EVALUATION OF RADIONUCLIDES SPECIFIC ACTIVITY OF GROUNDWATER RESOURCES. A CASE OF DIRE DAWA CITY, ETHIOPIA

The purpose of this work is to study specific activity of natural radioactivity concentrations of 226Ra, 232Th, 40K in different water sample locations of Dire Dawa city. The samples were collected from groundwater resources of the city in two different seasons. High resolution gamma ray spectrometry was used to assess the natural radioactivity levels concentration of, and to measure the annual effective does, radium equivalent, absorbed dose rate, external hazard and internal hazard. The result revealed that the range of radioactivity level concentration in summer season of 4.30−6.01 Bq·L−1, 3.75−12.74 Bq·L−1, 3.04−122.48 Bq·L−1, for 226Ra ,232Th and 40K respectively. For the sample that was collected in winter season the range of radioactivity level concentrations of 226Ra, 232Th and 40K are 0.70–6.02 Bq·L−1, 1.11–9.72 Bq L−1 and 12.2–134 Bq·L−1 respectively. The outdoor absorbed dose rate varies from 0.006 to 0.019 nGyh−1 with an average of 0.014 ± 0.032. The effective radium equivalent specific activity concentration is peak in summer than in winter season in one of the groundwaters. The activity level of the radioactivity elements was lower than the world average values.