Radiochemistry

The row of 15 chemical elements from Ac to Lr with atomic numbers from 89 to 103 are known as the actinides, which are all radioactive. Among them, uranium and plutonium are the most important as they are used in the nuclear fuel cycle and nuclear weapon production. Since the beginning of national nuclear programs and nuclear tests, many radioactively contaminated nuclear legacy sites, have been formed. This mini review covers the latest experimental, modeling, and case studies of plutonium and uranium migration in the environment, including the speciation of these elements and the chemical reactions that control their migration pathways.

Phosphogypsum is a high volume by-product from Phosphate fertilizer factory, named the Triple Superphosphate complex of Bangladesh containing naturally occurring radionuclide. Distribution of 226Ra, 210Pb and 210Po in the fertilizer factory byproduct, phosphogypsum, has been determined using alpha and gamma-spectrometry. Both nuclides (226Ra and 210Po) were found to be concentrated in the finest-grained materials of phosphogypsum. The investigated radionuclide concentration values in PG obtained were comparable with data reported in the phosphogypsum literature, while lower values were found for these radionuclides. Moreover, laboratory radium and polonium leaching experiments of phosphogypsum by deionized water and selective extraction solution have been performed. Radium leaching results showed that fresh phosphogypsum produced the highest concentration of Ra in solution and old phosphogypsum showed a very low transfer to the water. Polonium leaching experiments have shown that only a small amount of polonium is dissolved in filtrated fresh water, this amount is increased when the pH is decreased. It was observed that some extraction solution is more effective at releasing polonium to water from the gypsum matrix. Approximately 32% of 210Po is present on the gypsum surface and not inside the lattice; this position is easily exchangeable with Journal of Environmental Science and Public Health 185 contact of external media (i.e., MgCl2 extraction solution) and 95% of PG was soluble with concentrated cocktail acid solution and a value of 14% 210Po was released with contact of 0.02M sulfuric acid solution. The results obtained in this study can be utilized to verify the environmentally safe use of phosphogypsum as an amendment to agricultural soils.

This study explored linear dose-responses of nano-graphene oxide (GO) using quantitative percent transmittance values in FTIR spectroscopy. First, the samples containing nano-graphene oxide powder were gamma-irradiated in the range of 0–80 kGy. Immediately after the irradiation, the samples underwent various tests including HRTEM and FTIR for characterization purposes. The primary results indicated that depending on the dose, gamma-rays could induce different defects and breaks in the irradiated samples. After the qualitative and quantitative analyses, dose-responses with high degrees of linearity (R2 > 0.99) were found in the analysis of the quantitative values of percent transmittances in different FTIR wavenumbers ranging from 1430 to 1450 cm−1. In this study, the FTIR analysis was successfully done for the first time to achieve the study objectives, and it can be potentially applied for larger dose ranges.
Keywords
Linear dose-response
Graphene oxide
Radiation processing
Dosimetry
FTIR Spectroscopy

ABSTRACT The sorption properties of solid-phase extractants (SPEs) prepared by impregnation of Taunit carbon nanotubes with adducts of diphenyl(dibutylcarbamoylmethyl)phosphine oxide (CMPO) and tri-n-octylphosphine oxide (TOPO) in HNO3 solutions were studied. The SPEs exhibit high ability to sorb U(VI), Pu(IV), Np(V), Am(III), and Eu(III) from nitric acid solutions, with good kinetic properties. The impregnation conditions and distribution coefficients of the radionuclides in their recovery from 3 M HNO3 were determined. The possibility of preparing SPEs by Taunit impregnation in HNO3 solutions with adducts of tributyl phosphate (TBP) and N,N′-dimethyl-N,N′-dioctylhexylethoxymalonamide (DMDOHEMA) and with Cyphos IL-101 phosphonium ionic liquid was demonstrated.

A new and regioselective strategy was developed for the preparation of fluorine-18-labeled insulin as a novel positron emission tomography (PET) tracer. [18F]-4-Fluorobenzoic acid (4-18FBA), which was produced in 83 +/- 8% yield (n = 10), through the use of succinimidyl [18F]-4-fluorobenzoate (4-(18)FSB), was conjugated through a short spacer (6-aminohexanoic acid, AHx) to the PheB1 residue of a protected form of insulin. 18FB-AHx-insulin (8b) was repeatedly prepared in practical quantities (10-20 mCi, 370-740 MBq) in good radiochemical yield (9 +/- 5%, n = 9) and in a specific activity of 7.8 mCi/micromol. The final product was characterized by comparing the radioHPLC and radioTLC of 8b with that of the 19F-analogue (19FB-AHx-insulin, 8a) and by analyzing a carrier-added synthesis by mass spectrometry. Dithiothreitol and endoproteinase Glu-C digestion experiments on 8a confirmed that the prosthetic group was in fact conjugated to the PheB1 residue. An insulin receptor (IR) phosphorylation assay using CHO-hIR cells overexpressing recombinant human insulin receptors indicated no statistical difference in the extent of autophosphorylation stimulated by 8a as compared to that for human insulin (EC50 values of 0.82 nM and 1.0 nM, respectively). The stimulation of 2-deoxyglucose uptake in 3T3-L1 mouse adipocytes utilizing 8a versus unmodified human insulin gave similar EC50 values of 0.68 nM and 0.41 nM, respectively. The IC50 values for 8a versus native insulin for the displacement of 125I-insulin from HEK-293 cells were also the same within experimental error (2.6 nM for 8a versus 2.4 nM for unmodified human insulin). These results support the use of the 18F-insulin analogue as a PET tracer for imaging the distribution of insulin in vivo.

The sorption of Eu(III) onto montmorillonite samples from different deposits such as those of Kutch (India), 10th Khutor deposit (Russia), and Cortijo de Archidona (Spain) was studied over a wide range of experimental conditions by varying the total Eu concentration, pH, and ionic strength. Various bentonite samples showed quantitative sorption at all pH values at low ionic strengths of the solution because of ion exchange interactions. At a higher ionic strength (1 M NaClO4), the sorption is pH-dependent because of the interaction with edge sorption sites and it differed from sample to sample. The difference in the mechanism of interaction at different ionic strengths was confirmed by time-resolved laser-induced fluorescence. Thermodynamic modeling was performed with all experimental data for montmorillonite samples from different sources to create a generalized model for describing their interaction with Eu(III).

Differences and similarities between LiF-based LiF:Mg,Ti and LiF:Mg,Cu,P are discussed, with respect to their dosimetric properties--sensitivity, non-linearity of dose response and heavy charged particle efficiency, as related to the concentration and the individual role of the Mg, Ti, Cu and P dopants. To study further the role of these dopants, the properties of some new, 'hybrid' phosphors: LiF:Mg,Cu,Ti and LiF:Mg,P, specially developed for this purpose, are also discussed. In the glow curve of LiF:Mg,Cu,P with a low concentration of Mg a new peak was found, which appears to be an analogue of peak 4 in LiF:Mg,Ti, Magnesium apparently controls most of the dosimetric properties of LiF-based phosphors. For instance, charged-particle efficiency appears to be anti-correlated with the concentration of Mg, being much less dependent on the content of other dopants. On the other hand, some properties of LiF-based systems seem to be correlated with changes in the emission spectra. It is suggested that Ti hampers the acceptance of any increased amount of Mg into more traps in LiF:MgTi. The absence of Ti, not the presence of P or Cu, is therefore a key to the high sensitivity of LiF:MgCuP.

Photon energy response of MTS-N (LiF:Mg,Ti) detectors (TLD Poland) and of MTS-N detectors sensitised with 200 Gy of 60Co gamma rays, followed by UV irradiation (sMTS-N), has been determined using X rays with narrow energy spectra, in the energy range from 20 to 300 keV. The over-response of LiF:Mg,Ti detectors for X rays (relative TL efficiency eta = 1.1) can be explained as an ionisation density effect. Low energy X rays produce short electron tracks, which locally deposit a high radiation dose and, consequently, lead to an enhanced (supralinear) response. This over-response has not been observed in sensitised MTS-N where supralinearity in the response after gamma ray doses above 1 Gy is not seen. Using the dose-response curves measured for MTS-N detectors after 137Cs gamma ray irradiation and local doses calculated using Monte Carlo generated electron tracks, it was possible to predict the relative TL effectiveness for different X ray energies. The calculation procedure can be applied to predict the photon energy response of LiF:Mg,Ti detectors in an arbitrary photon field.

There are two widely applied types of thermoluminescent detectors based on LiF:Mg luminophor: Lif:Mg,Ti and highly sensitive LiF:Mg,Cu,P. The role of luminescence centres in these materials is usually attributed to defects connected with, respectively, titanium and phosphorus dopants. In order to check how composition of dopants introduced into the LiF lattice influences emission spectra, measurements on a series of variously doped LiF:Mg samples were performed. Apart from LiF:Mg,Cu,P and LiF:Mg,Ti detectors with different concentration of activators, an experimental sample being a kind of a 'hybrid' between both standard materials was also prepared. It was synthesised with concentrations of magnesium and copper identical to those used for LiF:Mg,Cu,P preparation. but instead of phosphorus it was doped with titanium (LiF:Mg,Cu,Ti). The measurements of the emission spectra were performed by using a liquid nitrogen cooled CCD 1024E detector with an SP150 spectrograph. During the measurements the samples were placed inside a cryostat in a vacuum. Resulting data were numerically deconvoluted for individual peaks with respect to the wavelength and the temperature. The glow curve shape of this material resembles that of LiF:Mg,Cu,P, while sensitivity is at the level of LiF:Mg,Ti. Preliminary results indicate that emission of the LiF:Mg,Cu,Ti sample is similar to that of LiF:Mg,Cu,P rather than to LiF:Mg,Ti, showing a maximum for wavelengths well below 400 nm.

A previous study that explored the age and growth of red steenbras Petrus rupestris (Valenciennes, 1830), a large sparid (family Sparidae, seabreams or porgies) endemic to South Africa and reported to approach 2 m in length, provided estimates as a moderately slow-growing species with a maximum age near 30 years. The stock is considered collapsed and a fishing moratorium was imposed in 2012, resulting in this species being assessed as Endangered by the IUCN. One consideration in addressing population status is validation of life-history traits. In this study, estimates of age for red steenbras from thin-sectioned otoliths were reassessed visually in terms of both the original ages and revised estimates using a different age-reading pattern. The revised ages exceeded the original ages by up to 30 years, with a maximum estimated age of 55 years from a well-defined otolith section that provided a basis for the revised age-reading procedure. Bomb radiocarbon (14C) dating revealed there was an offset in the timing of the 14C rise on the Agulhas Bank that, when coupled with considerations for regional oceanography, provided support for the revised age-reading pattern and an estimated longevity that exceeds 50 years. These findings were further supported by the fortuitous recapture of a tagged red steenbras that was at liberty for 22 years.

2'-Deoxyguanosine in aqueous solution (5 x 10(-4) mol/dm3) was irradiated with 60Co gamma-rays under N2O. Products were separated by gel chromatography (Cellulofine GC-15-m) and high performance liquid chromatography (Inertsil ODS-2). 2-Amino-4-hydroxy-5-formamido-6-(2'-deoxyribosyl)-aminopyrimidine was one of the main radiolytic products. The formation of 2,5-diamino-4- hydroxy-6-(2'-deoxyribosyl)-formamidopyrimidine was detected, this compound being verified by measuring its ultraviolet absorption spectrum and analyzing its trimethylsilylated derivative by gas chromato-mass spectrometry. Its yield in terms of 2-amino-4-hydroxy-5-formamido-6-(2'-deoxyribosyl)- aminopyrimidine was 1:3.

2'-Deoxyguanosine in aqueous solution (5 x 10(-4) mol/dm3) was irradiated with 60Co gamma-rays under N2O. Products were separated by gel chromatography (Cellulofine GC-15-m) and high performance liquid chromatography (Inertsil ODS-2). 2-Amino-4-hydroxy-5-formamido-6-(2'-deoxyribosyl)-aminopyrimidine was one of the main radiolytic products. The formation of 2,5-diamino-4- hydroxy-6-(2'-deoxyribosyl)-formamidopyrimidine was detected, this compound being verified by measuring its ultraviolet absorption spectrum and analyzing its trimethylsilylated derivative by gas chromato-mass spectrometry. Its yield in terms of 2-amino-4-hydroxy-5-formamido-6-(2'-deoxyribosyl)- aminopyrimidine was 1:3.

The exchange (ex) and the accompanying isomerization (isom) in the reaction of methyl (E)- and (Z)-β-chloro-α-cyano-p-nitrocinnamates [(E)-5 and (Z)-5] with 36Cl‾ in acetonitrile were investigated. Exchange was much faster than isomerization, kex/kisom = 54 [(E)-5] and 123 [(Z)-5]. Both exchange and isomerization were faster for (Z)-5 than for (E)-5. The exchange was a relatively fast process, and extrapolation suggested that kex(Cl‾)/ksubstitution(piperidine) of 5 is 2.7. The results are discussed in terms of formation of intermediate carbanion, which exchanged the chloride with highly preferred retention. The modes of rotations leading to inversion (isomerization) were analyzed, and it was shown that isomerizations via 120° counterclockwise rotation and 180º clockwise rotation around the Cα-Cβ bond in the carbanion are distinguishable in principle, although we failed to determine the mode of rotation in our system. The relatively high nucleophilicity of Cl‾ was ascribed to lower hidden reversal of the nucleophilic attack by Cl‾ than in less activated systems. The differences in reactivity
of (Z)-5 and (E)-5 were analyzed in terms of steric interactions in the transition states for the 60° and 120° internal rotations.