Kent D. Abney

Use of PVC plasticized membranes for uptake of radioactive cesium and strontium

A new type of sorbent for the selective uptake of elements based on the use of PVC plasticized membranes, commonly used in electrochemistry as ion selective (ISE) membranes, is described. It is theoretically derived that the material acting as a selective ion sensor of ISE must be also effective as a sorbent. In experimental verification of the hypothesis, the cobalt dicarbollide and sodium tetraphenylborate with the addition of a synergist of the polyethyleneglycol type were dissolved in several solvents mixed with a tetrahydrofurane solution of 5% PVC and evaporated to produce a membrane used for the sorption experiments. It was found that PVC, besides functioning as a solid support, does not influence significantly the behavior of the prepared materials; however, the kinetics are slower than for the analogous solvent extraction techniques. Practical applications of such membranes for the isolation of radioactive cesium and strontium from acidic and alkaline solutions with a high of Na{sup +} ions content are shown, with emphasis on nontoxic solvents as substitutes for the toxic nitrobenzene. 25 refs., 3 figs., 6 tabs.

Synthesis and structure of N-heterocyclic carbene complexes of uranyl dichloride

Treatment of UO2Cl2(thf)3 in THF with two equivalents of 1,3-dimesitylimidazole-2-ylidene (IMes) or 1,3-dimesityl-4,5-dichloroimidazole-2-ylidene (IMesCl2) yields novel monomeric uranyl N-heterocyclic carbene complexes, representing the first examples of actinyl carbon bonds.

Trimethylsilyl iodide as a halide exchange reagent in inorganic chemistry: synthesis and structure of Cp2*ThI2 (Cp* = η5-C5Me5)

Abstract The bis(pentamethylcyclopentadienyl)thorium(IV) complex Cp2*ThI2 (Cp* = η5-C5Me5) was readily synthesized from the dibromo derivative Cp2*ThBr2 using a slight excess of trimethylsilyl iodide (Me3SiI). The thorium complex Cp2*ThI2 exhibits a ‘bent metallocene’ structure, as determined by single-crystal X-ray diffraction (monoclinic, space group P21/n; a = 8.572(2), b = 16.718(3), c = 15.881(2) A; β = 98.16(2)o; V = 2252.8(8) A3; Z = 4).

Plutonium Oxide Polishing for MOX Fuel Production

Abstract: Los Alamos National Laboratory (LANL) has been tasked to produce 120 kg of plutonium as highly purified PuO2 for the European Mixed Oxide (MOX) Lead Test Assembly managed by Duke, COGEMA, Stone & Webster (DCS). To meet stringent and challenging technical requirements for PuO2 production, the LANL aqueous polishing team recently established consistency in generating quality material from weapons-grade PuO2. Polishing was required to remove undesirable quantities of trace-metal impurities, particularly gallium, and to produce a material with appropriate powder characteristics, such as particle size and surface area. The process flow sheet for PuO2 polishing was based on aqueous purification and included the unit operations of dissolution, ion exchange, oxalate precipitation, and calcination.

Breakthrough volumes of TcO 4 − on Reillex™-HPQ anion exchange resin in a Hanford Double Shell Tank simulant

The breakthrough volumes on Reillex™-HPQ anion exchange resin columns for TcO4− solutions have been determined. The feed solutions were a Handford Double Shell Tank Slurry (DSS) simulant of ionic strength (μ) of 6.22 M and a TcO4− of 5.00×10−5 M and a 1∶3 dilution of the DSS simulant, μ =2.07 M, with a TcO4− of 1.67×10−5 M. The DSS flow rates {mL simulant/(cross section area of column.min)} through the column varied from 0.19 to 20.5 cm/min. The 1% breakthrough volumes varied from 50.0 to 1.3 bed volumes (BV), respectively. The 1∶3 DSS flow rate varied from 0.95 to 11.0 cm/min and had 1% breakthrough volumes ranging from 94 to 20 BV, respectively. At a flow rate of 1.0 cm/min, the breakthrough bed volumes are 10.2 and 95.8 BV for the DSS and 1∶3 DSS solutions, respectively. Obviously, there is an advantage in processing the 1∶3 dilution of the feed stream.

Americium Separations from Nitric Acid Process Effluent Streams

Plutonium recovery operations offer several points at which americium removal may be attempted, and we are evaluating two classes of materials targeted at different steps in the process. Extraction chromatography resin materials loaded with three different alkylcarbamoyl phosphinates and phosphine oxides are assessed for Am removal efficiency and Am/Fe selectivity from 1–7M nitric acid solutions. Commercial and experimental anion exchange resins are evaluated for total alpha-activity removal from post-evaporator solutions whose composition, relative to the original nitric acid effluent, is reduced in acid and greatly increased in total salt content. With both classes of materials, americium and/or total-alpha reduction is sufficient to meet regulatory requirements even under sub-optimal conditions. Batch distribution coefficients and column performance data are presented.

Molecular structure of ThBr4(DME)2 (DME = 1,2-dimethoxyethane)

The molecular structure of ThBr4(DME)2 (DME = 1,2-dimethoxyethane), the first structurally characterized thorium complex containing a simple bidentate ether ligand, is described. The eight-coordinate complex presents a distorted dodecahedral geometry, with Th—Br and Th—O bond lengths in the ranges 2.8516(13)–2.8712(13) Å and 2.564(8)–2.620(8) Å, respectively. ThBr4(DME)2 is monoclinic, space group P21/n, a = 7.672(1), b = 14.581(1), c = 15.847(2) Å, β = 102.24(1)°, V = 1732.4(3) Å3, and Z = 4.

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.

Analysis of solid uranium samples using a small mass spectrometer

Abstract A mass spectrometer for isotopic analysis of solid uranium samples has been constructed and evaluated. This system employs the fluorinating agent chlorine trifluoride (ClF 3 ) to convert solid uranium samples into their volatile uranium hexafluorides (UF 6 ). The majority of unwanted gaseous byproducts and remaining ClF 3 are removed from the sample vessel by condensing the UF 6 and then pumping away the unwanted gases. The UF 6 gas is then introduced into a quadrupole mass spectrometer and ionized by electron impact ionization. The doubly charged bare metal uranium ion (U 2+ ) is used to determine the U 235 /U 238 isotopic ratio. Precision and accuracy for several isotopic standards were found to be better than 12%, without further calibration of the system. The analysis can be completed in 25 min from sample loading, to UF 6 reaction, to mass spectral analysis. The method is amenable to uranium solid matrices, and other actinides.

Strontium and cesium extraction into hydrocarbons using alkyl cobalt dicarbollide and polyethylene glycols

The extraction of strontium and cesium ions from high ionic strength acid, base, and salt solutions into an organic extractant consisting of alkyl cobalt dicarbollide and polyethylene glycol (PEG) in diethylbenzene was investigated. Adding hexaethylene glycol or PEG-400 improved the strontium extraction ≥100-fold, while cesium extraction was decreased at high PEG concentrations. The extractions are rapid and selective, even in the presence of molar concentrations of sodium ion, suggesting that alkyl cobalt dicarbollide extractants are useful for the treatment of alkaline nuclear wastes. A method for the synthesis of tetra-n-hexyl(cobalt dicarbollide) is described.