Incorporation Modes of Iodate in Calcite.

Iodate (IO) incorporation in calcite (CaCO) is a potential sequestration pathway for environmental remediation of radioiodine-contaminated sites (e.g., Hanford Site, WA), but the incorporation mechanisms have not been fully elucidated.

Importance of interlayer H bonding structure to the stability of layered minerals.

Layered (oxy) hydroxide minerals often possess out-of-plane hydrogen atoms that form hydrogen bonding networks which stabilize the layered structure. However, less is known about how the ordering of these bonds affects the structural stability and solubility of these minerals. Here, we report a new strategy that uses the focused electron beam to probe the effect of differences in hydrogen bonding networks on mineral solubility.

Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4).

Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sublattice.

Technetium Incorporation into Goethite (α-FeOOH): An Atomic-Scale Investigation.

During the processing of low-activity radioactive waste to generate solid waste forms (e.g., glass), technetium-99 (Tc) is of concern because of its volatility.

Development of Online Spectroscopic pH Monitoring for Nuclear Fuel Reprocessing Plants: Weak Acid Schemes.

In nuclear fuel reprocessing, separating trivalent minor actinides and lanthanide fission products is extremely challenging and often necessitates tight pH control in TALSPEAK (Trivalent Actinide-Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexes) separations. In TALSPEAK and similar advanced processes, aqueous pH is one of the most important factors governing the partitioning of lanthanides and actinides between an aqueous phase containing a polyaminopolycarboxylate complexing agent and a weak carboxylic acid buffer and an organic phase containing an acidic organophosphorus extractant. Real-time pH monitoring would significantly increase confidence in the separation performance.

Conditions for critical effects in the mass action kinetics equations for water radiolysis.

We report on a subtle global feature of the mass action kinetics equations for water radiolysis that results in predictions of a critical behavior in H2O2 and associated radical concentrations. While radiolysis kinetics have been studied extensively in the past, it is only in recent years that high-speed computing has allowed the rapid exploration of the solution over widely varying dose and compositional conditions. We explore the radiolytic production of H2O2 under various externally fixed conditions of molecular H2 and O2 that have been regarded as problematic in the literature-specifically, "jumps" in predicted concentrations, and inconsistencies between predictions and experiments have been reported for α radiolysis.

Photophysics and luminescence spectroelectrochemistry of [Tc(dmpe)3](+/2+) (dmpe = 1,2-bis(dimethylphosphino)ethane).

The ligand-to-metal charge transfer (LMCT) excited state luminescence of [Tc(dmpe)3](2+) (dmpe is 1,2-bis-(dimethylphosphino)ethane) has been measured in solution at room temperature and is compared to its Re analogue. Surprisingly, both [M(dmpe)3](2+)* (M = Re, Tc) species have extremely large excited-state potentials (ESPs) as oxidants, the highest for any simple coordination complex of a transition metal. Furthermore, this potential is available using a photon of visible light (calculated for M = Tc; E°'* = +2.