Annual effective dose due to combined concentration of 226Ra and 228Ra in the groundwater system: a case study of the University of Ilorin Main Campus, Nigeria

An estimation of the annual effective dose received by the population as a result of the ingestion of 226Ra and 228Ra in the groundwater within the Main Campus of the University of Ilorin, Nigeria has been made. Groundwater samples from existing boreholes sited inside the campus were analyzed by gamma-ray spectroscopy to determine the suitability of the water for human consumption. The activity concentration values from the analysis range from 0.03+/-0.02 to 4.79+/-1.26 Bq/l for 226Ra and from 0.01+/-0.00 to 4.79+/-1.82 Bq/l for 228Ra. The computed annual effective dose received by the population as a result of the ingestion of 226Ra and 228Ra is thus estimated to range from 0 to 0.49 mSv/y and 0.003 to 1.21 mSv/y respectively. The total annual effective dose received as a result of the combined ingestion of 226Ra and 228Ra is consequently found to range from 0.003 to 1.45 mSv/y with an average of 0.59 mSv/y. It is therefore, observed that although the average combined contribution of 226Ra and 228Ra activities to the committed effective dose from a year's consumption of drinking water in the study area is less than the ICRP's recommended limit of 1 mSv/y, the groundwater from some of the boreholes is more than 1 mSv/y. For this reason, it is recommended that adequate measures should be taken to protect the young populace in the study area from consuming radiologically unsafe drinking water from the affected boreholes