Studying radon exhalation rates variability from phosphogypsum piles in the SW of Spain

•Variability of radon exhalation rates from PG piles has been studied using numerical simulation supported by experimental data.•Most relevant parameters controlling the exhalation rate are radon potential and moisture saturation.•Piling up the waste increasing the height instead of the surface allo...

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Bibliographic Details
Published in:	Journal of hazardous materials 2014-09, Vol.280, p.464-471
Main Authors:	López-Coto, I., Mas, J.L., Vargas, A., Bolívar, J.P.
Format:	Article
Language:	eng
Subjects:	Air Pollutants, Radioactive - analysis Applied sciences Calcium Sulfate - chemistry Enginyeria química Exact sciences and technology Exhalation rate General treatment and storage processes Impacte ambiental Mitigation Phopsphogypsum piles Phosphorus - chemistry Pollution Radioactive wastes Radiometry Radon Radon - analysis Radó Spain Variability Wastes Àrees temàtiques de la UPC
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Summary:	•Variability of radon exhalation rates from PG piles has been studied using numerical simulation supported by experimental data.•Most relevant parameters controlling the exhalation rate are radon potential and moisture saturation.•Piling up the waste increasing the height instead of the surface allows the reduction of the exhalation rate.•A proposed cover here is expected to allow exhalation rates reductions up to 95%. Nearly 1.0×108 tonnes of phosphogypsum were accumulated during last 50 years on a 1200ha disposal site near Huelva town (SW of Spain). Previous measurements of exhalation rates offered very variable values, in such a way that a worst case scenario could not be established. Here, new experimental data coupled to numerical simulations show that increasing the moisture contents or the temperature reduces the exhalation rate whilst increasing the radon potential or porosity has the contrary effect. Once the relative effects are compared, it can be drawn that the most relevant parameters controlling the exhalation rate are radon potential (product of emanation factor by 226Ra concentration) and moisture saturation of PG. From wastes management point of view, it can be concluded that piling up the waste increasing the height instead of the surface allows the reduction of the exhalation rate. Furthermore, a proposed cover here is expected to allow exhalation rates reductions up to 95%. We established that the worst case scenario corresponds to a situation of extremely dry winter. Under these conditions, the radon exhalation rate (0.508Bqm−2s−1) would be below though close to the upper limit established by U.S.E.P.A. for inactive phopsphogypsum piles (0.722Bqm−2s−1).
ISSN:	0304-3894 1873-3336