Natural radioactivity levels and estimation of radiation exposure from soils in Bahi and Manyoni Districts

Leonid Leopold Nkuba; Pendo Butongwa Nyanda

doi:10.15392/bjrs.v5i3.306

Authors

Leonid Leopold Nkuba Tanzania Atomic Energy Commission
Pendo Butongwa Nyanda Tanzania Atomic Energy Commission

DOI:

https://doi.org/10.15392/bjrs.v5i3.306

Keywords:

Uranium deposit, Soils, Radioactivity, Radiological hazards or effects

Abstract

Soils samples from Bahi and Manyoni were analyzed for radionuclides. The activity levels of Ra-226, Th-238, and K-40 were measured by direct γ‐ray spectrometry using HPGe detector by Compton suppression method. The results show that the average radioactivity concentration in soil samples ranges from 10.80 Bq/kg – 835.00 Bq/kg for R-226, 12.30 – 105.00 Bq/kg for Th-232 and 47.20 Bq/kg – 808.00 Bq/kg for K-40. The results from this study have been compared with those from other areas in Tanzania and of different countries of the world. To assess the radiological effects and hazards from natural radionuclides (Ra, Th and K), the absorbed dose rate (DR), the annual effective dose equivalent (AEDR), Excess Lifetime Cancer Risk (ELCR), the radium equivalent activity (Raeq), the external (Hex), the alpha index (Iα) and the radioactivity level index (I_ɤ), were calculated. Except for DR in all the soil samples; Raeq, Hex and Iα exceeds the recommended limits due to high activity of Ra-226 in Membeta soils. Also Iɤ was above the limits due to higher Ra-226 in soils from Membeta and Th-232 in Ilindi and Nala. Whilst the other radiological parameters (AEDR and ELCR) as well as the Raeq, Hex, Iα and Iɤ in same areas were far below the recommended limits. However, this does not guarantee the safety. Therefore the probability of occurrence of the health effects from radiation is significant. The study recommends that the soils from Membeta should not be used as building material because they might expose the population to radiation.

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