tailieunhanh - Radiation and Health - Chapter 7

Con người sống được bao quanh bởi các nguồn phóng xạ tự nhiên. Có các đồng vị phóng xạ trong cơ quan, nhà ở, nước, không khí và trong đất. Trong chương này, bức xạ tự nhiên sẽ được thảo luận chi tiết hơn, cụ thể là bao nhiêu người bức xạ tự nhiên được tiếp xúc mỗi ngày. Các nguồn bức xạ thông thường của được trình bày trong hình . Liều lượng hàng năm thay đổi từ vùng này sang vùng khác, nhưng ít nhiều bằng những người được hiển thị trong hình | Chapter 7 Natural Radiation Introduction People live surrounded by natural radioactive sources. There are radioactive isotopes in our bodies houses air water and in the ground. In this Chapter natural radiation will be discussed in more detail in particular how much natural radiation people are exposed to every day. Common sources of radiation are presented in Figure . The annual doses vary from one area to another but are more or less equal to those shown in the figure. Cosmic Radiation Annual dose to mSv The atmosphere is continuously exposed to particles from outer space. A stream of particles consisting of protons about 85 a-particles about 13 and a small fraction of larger particles hit the outer atmosphere. Some of the particles have very large energies when hitting the atmosphere up to 1014 MeV . When the particles interact with the atoms in the atmosphere their energy gradually decreases and a number of new high energy particles are formed. 2003 Taylor Francis 64 Radiation and Health Figure . Natural radiation sources and their annual doses. The particular dose levels given are for Scandinavia. The annual doses are given in mSv. When cosmic radiation reaches both the inner atmosphere and the ground it is accompanied by Y-radiation neutrons and various other small particles. In addition some new radioactive isotopes are formed. The more important of these cosmogenic radionuclides are H-3 tritium Be-7 C-14 and Na-22. In addition to the radiation from space which is rather constant cosmic radiation contains particles and electromagnetic radiation from the sun. The radiation from the sun is variable due to sunspot activity which has a period of about 11 years . The energies of these solar particles are small contributing only a tiny fraction of the total dose from cosmic radiation. The contribution of neutrons that accompany cosmic radiation increases with height above sea level. This influences the dose since neutrons have a radiation weighting .