ANALYSIS FOR METAL ELEMENTS AND RADIOACTIVE ISOTOPES IN FLY-ASH PRODUCED IN LIGNITE COMBUSTION AT A THERMAL POWER-PLANT

We determined the composition of fly ash from a thermal power plant and from the lignites used as mixed fuels at the plant. Heavy metals were analysed for qualitatively by emission spectrography and quantitatively by X-ray fluorescence. On the other hand, radioactive actinide elements were assayed by gamma and alpha spectrometry, and sulphur and carbon were determined by combustion. The analysis of the two types of sample showed the presence of alpha-emitting radioactive elements of the 4n and 4n + 2 series in much larger amounts than in other natural samples (calcined lignites featured higher activities than fly ash by a factor of 2.2). Likewise, the sulphur content of the lignites was typically 8 times higher than that of the ash -irrespective of the amounts released directly into the atmosphere- as a result of the plant using a mixture of coals from different sources.