Locked up in rock shale for millions of years are large amounts of natural uranium and its decay products.
These decay products are sometimes called 'daughters', 'granddaughters' or 'progeny' , e.g. radium-226, radon-222, bismuth 214, lead-210 and polonium-210.
Locked deep under the ground these are safe enough. Brought up to the surface in leakage from the fractured shale and in wastewater, they can contaminate both the fracking site and the wider environment, where they can become a serious health problem.
Wastewater dissolves radium-226 and brings it to the surface where it (i)accumulates as scale on the surface of pipes and tanks on the fracking site, (ii) is left on the ground near the bore heads and distribution facilities and (iii) can contaminate the local environment (particularly the water sources).
Radon-222 gas
The degree of danger represented by radon-222 gas brought to the surface in the gas and wastewater depends on three factors:
- The level of radioactivity of the gas naturally occurring in the shale
- The time that lapses between its arrival at the surface and its coming into contact with a living creature
- The radioactivity and half-life* of its decay products (see below)
Wastewater from fracking is likely to contain higher levels of radon-222 than wastewater from conventional 'reservoir' gas extraction because fractured shale has a greater surface area per ton from which the gas can leak than rock from the walls of gas reservoirs.
Radon-222 decay products
Radon-222 is also dangerous because of its decay products. One is the highly radioactive metal lead-210, which builds up as a fine dust and has a half-life of 22 years. Lead-210 itself decays to bismuth-210, which immediately decays to the radioactive metal polonium-210, which has a half-life of 138 days.
Definition
Half life - the amount of time required for a property of a substance to fall to half of its value as measured at the beginning of the time period. Where the property measured is radioactivity, it means 'the time required for half of the unstable, radioactive atoms in a sample to decay'.
Authorship
Dr. Chris Busby is an expert on the health effects of ionising radiation and was the Scientific Secretary of the European Green Party's European Committee on Radiation Risk.
From article by Dr. Chris Busby in RadioactivityTimes.com
(16424) Nick Anderson. Green Health Watch Magazine 46:21 (28.8.2013)
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