Band 106, Heft 9

The (n,2n) cross sections and their isomeric cross-section ratios (σ m /σ g ) in the neutron energy range 13–15 MeV have been measured for 85,87 Rb by an activation and off-line γ-ray spectrometric technique using the Pd-300 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). The natural Rb samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The neutrons were produced via the 3 H( d , n ) 4 He reaction. The pure cross section of the ground-state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. The 85 Rb(n,2n) 84m,g Rb and 87 Rb(n,2n) 86m,g Rb reaction excitation functions and their isomeric cross-section ratios were also calculated theoretically using the TALYS-1.8 code with different level density options. Results are discussed and compared with the corresponding literature data.

The adsorptive extraction of uranium (VI) was investigated using multiwalled carbon nanotubes functionalized with dihydroimidazole (DIM-MWCNTs). Dihydroimidazole was grafted onto the surface of MWCNTs via silane coupling agent, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole. The new adsorbent was characterized using Fourier transform infrared, scanning electron microscope and X-ray Photoelectron Spectroscopy. DIM-MWCNTs were compared with MWCNTs and amidoxime modified MWCNTs (AO-MWCNTs) for uranium adsorption under seawater conditions. The adsorption capacity of uranium onto DIM-MWCNTs was 54.9 mg g −1 at 298 K, which was about 4 times of MWCNTs and similar to that of AO-MWCNTs. Compared with AO-MWCNTs, DIM-MWCNTs were more suitable for seawater pH, and less affected by vanadium. Although DIM-MWCNTs were more affected by carbonate than AO-MWCNTs, DIM-MWCNTs maintained a higher adsorption capacity than AO-MWCNTs due to its alkali resistance. Pyridine-like nitrogen (CH=N–CH) contributed to the adsorption of uranium. The results suggested that DIM-MWCNTs were a potential effective adsorbent for the separation of uranium under seawater condition.

Diatomite was modified with TiO 2 . The synthesized materials were characterized and used for removal of U(VI) from aqueous solutions. The influences of pH, contact time and temperature on U(VI) adsorption onto TiO 2 @diatomite were studied by batch technique, and X-ray photoelectron spectroscopy (XPS) was employed to analyze the experimental data. We compared the adsorption of U(VI) onto natural diatomite, TiO 2 and TiO 2 @diatomite made by sol-gel method. The dynamic process showed that the adsorption of U(VI) onto TiO 2 @diatomite matched the pseudo-second-order kinetics model, and the adsorption of U(VI) was significantly dependent on pH values. Through simulating the adsorption isotherms by Langmuir, Freundlich and Dubini–Radushkevich (D–R) models, respectively, it could be seen that the adsorption patterns of U(VI) onto TiO 2 @diatomite were mainly controlled by surface complexation, and the adsorption processes were endothermic and spontaneous. The modification of diatomite by TiO 2 shows a novel material for removing U(VI) from water environment for industrialized application.

Cross sections for the production of 181−184 Re isotopes from proton irradiated thin nat WO 3 target at 20.9, 17.9, 14.9, 11.9 and 8.8 MeV projectile energies have been measured. An acceptable agreement between experimentally obtained data and available literature reports was found. The produced no-carrier-added (NCA) Re radionuclides have been separated from bulk tungsten target by liquid-liquid extraction (LLX) using trioctyl amine (TOA) and di-(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in cyclohexane. A clear separation has been observed at 0.1 M and 1 M TOA with 0.1 M HNO 3 concentration. However, by using HDEHP NCA Re radionuclides could not be separated from bulk W target without its contamination.

The present study was oriented to synthesis radioiodinated celiprolol (Cel) for a potential cardiac imaging. Celiprolol has been labeled using 125 I with chloramine-T (Ch-T) as an oxidizing agent. The key effective factors such as amount of oxidizing agent, amount of substrate, pH, reaction temperature and reaction time, have been systematically studied to optimize the iodination. The biological distribution indicates the suitability of radioiodinated Cel as a novel tracer to image heart.

A nuclear analytical technique, namely instrumental photon activation analysis (IPAA), was used to determine Sr and Ca concentrations in human teeth. This work was conducted using the first accelerator facility, an off-shelf clinical linear accelerator (cLINAC), in Turkey. The tooth samples supplied by the Akdeniz University Faculty of Dentistry were analyzed for determination of the Sr/Ca element ratio. The results were obtained to demonstrate the impact of socioeconomic changes on dietary habits. A calibration material (CM; a mixture of calcium and strontium oxides) was required for quantification of the analytical results. The tooth samples, together with the CM, were exposed to 18 MeV end-point energy bremsstrahlung photons from the cLINAC. Thereafter, the γ-ray spectra of the samples and the CM were obtained using high resolution γ spectroscopy. Variations in the Sr/Ca ratio in the teeth of patients fed with beef and fizzy beverages were investigated in this study.

Our laboratory of neutron activation analysis is highly involved in nutrition applications in the framework of research activities using the Algerian research reactor. The medicinal and aromatic plants of Mentha pulegium L. have been largely used in traditional medicine for several centuries to contribute significantly to human health related to digestive ailments, it is also used to reduce nervousness and anxiety. The present study focuses on the analysis of leaves of M. pulegium L., for evaluation of essential and toxic elements using a sensitive nuclear analytical technique based on instrumental neutron activation analysis (INAA). Twenty-one elements were assessed (As, Ba, Br, Ca, Ce, Cr, Cs, Co, Eu, Fe, Hf, K, La, Na, Rb, Sb, Sc, Sm, Sr, Yb and Zn) and the accuracy of the method was evaluated by analyzing the Certified Reference Materials (CRMs) GBW 07605 (tea leaves) and NIST-SRM 1573a (tomato leaves). The daily intake of essential and toxic elements was determined and compared with the recommended values and was found to be well below the tolerance limits.

Nonisothermal dehydration of un-irradiated and γ-ray irradiated holmium acetate tetrahydrate with 10 3 kGy total γ-ray dose absorbed was studied in air atmosphere. The thermal decomposition experiments were conducted at heating rates of (5, 7.5 and 10°C/min). The results showed that for un-irradiated material, the dehydration process proceeds in two decomposition steps with the elimination of 3.0 and 1.0 moles of H 2 O, respectively. The apparent activation energy, E a , as given by both linear and nonlinear isoconversional methods showed dependence upon the conversion degree, α , in the range of 0.2–0.75 for the two dehydration steps. In the first dehydration step, the E a decreases from 228.0 kJ/mol at the beginning of the decomposition to ≈64.0 kJ/mol at the end of the process. In the second dehydration step, the E a increases from 42.0 to 72.0 kJ/mol by progressively increasing in α . Compared with solid state reaction models, the two reactions are best described by diffusion ( D 4 ) and nucleation ( A 3 ) models for the first and second dehydration steps, respectively. The results derived from nonisothermal data present a reliable prediction of isothermal kinetics. Straight lines and reduced time plots methods were applied for the determination of the kinetic triplet [ E a , ln A , and reaction model f ( α )] from predicted isothermal data. For γ-ray irradiated samples of Ho(CH 3 COO) 3 ⋅4H 2 O with 10 3 kGy total absorbed dose, the dehydration proceeds in two overlapped steps controlled by D 3 model. X-ray data showed phase transformation from monoclinic ( SG P 2/ m ) to tetragonal phase ( SG P 4/ mmm ) by the elimination of water content from the entire structure of Ho(CH 3 COO) 3 ⋅4H 2 O. γ-Ray irradiation effects on the thermal decomposition of Ho(CH 3 COO) 3 ⋅4H 2 O were evaluated and discussed based on the formation of trapped electrons, point defects, cation and anion vacancies and cluster imperfections in the host lattice of Ho(CH 3 COO) 3 ⋅4H 2 O.

A fast radioanalytical method has been developed to measure 210 Po in tobacco samples. After microwave digestion polonium is extracted quantitatively from a 1 M hydrochloric acid solution into a solution of triisooctylamine in toluene. The extract was measured by liquid scintillation counting in α mode. Caused by the high counting efficiency the counting time per sample can be reduced significantly compared to conventional α spectrometry, allowing for high sample throughput. The method was applied to 11 brands of cigarettes, beedis and or chewing tobaccos from India. Based on the resulting activity concentrations and typical consumption habits, annual and lifetime equivalent doses were calculated. They were found to be ~100–700 μSv/a or ~5–35 mSv, respectively.

The main objective of this study is directed to remove 226 Ra, 228 Ra radionuclides from TENORM scale waste without seriously degradation the physicochemical characteristics of soils or generating waste. It was found that 82, 87% removal of total radioactivity using successive washing by commercial and TX-100 solutions, respectively, after seven cycles. Some radiation risk before and after treatment with surfactants were determined. It is a promising and efficient as well as economic process. Our results from this task could provide a useful information for defining the establishing and operating on a pilot-scale plant for efficient and economic TENORM treatment.