Band 110, Heft 11

This review provides an overview of the chemical thermodynamics on ternary earth-alkaline metal-actinyl-tricarbonate systems (i.e., M-AnO 2 -CO 3 , M = Mg, Ca, Sr, and Ba) and discusses the aqueous complexation and dissolution/precipitation equilibrium for these ternary aqueous systems. The aqueous ternary U(VI) carbonate species are remarkably predominant in the U(VI) speciation under natural environmental conditions at ambient temperature and moderate ionic strength condition, while the omnipresence, according to recent studies, would be hindered by an increase in temperature and ionic strength. With respect to the ternary solid U(VI) carbonate phases, most of the previously reported data have been focused on physical properties and thus a notable lack of available data on chemical thermodynamic properties, i.e., solubility product constant, has been identified. Nevertheless, substantial influences of these ternary M-AnO 2 -CO 3 systems on the aqueous speciation and the solubility limiting phase under the natural environmental condition are taken into account according to the thermodynamic calculation. The authors point out that the completeness of the chemical thermodynamic model for predicting the chemical behavior of actinides in nature can be further improved on the basis of a sufficient understanding of ternary M-AnO 2 -CO 3 systems.

Activation cross-sections of the nuclear reactions nat Ba(p,x) 135,132g La, 135m Ba and nat Ce(p,x) 142,139,138m Pr, 141,139,137m Ce have been measured experimentally at the MGC-20 cyclotron, Cairo, Egypt, from their respective threshold energies up to about 14.7 MeV. Stacked foil irradiation technique and high-resolution gamma-ray spectroscopy were used. A comparison between the experimental and theoretical data derived from the nuclear model codes EMPIRE and TALYS (in the form of the TENDL library) was performed. The agreement in the low-energy region is fairly good. Integral yields of the produced radioisotopes were estimated from the present cross-section data and the results are discussed in terms of their production possibilities.

Although bioreduction induced by microorganisms has been considered to play an important role in the chemical and migration behaviors of uranium in nature, the accurate determination of tetravalent uranium reduced by microorganisms is still difficult to achieve. In this work, potentiometric titration via K 2 Cr 2 O 7 was used to quantitatively determine the microorganism reduced tetravalent uranium (U(IV)) for the first time. By evaluating the influence of microorganism substance content on the titration of U(IV), the appropriate determination range of U(IV) and biomass was confirmed, and U(IV) induced by bioreduction in three microorganisms was determined. With this method, U(IV) of more than 0.12 mg in microorganisms can be quantitatively measured with an accuracy of 2.2% and a precision of 1.3%, which has been established with the premise that the pretreatment biomass and quantity of U(IV) are in an appropriate range. Compared with the estimated values via the changes in hexavalent uranium (U(VI)) concentration in the bioreduction system, the results obtained by this method can more accurately reflect the quantity of U(IV) in microorganisms. This work can help us to better understand the bioreduction behavior of uranium in the environment.

Two alkali strontium borate glasses containing Cu 2+ or Zn 2+ ions (0.15 mol%) has been prepared by melting annealing method. Some of the glasses dosimetric measurements have been performed; they were checked by ultraviolet-visible light measurement showing the specific peaks of Cu + /Cu 2+ and Zn 2+ ions. Upon γ -rays, glasses are sensitive to the absorbed dose in the range 0.4–15 kGy, revealing their light absorption. A gradual decrease in optical absorbance and DC electrical conductivity was detected with progressive irradiation. While a gradual increase in optical energy bandgap (Eopt) and electron paramagnetic resonance (EPR) was observed. The presence of transition metal ion (TM) with their variable configurations helps to trap the radiolytic electrons or holes during the color center recovery rates. UV–Vis and EPR dosimetric characteristics have high color stability with excellent short and long-term stability revealing their possible use as glass dosimeters in medical sterilization and food irradiation processing.

Ionizing radiation is used in many fields in energy, medicine, and industrial applications. Those who are in these areas or cancer patients receiving radiotherapy are at risk for acute or long-term exposure to radiation damage due to these ionizing radiations. Non-toxic new agents are needed to protect intact tissue and cells. In this study, we aimed to determine the gamma and neutron radiation attenuation characteristics of seven different natural compounds (quercetin, menadione, naphthol, caffeine, quinine sulphate, cholesterol and riboflavin) to help users in radiation applications. Gamma radiation attenuation parameters such as the mean free path, mass attenuation coefficient, effective atom number, linear attenuation coefficient, and half-value layer were calculated theoretically with WinXCom software for the energy range 0.015–15 MeV. Fast neutron attenuation criteria, such as mean free path, half-value layer, effective removal cross-sections and transmission neutron number, were theoretically determined with Monte Carlo simulation codes (Geant4). Neutron absorption measurement experiments were also applied in addition to the theoretical results. The neutron radiation absorption capacities were determined for samples with an 241 Am-Be 4.5 MeV energy neutron source and portatif-type Canberra brand BF 3 gas neutron detector. Neutron attenuation parameters were compared with paraffin to determine the absorption capability of the samples. It was found that the dose 1.1094 (μSv/h) from the source was absorbed by the samples to the following extent: 31.76% (Quercetin), 21.85% (Menadione), 28.85% (Naphthol), 22.94% (Caffeine), 12.51% (Quinine sulphate), 40.44% (Cholesterol) and 20.94% (Riboflavin). From the results, it can be clearly seen that all these drug samples had a good neutron radiation attenuation capacity. This revealed that the examined samples had radiation absorption abilities. It was found that the cholesterol sample had an especially excellent absorption power for both neutron and gamma radiation. The samples investigated in this study could be used to develop radiation-protective drugs.

The Bi 2 O 3 –PbO–CdO–B 2 O 3 glasses were shaped via the melt-quenching process. The XRD spectra reveal that the glasses are composed of amorphous material. Four distinct bands may be seen in the FTIR spectra at wavelengths between 400 and 600, 600–800, 800–1200, and 1200–1500 cm −1 range. This is due to a variety of bond stretching and vibration modes present in the system. A Monte Carlo simulation was used to verify the radiation shielding capabilities. The µ values grow as the amount of Bi 2 O 3 in the manufactured glasses increases. The rise in µ values was coupled with a drop in the Δ 0.5 values when the Bi 2 O 3 concentration was increased. Additionally, the TF and RPE values were influenced by the enhancement in the µ values, with the RPE increasing from 34.61 to 44.42 percent and the TF values decreasing from 65.39 to 55.58 percent at 0.662 MeV when the Bi 2 O 3 concentration was increased. The study showed that raising the Bi 2 O 3 content improves the shielding capabilities. Thus, the produced glass samples, particularly BPCB25, exhibit excellent shielding capabilities, making them suitable for use in radiation shielding fields.