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Abstract(s)
Coal contains trace elements and naturally occurring radionuclides such as 40K,
232Th, 238U. When coal is burned, minerals, including most of the radionuclides, do
not burn and concentrate in the ash several times in comparison with their content in
coal. Usually, a small fraction of the fly ash produced (2-5%) is released into the
atmosphere.
The activities released depend on many factors (concentration in coal, ash content
and inorganic matter of the coal, combustion temperature, ratio between bottom and
fly ash, filtering system). Therefore, marked differences should be expected between
the by-products produced and the amount of activity discharged (per unit of energy
produced) from different coal-fired power plants. In fact, the effects of these releases
on the environment due to ground deposition have been received some attention but
the results from these studies are not unanimous and cannot be understood as a
generic conclusion for all coal-fired power plants.
In this study, the dispersion modelling of natural radionuclides was carried out to
assess the impact of continuous atmospheric releases from a selected coal plant.
The natural radioactivity of the coal and the fly ash were measured and the
dispersion was modelled by a Gaussian plume estimating the activity concentration
at different heights up to a distance of 20 km in several wind directions.
External and internal doses (inhalation and ingestion) and the resulting risk were
calculated for the population living within 20 km from the coal plant. In average, the
effective dose is lower than the ICRP’s limit and the risk is lower than the U.S. EPA’s
limit. Therefore, in this situation, the considered exposure does not pose any risk.
However, when considering the dispersion in the prevailing wind direction, these
values are significant due to an increase of 232Th and 226Ra concentrations in 75%
and 44%, respectively.
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South Pacific Environmental Radioactivity Association