Band 102, Heft 4

Green rust (GR) as sodium sulphate form, NaFe(II) 6 Fe(III) 3 (OH) 18 (SO 4 ) 2  · 12H 2 O, is reacted with an aqueous solution of neptunyl ions (NpO 2 + ) and the resulting Np(IV) solid phase is investigated at a nanometer scale by different transmission electron microscopy (TEM) techniques, including high-resolution TEM (HRTEM), high-angle annular dark-field scanning TEM (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDXS), and electron energy-loss spectroscopy (EELS). The aim of the analyses is to achieve insight into the potential immobilization mechanism for Np(V) in the context of safety assessment of a nuclear-waste repository. The neptunium is found to be immobilized at the edge of the green rust platelets, in a rim composed of nanocrystallites about 2–3.5 nm in size. The EELS results and more particularly the HRTEM findings are consistent with NpO 2 crystallizing in a fluorite-type structure. Furthermore, the Np-O 4,5 edges recorded by EELS at the Np(IV) phase are presented, expanding the EELS-data set currently available in the literature for Np.

Identification of various soluble organic acids formed during the pyrohydrolysis of uranium-plutonium mixed carbide [(U,Pu)C] was carried out using ion chromatography. This has significant importance as the soluble organic acids can cause severe interferences during the ion chromatography separation and determination of Cl − and F − in the pyrohydrolysis distillate of (U,Pu)C. Determination of Cl and F is important in the chemical quality control of nuclear materials as these two elements can cause corrosion and hence, their concentrations in all nuclear materials are restricted to certain specified values. Since the pyrohydrolysis distillates contain both inorganic and organic acid anions, for the sake of separating and identifying organic acid anions from the common inorganic anions, three independent isocratic elutions using varying concentrations of NaOH eluent were employed for the separation of weakly, moderately and strongly retained anions. It was observed that pyrohydrolysis of (U,Pu)C also produced soluble organic acids as in the case of nitric acid dissolution of UC. The present investigation revealed the presence of formic, acetic, propionic, butyric, oxalic acid anions in the pyrohydrolysis distillate of (U,Pu)C in trace or ultra-trace concentrations. The presence of each organic acid identified in the chromatogram was confirmed with spike addition as well as by separating them by capillary electrophoresis method. The presence of lower aliphatic acids viz. formic and acetic acids was reconfirmed by carrying out an independent separation with tetraborate eluent. It is suggested that nitric acid being formed during pyrohydrolysis could be responsible for the formation of organic acids. Based on the findings, an ion chromatography separation method has been proposed for the interference-free determination of chloride and fluoride in pyrohydrolysis distillate of (U,Pu)C.

The sorption of actinides in different valence states – Am(III), Th(IV), Np(V) and U(VI) onto hematite have been revisited with the special emphasis on the equilibrium constants of formation of surface species. The experimental sorption data have been treated using surface complexation modeling from which the set of new values of equilibrium constants were obtained. Formation of inner sphere monodentate surface species adequately describes the pH-sorption edges for actinide ions indicative the ionic electrostatic nature of bonding with small or no covalency contribution. The linear free energy relationship representing the correlation between the hydrolysis constants and surface complexation constants has been developed for various cations including K(I), Li(I), Na(I), Ag(I), Tl(I), Sr(II), Cu(II), Co(II), La(III), Eu(III), Ga(III), Am(III), Th(IV), Np(V), U(VI).

The corrosion of the UAl x -Al research reactor fuel type in synthetic MgCl 2 -rich brine (static batch-type experiments) was investigated with respect to the long-term safety of directly disposed research reactor fuel elements in salt formations. During corrosion, crystalline secondary phases were formed, which may serve as a barrier against radionuclide migration. For an optimized identification and quantification of the secondary phases using X-ray diffraction, a sample treatment to separate and enrich the secondary phases is necessary. A grain size fractionation was carried out in iso-propanol. A chemical composition and phase characterization of the secondary phases was accomplished. The results of the chemical investigations reveal that only traces of Al and U were dissolved. The separation and enrichment of secondary phases were carried out reproducible and successfully. Due to the phase characterization by scanning electron microscopy/energy dispersive X-ray spectroscopy and X-ray diffraction the following secondary phases were unambiguously identified: Mg-Al-Cl layered double hydroxide, lesukite, Fe layered double hydroxide (green rust), lawrencite, Fe (elemental), and traces of uncorroded fuel (UAl 4 ). The quantitative analysis showed that LDH compounds and lesukite are the major crystalline phases. All other observed compounds were only present in trace amounts, i.e. constituting accessories. The Rietveld analysis also revealed the high content of amorphous phases of approximately 30%, which are expected to include the uranium as U(OH) 4 .

Rhenium-186g is a radionuclide with a high potential for therapeutic applications. It emits therapeutic β − particles accompanied by low energy γ -rays, which allows for in-vivo tracking of the radiolabeled compound and dosimetry estimates. The current reactor production pathway 185 Re( n ,  γ ) 186g Re produces low specific activity 186g Re, thereby limiting its therapeutic application. Work is underway to develop an accelerator-based, charged particle induced production method for high specific activity 186g Re from targets of enriched 186 W. To optimize the chemical 186g Re recovery method, batch studies have been performed to characterize the adsorption behavior of Re and W on a strongly basic anion exchange resin. An in-depth physicochemical profile was developed for the interaction of Re with resin material, which showed the reaction to be endothermic and spontaneous. Basic (NaOH) and acidic (HNO 3 ) matrices were used to determine the equilibrium distribution coefficients for Re and W. The resin exhibits the best affinity for Re at slightly basic conditions and little affinity above moderately acidic concentrations. Tungsten has low affinity for the resin above moderately basic concentrations. A study was performed to examine the effect of W concentration on Re adsorption, which showed that even a high ionic WO 4 2 – strength of up to 1.9 mol kg – 1 does not significantly compromise ReO 4 – retention on the resin.

The chronological development of element concentrations during growth and ripeness of grapes described in the literature has only been concerned with the macro elements Mg, K, and Ca. Concentrations of trace elements in must are only described as a snapshot at the end of the ripeness. Therefore, the motivation for the present work was to accompany the growth and the ripening process of grapes successively by systematically determining element concentrations in grapes of Riesling and Cabernet Sauvignon by neutron-activation analyses. While for a number of elements, the concentrations in the grapes increased as a function of grape development ( e.g. , Na, K, Rb, Al), other concentrations decreased ( e.g. , Mg, Ca, Mn). These decreases are not only to be attributed to a dilution by an increasing uptake of water during growth, but also by an active transport of the cations out of the berries. Furthermore, the interest focused on the influence of mineral substances on the process of fermentation and on the uptake of trace elements by the yeasts.

Proton conducting membrane composed of grafted basic moiety doped with phosphoric acid (PA) was studied. The membrane denoted as PVDF-g-4-VP/PA was prepared by radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(vinylidene fluoride) (PVDF) films followed by doping with PA. The effect of grafting conditions on the degree of grafting ( G %) was investigated. The acid doping conditions ( G %, time and PA concentration) were also investigated with respect to doping level. The grafted precursors and the acid doped membranes were characterized by means of Fourier transform infrared (FTIR), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM). The membranes showed a thermal stability up to a temperature of ∼ 160 ℃, above which they undergo a multi-step degradation pattern due to decomposition of the protonated functions, poly(4VP) grafts and PVDF matrix, respectively. The proton conductivities of the membranes were found to increase with the increase in G % ( doping level) and the temperature with a maximum proton conductivity of 62 mS cm −1 achieved at 100 ℃ without any humidification. The results of the present study show that the prepared membrane has a potential to be proposed for operating polymer electrolyte membrane fuel cell above 80 ℃.

Zirconium-titanium-phosphate nanoparticles (ZTP) of different sizes were synthesized using tritron X-100 (polyethylene glycol- p -isooctylphenyl ether) surfactant. The materials were characterized by FTIR and powdered X-ray diffraction (XRD). The structural and morphological details of the material were obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM study was followed by energy dispersive spectroscopic analysis (EDS) for elemental analysis of the sample. The important peaks of the XRD spectra were analyzed to determine the probable composition of the material. The particle sizes were determined by dynamic light scattering (DLS) method. Ion exchange capacity was measured for different metal ions with sizes of the ZTP nanoparticles and size-dependent ion exchange property of the material was investigated thoroughly. The nanomaterial of the smallest size of around 5 nm was employed to separate carrier-free 137m Ba from 137 Cs in column chromatographic technique using 1.0 M HNO 3 as eluting agent at pH = 5.