自古以来,人类就不断的受到天然辐射源的照射。来自宇宙空间的高能粒子,在地球大气层外称初级宇宙射线;进入大气层后,初级宇宙射线所带的能量和粒子与大气相互作用、产生次级宇宙射线。来自地表的天然辐射源,可分为三类:一是铀、锕、钍三个天然放射系中的核素,二是地壳中存在的除上述三个放射 Since ancient times, mankind has been constantly exposed to natural radiation. High-energy particles from cosmos, outside the Earth’s atmosphere, are called primary cosmic rays. After entering the atmosphere, the energy and particles carried by the primary cosmic rays interact with the atmosphere to produce secondary cosmic rays. Natural radiation from the surface can be divided into three categories: one is uranium, actinides, thorium three natural radionuclides in the second is the existence of the crust in addition to the above three emissions