[en] A method based on the separation of Sr-90 by extraction chromatography and beta determination by Liquid Scintillation Counting (LSC) technique was used for strontium analysis in food samples. The methodology consisted in prior sample treatment (drying and incineration) followed by radiochemical separation of Sr-90 by extraction chromatography, using the Sr-resin. The chemical yield was determined by gravimetric method, adding stable strontium to the matrix. Beta activity (Sr-90/Y-90) was determined using a low background liquid scintillation spectrometer (Tri-Carb 3170 TR/SL, Packard). The accuracy and the precision of the method, was performed previously through recovery trials with Sr-90 spiked samples, using the same type of matrices (milk, complete meals, meat and vegetables). A reference material (IAEA₃21) was now used to measure the accuracy of the procedure. Participation in interlaboratory comparison exercises was also performed in order to establish an external control on the measurements and to ensure the adequacy of the method. - Highlights: • Blank and background samples were analyzed according to internal quality control program established. • Analysis of certified reference material was carried out to perform additional evaluation of the accuracy. • Analysis of interlaboratory comparison sample showed Z-score and Z (ML) acceptable values. • The Sr-90 activity measured in wild bilberry powder sample was in agreement with the reference value

[en] Ionisation currents induced by γ-radiation in gaseous and liquid sulphur hexafluoride were studied as a function of the electric field strength. From the saturation currents in gaseous SF₆ a value of W=(34+-0.4) eV for the production of one ion pair was determined. In liquid SF₆ the free-ion yield up to E=20 kV cm^-1 was measured. At E=0 a value of Gsub(FI)(0)=(0.085+-0.008) was obtained. (author)

[en] We used a consistent and robust solar model to obtain upper limits placed by neutrino telescopes, such as IceCube and Super-Kamiokande, on the dark matter-nucleon scattering cross-section, for a general model of dark matter with a velocity dependent (p -wave) thermally averaged cross-section. In this picture, the Boltzmann equation for the dark matter abundance is numerically solved, satisfying the dark matter density measured from the cosmic microwave background. We show that for lower cross-sections and higher masses, the dark matter annihilation rate drops sharply, resulting in upper bounds on the scattering cross-section that are one order of magnitude above those derived from a velocity independent (s -wave) annihilation cross-section. Our results show that upper limits on the scattering cross-section obtained from dark matter annihilating in the Sun are sensible to the uncertainty in current standard solar models, fluctuating by a maximum of 20% depending on the annihilation channel.

[en] The emerging field of asteroseismology allows the direct study of stellar interiors with an incredibly high precision. We used a seismic parameter based on the phase shift as a diagnostic tool to infer the presence of a new layer of rapid variation in the external layers of the primary component of the stellar system Alpha Centauri AB. This layer is, apparently, a thin region where the acoustic modes suffer a strong scattering. Our tests indicate that this layer should be located at an acoustical depth of approximately 1400 s (0.939 R), which corresponds to a depth of 6% below the surface of the star. This is somehow unexpected since the internal structure of this sun-like star is predicted to be similar to the Sun. (paper)

[en] The Nuclear and Technological Institute (ITN) has the legal responsibility to carry out the environmental radiological monitoring at a national level. This survey was planned to provide relevant information on radioactivity levels in different components of the ecosystem. In what concerns the terrestrial environment the evaluation of the ⁹⁰Sr activity concentrations in foodstuffs has been performed using a method based on the separation of ⁹⁰Sr by extraction chromatography and beta determination by liquid scintillation counting (LSC) technique. The trials were carried out using 7 g of ash samples and 3 g of commercial Sr-resin (Eichrom). Validation trials were also performed using ⁹⁰Sr spiked samples. The chemical yields were determined by gravimetric method, after the addition of stable strontium to the foodstuffs. The ⁹⁰Sr activity concentrations in complete meals, meat and vegetables were determined after ⁹⁰Y in growths in the region 12-862 keV, using the Tri-Carb 3170 TR/SL scintillation counter in normal mode and a counting time of 120 min. The results obtained were low and of the same order of magnitude of those reported by other European countries. (author)

[en] Short communication

[en] Short communication

[en] The high quality data provided by helioseismology, solar neutrino flux measurements, spectral determination of solar abundances, nuclear reactions rates coefficients among other experimental data, leads to the highly accurate prediction of the internal structure of the present Sun - the standard solar model. In this talk, I have discussed how the standard solar model, the best representation of the real Sun, can be used to study the properties of dark matter, for which two complementary approaches have been developed: - to limit the number of theoretical candidates proposed as the dark matter particles, this analysis complements the experimental search of dark matter, and - as a template for the study of the impact of dark matter in the evolution of stars, which possibly occurs for stellar populations formed in regions of high density of dark matter, such as stars formed in the centre of galaxies and the first generations of stars. (paper)

[en] Most of the old uranium mines in Portugal are located in the granite regions of the centre-north of Portugal (Beiras), in regions with relatively high population density. Most of the public water supplies for the villages and cities are from groundwater or from surface water reservoirs constructed on the rivers of the region. A survey of the radioactivity in the water supplies was carried out in order to investigate the concentration of radionuclides from the uranium family such as uranium, radium, polonium and lead radioisotopes. Radon was also determined, as well as total alpha and total beta radioactivity, in order to assess the human exposure through consumption of drinking water. In general the radioactivity content of waters is reasonably low, not too high for human consumption. In several cases, however, the concentrations of radionuclides such as dissolved radon, polonium and radium, or even uranium, are elevated with total alpha concentrations above 0.1 Bq/L. Cases of public water supplies with very high concentrations of dissolved radionuclides are rare and in general apply to spring waters that may come into contact with rocks containing localized mineralizations of uranium. The highest concentrations of radionuclides were measured in water from wells in areas under the influence of old mines, especially the ones where in situ leaching with sulphuric acid had been performed in the past. This is the case, for example, for Cunha Baixa and Quinta do Bispo, two old mines draining into the same valley. At present, most of these wells are used for irrigation purposes and drinking water comes from other supply sources. Consideration is given to the radiation doses to members of the public through water consumption from public supplies of these regions. (author)

[en] The gross beta and tritium activities in the forty Portuguese drinking waters analyzed using the ISO standard methods (Portuguese Guidelines) are below the guidance levels proposed in the Portuguese Drinking Water Quality Guidelines. In what concerns the gross alpha activity only 18% exceeded the recommended level. In general, it can be concluded that the ingestion of these drinking waters does not create a radiological hazard to the human consumption, however, more detailed analyses will be necessary mainly the determinations of the individual alpha emitters radionuclide concentrations. The minimum gross alpha and gross beta detectable activities by L.S.C. methodology are higher than for the proportional counting technique (ISO method). Higher concentration factors will be needed to reach lower required detection limits. (authors)