Since the beginning of mining operations in the Witwatersrand basin, more than six billion tons of tailings have been produced. The average uranium concentration in these tailings is about 100 mg/kg, translating to over 600 000 tons of uranium oxide being exposed to the open environment.
This was highlighted during the inaugural lecture of Prof Makondelele Victor Tshivhase, director of the Centre for Applied Radiation Science and Technology.
His inaugural lecture titled “Nuclear material: from the belly to the grave” took place on the North-West University’s (NWU’s) campus in Mahikeng on 22 August 2019.
During his lecture Prof Tshivhase presented three selected studies to demonstrate the line of research carried out.
The aim of the first study was to assess the effectiveness of ion exchange, reverse osmosis and coagulation filtration, three of the best available treatment methods in the removal of radioactivity and heavy metals from Acid Mine Drainage (AMD).
The study provided recommendations on the most appropriate method South Africa can employ in the treatment of AMD. According to the findings, ion exchange was identified as the best method for the removal of both radioactivity and heavy metals from AMD, since it produces small amounts of solid waste and has high radioactivity and metal removal rates.
The second study focused mainly on the actual mine dump. This study considered it as the main source of water pollution, and calculated the estimated radiological dose due to direct ingestion of untreated water.
According to the findings, the dose limits set by the Strahlenschutzkomission, the World Health Organisation and the South African National Nuclear Regulator were all exceeded. The study recommended that residents should avoid using contaminated water at all costs.
The last study aimed to evaluate the soil radionuclides' activity concentrations and environmental outdoor gamma dose rates in the Tudor Shaft mine environs. The study also calculated excess lifetime cancer risks.
Outdoor gamma dose rates were determined in 45 soil samples taken from nine locations. Uranium 238 activities – the most common isotope of uranium found in nature – were high, with an average value almost 10 times the world average concentration. Annual effective gamma doses and the excess life-time cancer risks were also higher than the world's average.
The study determined and concluded that the Tudor Shaft was not suitable for long-term human occupation due to the significant cancer risk over a person’s lifetime.
Prof Tshivhase said his research focused on understanding the problems and risks mine dumps could hold for people living in and around the affected areas.
“My research explored the remediation methods, modeling of long-term exposure and determination of existing conditions. It also focused on determining baseline data which can be used to monitor changes in environmental radioactivity, if any,” he added.
Prof Eno Ebenso, executive dean of the Faculty of Natural and Agricultural Sciences, congratulates Prof Tshivhase after delivering a successful inaugural lecture.
