Determination of <sup>238</sup>U and <sup>232</sup>Th Levels in Well Water and Associated Radiological Hazards in the Municipality of Ivato Airport, Madagascar

Groundwater always contains uranium and thorium but with varying concentrations depending on the area geological formation. Long-term ingestion of water containing high natural radioactivity levels could cause diverse effects to human health. This is the reason why the study of two radionuclides <sup>238</sup>U and <sup>232</sup>Th was conducted in the well water in the Municipality of Ivato airport, Madagascar. Measurements have been performed by high-resolution gamma spectrometry system with coaxial HPGe detector to determine the specific activities of two radionuclides in ten samples. The samples were put into 1 litre Marinelli beakers, sealed hermetically and stored for three weeks to reach secular equilibrium between <sup>226</sup>Ra and its daughters before analyses. Results obtained showed that the specific activities vary from (4.08 ± 0.52) Bq.kg<sup>-1</sup> to (4.48 ± 0.70) Bq.kg<sup>-1</sup> with an average value of (4.36 ± 0.12) Bq.kg<sup>-1</sup> and from (4.40 ± 0.42) Bq.kg<sup>-1</sup> to (4.80 ± 0.73) Bq.kg<sup>-1</sup> with an average value of (4.61 ± 0.12) Bq.kg<sup>-1</sup> respectively. The effective annual dose rate due to ingestion were also determined, and compared to the worldwide average values, the WHO reference value and the permissible limit value of public. Statistical studies of the data were carried out to understand the behavior of uranium and thorium elements in these waters. Generally, radionuclides present in well water have normal levels of radioactivity. This means that these levels do not present any radiological risks to the local population.