Volume 106, Issue 7

Several experiments on the study of the electron neutrino mass are based on high-statistics measurements of the energy spectrum following electron capture of the radionuclide 163 Ho. They rely on the availability of large, radiochemically pure samples of 163 Ho. Here, we describe the production, separation, characterization, and sample production within the Electron Capture in Holmium-163 (ECHo) project. 163 Ho has been produced by thermal neutron activation of enriched, prepurified 162 Er targets in the high flux reactor of the Institut Laue-Langevin, Grenoble, France, in irradiations lasting up to 54 days. Irradiated targets were chemically processed by means of extraction chromatography, which allowed separating the formed Ho from the 162 Er target-material and from the main byproducts 170 Tm and 171 Tm, which are co-produced in GBq amounts. Decontamination factors of >500 for Er and of >10 5 for Tm and yields of 3.6·10 16 and 1.2·10 18 atoms of 163 Ho were obtained, corresponding to a recovery yield of 95 % of Ho in the chemical separation. The Ho-fraction was characterized by means of γ-ray spectrometry, Inductively-Coupled-Plasma Mass Spectrometry (ICP-MS), Resonance Ionization Mass Spectrometry (RIMS) and Neutron Activation Analysis (NAA). In this process, the thermal neutron capture cross section of 163 Ho was measured to σ Ho-163 to Ho-164m = (23±3) b and σ Ho-163 to Ho-164g = (156±9) b for the formation of the two isomers of 164 Ho. Specific samples were produced for further purification by mass separation to isolate 163 Ho from the Ho-isotope mixture, as needed for obtaining the energy spectrum within ECHo. The partial efficiency for this second separation step is (32±5) %.

Experimental investigations have been carried out on the production of a promising therapeutic radionuclide 67 Cu via the 67 Zn(n,p) 67 Cu, 68 Zn(n,x) 67 Cu, and 68 Zn(γ,p) 67 Cu reaction routes. Natural zinc metal foils were irradiated with 14.1 MeV neutrons and bremsstrahlung of end-point energy 15 MeV. Radioactivity levels of 67 Cu and other radioisotopes co-produced were determined by the quantification of photo-peaks by off-line γ-ray spectrometry. No carrier added 67 Cu was separated from the irradiated zinc by solvent extraction. Yields >90% and high levels of radionuclidic purity were achieved. These studies indicate that the growth and development of intense fast neutron sources and photonuclear technology, will possibly aid in the sustained supply of 67 Cu.

The sorption of hexavalent uranium on muscovite as a function of pH, background electrolyte, temperature and humic acid (HA) was investigated in detail using batch experiments. The results showed that the uranium sorpiton on muscovite was kinetic fast, the kinetic process was fitted well by pseudo-second-order kinetic model. The sorption of uranium depended strongly on pH while weakly on background electrolyte concentration, indicating that surface complexation dominated the sorption process. The escalation of temperature and humic acid concentration were favorable to uranium sorption on muscovite. The sorption isotherms at pH 6.0 could be described better by Langmuir model than Freundlich or Dubinin-Radushkevich (D-R) model, thermodynamic data indicated that the uranium sorption process on muscovite was spontaneous and endothermic process. The findings in present work can provide important experimental reference for understanding the environmental behavior of uranium in mica-rich terrains.

The objective of this work is to find a new, efficient and alternate low-cost adsorbent for preconcentration and spectrophotometric determination of uranyl ions U(VI) from aqueous solution. For this reason the new impregnated resin (ZnO/7HP) has been prepared by sol-gel technique. Characterization of ZnO/7HP was conducted using scanning electron microscopy/energy-dispersive X-ray spectrometer and X-ray diffraction, and Fourier transforms infrared spectroscopy. Several important parameters influencing the U(VI) adsorption such as pH, adsorbent amount, initial U(VI) concentration, contact time and temperature were investigated systematically by batch experiments. The obtained results showed that the equilibrium adsorption data were well fitted to the Langmuir model with a maximum adsorption amount of 24.96 mg/g. While the adsorption kinetics data were described well by the pseudo-second order model. This result indicates that the adsorption process is chemisorption. Thermodynamic results indicate that the U(VI) adsorption process is endothermic nature and favors at high temperature. Hydrochloric acid was used for preconcentration of U(VI) and detected spectrophotometry after the reaction with Arsenazo III. According to the definition of International Union of Pure and Applied Chemistry, the detection limit of this method was 0.12 μg/L. The relative standard deviation under optimum conditions is less than 3.0 % (n=5). The new impregnated resin ZnO/7HP is a promising adsorbent for preconcentration and spectrophotometric determination of U(VI) in aqueous solutions.

In this work, batch experiments were carried out to explore the sorption properties for perrhenate (ReO 4 − , a surrogate for TcO 4 − ) by two types of commercial bifunctional anion-exchange resins (Purolite A530E and A532E). It is found that these two bifunctional anion-exchange resins could rapidly remove ReO 4 − from aqueous solution within 150 min and the maximum sorption capacity for ReO 4 − reached as high as 707 and 446 mg/g for Purolite A530E and A532E, respectively. The sorption properties were independent of pH over a wide range from 1 to 13. More importantly, both Purolite A530E and A532E exhibited excellent selectivity for the removal of ReO 4 − in the presence of large excess of NO 3 − and SO 4 2− . Finally, the removal percentage of ReO 4 − by these two resins could be >90% and 80%, respectively, from the Hanford low-level waste melter off-gas scrubber simulant stream. Such high selectivity of Purolite A530E and A532E for the removal of ReO 4 − might be due to the presence of the long-chain group of –[N(Hexyl) 3 ] + , which favored hydrophobic and large anions such as ReO 4 − /TcO 4 − rather than NO 3 − .

In this study, magnetic biosorbent was fabricated by chemical co-precipitation of Fe(II) and Fe(III) on the surface Paeclomyces catenlannulatus ( P. catenlannulatus ) by adding NaOH solution under N 2 conditions. The influence of water chemistries (i. e. pH, reaction time, temperature, concentration and ionic strength) on Eu(III) biosorption towards magnetic biosorbent was elucidated by batch technique. The batch experiment showed that Eu(III) biosorption on magnetic biosorbent was independent of ionic strength, suggesting that inner-sphere-surface-complexation predominated Eu(III) biosorption. The biosorption kinetics showed the sorption equilibrium was achieved at reaction time of 24 h, and the maximum biosorption capacity of Eu(III) on magnetic biosorbent calculated by Langmuir model was 69.45 mg/g at pH 3.5 and 298 K. The regeneration experiments showed the slight decrease of biosorption capacity after the fifth recycles. These results suggested that this magnetic biosorbent presented the fast biosorption rate and high biosorption capacity for Eu(III). The results of XPS analysis revealed that various oxygenated function groups (e.g. carboxyl, hydroxyl groups) were responsible for the high effective biosorption of Eu(III). These findings manifested that this magnetic biosorbent could be as a high-effective material for the immobilization and pre-concentration of radionuclides from aqueous solution in environment remediation.

Human epidermal growth factor receptor 2 (HER2) is overexpressed in several cancers. Today’s tumor targeting is receiving more attention due to its specificity to target receptor-dependent cancers. The aim of this study was to evaluate the 99m Tc-HYNIC-(tricine)-(Ser) 3 -LTVPWY peptide for tumor targeting and imaging with overexpression of HER2. HYNIC-(Ser) 3 -LTVPWY peptide was labeled with 99m Tc using tricine as a co-ligand at room temperature. Specific binding of this radiolabeled peptide was assessed on four cancer cell lines with different levels of HER2 receptor expression. Also the affinity of 99m Tc-HYNIC-(tricine)-(Ser) 3 -LTVPWY peptide to the HER2 receptor was evaluated in the SKOV-3 cell line. Biodistribution study of this radiolabeled peptide was performed in SKOV-3 tumor bearing nude mice. The HYNIC conjugated peptide was simply labeled with 99m Tc radionuclide with high labeling efficiency about 98±1% showing favorable stability in normal saline and human serum. In the presence of unlabeled peptide as competitor, the HER2 binding capacity of the radiolabeled peptide reduced (approximately five-fold). The K D and B max values were found 2.6±0.5 nM and (2.6±0.1)×10 6 , respectively. The tumor/muscle ratios for this radiotracer were determined 1.17±0.77, 1.15±0.32 and 2.65±0.32 at 1, 2 and 4 h after injection, respectively. Presaturation of HER2 receptors in SKOV-3 xenografted nude mice showed a reduction in the tumor/muscle ratio confirming in vivo specificity of the peptide. According to SPECT imaging, the tumor was visualized in mouse after 4 h postinjection of radiolabeled peptide. 99m Tc-HYNIC-(tricine)-(Ser) 3 -LTVPWY peptide exhibited overexpressed HER2 tumor targeting.

Lignite coal (LC) is a key energy source for electricity generation in Turkey. During lignite burning, huge amounts of fly ash (FA), bottom ash and slag are produced as by-products which contain radionuclides in the natural radioactive series of uranium and thorium, and radioactive potassium. These radionuclides may lead to radiological exposure of workers and the public and cause environmental problems. Therefore, finding diverse uses for the by-products in the construction sector and earthwork applications has considerable economic and environmental importance. In this study, the activity concentrations of 226 Ra, 232 Th and 40 K in and radon emanating power (EP) and radon mass exhalation rate (EXR M ) from LC, slag and FA obtained from the Kangal lignite-burning power plant with a power of 457 MWe were measured using gamma-ray spectroscopy. The major chemical components (SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO and MgO) of fly ash samples were analysed using an energy dispersive X-ray fluorescence spectrometer. The annual effective doses received by workers and members of the public were estimated using different scenarios specified in Radiation protection 122. The average activity concentrations of 226 Ra, 232 Th and 40 K in LC, slag and FA samples were 187±21, 16±1 and 99±9 Bq kg −1 , 620±18, 41±2 and 330±13 Bq kg −1 , and 937±30, 38±2 and 272±17 Bq kg −1 , respectively. The average values of EP and EXR M of the lignite, slag and FA samples were 8 %, 7 % and 10 %, and 0.1, 0.3 and 0.7 Bq kg −1 h −1 , respectively. The highest average of the total annual effective dose is estimated at 153 μSv for members of the public and 74 μSv for workers, lower than the recommended annual limit of 1000 μSv.