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  • Author or Editor: J. Paniagua x
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Abstract  

The radioactive concentrations of226Ra,232Th,235U and40K in surface soil of the province of Cáceres (Spain) were studied as a function of the geology and grain size. The activities of the four radionuclides in granitic and metamorphic soils have normal frequency distributions, with the mean value being significantly higher for the granitic soils than for the metamorphic soils. Sedimentary soils present asymmetric distributions, and their activities lie between the previous two types. The specific activities of the four radionuclides rises as the particle radius decreases. The equationA e =(P 1/R)+P 2 describes the dependence of the specific activityA e on radiusR, P 1 andP 2 being parameters that are related to the surface area and volume activities of the grains. The isotopes226Ra,232Th and235U accumulate with greater intensity on the surface of the grains than40K. This effect is more pronounced in granitic and sedimentary soils than in metamorphic soils.

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Abstract  

With the object of quantifying the radiological impact that the Almaraz Nuclear Power Station, situated beside the Tajo river in Spain, induces on its ecosystem, since 1986 we have been carrying out multiple gamma-spectrometric studies and determinations of90Sr concentrations on the receptor media: surface waters, sediments, fishes, aerosols, and soils, in the two likeliest critical transmission pathways of transmission of the radioactive contamination. The principal results are summarized in the present work, and they allow the impact to be quantified, as well as the most probable source to be assigned for each of the levels detected.

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Abstract  

An analysis has been made of the surface distribution of137Cs and90Sr in soils of the province of Cáceres (Spain), of some 20.000 km2 area, situated on the frontier with Portugal. From the distribution of depth profiles of concentrations of these radionuclides and their fit to a negative exponential, determination was made of the mean values of the respective inventories and of the corresponding137Cs/90Sr ratio. The external dose rates from the presence of these man-made isotopes in the soil are calculated and compared with that originating from the concentrations of natural radioisotopes.

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Abstract  

We have quantified the evolution during 1994 of the impact on the Tagus river of liquid releases of3H (51.3 TBq in the cited year), originating from the functioning of the Almaraz Nuclear Power Plant, and conditioned by the management of the cooling reservoir water. Taking into account, on the one hand, that tritiated water is hydrodynamically indistinguishable from untritiated water when both form part of the same mass of liquid, and, on the other, the practically null stratification and forced circulation of the water in the cited cooling reservoir, together with the hydrological fluxes interchanged between the said reservoir and the Tagus river (which is entirely regulated in the section under study and, because of prolonged drought, had a relatively small flow during the study period), we were able to model satisfactorily the temporal evolution of the3H activity in the cooling reservoir.

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Abstract  

The mean weekly levels of7Be in the atmosphere of Cáceres (Spain) was measured for three consecutive years, from 1992 to 1994. The values showed a strongly seasonal behavior, conditioned fundamentally by two effects: (1) the incorporation of7Be into the low layers of the troposphere due to the displacement of masses of air from higher layers caused by the solar irradiation, and (2) the washing of7Be out of the atmosphere by rain. From the quantification of these two effects, the residence time of7Be was determined in the atmosphere at ground level as 10.3 days, with an interval for the standard error of 9.0 and 12.1 days. Modelling the temporal evolution of this radionuclide we were able to explain 90.72% of the variance of the measured activity levels. Using the effective residence time of7Be, we were able to justify the diversity of values obtained for the deposition of137Cs in different soils of the province of Cáceres due to the fallout from atmospheric nuclear blasts.

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