Radon activity and exhalation rates in Indian fly ash samples

Abstract

Fly ash is the by-product of burnt coal which is naturally occurring radioactive material (NORM). Because of human activity and its use in manufacturing of bricks, sheets, cement, land filling etc may present a radiation hazard to people and the environment Thus, it is very important to carry out radioactivity measurements in fly ash from the health and hygiene point of view In the present study, the activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K have been varied from 99 ± 2 to 203 ± 4 Bq/kg, 145 ± 2 to 288 ± 4 Bq/kg, and 355 ± 5 to 516 ± 6 Bq/kg, respectively in various fly ash samples The radium equivalent activity was varied from 317 to 614 Bq/kg, radon activity varied from 214 to 590 Bq/m³, radon exhalation rate varied from 7.8 to 21.6 mBqkg^-1h^-1 for mass exhalation rate and from 138 to 381 mBqm^-2h^-1 for surface exhalation rate in the fly ash samples used in the present investigation The absorbed dose varied from 143 to 277 nGyh^-1, the indoor annual effective dose varied from 0.70 to 1.36 mSv and the outdoor annual effective dose varied from 0.17 to 0.34 mSv In all the samples, the activity concentration of ²³⁸U, ²³²Th and ⁴⁰K was found to be below the permissible levels A strong positive correlation has been observed between uranium concentration, radon activity and radon exhalation rate.