ABSTRACT Uranium dioxide pellets (UO2) used as fuel in nuclear power reactors are subjected to high thermal gradients and may undergo swelling during reactor operation. The swelling of UO2 pellets, resulting from the fission products, causes cracking of the material and it is thus critical to study their behaviour. This study evaluated the application of the ultrasonic method in obtaining the elastic constants of UO2 pellets. Due to the difficulties in handling nuclear material, we used tablets of alumina (Al2O3) for a comparative study. For this, two sets of 10 Al2O3pellets with densities of 92% and 96% were fabricated. Ultrasonic transmission technique was used for obtaining measurements of the travel time of longitudinal and transverse ultrasonic waves. Equations relating material density and velocity of the ultrasonic wave to the elasticity, shear and Poisson’s modules allowed the determination of these elastic constants, whose values showed excellent agreement with those available in the literature for Al2O3.

This paper presents a numerical procedure for estimation of the precision and accuracy of the acoustic birefringence technique for evaluation of residual and applied stresses in civil structures and components. This procedure accounts in an automatic and systematic way for the uncertainties in the input data and their propagation throughout the calculations. The acoustic birefringence is defined from the speeds of two mutually orthogonal volumetric waves of normal incidence, but when the use of a pulse-echo measurement system is feasible, the birefringence can be defined directly from the time-of-flight of the waves, since they travel the same physical space. The times-of-flight of the waves are estimated by coupling the mathematical techniques of cross correlation and data interpolation, whereas the material’s acoustoelastic constant is determined via a weighted linear regression. As an example, the estimation of the precision and accuracy in the evaluation of the stresses in a beam under bending is discussed. components calculations incidence pulseecho pulse echo feasible timeofflight time flight space timesofflight times interpolation materials material s regression example discussed

A campilobacteriose é uma infecção frequentemente adquirida pelo consumo de produtos de origem animal. O frango é o principal responsável na cadeia de transmissão da enfermidade. A radiação ionizante foi utilizada para verificar a redução da carga bacteriológica de Campylobacter jejuni presente em fígados de frango, que podem apresentar, in natura, contaminação em até 100% dos casos. As doses de irradiação utilizadas foram 0,20 kGy, 0,27 kGy, 0,30 kGy e 0,35 kGy, sendo as amostras adquiridas em aviário, supermercado de bairro, supermercado popular e supermercado de grande porte. O processamento das amostras foi feito no Setor de Campylobacter, FIOCRUZ, e as irradiações feitas na COPPE na UFRJ, com irradiador gama provido de fonte de Cobalto 60. Somente a amostra congelada, adquirida em supermercado de bairro, não continha a bactéria. Em todas as outras amostras, pôde-se observar a presença de Campylobacter sp., mesmo quando usados procedimentos e tecnologias que visam impedir sua presença no alimento e, consequentemente, proteger a saúde humana. Alguns resultados se apresentaram abaixo do esperado, porém é sabido que as condições de crescimento exigidas por esta bactéria são incomuns quando comparadas às de outros enteropatógenos.

Campylobacteriosis is an infection frequently acquired through the consumption of animal origin products. Chicken can be considered the main responsible cause in the transmission chain of this disease. Ionizing radiation was used to verify the reduction of the microbiological load of Campylobacter jejuni present in chicken liver, which, in natura, can present contamination in up to 100% of the cases. The doses of irradiation used were: 0.20 kGy, 0.27 kGy, 0.30 kGy and 0.35 kGy. The samples of chicken liver were acquired in aviaries, local supermarkets and large chain supermarkets. The samples were analyzed for Campylobacter at FIOCRUZ. Irradiation was performed at COPPE/UFRJ, using a Gamma Cell Irradiator with a 60Co gamma source. Only the frozen sample acquired at the local supermarket did not contain the bacterium. Campylobacter sp. was present in all other samples, even when using procedures and technologies that aimed at the impediment of the presence of this bacterium in food and, consequently, at the protection of human health. On the whole, the results were satisfactory; nevertheless, it is known that the bacterial growth conditions required by this bacterium are uncommon when compared to other enteropathogenic bacteria.

Changes to the microestructure during thermal aging treatment at 610 ºC in Fe-xMo-5Ni-0.05C alloys were studied for different aging times with different Mo concentrations. The heat treatment at 610 ºC induces carbide precipitation into the metallic matrix near Fe2Mo phase. The X-ray diffraction studies revealed a more intense precipitation of α-FeMo, Fe3Mo, R(Fe63Mo37) phases and MoC, Fe2MoC carbides for the alloys containing 15 and 11% Mo, respectively. This work shows that hardness and coercive force changes are function of the molybdenum content and aging time variation. Vickers hardness and coercive force both increase with the increase of molybdenum content and reach maximum values at 4 and 1h of aging, respectively.