Effective Radiation Dose From Indoor Rn-220 Concentration
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Date
2017-10-03
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Addis Ababa University
Abstract
Equilibrium equivalent concentration of thoron (EECTh)were measured in theNuclear
Physics laboratory of the Addis AbabaUniversity over a period of 21 days in the months
of April andMay 2017. The laboratory is located in the first floor of the Department’s
building. The method, used in this work, is based on gross beta counting of filtered
aerosol samples counted over successive time intervals using an end-windowGeiger-
Müller detection system. i.e., grab sampling of air followed by absolute beta counting
was used to determine thoron concentration.
The gross beta-count was then fitted to a mathematical model using least-square
fitting method. The concentrations of the radon and thoron daughter products were
determined from the best fit. Equilibrium Equivalent Concentrations of Radon and
Thoron were calculated from the concentrations of the progeny. This EEC was used
to determine the effective indoor inhalation dose due to thoron.
It was found that the effective annual effective doses for thoron inhalation by the
inhabitantswere found to vary in the range (0.06 - 0.20mSv/y) with a mean of 0.1 mSv
y .
These results are close to the maximum permissible dose (0.1mSv/y) to the public
due to thoron progeny recommended by (ICRP, 1990).
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Keywords
Effective Radiation, Indoor Rn-220, Concentration