Aerosol emissions from the destroyed power-generating unit of the Chernobyl nuclear power plant in 1986 and 2003–2005

The results of measurements of the volume activity and dispersity of aerosol carriers of β-emitting radionuclides during the acute phase of the accident and 20 years later are presented. It is determined that in August–October 1986, when samples were taken 10–50 m from the surface of the destroyed reactor, the concentration was about 1 kBq/m³, which is 100–1000 times higher than the value recorded in July–August of the same year from an aircraft flying at altitudes 200–1000 m. Thus, already in mid-summer 1986, because of the decrease in temperature, the aerosol emissions did not reach the survey altitude of the aircraft. Therefore, the sampling performed from the aircraft did not permit a quantitative assessment of the emissions of radioactive materials during this period of time. In 2003–2005, the total β activity was 10–100 times less than in fall 1986, because of the radioactive decay of ⁹⁵Zr, ⁹⁵Nb, ^103,106Ru, ¹³⁴Cs, ^141,144Ce, and other radionuclides. Since the ¹³⁷Cs concentration decreased negligibly, it seems that the roof constructed in 1986 above the Shelter was of little use. __________ Translated from Atomnaya énergiya, Vol. 100, No. 4, pp. 276–282, April, 2006.