Assessment of radiation hazards related to phosphate ore processing around Kpeme plant in Togo: multivariate statistical approach

The activity concentrations of U-238, Ra-226, Th-232 and K-40 were carried out on soil samples from phosphate ore processing site at Kpeme, Togo. Spatial distribution of the activity concentrations of all radionuclides and associated risk hazards parameters were performed using multivariate statistical analysis such as Kendall's, Spearman's and Pearson's correlations and principal components analysis. The level of exposure due to gamma-ray radiations was estimated. The results concerning the activity concentrations of U-238, Ra-226, Th-232 showed values higher than the recommended limit except K-40. The total average values of the radium equivalent activity index, absorbed gamma dose rate in air, internal and external hazard indices, I-gamma and excess lifetime cancer risk were 381.27 Bq kg(-1), 175.11 nGy h(-1), 1.94, 1.03, 1.02 and 0.00075, respectively. These values were higher than the worldwide maximum admissible value. However, the exposed dose to workers and the public was below the limit recommended. Statistical analysis indicated strong positive correlation between U-238, Ra-226 and Th-232, and negative correlation between the previous radionuclides with K-40. The Pearson's correlations related to the parameters is linearly the best approximation of the measured values. Principal component analysis indicated that the responsible of radiological risk's variations in the vicinity of Kpeme plant are uranium and its decay products. The radon mass exhalation rate was investigated and its maximum value was around 16% of the worldwide admissible value. Hence it was assumed that the use of Kpeme soil as building material is safe but requires aeration to avoid the accumulation of radon gas.