MANAGEMENT OF NORM IN THE PETROLEUM INDUSTRY Akpojevwa Tega Naomi, october 2016 | Page 16

cause ionizations in the stopping tissue. Upon intake, irradiation from inside the
body can occur.
1.2.2 NORM Decay Series
In nature, there are three naturally occurring radioactive decay series.
The first series, known as thorium series, consists of a group of radionuclides
related through decay in which all the mass numbers are evenly divisible by the
number four, (4n) series. This series has its origin radionuclides Thorium-232.
The terminal nuclide in this decay series is the stable Lead-208. In this series,
the transformation from the original parent Thorium-232 to the final product
Lead-208 requires 7 beta-β and 4 alpha-α decays. ( Jonkers et al, 1997)
The second series is the uranium series, the parent radionuclide in this series is
U-238 (4n+2) abundance = 99.27 %, which undergoes alpha-α decay. The
stable product of the uranium series is Lead (Pb)-206, which is reached after 8α
and 6β -decay steps. This is a particularly important series in nature since it
provides the more important isotopes of elements Radium, Radon and
Polonium, which can be isolated in large amounts in the processing of uranium
minerals. Each ton of uranium is associated with 0.34 g of Radium-226.
The third radioactive decay series, known as the actinium series, the head of this
series is Uranium-235, which has an abundance of 0.72 %. The stable end
product of this series is Pb-207, which is formed after 7α and 4β -decay steps.
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