RADIOACTIVITY LEVELS AND DOSE RATES FROM ROCKS IN SELECTED MINING AREAS AND QUARRIES IN EASTERN UGANDA

Abstract

The aim of this study was to determine the radioactivity levels and dose rates due to natural radionuclides in rocks from selected mining areas and quarries in Eastern Uganda. 60 rock samples collected from six mines and quarries were analyzed using a NaI gamma detector. The specific activities of 238 U, 232 Th and 40 K in the samples were measured, the gamma dose rate and annual effective dose outdoor were determined. The specific activities ranged from 13.95±0.31 to 698.02±3.38 Bq kg -1 for 238 U, 98.68±1.30 to 2397.78±19.64 Bq kg -1 for 232 Th, and 45.97±2.48 to 2183.80±17.89 Bq kg -1 for 40 K. The absorbed dose rates were calculated and the values obtained at all sites are above the world average of 59 nGy h -1 . The annual effective dose rate outdoor for all the sites ranges from 0.30 to 1.37 mSv y -1 . The average annual effective dose rate outdoor for some areas are below 1.00 mSv y -1 , the lowest permissible limit set by the International Commission on Radiation Protection (ICRP); while other sites have the annual effective dose rates higher than unity which suggests a health risk to the inhabitants of the areas. Therefore, the National Environmental Management Authority (NEMA) should monitor the disposal of radioactive wastes from the mines in this region for human safety.