Investigation of environmental natural penetrating radiation level in Hubei Province

The methods and results of the investigation on natural penetrating radiation level in Hubei Province are presented, 290 measuring points of 25 x 25 km-grid were set uniformly up all over the province, with 385 densely measuring points of different types added. The results show that: (1) The area-weighted, population-weighted and point-weighted average value of natural γ radiation dose rate for field is 60.8, 58.5 and 60.9 nGy ·h-1, respectively; (2) The point-weighted average value of natural γ radiation dose rate for road is 55.3 nGy·h-1; (3) The population-weighted and point-weighed average value of natural γ radiation dose rate inside buildings is 94.5 and 93.2 x 10 nGy·h-1, respectively; (4) The point-weighted and population-weighted average value of the dose rate inside buildings from cosmic ray is 27.8 and 26.3 nGy·h-1, and outside buildings is 31.8 and 30.4 nGy·h-1, respectively; (5) The point-weighted and population-weighted average value of natural penetrating radiation dose rate inside building is 121.0 and 120.7 nGy·h-1, outside buildings is 92.8 and 88.9 nGy·h-1, respectively; (6) The annual effective dose equivalent from cosmic ray, natural γ radiation and natural penetrating radiation is 0.24, 0.52 and 0.76 mSv, respectively; and correspondingly, the annual collective effective dose equivalent is 1.2, 2.5 and 3.7 x 104 man·Sv, respectively