Volume 107, Issue 12

This study aims to determine forensic signatures for processing history of UO 2 based on modifications in intermediate materials within the uranyl peroxide route. Uranyl peroxide was calcined to multiple intermediate U-oxides including Am-UO 3 , α-UO 3 , and α-U 3 O 8 during the production of UO 2 . The intermediate U-oxides were then reduced to α-UO 2 via hydrogen reduction under identical conditions. Powder X-ray diffractometry (p-XRD) and X-ray photoelectron spectroscopy (XPS) were used to analyze powders of the intermediate U-oxides and resulting UO 2 to evaluate the phase and purity of the freshly synthesized materials. All U-oxides were also analyzed via scanning electron microscopy (SEM) to determine the morphology of the freshly prepared powders. The microscopy images were subsequently analyzed using the Morphological Analysis for Materials (MAMA) version 2.1 software to quantitatively compare differences in the morphology of UO 2 from each intermediate U-oxide. In addition, the microscopy images were analyzed using a machine learning model which was trained based on a VGG 16 architecture. Results show no differences in the XRD or XPS spectra of the UO 2 produced from each intermediate. However, results from both the segmentation and machine learning proved that the morphology was quantifiably different. In addition, the morphology of UO 2 was very similar, if not identical, to the intermediate material from which it was prepared, thus making quantitative morphological analysis a reliable forensic signature of processing history.

The extraction behaviour of U(VI), Th(IV) and Nd(III) was investigated as a function of nitric acid concentration for diamide based extractants, namely, N,N,N ′, N ′-tetraoctyl-3-carbonylpentanediamide (TOCPDA) and 4-carbonyl-heptanedioic acid bis-dioctylamide (CHADA). In addition, the distribution ratio was also measured for Pu(IV) and Sr(II) with 1.1 M CHADA in n -dodecane. These extractants were synthesized by adopting simple acid, amine coupling reaction with DCC (dicyclohexylcarbodiimide) and DMAP ( N,N ′-dimethylaminopyridine) as the coupling agent. The newly synthesized extractants were characterized by FT-IR, NMR, Mass, CHNS and HPLC. The extraction results indicated that CHADA shown has better extraction behavior for U(VI) compared to TOCPDA. In addition, CHADA coated HPLC column was examined for the retention behaviour of U(VI), Th(IV), and Nd(III). Computation studies based on density functional theory (DFT) were carried out to understand the complexing behaviour of U(VI), Pu(IV) and Sr(II) with CHADMA and TMCPDA.

The present work was devoted to study of sorption parameters of resorcinol-formaldehyde resins synthesized through introduction of an inorganic filler (in amounts of 10 and 25 wt.%) with its subsequent leaching. The surface morphology and composition of ion-exchange resins have been investigated by means of the method of scanning electron microscopy. The effect of internal diffusion on the peculiarities of the ion-exchange process has been determined. It has been revealed that the ion-exchangers destruction upon a prolonged contact with highly alkaline solutions is followed by the decrease of internal diffusion coefficients and selectivity toward Cs-137 micro-quantities. The sorption properties of resins under dynamic conditions at high solution feeding rates have been studied. A sample with the highest efficiency of Cs-137 removal from highly mineralized solutions has been identified.

Samples of Chernobyl fuel debris such as corium and “lava” had been studied using repeated static leach test MCC-1 at temperature of 25 and 90 °C in distilled water and simulated seawater. A normalized 137 Cs mass loss (NL Cs ) estimated for corium samples after 168 days in distilled and seawater was 3.2–3.5 g/m 2 at 25 °C and 113–114 g/m 2 at 90 °C. For “lava” samples NL Cs varied from 1.4 to 13.2 g/m 2 at 90 °C for 56 days (in distilled and seawater) and from 0.1 to 0.4 g/m 2 at 25 °C in seawater for 140 days. Chemical durability of Chernobyl “lava” in distilled and seawater evaluated using 137 Cs specific activity in leachates is higher than one for corium. Further study is proposed in order to obtain more quantitative data.

With the speedy growth of nuclear power production, the removal and disposal of radioactive nuclides such as 129 I, 99 Tc, 79 Se, 36 Cl, 93 Mo, and 137 Cs become major environmental security issues. Retention of these radionuclides, especially anionic species such as 129 I (t 1/2 1.7 × 10 7 years), 93 Mo (t 1/2 4 × 10 3 years) and 79 Se (t 1/2 3.27 × 10 5 years) has been challenging. 129 I, 93 Mo and 79 Se bind very weakly to most sorbents and deposits. This study has examined the sorption potential of Metal hydroxide sludge (MHS) for 125 I (t 1/2 60.2 days), 99 Mo (t 1/2 2.75 days) and 75 Se (t 1/2 120 days) as a surrogate for 129 I, 93 Mo and 79 Se, respectively. MHS has been characterized by different techniques and the factors affecting the sorption processes were investigated. The experimental data were analyzed using kinetic models and thermodynamic parameters. The results showed that the kinetics of sorption of 125 I and 99 Mo on MHS proceeds according to the pseudo-first-order, on the contrary of 75 Se sorption follows pseudo second-order kinetic model. The maximum sorption capacity of MHS was found to be 51.2 mg/g, 46.5 mg/g and 40.2 mg/g for 125 I, 99 Mo and 75 Se, respectively. It can be concluded that, in the case of release of anionic radionuclide species to the surroundings the MHS could act as a succeeded and economical sorbent material for retention of different anionic radionuclides such as 133, 129 I, 79 Se, 36 Cl, 93, 99 Mo, and 99 Tc. To avoid the release of such anionic species from the stored nuclear wastes to the environment.

This work reports thermodynamic characterizations of lanthanide β-diketonates for use in nuclear fission product separation. Adsorption and sublimation enthalpies have been shown to be linearly correlated, therefore there is motivation to determine sublimation thermodynamics. An isothermal thermogravimetric analysis method is employed on fourteen lanthanide chelates for the ligands 2,2,6,6-tetramethyl-3,5-heptanedione and 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione to determine sublimation enthalpies. No linear trend is seen across the series; values show a cyclical nature, possibly indicating a greater influence of chemisorption for some complexes and less of a role of physisorption in dictating adsorption differences between lanthanides in the same series. This is in line with previous reports in terms of the chromatographic separation order of the lanthanides. The results reported here can be used to manipulate separations parameters and column characteristics to better separate these lanthanide chelates. Fourteen chelates of the ligand 1,1,1-trifluoro-2,4-pentanedione are also thermally characterized but found to not sublime and be undesirable for this method. Additionally, all chelates are characterized by constant heating thermogravimetric analysis coupled with mass spectrometry, melting point analysis, elemental analysis and FTIR.

In preclinical research radiolabeled nanoparticles have been attracting interest as a new class of imaging probes. Assuming good stability of solid lipid nanoparticles (SLNs) under physiological conditions, radiolabeled SLNs can be used for imaging and measuring uptake in target tissue. Present study was performed to evaluate biological behavior of temozolomide (TMZ) loaded solid lipid nanoparticles (SLN-TMZ) in vivo and in vitro . Lipid nanoparticles were prepared by emulsification and low-temperature solidification method. ζ potential, morphology and particle size of nanoparticles were determined. Biological behavior of 99m Tc(CO) 3 + radiolabeled SLN-TMZ were investigated in vitro on U87/Daoy cell lines and in vivo on female Wistar Albino rats. Obtained results of in vitro incorporation, in vivo biodistribution and gamma imaging studies on radiolabeled SLN-TMZ show that the radiolabeled solid lipid nanoparticles could have potential as a drug delivery system for TMZ.

The high importance of zirconium-89 (T 1/2  = 78.41 h) is related to its applications in medical imaging. It can be produced at low-energy cyclotrons by the reaction 89 Y(p,n) 89 Zr. There exist several publications on its production at low and intermediate energies but there is discrepancy with simulated data. In this study we considered the experimental parameters for four different types of yttrium foil targets reported in literature. The experimental parameters considered were the target geometry, beam profile, and angle of the target relative to the beam during irradiation. The Monte-Carlo code FLUKA was used to calculate production yields. The resulting values obtained by FLUKA from pencil beam or spread energy beam were compared to the theoretical yields obtained from the excitation function and the experimental ones. The FLUKA prediction for 89 Z-yield reached ≈50 MBq/μA · h which agrees to a high extent with experimental and theoretical yields reported for the different targets.

A scheme of an “inverse” generator based on an inorganic sorbent (annealed zirconium and yttrium mixture oxides) has been proposed and tested. The generator demonstrated high yield of the 213 Bi product (up to 97 % in 0.5 mL of eluate), high degree of purification from the actinium isotopes (up to 10 −2 % of initial 225 Ac in 3 M NaNO 3 solution), as well as the products of 227 Ac decay, and low radiation impact on the sorbent. Application of circulating approach to the sorption of 213 Bi provides decreasing processing time to 5 min at higher yield of the product.