Preliminary assessment of natural radioactivity and associated radiation hazards in a phosphate mining site in southern area of Togo

摘要

Introduction Because of the increasing use of phosphate in industries worldwide, especially in Togo, it is interesting to investigate the potential radioactivity exposure of phosphate ores, especially in the one being exploring in Togo nowadays. Material and methods The contents of natural radionuclides (~(40)K, ~(226)Ra, ~(232)Th, ~(235)U and ~(238)U) were assessed in phosphate soil samples from Kpogame, Dagbati and Kpeme in the maritime region of Togo by using gamma spectrometry-based Broad Energy Germanium detector (BEGe6530). Since no study was made prior to the exploitation, the samples from the control area of Anfoin-Kpota far away from the three others were considered as reference. Results and discussion The results are discussed and compared with the data from other countries. The activity concentration of ~(40)K, ~(226)Ra, ~(232)Th, ~(235)U and ~(238)U are between (59.45 and 129.99), (20.19 and 779.93), (16.81 and 121.42), (2.26 and 52.03) and (16.66 and 841.14) Bq kg~(-1), respectively. The values obtained shows that the exploitation sites (Dagbati and Kpogame) and treatment site (Kpeme) have a very high level of radioactivity than the control area (Anfoin-Kpota). The Kpogame and Dagbati exploitation and Kpeme waste discharging phosphate deposit sites were found to have higher activity concentration than many others exploited phosphate sedimentary deposits around the world. The average annual effective dose of the above studied sites is 0.36, 0.24 and 0.48 mSv year~(-1), respectively. The value related to the discharge waste site is about 2% of the 1.0 mSv year~(-1) recommended by the International Commission on Radiological Protection as the maximum annual dose to the public. Conclusions The obtained result of both radioactivity and radiological level in the studied areas will be considered as a pre-operational baseline to estimate the possible radiological impacts due to mining and processing phosphate industrial activities.