Volume 109, Issue 8

The properties and stability of ozone in aqueous solutions of various compositions in the рН range of 0–14 were considered. The effect of anions and cations, which are involved in the redox reactions of actinides, on the stability of ozone and its reactivity has been studied. The reactions of О 3 with ions of d- and f-elements were analyzed. Depending on the solution composition and рН value, the reaction can occur directly with the O 3 molecule (direct mechanism) and/or with short-lived ion-radical products ( • OH, HO2•/O2−•${\text{HO}}_{2}^{{\bullet}}/{\text{O}}_{2}^{-{\bullet}}$, H 2 O 2 /HO2−${\text{HO}}_{2}^{-}$, O3−•${\text{O}}_{3}^{-{\bullet}}$) formed upon ozone decomposition in water (indirect mechanism). Ions with inert coordination sphere react with О 3 in the outer-sphere fashion with electron transfer. Polyvalent ions with labile coordination spheres are oxidized in acidic medium via О atom transfer, possibly, with intermediate peroxy addition (H 2 O 2 , HNO 4 , H 2 SO 5 , etc.). In alkaline medium, О 3 is converted to the O3−•${\text{O}}_{3}^{-{\bullet}}$radical ion, which is the key oxidant for actinides. The results of studies and the mechanisms of reactions of ozone and its intermediates decomposition products with U, Np, Pu, and Am in various oxidation states and with some transition metals (Fe, Mn, Ag, Co, etc.) in aqueous solutions are presented and discussed.

Radiation stability is one of the key properties to enable the efficient use of extractants in spent nuclear fuel with high radioactivity. The last several decades have witnessed a rapid progress in the radiation chemistry of extractants. A variety of studies and reviews pertinent to the radiation stability of extractants have been published. However, a thorough summary for the alpha radiolysis results of extractants is not available. In this review, we survey the development of alpha radiolysis of extractants for actinide lanthanide separation and compare their radiolysis behaviors induced by alpha particles and gamma rays. The discussion of alpha radiolysis of extractants is divided into three parts according to the functional groups of extractants (i.e., phosphine oxide, amide and bis-triazinyl bipyridines). Given the importance of radiation source to carry out alpha irradiation experiment, we first give a brief introduction to three practicable alpha radiation sources including alpha emitting isotopes, helium ion beam and reactor. We hope this review will provide useful information and unleash a broad palette of opportunities for researchers interested in radiation chemistry.

The formation of third phase is a detrimental phenomenon witnessed in the nuclear separation processes during the extraction of certain metal salts by an organic solution, which comprises of a neutral extractant, tri- n -butyl phosphate dispersed in a non-polar diluent, n -dodecane ( n -C 12 H 26 ). In the present work, a comparative analysis on the third phase formation behaviour of three trialkyl phosphates, TBP, its linear and branched higher homologues tri- n -amyl phosphate and tris(2-methylbutyl) phosphate (T2MBP), respectively, have been provided which will be useful for the identification of an extractant with minimum third phase formation tendency. The organic phase splitting behaviour during the extraction of three mineral acids (HClO 4 , HCl and HNO 3 ) and two tetravalent metal nitrates (Th(IV) and Zr(IV)) by trialkyl phosphates has been investigated to understand the influence of anionic and cationic components, respectively, in third phase formation of trialkyl phosphates. The effect of structure of the alkyl groups of trialkyl phosphate and chain length of diluents on third phase formation during Zr(IV) extraction from HNO 3 media have also been studied. Overall, the third phase formation behaviour of T2MBP was found to be lower both for the extraction of mineral acid and Zr(IV), thereby indicating its potentiality for applications in various solvent extraction processes.

The Iranian ethalonic extract of propolis (EEP) were analyzed to determine their antioxidant activities and total phenolic and flavonoid contents, with and without gamma irradiation processing under various dosage of gamma (10, 20, 30, 40 and 50 kGy). The analysis results show that the gamma irradiated EEP at 10 KGy can scavenge free radicals and exhibit higher antioxidant-reducing power to the other groups ( P  < 0.05). It is noted that gamma irradiated EEP has higher total phenolic contents compared to gamma irradiated EEP at 30, 40 and 50 KGy and non-irradiated EEP ( P  < 0.05). The flavonoid compounds as indicated by C-13 NMR analysis were found to be higher in gamma irradiated EEP at 10 kGy compared with the other groups. In conclusion, gamma irradiation processing of EEP causes can enhanced antioxidant activities phenolic and flavonoid compounds at dose of 10 KGy.

Mica group minerals have been utilized in various industries such as paint, cement, rubber, plastic, paper, automotive, cosmetics, textile, etc. due to their unique electrical, thermal, and mechanical properties. In this study, the radiometric properties of 58 mica samples collected from three quarries operated commercially in Turkey were investigated using gamma-ray spectroscopy with an HPGe detector. The average activity concentrations of 226 Ra, 232 Th, and 40 K analyzed in mica samples were found as 12, 44, and 2763 Bq kg −1 , respectively. The radon emanation coefficient and radon mass exhalation rate of mica samples varied from 4 to 22% with an average of 10% and 0.4–5.9 µBq kg −1  s −1 with an average of 2.6 µBq kg −1  s −1 , respectively. The radiological hazard caused by the utilization of mica samples as raw materials in the cement and concrete industry was evaluated for adults by calculating the gamma index and annual effective dose due to external exposure indoor. The study results revealed that there are no significant radiological hazards associated with the utilization of mica samples as building raw materials.