Radiation impact from lignite burning due to 226Ra in Greek coal-fired power plants.

Lignite contains naturally occurring radionuclides arising from the uranium and thorium series as well as from 40K. Lignite burning is, therefore, one of the sources of technologically enhanced exposure to humans from natural radionuclides. Emissions from thermal power stations in gaseous and particulate form contain radioisotopes, such as 226Ra, that are discharged into the environment causing radiation exposures to the population. About 11,672 MBq y-1 of 226Ra are discharged into the environment from four coal-fired power plants totalling 3.62 GW electrical energy in the Ptolemais Valley, Northern Greece, in which the combustion of 1.1 x 10(10) kg of lignite is required to produce an electrical energy of 1 GW y. The collective committed equivalent dose to lung tissue per unit power generated resulting from atmospheric releases of 226Ra was estimated to be 1.1 x 10(-2) person Sv (GW y)-1; i.e. more than 15 times higher than the average value for a modern type coal-fired power plant according to the UNSCEAR 1988 data.