Natural radioactivity, radon exhalation rate and radiation dose of fly ash used as building materials in Xiangyang, China

Natural radioactivity level, radon exhalation rate and radiation hazard of fly ash used as building materials in Xiangyang, China were determined. The activity concentrations of Ra-226, Th-232 and K-40 in the investigated fly ash samples range from 90.3 to 1799.4, 59.9 to 145.6 and 309.0 to 906.3Bqkg(-1) with an average of 440.5, 110.3 and 510.1Bqkg(-1), respectively. Ra-226 and K-40 are the main contributors of total activity concentration in red fly ash and grey fly ash, respectively. Radon exhalation rates of the studied fly ash samples vary from 4.7 to 74.2Bqm(-2)h(-1) with the mean of 21.1Bqm(-2)h(-1). The relative hazard indexes, i.e. radium equivalent activity, external hazard index, internal hazard index, indoor air absorbed dose rate and annual effective dose, indoor radon exposure dose, outdoor air absorbed dose rate and annual effective dose were calculated to assess the radiation hazard of fly ash when it was used as building materials or piled on the ground. The assessment results show that the studied fly ashes would cause excessive radiation risks to inhabitant and they are not suitable to use as building material. The ash storage pond is a high radiation risk area and the population living around ash pond would be exposed to higher radiation.