Levels of external natural radiation and doses to population in Heilongjiang province

The external natural radiation level in Heilongjiang Province was measured by using China-made FD-71 scintillation radiometers and RSS-111 high pressure ionization chambers. The doses of external radiation to population were also calculated. The population-weighted average value of the absorbed dose rate from terrestrial γ-radiation was 7.2 x 10-8 Gy.h-1 for outdoors, and 10.8 x 10-8 Gy.h-1 for indoors. The population-weighted average absorbed dose rate in air from cosmic rays was 3.3 x 10-8 Gy.h-1. The annual population-weighted average effective dose equivalent and the annual collective effective dose equivalent from the environmental γ-radiation were 620 μSv and 20.1 x 103 man.Sv, respectively. The corresponding figures from cosmic rays were 260 μSv and 8.7 x 103 man.Sv, respectively