14521-18-7

The structural unit of the pentafluorides MF//5 (M equals Ru, Rh, Os, Ir, Pt) consists of M//4F//2//0 tetramers with the transition elements occupying the corners of the rhombus. In the case of RuF//5 the magnetic susceptibility vs. temperature curve shows a broad maximum at T approximately equals 40 K. Neutron diffraction experiments below and above this temperature show that this maximum does not correspond to a magnetic three-dimensional ordering. Theoretical calculations based on isolated tetranuclear clusters of identical S equals 3/2 spins have been applied. The intracluster exchange interactions are antiferromagnetic. The fitting of the susceptibility data leads to an exchange constant of J/k equals minus 8. 3 K.

Published data on sorption decontamination from RuF5 of UF 6 formed in the course of gas-fluoride reprocessing of spent nuclear fuel are summarized. Sorption of individual RuF5 on granulated fluoride sorbents, NaF (at 100

Nitrogen trifluoride (NF3) was used to fluorinate the metallic residue from the dissolution of a high burnup, boiling water reactor fuel (～70 MWd/kgU). The washed residue included the noble-metal phase (containing ruthenium, rhodium, palladium, technetium, and molybdenum), smaller amounts of zirconium, selenium, tellurium, and silver, along with trace quantities of plutonium, uranium, cesium, cobalt, europium, and americium, likely as their oxides. Exposing the noble metal phase to 10% NF3 in argon, between 400 and 550 °C, removed molybdenum and technetium near 400 °C as their volatile fluorides, and ruthenium near 500 °C as its volatile fluoride. The events were thermally and temporally distinct and the conditions specified provide a recipe to separate these transition metals from each other and from the nonvolatile residue. Depletion of the volatile fluorides resulted in substantial exothermicity. Thermal excursion behavior was recorded with the thermal gravimetric instrument operated in a non-adiabatic, isothermal mode; conditions that typically minimize heat release. Physical characterization of the noble-metal phase and its thermal behavior are consistent with high kinetic velocity reactions encouraged by the nanoparticulate phase or perhaps catalytic influences of the mixed platinum metals with nearly pure phase structure. Post-fluorination, only two products were present in the residual nonvolatile fraction. These were identified as a nano-crystalline, metallic palladium cubic phase and a hexagonal rhodium trifluoride (RhF3) phase. The two phases were distinct as the sub-μm crystallites of metallic palladium were in contrast to the RhF3 phase, which grew from the parent, nano-crystalline noble-metal phase during fluorination, to acicular crystals exceeding 20-μm in length.