Band 103, Heft 8

The oxidative action of a Cu(III) periodate compound toward Am(III) in nitric acid was studied. The extent of oxidation of Am(III) to Am(VI) was investigated using a constant initial Cu(III)-to-Am(III) molar ratio of 10:1 and varying nitric acid concentrations from 0.25 to 3.5 mol/L. From 0.25 to 3 mol/L HNO 3 , more than 98% of the Am(III) was oxidized to Am(VI); however, at 3.5 mol/L HNO 3 , the conversion to Am(VI) was only 80%. Increasing the Cu(III)-to-Am(III) molar ratio to 20:1 in 3.5 mol/L HNO 3 resulted in 98% conversion to Am(VI). For comparison, oxidation of Am(III) with NaBiO 3 was studied at 3.5 mol/L HNO 3 and the same stoichiometric excess of Bi(V) oxidant over Am(III) (stoichiometric ratio of 3.33:1). With NaBiO 3 , the extent of Am(III) conversion to Am(VI) was only 19%, while with the Cu(III) compound this value was found to be about 4 times higher under otherwise identical conditions. Similar results were obtained with other Bi(V) salts. These results show that the Cu(III) periodate compound is a superior oxidant to NaBiO 3 , yielding rapid conversion to Am(VI) in a homogeneous acidic solution, and is, therefore, an excellent candidate for further development of Am separation systems.

Previous studies have shown that mineral surfaces may facilitate the reduction of plutonium though the mechanisms of the reduction are still unknown. The objective of this study is to use batch sorption and attenuated total reflectance Fourier transform infrared spectroscopy experiments to observe the surface-mediated reduction of plutonium on hematite nanoparticles. These techniques allow for in situ measurement of reduction of plutonium with time and may lead to a better understanding of the mechanisms of surface mediated reduction of plutonium. For the first time, ATR FT-IR peaks for Pu(VI) sorbed to hematite are measured at ∼ 916 cm – 1 , respectively. The decrease in peak intensity with time provides a real-time, direct measurement of Pu(VI) reduction on the hematite surface. In this work pseudo first order rate constants estimated at the high loadings (22 mg Pu /g hematite , 1.34 · 10 – 6  M Pu /m 2 ) for ATR FT-IR are approximately 10 × slower than at trace concentrations based on previous work. It is proposed that the reduced rate constant at higher Pu loadings occurs after the reduction capacity due to trace Fe(II) has been exhausted and is dependent on the oxidation of water and possibly electron shuttling based on the semiconducting nature of hematite. Therefore, the reduction rate at higher loadings is possibly due to the thermodynamic favorability of Pu(IV)-hydroxide complexes.

The objective of this study was to investigate the dissolution rate of ThO 2 which was synthesised to approximate, as closely as possible, the microstructure of UO 2 in a nuclear fuel matrix. The optimal sintering temperature for ThO 2 pellets was found to be 1750 ℃, which produced pellets with a microstructure similar to UO 2 nuclear fuel pellets, with randomly oriented grains ranging in size from 10 to 30 μm. Dissolution was conducted using ThO 2 particles of different size fractions (80 to 160 μm and 2 to 4 mm) in the presence and absence of carbonate, in solutions with pH from 2 to 8 and at 80 ℃. Dissolution rates were calculated from Th released from the solid phase to solution. Particles of ThO 2 were also leached with 1 M HNO 3 at 80 ℃ in order to investigate the morphological changes at the particle surfaces. The concentration of Th was found to be ≥ 10 – 9  mol/L at pH ≤ 4, lower than the theoretical solubility of crystalline ThO 2 . At higher pH values, from 4 to 8, the measured concentrations (10 −10 to 10 – 12  mol/L) were between the theoretical solubility of ThO 2 and Th(OH) 4 . Grain boundaries were shown to exert an influence on the dissolution of ThO 2 particles. Using high resolution aqueous solution analysis, these data presented here extend the current understanding of Th solubility in solution.

The rare earth isotope 163 Ho is of interest for neutrino mass measurements. This report describes the isolation of 163 Ho from a proton-irradiated dysprosium target and its purification. A Dy metal target was irradiated with 16 MeV protons for 10 h. After target dissolution, 163 Ho was separated from the bulk Dy via cation-exchange high performance liquid chromatography using 70 mmol dm – 3 α -hydroxyisobutyric acid as the mobile phase. Subsequent purification of the collected Ho fraction was performed to remove the α -hydroxyisobutyrate chelating agent and to concentrate the Ho in a low ionic strength aqueous matrix. The final solution was characterized by MC-ICP-MS to determine the 163 Ho/ 165 Ho ratio, 163 Ho and the residual Dy content. The HPLC purification process resulted in a decontamination factor 1.4E5 for Dy. The isolated Ho fraction contained 24.8 ± 1.3 ng of 163 Ho corresponding to holmium recovery of 72 ± 3%.

The basic parameters related to radiochemical separation of iodine from tellurium and antimony by anion-exchange chromatography using the resin Amberlyst A26 were studied. The separation yield of 124 I amounted to 96% and the decontamination factor from 121 Te and 122 Sb was > 10 4 . The method was applied to the production of 124 I via the 123 Sb( α , 3 n ) reaction. In an irradiation of 110 mg of nat Sb 2 O 3 (thickness ∼ 0.08 g/cm 2 ) with 38 MeV α -particles at 1.2 μA beam current for 4 h, corresponding to the beam energy range of E α  = 37 → 27 MeV, the batch yield of 124 I obtained was 12.42 MBq and the 125 I and 126 I impurities amounted to 3.8% and 0.7%, respectively. The experimental batch yield of 124 I amounted to 80% of the theoretically calculated value but the level of the radionuclidic impurities were in agreement with the theoretical values. About 96% of the radioiodine was in the form of iodide and the inactive impurities (Te, Sb, Sn) were below the permissible level. Due to the relatively high level of radionuclidic impurity the 124 I produced would possibly be useful only for restricted local consumption or for animal experiments.

Objective: The objective of the present work is to develop and evaluate freeze-dried DOTMP kit, which could be utilized for the convenient and single-step preparation of clinical-scale 177 Lu-DOTMP and 153 Sm-DOTMP, both of which have shown potential as alternative agents for metastatic bone pain palliation. Experimental: Freeze-dried DOTMP kits, each comprising a lyophilized mixture of 20 mg DOTMP and 8.75 mg NaOH, were prepared. The kits were used for the preparation of clinical-scale 177 Lu-DOTMP and 153 Sm-DOTMP complexes. The agents were prepared by dissolving the lyophilized powder in 1 mL of normal saline and incubating with 177 LuCl 3 or 153 SmCl 3 , produced in-house, for 15 min at room temperature. Pharmacokinetic behavior and biological distribution of the agents were studied by carrying out biodistribution as well as scintigraphic studies in normal male Wistar rats. Shelf-life of the freeze-dried kits was also ascertained. Results: Clinical-scale 177 Lu-DOTMP and 153 Sm-DOTMP complexes, comprising up to 3.7 GBq (100 mCi) of activity, were prepared with > 99% radiochemical purity using the freeze-dried kits. The complexes exhibited high in vitro stability when stored at room temperature. Biological studies showed selective skeletal accumulation and insignificant uptake of the radiotracers in any of the vital organs/tissue. The non-accumulated activity exhibited primary urinary clearance. The kits had a shelf-life of 2 years when stored at 4 ℃ temperature. Conclusion: Freeze-dried DOTMP kits, suitable for the preparation of clinical-scale 177 Lu-DOTMP and 153 Sm-DOTMP, have been developed and the radiochemical and biological behaviors of the radiolabeled agents have been studied. The use of the kit at the hospital radiopharmacy is expected to make the preparations easy and convenient. This in turn will enable the widespread dissemination of these promising agents towards their application for regular use.

Preparation and characteristics evaluation of the polycarbonate films 20 μm in thickness containing Dansyl chloride as a routine dosimeter in radiation processing facilities were studied. The sensitivity of these films and the linearity of dose-response curves were investigated under 60 Co γ -rays in a dose range of 0–100 kGy, and the obtained results were compared with the commercial CTA and FWT film dosimeters. The results show that the maximum absorbance appeared at 370 nm in all the investigated dose range. The dyed films were found to be stable enough in mediums with high degrees of humidity and temperature, to be reliably used in radio-applications. The effects of pre-irradiation (shelf-life) and post-irradiation storage in dark and in indirect sunlight were also discussed. The films which were made displayed stable characteristics when stored in dark, within 1% at 25 ℃, 3 months after irradiation.