Radioactivity of ash from coal fired power stations (Macedonia)

In the lignite of the thermal power plant's surface mines there are uranium and thorium traces. Thorium-232 isotopes and uranium -238 and 235 isotopes are natural radioactive with a long period of half-decay. With the lignite combustion, thorium and uranium concentration occurs into the ash. Because of the fossil material old age, the products of the radioactive decay of all three radioactive series are in stationary condition, which results an equal activity of all isotopes in the series. Between the radioactive isotopes of each series there are α and β emitters which radiate γ quantum as well. The energy of α and β particles is of grate value for the radiation dose determination. While the γ quantum, because of its own penetration, play a special role in radiation intensity determination, as well as isotopes identification. In this paper the ash samples from the Thermal Power Plant 'Bitola' (Macedonia) are analysed. Gamma spectrometric analysis of the ash samples is done and presence of several isotopes of radioactive thorium and uranium series is confirmed. With the obtained results, the permitted doses of ash inhalation of neighbourhood population are defined