The Structure of the Plutonium Oxide Nanocluster [Pu₃₈O₅₆Cl₅₄(H₂O)₈]¹⁴⁻

LLNL SFA FY11 Program Management and Performance Report: Environmental Transport of Plutonium

“…Recent work by Neck et al (2007)and Soderholm et al (2008) sheds light on previously conflicting Pu(IV) solubility studies, suggesting that aqueous Pu(V) and 2-to 20-nm Pu colloids are expected to be present in solution. Thus, most laboratory Pu "sorption" experiments carried out at Pu concentrations greater than 10 -9 M Pu(IV) should, in fact, be regarded as reflecting adsorption of Pu in multiple oxidation states and the interaction of colloidal Pu(IV) clusters with mineral surfaces.…”

Development of a Composite Non-Electrostatic Surface Complexation Model Describing Plutonium Sorption to Aluminosilicates

“…Neck et al (2007) recently determined an equilibrium constant of log K = -8.3 +/-1.0 for Pu(IV) colloid . Soderholm et al (2008) determined that aggregated Pu colloids are comprised of ~2 nm crystalline Pu colloids. Oxidation state measurements by Rai et al (1999) and Neck et al (2007) have verified aqueous Pu(V) and Pu(VI) in Pu solubility experiments.…”

“…They reported that Pu polymers will be present at a constant level of log[Pu(IV)] coll = -8.3 ± 1.0. Recently, Soderholm et al (2008) observed monodispere, nanometer sized Pu "nanoclusters" which persisted in solution indefinitely. Colloids of this nature are not expected in this work due to the relatively low Pu concentration (10 -10 M).…”

“…The 3k MWCO filters have approximately a 4 nm pore size. Soderholm et al (2008) found that concentrated Pu solutions form roughly 2 nm particles that may aggregate to greater than 20 nm particles. Recent work in our laboratory has shown that colloidal Pu(IV) sorbs to synthetic goethite crystals in approximately the same size range but is dominated by 2 nm colloids that aggregate to form <20 nm particles.…”

Neptunium_Oxide_Precipitation_Kinetics_AJohnsen

“…One key finding about this oxide structure is that, because the X-ray scattering in these solid phases is dominated by plutonium, whose lattice positions remain consistent despite the addition of oxygen to the system, the changes in the oxygen content are almost undetectable via XRD. In fact, the variation in the PuO 2+x lattice parameter from 2.0  balancing chloride ions and water molecules [29]. While there is currently no evidence for such solids in neptunium(IV) oxide solids formed in aqueous solutions, these kinds of alternate plutonium structures raise the possibility of related neptunium solids that may provide pathways for additional neptunium-related chemical processes occurring in our experimental solutions beyond that specified by Eq.…”