Trace Actinide Signatures of a Bulk Neptunium Sample.

In nuclear forensic analyses, measurements of actinide elements in a sample can assist with identifying interdicted or unknown materials. While these radiochemical signatures have been extensively investigated in uranium materials, less is known about bulk neptunium samples. This paper describes the measurement of trace actinide concentrations and isotopic profiles in a 237Np oxide sample. Uranium, plutonium, americium, and curium concentrations and isotopic profiles in the sample were determined and deemed potentially useful for distinguishing different sources of 237Np. Several different potential radiochronometry systems were also investigated; discordant results indicate that the Np sample was never completely purified of other actinide elements, or that subsequent contamination of the sample occurred. Few prior studies of neptunium materials have been reported, and these data suggest that trace actinide constituents could provide unique signatures to identify material out of regulatory control.

Photochemical separation of plutonium from uranium.

Plutonium-based technologies would benefit if chemical hazards for purifying plutonium were reduced. One critical processing step where improvements could be impactful is the adjustment of plutonium oxidation-states during separations. This transformation often requires addition of redox agents. Unfortunately, many of the redox agents used previously cannot be used today because their properties are deemed incompatible with modern day processing facilities and waste stream safety requirements. We demonstrated herein that photochemistry can be used as an alternative to those chemical agents. We observed that (1) Pu4+ → Pu3+ and UO22+ → U4+ photoreduction proceeded in HCl(aq) and HNO3(aq) and (2) photogenerated Pu3+(aq) and U4+(aq) could be separated using anion exchange chromatography (high yield, >90%; good separation factor, 322).

Measurements of extinct fission products in nuclear bomb debris: Determination of the yield of the Trinity nuclear test 70 y later.

This paper describes an approach to measuring extinct fission products that would allow for the characterization of a nuclear test at any time. The isotopic composition of molybdenum in five samples of glassy debris from the 1945 Trinity nuclear test has been measured. Nonnatural molybdenum isotopic compositions were observed, reflecting an input from the decay of the short-lived fission products (95)Zr and (97)Zr. By measuring both the perturbation of the (95)Mo/(96)Mo and (97)Mo/(96)Mo isotopic ratios and the total amount of molybdenum in the Trinity nuclear debris samples, it is possible to calculate the original concentrations of the (95)Zr and (97)Zr isotopes formed in the nuclear detonation. Together with a determination of the amount of plutonium in the debris, these measurements of extinct fission products allow for new estimates of the efficiency and yield of the historic Trinity test.

Concurrent determination of 237Np and Pu isotopes using ICP-MS: analysis of NIST environmental matrix standard reference materials 4357, 1646a, and 2702.

An optimized method was developed to analyze environmental soil and sediment samples for (237)Np, (239)Pu, and (240)Pu by ICP-MS using a (242)Pu isotope dilution standard. The high yield, short time frame required for analysis, and the commercial availability of the (242)Pu tracer are significant advantages of the method. Control experiments designed to assess method uncertainty, including variation in inter-element fractionation that occurs during the purification protocol, suggest that the overall precision for measurements of (237)Np is typically on the order of ± 5%. Measurements of the (237)Np concentration in a Peruvian Soil blank (NIST SRM 4355) spiked with a known concentration of (237)Np tracer confirmed the accuracy of the method, agreeing well with the expected value. The method has been used to determine neptunium and plutonium concentrations in several environmental matrix standard reference materials available from NIST: SRM 4357 (Radioactivity Standard), SRM 1646a (Estuarine Sediment) and SRM 2702 (Inorganics in Marine Sediment).

Kläui ligand thin films for rapid plutonium analysis by alpha spectrometry.

As part of a nuclear forensics capability, rapid and effective methods to analyze for plutonium and other actinide metals are needed. A key requirement of these methods is that they afford a high chemical yield while still providing isotopic information necessary for forensic evaluation. Toward this objective, a new method for binding plutonium for analysis by alpha spectrometry has been developed. Thin films of Kläui-type tripodal oxygen donor ligands were prepared by spin-casting solutions onto glass substrates. Three different ligands were evaluated for plutonium binding, and the best results were obtained using the ethyl-substituted complex Na[Cp*Co(P(O)(OEt)2)3], which bound 80-88% of the dissolved Pu under equilibrium conditions. The thin films are simple and inexpensive to prepare and exhibit excellent alpha spectral resolution, having line widths of ~33 keV. The method has been successfully applied to analyze for plutonium in both an archived nuclear debris sample and a certified environmental soil sample. The results obtained from the soil analysis are in good agreement with the certified values, demonstrating the effectiveness of the method for rapid plutonium analysis.

Coordination chemistry of the bis(trifluoromethylsulfonyl)imide anion: molecular interactions in room temperature ionic liquids.

Room temperature ionic liquids composed of bis(trifluoromethylsulfonyl)imide anions and 1,3-ethylmethylimidazolium (EMI) cations are shown to stabilize monomeric ligand deficient transition metal complexes via four distinct binding modes: monodentate nitrogen or oxygen coordination and/or bidentate oxygen-oxygen' or nitrogen-oxygen coordination (eta1-N, eta1-O, eta2-O,O' and eta2-N,O).

Binuclear rhenium(I) complexes with bridging [2.2]paracyclophane-diimine ligands: probing electronic coupling through pi-pi interactions.

Two pseudo-para substituted bis-diimino[2.2]paracyclophane ligands (4,16-bis(picolinaldimine)-[2.2]paracyclophane (BPPc) and 4,16-bis(methyl-picolinaldimine)-[2.2]paracyclophane (BmPPc)) were prepared by the condensation reaction of the appropriate picolinaldimine with 4,16-diamino-[2.2]paracyclophane (2). An improved synthesis of 2 from [2.2]paracyclophane also is reported. BPPc (3a): monoclinic, P2(1)/c, a = 8.2238(11) A, b = 15.336(2) A, c = 8.4532(11) A, beta = 98.578(3) degrees, V = 1054.2(2) A(3), Z = 2. To investigate the binding properties of the bis-diimino[2.2]paracyclophane ligands, binuclear rhenium(I) tricarbonyl chloride complexes [Re(CO)(3)Cl](2)(micro-BPPc) (5a) and [Re(CO)(3)Cl](2)(micro-BmPPc) (5b) were prepared and fully characterized by infrared spectroscopy, (1)H NMR spectroscopy, elemental analysis, UV-visible absorption spectroscopy, and cyclic voltammetry. Two model complexes, Re(tolyl-pyCa)(CO)(3)Cl (4) (tolyl-pyCa = N-(p-tolyl)-2-pyridinecarboxaldimine) and [Re(CO)(3)Cl](2)(micro-PBP) (6) (PBP = p-phenylenebis(picolinaldimine)), also are reported. The dimeric compounds 5 and 6 each undergo two one-electron, predominantly diimine-centered reduction processes. Spectroscopic data and comproportionation constants (5a, 23 +/- 9; 5b, 23 +/- 9; 6, 2750 +/- 540) are consistent with relatively weak interactions between the diimine groups mediated by the paracyclophane bridging group, and these results are consistent with steric and electronic factors.

Chloroheptakis(dimethyl sulfoxide)uranium(IV) trichloride.

In the title complex, [UCl(C(2)H(6)OS)(7)]Cl(3), the uranium metal center is coordinated in a distorted bicapped trigonal prism geometry by seven O atoms from dimethyl sulfoxide ligands and by a terminal chloride ligand. Charge balance is maintained by three outer-sphere chloride ions per uranium(IV) metal center. Principle bond lengths include U-O 2.391 (2)-2.315 (2) A, U-Cl 2.7207 (9) A, and average S-O 1.540 (5) A.