Sm, Nd, Ru, Rh, and Pd from simulated U 3 O 8 -based spent fuel. Thermodynamic analysis and experimental validation reveal that decomposition of NH 4 Cl at elevated temperatures serves as the generator of NH 3 /HCl gas mixture capable of selectively chlorinating Sm 2 O 3 and Nd 2 O 3 into soluble chlorides while reducing U 3 O 8 to UO 2 and converting RuO 2 , Rh 2 O 3 , and PdO to their metallic states (Ru, Rh, Pd). Subsequent dissolution tests in LiCl-KCl confirm that Sm and Nd are almost completely removed, with chlorination efficiencies of nearly 100%, while uranium loss can be minimized by controlling direct NH 4 Cl contact. The coupled liquid Sn extraction at 1173 K enabled the recoveries of metallic Rh, Rh, and Pd with a promising extraction efficiency. This integrated approach significantly simplifies the partitioning of key neutron poisons (Sm, Nd, Ru, Rh, Pd) compared to conventional aqueous or pyrochemical routes, reduces secondary waste, and preserves uranium in its UO 2 form.