Production, isolation, and shipment of clinically relevant quantities of astatine-211: A simple and efficient approach to increasing supply.

The alpha emitter astatine-211 (211At) is a promising candidate for cancer treatment based on Targeted Alpha (α) Therapy (TAT). A small number of facilities, distributed across the United States, are capable of accelerating α-particle beams to produce 211At. However, challenges remain regarding strategic methods for shipping 211At in a form adaptable to advanced radiochemistry reactions and other uses of the radioisotope. PURPOSE: Our method allows shipment of 211At in various quantities in a form convenient for further radiochemistry. PROCEDURES: For this study, a 3-octanone impregnated Amberchrom CG300M resin bed in a column cartridge was used to separate 211At from the bismuth matrix on site at the production accelerator (Texas A&M) in preparation for shipping. Aliquots of 6 M HNO3 containing up to ≈2.22 GBq of 211At from the dissolved target were successfully loaded and retained on columns. Exempt packages (<370 MBq) were shipped to a destination radiochemistry facility, University of Texas MD Anderson Cancer Center, in the form of a convenient air-dried column. Type A packages have been shipped overnight to University of Alabama at Birmingham. MAIN FINDINGS: Air-dried column hold times of various lengths did not inhibit simple and efficient recovery of 211At. Solution eluted from the column was sufficiently high in specific activity to successfully radiolabel a model compound, 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (1), with 211At. The method to prepare and ship 211At described in this manuscript has also been used to ship larger quantities of 211At a greater distance to University of Alabama at Birmingham. PRINCIPAL CONCLUSIONS: The successful proof of this method paves the way for the distribution of 211At from Texas A&M University to research institutions and clinical oncology centers in Texas and elsewhere. Use of this simple method at other facilities has the potential increase the overall availability of 211At for preclinical and clinical studies.

Complexation of Astatine(III) with Ketones: Roles of NO3- Counterion and Exploration of Possible Binding Modes.

Ketones have been proven effective in extracting astatine(III) from aqueous solvents. Previous theoretical studies suggested a mechanism where the "sp2" lone pair on the carbonyl oxygen donates electron density into the π system of the AtO+ molecular cation to form a dative-type bond. In this study, co-extraction of NO3- as AtO(NO3)·(O═CR1R2) species into the organic phase appears to be a key factor. Adjusting the electronic properties of the ketone, by having an aryl group instead of an alkyl group in the alpha position of the ketone, increased the electron density on C═O, increased the bond strength between the ketone and AtO+, and in turn increased the extraction of 211At into the organic phase. Extraction with diketones shows dependence on the bridging distance between the two carbonyl moieties, where a C3 or longer bridge results in a 10-fold increase in extraction into the organic phase. DFT calculations show the longer bridge allows for the chelation of AtO(NO3) by either the second carbonyl or the phenyl ring.

Spectroscopic characterization of neptunium(VI), plutonium(VI), americium(VI) and neptunium(V) encapsulated in uranyl nitrate hexahydrate.

The coordination of crystalline products resulting from the co-crystallization of Np(vi), Pu(vi), Am(vi), and Np(v) with uranyl nitrate hexahydrate (UNH) has been revealed through solid-state spectroscopic characterization via diffuse reflectance UV-Vis-NIR spectroscopy, SEM-EDS, and extended X-ray absorption fine structure (EXAFS) spectroscopy. Density functional and multireference wavefunction calculations were performed to analyze the An(vi/v)O2(NO3)2·2H2O electronic structures and to help assign the observed transitions in the absorption spectra. EXAFS show a similar coordination between the U(VI) in UNH and Np(vi) and Pu(vi); while Am resulted in a similar coordination to Am(iii), as reduction of Am(vi) occurred prior to EXAFS data being obtained. The co-crystallization of the oxidized transuranic species-penta- and hexavalent-with UNH, represents a significant advance from not only a practical standpoint in providing an elegant solution for used nuclear fuel recycle, but also as an avenue to expand the fundamental understanding of the 5f electronic behavior in the solid-state.

Astatine partitioning between nitric acid and conventional solvents: indication of covalency in ketone complexation of AtO.

Astatine-211 has been produced at Texas A&M University on the K150 cyclotron, with a yield of 890 ± 80 MBq through the 209Bi(α,2n)211At reaction via an 8 h bombardment with a beam current of 4-8 µA and an α-particle beam energy of 28.8 MeV. The target was then dissolved in HNO3 and the extraction of 211At was investigated into a variety of organic solvents in 1-3 M HNO3. Extraction of 211At with distribution ratios as high as 11.3 ± 0.6, 12.3 ± 0.8, 42.2 ± 2.2, 69 ± 4, and 95 ± 6 were observed for diisopropyl ether, 1-decanol, 1-octanol, 3-octanone, and methyl isobutyl ketone, respectively, while the distribution ratios for 207Bi were ≤0.05 in all cases. The extraction of 211At into both methyl isobutyl ketone and 3-octanone showed a strong, linear dependence on the HNO3 initial aqueous concentration and better extraction than other solvents. DFT calculations show stronger binding between the carbonyl oxygen of the ketone and the At metal center.

Correction: Solid state characterization of oxidized actinides co-crystallized with uranyl nitrate hexahydrate.

Correction for 'Solid state characterization of oxidized actinides co-crystallized with uranyl nitrate hexahydrate' by Jeffrey D. Einkauf et al., Dalton Trans., 2020, 49, 608-612.

Solid state characterization of oxidized actinides co-crystallized with uranyl nitrate hexahydrate.

Characterization of the penta- and hexavalent dioxo cations of NpO2+, NpO22+, PuO22+, and AmO22+ has been carried out by diffuse reflectance UV-Vis-NIR spectroscopy, with the first observations of NpO2+, NpO22+, and AmO22+ in the solid state. Absorbance measurements confirmed the presence of the higher actinides of Np, Pu, and Am, with shifts in their absorbance bands indicating the formation of the dinitrate species in the crystalline phase. The oxidized actinides were prepared in the solid state by co-crystallization with UO2(NO3)2·6H2O by a simple reduction in temperature. The hexavalent species were all co-crystallized in near proportion to UO22+ and the pentavalent species was co-crystallized in a slightly less efficient manner, roughly 83% of that of UO22+.

Solubility and Complexation of the Bismuthate Ion in Nitric Acid Systems.

The dissolution rate and solubility of NaBiO3 have been investigated in nitric acid systems ranging from 4 to 6 M HNO3 and were found to be 58-76 µg/cm2·d and 490-830 mM, respectively. The presence of 50 mM U(VI) drastically increased the solubility to 540-1200 mM, while rates of dissolution were relatively unchanged. The solubility of NaBiO3 increased with an increase in U(VI) concentrations at 4 M HNO3, with log-log analysis indicating a one-to-one complex between Bi and U and infrared spectroscopic evidence monitoring uranyl stretching, suggesting complex formation. Absorbance spectra were obtained experimentally and computationally with an absorbance band in the range of 450-600 nm that has been attributed to Bi(V). The ingrowth and decay of Bi(V) in solution was also studied as a function of mass of solid NaBiO3 present, acidity, and temperature. The activation energies of dissolution and decomposition were calculated to be 39 ± 4 and 61 ± 6 kJ/mol, respectively. These results indicate that dissolution of NaBiO3 into the respective Na+ and BiO3-occurs prior to undergoing reduction, a process which conventionally has been believed to occur in the reverse order.

Group Hexavalent Actinide Separations: A New Approach to Used Nuclear Fuel Recycling.

Hexavalent Np, Pu, and Am individually, and as a group, have all been cocrystallized with UO2(NO3)2·6H2O, constituting the first demonstration of an An(VI) group cocrystallization. The hexavalent dioxo cations of Np, Pu, and Am cocrystallize with UO2(NO3)2·6H2O in near proportion with a simple reduction in temperature, while the lower valence states, An(III) and An(IV), are only slightly removed from solution. A separation of An(VI) species from An(III) ions by crystallization has been demonstrated, with an observed separation factor of 14. Separation of An(VI) species from key fission products, (95)Zr, (95)Nb, (137)Cs, and (144)Ce, has also been demonstrated by crystallization, with separation factors ranging from 6.5 to 71 in the absence of Am(VI), while in the presence of Am(VI), the separation factors were reduced to 0.99-7.7. One interesting observation is that Am(VI) shows increased stability in the cocrystallized form, with no reduction observed after 13 days, as opposed to in solution, in which >50% is reduced after only 10 days. The ability to cocrystallize and stabilize hexavalent actinides from solution, especially Am(VI), introduces a new separations approach that can be applied to closing the nuclear fuel cycle.

Separation of americium from curium by oxidation and ion exchange.

Nuclear energy has the potential to be a clean alternative to fossil fuels, but in order for it to play a major role in the US, many questions about the back end of the fuel cycle must be addressed. One of these questions is the difficult separation of americium from curium. Here, we report the oxidation of Am in two systems, perchloric acid and nitric acid and the affect of changing the acid has on the oxidation. K(d) values were observed and a direct separation factor was calculated and was seen to be as high as 20 for four metal(IV) pillared phosphate phosphonate inorganic organic hybrid ion exchange materials. These ion exchangers are characterized by very low selectivity for cations with low charge but extremely high uptake of ions of high charge.