Volume 96, Issue 8 -

In the Gallium Neutrino Observatory (GNO) experiment solar neutrinos are studied. Low energy neutrinos interact with 71 Ga producing radioactive 71 Ge, which decays with a half-life of 11.43 days back to 71 Ga. This β + -decay is used for quantifying the number of solar neutrinos observed. Stable Ge isotopes are used as carriers when 71 Ge atoms are extracted from the GaCl 3 target for measuring their decay. The carrier serves at the same time for quantification of the chemical yield of the extraction process. Ge-removal from the GaCl 3 detector solution proceeds exponentially and a small amount of Ge carrier remains in the Ga-tank, which is removed only during the following extraction(s). The use of different stable enriched Ge isotopes ( 70 Ge, 72 Ge, 74 Ge and 76 Ge) in alternating sequence allows one to determine the extraction yield of the carrier by high precision isotope ratio measurements. The measurements are carried out using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The exact quantification of any residual Ge carrier from the preceding run is achieved through isotope dilution calculations and isotope mixture calculations. In this paper we describe the evaluation of the results using the two-isotopes and two-components approach, as well as the multi-isotope and three-components approaches. We could demonstrate that the measured isotopic composition of the carrier after extraction can be fully modelled by a mixture of the initially used Ge carrier, of the Ge carrier from the previous run and of a small, but non-negligible contribution of a natural Ge contamination.

A search for the α-decay of 239 Cm was carried out via the fusion reaction 232 Th( 12 C,5 n ) 239 Cm at GSI, applying nuclear chemistry techniques. The 239 Cm α-decay would provide a link between known nuclear masses and α-decay energies measured in the region of the superheavy elements. Three different 12 C beam energies were chosen in the present experiments. The α peaks of 238,240 Cm were observed clearly at a 12 C energy of 74 MeV, while 238 Cm disappeared at 70 MeV to provide an undisturbed α-spectrum for a sensitive search of 239 Cm decay. No α-events between 6.34 and 6.50 MeV, which could be assigned to 239 Cm with confidence, were observed in this experiment. The upper limit of the α-branch of 239 Cm was less than 1.0×10 −5 .

Cross sections of proton induced nuclear reactions on nat Cd, leading to the formation of 110g In, 111 In, 113m In, and 116m1 In for energies up to 14.7 MeV were measured using the stacked-foil irradiation technique and high resolution gamma-ray spectroscopy. Our experimental data were analyzed and the excitation functions for the studied radionuclides were compared with the previously reported data. Model codes ALICE-IPPE and EMPIRE-II were used for calculating the excitation functions theoretically. Integral yields of the radionuclides 110g In, 111 In, 113m In and 116m1 In were also calculated.

The dissolution data of UO 2 are important to develop the new process of uranium ore leaching and new head-end reprocessing of spent nuclear fuel. The dissolution experiments of UO 2 pellets in 8 M nitric acid by microwave heating and conventional heating were carried out respectively in the present work. Compared with the conventional heating, the microwave heating can remarkably promote the dissolution process of UO 2 pellets with a dissolution ratio increase of 26%–46%. The kinetics results show that the dissolution processes by microwave heating and conventional heating match well with the diffusion control model and the surface reaction control model, respectively.

Pyrite (FeS 2 ) is a mineral phase often present as inclusions in temperate soils. Moreover, it turns out to be a sorption sink for certain radionuclides in deep geological disposals. The present study was thus initiated to determine the capacity of pyrite to immobilize selenide (Se(-II)). Due to the fact that pyrite surface oxidizes readily, potentials were applied in order to minimise its surface evolution, and ensure the reducing conditions necessary for stabilizing Se(-II). The sorption experiments were carried out in NaCl electrolyte and were amperometrically controlled. After only several minutes of reaction, at least 97% of Se(-II) initially present in solution was disappeared. The K d values vary from 7–65 L/g and the isotherm curve shows site saturation at higher initial selenide concentrations and no pH-dependence. By means of several spectroscopic techniques, the reaction mechanism was investigated. The XRD and in situ XANES results indicate the presence of Se(0) on pyrite surface, which explain the rapid disappearance of Se observed in the sorption experiments. Moreover, XPS results obtained from Se-reacted pyrite particles reveal cleavage of S–S bonding which resulted in formation of S 2− on pyrite surface. Thus, we conclude that Se(-II) can be immobilized by pyrite via surface redox reaction: ≡FeS 2 + HSe − ⇔ ≡FeS + Se(0) + HS − .

Theoretical calculation of both the kinetics and thermodynamic parameters for the adsorption of ultrace amount of uranium ion in uranyl nitrate salt (UO 2 2+ ) on activated carbon showed the applicability of Langmuir isothermal model. Equilibrium isotherm studies gave the maximum calculated sorption capacity as 30.95 μg/g for 100 μg/L at 0.8 g activated carbon (AC), compared to the experimental result 24.9 μg/g, with correlation coefficient of 0.999 compared to 0.985 and 0.901 for Freundlich and/or D–R Dubinin–Raduschkevich, respectively. It was found that the adsorption process is mainly exothermic, where the thermodynamic parameters are as follows: Δ H ads −90.5 (kJ/mol), Δ S ° ads 0.224 (kJ/mol/K) and Δ G ads −23.75 (kJ/mol) ( T =298 K). Kinetically the process was assured the first order rate of reaction with the rate constant equal to 0.304 min −1 (100 μg/L) and 0.387 min −1 (50 μg/L) respectively, compared to 3.3×10 −4 and 4.4×10 −4 min −1 for the second order kinetics mechanism.

Clay minerals have been studied extensively because of their strong sorption and complexation ability. In this work, Na-montmorillonite was characterized by using acid-base titration, XRD and FTIR in detail. Sorption of Ni(II) on Na-montmorillonite was investigated under ambient conditions as a function of pH, ionic strength, and temperature. The results indicate that sorption of Ni 2+ on montmorillonite are strongly dependent on pH and ionic strength. The sorption of Ni 2+ is mainly dominated by ion exchange at low pH values and by inner-sphere surface complexation at high pH values. The relationships of pH– C eq , Q – C eq and pH– Q are compared and shown clearly in a 3-D plot, and all Q – C eq data lie in a straight line with slope (− V / m ) and intercept ( C 0 V / m ). The thermodynamic parameters (Δ H °, Δ S °, and Δ G °) are calculated from the temperature dependent sorption isotherms, and the results suggest that the sorption reaction of Ni(II) from solution to montmorillonite is endothermic and spontaneous.

Several ruthenium species compounds are typically encountered in waste management from nuclear fuel reprocessing operations. Ozone acting as a strong oxidizing agent in aqueous alkaline medium has some advantages for dissolving solid ruthenium deposits formed in process equipments, without generating troublesome by-products or secondary waste. This study is focused on oxidative dissolution of ruthenium(IV) oxyhydroxyde deposited on 304L stainless steel by ozone in alkaline medium. Oxidative dissolution of these deposits under various experimental conditions shows an analogous behaviour to that observed in a previous study with RuO 2 · x H 2 O suspensions, notably the autocatalytic effect of ruthenate ions RuO 4 2− for the oxidative dissolution of ruthenium deposits.

Chemoinformatics approaches open new opportunities for computer-aided design of new efficient metal binders. Here, we demonstrate performances of ISIDA and COMET software tools to predict stability constants (log K ) of the metal ion/organic ligand complexes in solution and to design in silico new molecules possessing desirable properties. The predictive models for log K of lanthanides complexation in water have been developed. Some new uranyl binders based on monoamides and on phosphoryl-containing podands were suggested theoretically, then synthesized and tested experimentally. Reasonable agreement between experimental uranyl distribution coefficients and theoretically predicted values has been observed.