Fly-ash waste from thermal power plants

Coal-based thermal power plants burn train-loads of coal in a day and the percentage of ash generated is of the order of 35-40%. This waste needs disposal, and the target buyers are cement manufacturers and brick makers. The bricks made out of this fly-ash are cheaper as compared to the conventional bricks. The fly ash contains the naturally occurring radionuclides coming from uranium and thorium series of elements and Potassium-40. These radionuclides are present in the coal in parts per million (ppm) levels and get concentrated in the fly ash. A few hundreds of Becquerel (unit to express the quantity of radioactivity) of the radioactivity per kg of the material are likely to be present in the fly-ash.

One of the daughter products in uranium and thorium series is the gaseous radon isotopes. Being gaseous, the radionuclides diffuse out of the bricks/walls made out of the fly ash. These are emitting alpha radiation, and give dose to the lungs when goes inside the lungs as an air contaminant via inhalation route.

From radiation protection considerations, it is suggested that before fly-ash is used for commercial exploitation, an assessment of the materials is made for their radioactive content and the probable dose it is likely to give. If necessary, the material should be processed to remove the radioactivity content as much as possible. Clearance from the appropriate national authorities such as Atomic Energy Regulatory Board in India, may be required before large scale use of the “waste” fly-ash materials in cement or bricks used for construction of residential buildings.