Monitoring of the radionuclides in fly-ash from lignite combustion and its use in building industry

Fossil fuels such as lignite are widely used in thermal power plants. A large amount of ashes is being produced, consisting of fly-ash and a bottom-ash. Lignite often contain high concentrations of naturally occurring radionuclides such as K-40, Th-232, U-238 and decay products of decay chains of last two mentioned. Produced ashes are enriched in these radionuclides in the combustion process. Large amounts of waste, especially fly-ashes and its proper disposal is a significant environmental problem. This waste, however, can be effectively used as a raw material in many industrial and other applications. It is widely used especially in building industry, because of its properties, which allow it to partially replace cement in concrete. Other applications include non-active additives in building industry, additives in metallurgy, filling of exploited mines and others. A limiting factor can be the natural radionuclide contents in fly-ashes. Its limit is given by the law and therefore activity of the fly-ashes should be monitored in order to avoid negative influence on the environment. A method of direct gamma spectrometry with high purity germanium detector was used to determine the activity of above mentioned natural radionuclides in fly-ash samples taken from the thermal plant TEZVO in Zvolen. A standard geometry of 450 ml Marinelli beaker for large volume samples was used. Preliminary results are in a good agreement with results published by several authors in recent works. The use of fly-ashes is a very effective way to reduce the amount of waste from lignite combustion to be disposed, and in many cases it saves alternative natural resources. With respect to all benefits arising from its use, its potential negative influence on the environment should be avoided by careful monitoring of its limiting properties (author)