Evaluation of the Caesium-137 Activity at the Rochedo Dam, Goiás, Brazil

Abstract

In 1987, in Goiânia (Goiás, Brazil) a radiological accident occurred due to the violation of a capsule containing Cs-137, previously used in radiotherapy equipment. The source contained caesium chloride and, due to the high solubility of this compound in water, there was contamination of people and consequent dispersion in the environment. The waste was discharged into the river network and after four years, a high concentration of Cs-137 was still observed in the sediments at the Rochedo dam, in Piracanjuba, Goiás, 80 kilometres downstream of the Metropolitan Region of Goiânia. This research analysed the Cs-137 activity in sediment samples and water samples from the Rochedo dam, with the purpose of updating the radiological monitoring data of the region and also to verify if the perceived values would indicate any threat to the environment and public health. The Cs-137 activity was detected in 93.8% of the analysed samples, whose values varied from traces to 2.25 Bq/L. The results for all water samples and for 53.8% of the sediment samples were below the minimum detectable activity by the equipment. This study showed that Cesium-137 activity seem to be very low in the water resources and sediments of the Rochedo dam and it seems to not offer radiological risks for public health and the environment.