Abstract
The RESRAD-onsite 7.2 code has been used to assess the total dose rate in Tudor shaft site contaminated over an area of 10 km2. The risk analysis simulation was span over a period of 1.0E+3 years. The maximum total dose of 1.64 mSv/yr was obtain at t = 8.17 ± 0.02 years. The total peak dose at time t = 0 yr. is 1.63 ± 1.0 mSv/yr for all pathways. This value is 6.53 times higher compare to the basic radiation dose limit of 2.5E-01 mSv/yr. The evaluated excess cancer risk was 3.46E-3 and is 10 times higher compared to the recommended limit of WHO. A cover layer depth of 1.25 m was simulated using the code and a total maximum peak dose for all pathways was 2.52E-01 mSv/yr at t = 5.0E+2 ± 1.0 years.
Highlights
A primary consideration in formulating key environmental decisions and policies depends on potential risk to human health and the environment (Bellamy et al, 2014)
The total peak dose at time t = 1 yr. due to 238U, 226Ra, 232Th and 40K were 3.35E-02 mSv/yr, 1.59 mSv/yr, 3.16E-03 mSv/yr and 5.86E-03 mSv/yr
The Derived Concentration Guideline Levels (DCGLs) values at t = 8.17 ± 0.02 yrs were calculated based the basic radiation dose limit (BRDL) of 0.25mSv/yr multiplied by the initial contaminant levels (Bq/g) of the radionuclides divided by the respective maximum total peak dose at time t = 8.17 ± 0.02 yrs
Summary
A primary consideration in formulating key environmental decisions and policies depends on potential risk to human health and the environment (Bellamy et al, 2014). Studying the possible impacts resulting from exposure to 238U, 226Ra, 232Th and 40K often requires the modelling of the contaminant transport in the environment. According to literature the South African gold mines are associated with high levels of radionuclides. Tudor Shaft is an informal settlement in Krugersdorp which is west of Johannesburg and is highly contaminated by 238U, 226Ra, 232Th and 40K due to the gold mine shaft and tailings dam. It is very obvious that people built their shacks on the tailings soil and grow their vegetables (resident farmer). The National Nuclear Regulator (NNR) in 2012, acting on advice from the local government began removing the Tudor Shaft waste dump. About half of the soil was removed, but environmentalists were alarmed that it was being done without risk-assessment studies or consultations
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