MANAGEMENT OF NORM IN THE PETROLEUM INDUSTRY Akpojevwa Tega Naomi, october 2016 | Page 20

the surface due to their radiation characteristics, all three Radium NORM show
different behaviour:
• Radium-228 is very quick (within two days) in secular equilibrium, after
which in a much slower process (about 10 years) Thorium-228, that was absent
in (deposits from) produced water, grows in (transient equilibrium)
• Radium-226 starts a secular equilibrium (within two weeks) of short-lived
NORM. The ingrowth of 210Pb occurs at a much slower rate (about 100 years).
• Radium-224 appears in produced water or its deposits without its immediate
parent Thorium-228, so it does not grow in anymore and quickly (within two
weeks) dies out.
This implies that only in freshly sampled fresh produced water Radium-224
may be detected. With the reappearance of Thorium-228, Radium-224 will also
reappear in more aged samples as member of the subseries.
1.2.3.3
Radon (Rn):
Radon isotopes are special as they, being a noble gas element, prefer the
(natural) gas phase for transport from the subsurface to the surface. As Radon-
220 (also known as thoron) only lives for minutes by the time that this NORM
reaches the surface, it will have decayed. 222Rn with a half-life of about four
days may appear in Natural Gas Liquids (NGL) processing installations, in the
gas cap of crude oil storage tanks (associated gas) or in Natural Gas (NG)
transmission lines. Ultimately it will decay to Lead-210, but as Radon-222 is
short-lived with respect to Lead-210, no equilibrium status will be reached.
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