Computational Hydrodynamic Modelling of the Fate and Impact of Natural Radionuclides in Liquid Effluent Discharges from The Gold Processing Plant at Aboso Goldmines in Damang Tarkwa, Ghana

ABSTRACT

Transport of radioactivity in surface water of mine-origin can occur either due to a controlled release from a working mine site (e.g. release of excess stored water) or uncontrolled release (e.g. erosion of material from a site). The radionuclides could concentrate during mining and mineral ore processing and incorporate in water bodies or traditional food stuffs, and thus contribute to the radiation dose received by the public. Eulerian approach to Partial Differential Equations (PDE) has been used to describe the relevant physical processes during radionuclide transport in the Taamang River. A computer programme has been written in MATLAB to implement the numerical solution of the PDE in order to estimate the activity concentration and annual committed effective dose to the public from natural radionuclides (NORM) in liquid effluent discharges from the gold processing plant at the Aboso goldmines in Damang, Tarkwa Ghana. The NORM elements of interest are 238U and 232Th decay chains. These radionuclides and some progenies such as 226Ra are long-lived. The key to understanding their distributions, therefore, is to understand the distribution of the source materials, and the physical and geochemical processes that lead to elevated concentrations of these radionuclides under specific conditions. The results obtained from the study revealed that the concentration of NORM in the Taamang River in Damang increases with time at the point of release and decreases due to its decaying character. For short-lived radionuclides, the concentration decreases rapidly as pollutants travel along the river corridor and approaches zero for both 224Ra and 210Po at 300 m from the discharged point. However, for long-lived radionuclides, the average activity concentrations were 0.06 Bq/L, 0.54 Bq/L and 0.78 Bq/L for 226Ra, 238U and 232Th respectively at 500 m from the discharged point where the water is used by the public. The corresponding average annual committed effective doses xvii estimated were 0.01 μSv/y, 0.06 μSv/y, and 0.11 μSv/y for 226Ra, 238U and 232Th respectively. The results indicate an insignificant exposure of the public to Natural Occurring Radioactive Materials (NORM) from the activities of the Goldmine. The model designed will serve as an essential tool for use in the regulatory control of routine discharges of radionuclides into the environment and also in planning measures to be taken in the event of accidental releases from the mine