Ultrafast Laser Filament-induced Fluorescence Spectroscopy of Uranyl Fluoride

Uranyl fluoride (UO2F2) is a compound which forms in the reaction between water and uranium hexafluoride, a uranium containing gas widely used for uranium enrichment. Uranyl fluoride exhibits negligible natural background in atmosphere; as a result, its observation implies the presence and active operation of nearby enrichment facilities and could be used as a tracer for treaty verification technologies. Additionally, detection of UO2F2 has a potential application in guiding remediation efforts around enrichment facilities. Laser-induced fluorescence (LIF) has been proposed in the past as a viable technique for the detection and tracking of UO2F2. We demonstrate that ultrafast laser filamentation coupled with LIF extends the capabilities of standard LIF to enable remote detection of UO2F2. An intense femtosecond laser pulse propagated in air collapses into a plasma channel, referred to as a laser filament, allowing for the extended delivery of laser energy. We first investigate the luminescence of UO2F2 excited by the second harmonic of an ultrafast Ti:sapphire laser and subsequently excite it using the conical emission that accompanies ultrafast laser filamentation in air. We measure the decay rates spanning 4.3-5.6 × 104 s-1 and discuss the characteristics of the luminescence for both ultrafast- and filament-excitation. Larger decay rates than those observed using standard LIF are caused by a saturated component of prompt decay from annihilation of dense excited states upon excitation with an ultrafast source. The reproducibility of such decay rates for the given range of incident laser intensities 1.0-1.6 × 1011 W cm-2 is promising for the application of this technique in remote sensing.

Plutonium segregation in glassy aerodynamic fallout from a nuclear weapon test

This study combines electron microscopy equipped with energy dispersive spectroscopy to probe major element composition and autoradiography to map plutonium in order to examine the spatial relationships between plutonium and fallout composition in aerodynamic glassy fallout from a nuclear weapon test. A sample set of 48 individual fallout specimens were interrogated to reveal that the significant chemical heterogeneity of this sample set could be described compositionally with a relatively small number of compositional endmembers. Furthermore, high concentrations of plutonium were never associated with several endmember compositions and concentrated with the so-called mafic glass endmember. This result suggests that it is the physical characteristics of the compositional endmembers and not the chemical characteristics of the individual component elements that govern the un-burnt plutonium distribution with respect to major element composition in fallout.

Unraveling the mystery of “tech red” – a volatile technetium oxide

A molecular Tc₂O₅ species is the likely identity of a volatile oxide which has remained uncharacterized for 50+ years.

Ion Selective Resins: Development and Applications for Nuclear Waste Management

Organic based ion selective resins have some similar attributes: case of synthesis, high metal ion complexation ability, and flexibility for different nuclear waste management applications. For most chelating polymers, the ligand is deemed to be of primary importance for the interaction with the targeted metal ion. The role of the polymer matrix is usually ignored. For ion specific resins, the polymer structure is formed to a specific metal ion. Using the molecular imprinting technique, resins can be formed with functional groups and cavities for a target metal ion. Ion selective resins have been developed for the separation of Cs. The methods and concepts used for the development of the Cs specific resins have been applied to the development of selective resins for Eu (a trivalent actinide model). The resulting resins are characterized by FTIR spectroscopy, moisture regain, and ion exchange capacity. The incorporation of 8-hydroxyquinoline into the resin increases selectivity for Eu over La. The results for the Eu study indicate ion specific resins can be developed for the separation of trivalent actinides from nuclear waste.