H. Moreno

Determination of 226Ra and 224Ra in drinking waters by liquid scintillation counting

A method for the determination of Ra-isotopes in water samples has been developed. Ra is coprecipitated with Ba as sulphate. The precipitate is then dissolved with EDTA and counted with a liquid scintillation system after mixing with a scintillation cocktail. The study of the temporal evolution of the separated activity gives the isotopic composition of the sample, i.e. the 224Ra and 226Ra contribution to the total activity. The method has been applied to some Spanish drinking waters.

Application of a Liquid Scintillation Technique to the Measurement of 226Ra and 224Ra in Samples Affected by Non-Nuclear Industry Wastes

Experiment procedures have been developed for the determination of 226Ra and 224Ra activity concentration in solid and liquid samples collected around a non-nuclear industrial area, by liquid scintillation counting. The different radiochemical procedures developed in this work, have been adaptations of a radiochemical procedure previously used, for 226Ra and 224Ra determinations by LSC in drinking water, which was improved, refined up and adapted to the type of sample to be applied. These improved radiochemical methods have been applied to waste samples (phosphogypsum) produced by two factories which are engaged in phosphoric acid production, and to waters collected from the Odiel river, where during the sampling period a fraction of these wastes were released. 226Ra activity concentrations in the phosphogypsum ranged from 673 to 1178 Bq/kg dry weight, indicating that the wastes are particularly enriched in this radionuclide. Consequently, high 226Ra levels were easily found in the river waters analysed, especially in the neighbouring zones of the waste discharges.

Performance of the LNL recoil mass spectrometer

Abstract The LNL recoil mass spectrometer, in operation for some years on line with the LNL XTU Tandem accelerator has been used primarily for the study of reaction products emitted at 0° to the beam direction. In agreement with the design goal this instrument has a good mass resolution, in the range of 1/300, even with large energy (±20%) and solid angle (> 7.5 msr) acceptances; the mass dynamic range is around ±6% of the central mass. The beam rejection factor at 0° ranges from 10 +6 to 10 +11 according to various experimental parameters. Advantages and limitations of the spectrometer are discussed.

Corona discharge in flowing synthetic air

The formation of ozone and nitrogen oxides in synthetic air by negative DC corona discharge has been experimentally investigated. The electrical discharge was generated using a coaxial wire-cylinder corona discharge reactor, and different gas flow rates were imposed through the discharge cell. Ultraviolet absorption spectroscopy was used to identify and quantify the generation of chemical species.

Physico-chemical modeling of positive corona discharge in carbon dioxide

Positive wire-to-cylinder corona discharge in pure CO2 has been simulated using a model that includes elementary plasma processes (ionization, electron attachment and detachment, ion recombination, etc.) and chemical reactions between neutral species. The plasma chemistry model is included in the continuity equations of species, which are coupled with Poissons equation for the electric field and the energy conservation equation for the gas temperature. The experimental values of voltage and current are used as input data into the numerical simulation, and the spatial distributions of electrons, ions, atoms and molecules are then predicted for different gas flow rates. The average concentrations of ozone and carbon monoxide inside the discharge reactor have been experimentally determined by means of ultraviolet and FTIR spectrometry, and their values are compared with the results of the numerical simulation.

Ozone and nitrogen oxides production by DC and pulsed corona discharge

The formation of nitrogen oxides (NO, NO₂, N₂O and N₂O₅) and ozone (O₃) by negative DC and pulsed corona discharge has been investigated. The corona discharge was generated using a wire-to-cylinder reactor, filled with different mixtures of nitrogen and oxygen at atmospheric pressure and ambient temperature. Ultraviolet absorption spectroscopy operating in the wavelength range of 190 to 330 nm was used to identify the species and quantify their concentrations.