Subatomic Physics – Environmental Radioactivity Lab

Radionuclides are found naturally in air, water, soil, plants and even human beings are radioactive. In the Earth crust, radioactivity is mainly incorporated in mineral crystals present in rocks or detrital sediments. Their radionuclide concentrations depend on the mineral properties and their origins. For geophysical studies, the heat produced by radioactive decay in rocks is of fundamental importance in understanding the thermal history of the Earth and interpreting amongst others the continental heat-flux data. The measurement of radionuclide concentrations is an alternative tool to explore the properties of geological structures.

The Environmental Radioactivity Laboratory (ERL) of the Department of Nuclear Physics (DNP), iThemba LABS, has been using radiation detectors for anthropogenic (‘man-made) and natural radioactivity measurements. The radiation detectors consist of the laboratory-based HPGe detector and field-based MEDUSA detector systems. In addition, a RAD7 monitor is available for measuring radon in-air and in-water (either in the laboratory or in the field). To assist with optimizing, testing and calibrations of the detectors, the Monte Carlo (MC) simulations codes are also being used.

Recently, the team is exploring the possibility of using neutron activation analysis (NAA) technique to add to the available methods.

The current focus of the ERL is on the measurement of activity concentrations of (primordial and anthropogenic) radionuclides in soils, sediment and water. Moreover, other samples can be counted provided they can be transformed into liquid or powder form.

Some of the past and current research activities include:

  • the exhalation of radon (an inert radioactive gas) from mine tailing dams,
  • the correlation between radon levels in domestic dwellings and source terms (soil, building material),
  • studies into potential use of radiometry to partially characterize the terroir associated with vineyards,
  • applications of radon in hydrogeology, the systematic effects that impact on the measurement of activity concentrations,
  • Monte Carlo simulations of the interaction of gamma-rays to optimize the detectors, investigating amongst others, density effect, geometry variation,
  • the use of naturally occurring radioactivity to optimize minerals processing, and
  • studies of the impact of environmental radioactivity on ecosystems.

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Fig.1 : MEDUSA detector mounted on a 4×4 vehicle during an in situ
Fig.2 :  Inside of lead castle showing the top of the ERL HPGe detector mapping campaign.