[Comparative analysis of the radionuclide composition in fallout after the Chernobyl and the Fukushima accidents].

The nuclear accident occurred at Fukushima Dai-ichi Nuclear Power Plant (NPP) (March 11, 2011) similarly to the accident at the Chernobyl NPP (April 26, 1986) is related to the level 7 of the INES. It is of interest to make an analysis of the radionuclide composition of the fallout following the both accidents. The results of the spectrometric measurements were used in that comparative analysis. Two areas following the Chernobyl accident were considered: (1) the near zone of the fallout - the Belarusian part of the central spot extended up to 60 km around the Chernobyl NPS and (2) the far zone of the fallout--the "Gomel-Mogilev" spot centered 200 km to the north-northeast of the damaged reactor. In the case of Fukushima accident the near zone up to about 60 km considered. The comparative analysis has been done with respect to refractory radionuclides (95Zr, 95Nb, 141Ce, 144Ce), as well as to the intermediate and volatile radionuclides 103Ru, 106Ru, 131I, 134Cs, 137Cs, 140La, 140Ba and the results of such a comparison have been discussed. With respect to exposure to the public the most important radionuclides are 131I and 137Cs. For the both accidents the ratios of 131I/137Cs in the considered soil samples are in the similar ranges: (3-50) for the Chernobyl samples and (5-70) for the Fukushima samples. Similarly to the Chernobyl accident a clear tendency that the ratio of 131I/137Cs in the fallout decreases with the increase of the ground deposition density of 137Cs within the trace related to a radioactive cloud has been identified for the Fukushima accident. It looks like this is a universal tendency for the ratio of 131I/137Cs versus the 137Cs ground deposition density in the fallout along the trace of a radioactive cloud as a result of a heavy accident at the NPP with radionuclides releases into the environment. This tendency is important for an objective reconstruction of 131I fallout based on the results of 137Cs measurements of soil samples carried out at late dates after the Fukushima accident.

[Results of radiation monitoring in Moscow]. / Rezul'taty radiatsionnogo monitoringa v Moskve.

The results of assessing the radiation situation due to global fallouts, obtained from measurement of 137Cs and 90Sr in over 400 samples from natural environmental objects in Moscow in 1979-1999 have indicated that the levels of the substances in the atmospheric fallouts are in agreement with the mean Russian levels and the mean annual activity of these radionuclides in the ambient air are 6 orders lower than the allowable values laid down in NRB-99. In Moscow, the mean effective dose of external exposure to natural and cosmogenic radionuclides is no greater than 1 m3v a year. The individual effective doses of internal and external exposures of the population to global fallouts averages 13 mu k3v a year.