Radiological impact of coal ash from the power plants in Hong Kong

Samples of coal, furnace bottom ash and pulverised fly ash were collected from the two electric companies in Hong Kong. The samples were collected over a period of 1 year and therefore they were representatives of the annual consumption of coal as well as the annual production of the ashes. Special procedures were taken to separately burn the coal bought from different places so that the origins of the ash samples are traceable. The radionuclide contents, radon emanating fraction and porosity of the samples were measured. Mathematical models were then used to evaluate the radiological hazard of the ash samples when used in the building industry. Both the γ and radon exposures due to the coal ash loaded concrete in buildings are not much different from that due to unloaded concrete. External γ dose rate and 222Rn concentration at the centre of an uncovered ash lagoon are estimated to be 0.165 μGyh−1 and 2.9 Bqm−3, respectively, again not much different from the local background. On the other hand, the committed effective dose due to inhalation of PFA of about 7.1 × 108 BμSv, where B is the PFA loading in air, can be an important source of exposure if resuspension of ash particles is not properly controlled.