External effective doses from soil samples due to artificial radionuclides in the Semipalatinsk Nuclear Testing Site and Chagan (Kazakhstan).

aExternal effective doses were calculated with the following formula: Hext = C•Dext•f•s.
where C is the activity concentration of detected artificial radionuclides (241Am, 137Cs and 60Co; halh-life > 1y) (kBq/m2; calculated from radionuclide concentration in Bq/kg and collected areas of soils (0–5 cm)), Dext is the dose conversion coefficient as kerma-rate in air at 1 m above ground per unit activity per unit area ((µGy/h)/(kBq/m2) for detected artificial radionuclides with the value of relaxation mass per unit area 10 g/cm2 (ICRU 1994)), f is the unit conversion coefficient (0.7 Sv/Gy (UNSCEAR 2000)), s is the decrease in the coefficient by a shielding factor against exposure with gamma rays from a deposit at 1 m above ground (0.7 under the condition of usual land (IAEA-TECDOC-1162)).