Talita Oliveira Santos

Determination of natural radioactivity in beach sand in the extreme south of Bahia, Brazil, using gamma spectrometry

The natural radionuclides activity concentrations in beach sand of the extreme south of Bahia, Brazil, was measured by Gamma Spectrometry. The Radium Equivalent Activity, the external hazard index, the absorbed dose rate and the annual effective dose were assessed and compared with internationally published values for external dose and activity concentrations. The activity concentrations of 226 Ra, 232 Th and 40 K in beach sand ranged from 8.4 to 8,300 Bqkg -1 with a mean value of 910 Bq.kg -1 , from 21 to 18,450 Bqkg -1 with a mean value of 2,220 Bqkg -1 and from 3.4 to 3,110 Bqkg -1 with a mean value of 352 Bqkg -1 , respectively. The results indicate that the absorbed dose rates range from 21 to 14,450 nGyh -1 with mean value of 1,792 nGy.h -1 . The highest value of gamma dose rates among the studied beaches were found in Cumuruxatiba (14,450 nGyh -1 ). The annual effective dose range between 0.03 and 17.70 mSvy -1 , with the mean value of 2.20 mSvy -1 . In four studied beaches, the assessed outdoor annual effective doses are above the worldwide average of 0.07 mSvy -1 as reported by the United Nations Scientific Committee on the Effects of Atomic Radiation. Especially in the area of black sands, a big part of Cumuruxatiba beach, whose annual effective dose of 17.70 mSvy -1 is much higher than worldwide average.

Use of radon isotopes, gamma radiation and dye tracers to study water interactions in a small stream in Brazil

In this study, natural (222Rn) and fluorescent (uranin) tracers were used to investigate the interactions between surface and subsurface waters in a small hydrographical basin located in the southeast region of Brazil. Levels of 222Rn were measured in 117 water samples with the use of an alpha solid-state detector. After the identification of the probable discharge sections along the stream, a measurement of the natural flows, upstream and downstream of these sections, was done with the use of a fluorimeter and fluorescent tracers. Also, scanning was done to verify a correlation between the natural gamma radiation and the 222Rn in the areas where its activity was higher. The results showed some sections where the 222Rn activity is more significant and contributed to the growth of the flows along the stream. It was possible to confirm a correlation between the discharge sections and the natural gamma radiation, what can be used as a preliminary approach to finding these sections in scenarios similar to the one studied here.

MONITORAMENTO DA RADIOATIVIDADE ALFA RELACIONADA AO RADÔNIO-222 EM ÁGUAS DE POÇOS DA REGIÃO METROPOLITANA DE CURITIBA-PR

This research objective was to assess the level of randon-222 concentration in well water of the metropolitan region of Curitiba, Parana. Current work presents the results of indoor 222Rn activity ground water samples from artesian wells from aquifers of the region. The studies of radon activity in water were performed using the radon detector AlphaGUARD. The calculations of initial radon activity in water were done considering the 222Rn decay correction as well as equilibrium level of 222Rn and 226Ra observed after 30 days of measurements. Obtained results show that about 70% of measured activity levels of 222Rn are higher than the recommended value of 11.1 Bq.L-1, which represent the risk for the human health associated with this radionuclide. The case study showed that previous measurements of radon are recommended for a construction project is implemented. In this case, it is observed that the radon concentrations decrease about 56% in the first water tank and 83% in the second water tank over the well. This fact shows that the actions for mitigation of radon are viable and do not require major modifications to the usual systems of construction.