Assessment of environmental radioactivity in soil, water and foods consumed in the northeastern state of Sergipe - Brazil

Measurements of radioactivity in the environment are of great importance in monitoring and control of radiation levels to which humans are exposed directly or indirectly. Two nuclear power plants are planned in the northeast Brazilian region by the Ministry of Mines and Energy under the National Energy Plan 2030. Even without defining the exact location where these new plants would be built, there is great speculation that new units will be built along the banks of the San Francisco River. This region is extremely poor in studies from the standpoint of determining the radioactivity in the environment, being practically non-existent in the literature data on the state of Sergipe. This study aimed to contribute to analysis of the occurrence of natural and artificial radioactive material in soil, water and food products of the State of Sergipe, focusing primarily on Neopolis Plateau region, which is located the banks of the Rio San Francisco. For this purpose, radionuclides found in all samples collected from soil and cement, fertilizer and food chain products were analyzed by gamma spectrometry, whose activity was measured employing an HPGe detector. The ingestion of contaminated food is a potentially important form of internal exposure. The internal dose due to ingestion depends on the concentration of radionuclides in food and their effective half-life. This study also presents new data for the activity of several natural radionuclides in some aliments produced in the region and the corresponding effective dose due to their intake. Be-7 was detected in organic fertilizers and lemon peel and Th-232 found in samples of soil and cement, both unprecedented results in the literature. The committed effective dose by radionuclides and the total average effective dose calculated for food and the activities of radionuclides measured in all kind of samples were below the Brazilian radioprotection law dose limits. However, it was also detected Cs-137 in some samples, due to the use of fertilizers and food additives imported from northern countries. Their activities do not pose a risk to the population. (author)