Page 21 - Professorial Lecture - Prof Oyedele

6. STUDIES ON THE RADIOACTIVITY IN DIFFERENT CITIES AND
TOWNS IN NAMIBIA.

6.1 MEASUREMENT OF THE CONCENTRATIONS OF RADIONUCLIDES IN SOILS

As I said earlier, if the concentration of radionuclides in the soil of a particular
area is high, it could lead to a higher level of ionizing radiation in the area.
In fact, it is well known that the radionuclides in the soil are the main
contributors to natural radioactivity in a given area (IAEA, 1987). Areas with
high level of radiation are called high background radiation area (Ghiassi-
nejad et al., 2002; Ramli et al., 2005). High background radiation area could
be a threat and it is not desirable to live in such areas. It is therefore of
interest to check whether or not our towns and cities - where we live - are
high background radiation areas. In fact, as I indicated earlier, a number of
citizens in different towns - especially those close to Mines – have asked (my
research group) if their towns have normal or “safe” background radiation.

A way to determine the level of radiation or assess the background
radiation in a given town is to determine the concentrations of
radionuclides in the soil of that town (Sahin and Cavas, 2008; Mujahid and
Hussain, 2010; Kapdan et al., 2012). More specifically, we take a relatively
small amount of soil – which we call a soil sample – in a place in the town
and we process the sample and subsequently measure the amount of
radiation emitted by each of the three radionuclides Uranium-238, Thorium-
232 and Potassium-40 (in the sample) using a radiation detector such as
HPGe (Knoll, 2000; L’Annunziata, 2004; Tsoulfanidis, 2011). We then calculate
the concentrations of the radionuclides from the amount of radiation
emitted. These concentrations will be substituted into some well-established
formulas to obtain the level of radiation and the hazards of radiation at the
point where the sample was collected (Oyedele, 2006a; Cam et al., 2013;
Oyedele and Shimboyo, 2013).

The above procedure is repeated for about 50 to 100 samples in a town
and the average concentrations (of 238 U, 232 Th and K), average radiation
40
level and average hazard indices are subsequently calculated for the town.
From these average values, we can know if the town is having a high
background radiation (and therefore hazardous) or if it is normal (Oyedele,