| Radon is a colorless, tasteless inert gas and radioactive elements, which is radioactive gases from Uranium, thorium decay. Radiation dose on human beings affected by major natural sources is about 2.4mSv/y, of which the contribution of indoor radon is 54%. Radon is one of the major carcinogens which is announced by the World Health Organization (WHO); And it is the second factor to lung cancer just lower to cigarettes. Radon exists everywhere in human life space, so it is very important to measure the concentration of indoor radon.In recent years, with the rapid development of the world economy, there have great change in people's living standards and working conditions, people's housing conditions, housing structure and the working environment. People are becoming more and more concerned about their own environment, especially the quality of the air in working and living environment. The problem of radiation hazards of indoor Radon has caught the concern of the public ,which has become one of severe issues. Since the 1980's, the public have paid more attention to the relationship between the human health and Radon in environment. In1989, the International Atomic Energy Agency proposed that the members should carry out the research work of the Radon in human environment. Since 1990, the United States have brought forward the effect of the indoor radon as a serious health issue and have propagated the indoor radon information to the public in order to guide people to take protective measures to reduce the harm. The United States Environmental Protection Agency (EPA) had named January in 2002 as the National Radon Action Month (NRAM), which improved and strengthened the National Radon Action Week activities lasting 12 years.We can learn the experience from the National Radon Action Month Events. In April 1, 1994 ,our state launched "standard methods for radon measurement in environmental air" and "People's Republic of China national standard" (GB/T14582-93), and developed a package of " Standard for controlling radon and its daughters in underground space " (GB16356-1996), and " Radiological protection standards for using geothermal water " (GB16367-1996);In 1995, the state also legislated " Control standards of radon concentration in dwellings " and"People's Republic of China national standard "(B/T16146-1995);In 2001, the state legislated "code for indoor environmental pollution control of civil building engineering" ("People's Republic of China national standard" GB/T50325-2001);"Law of the peoples Republic of china on prevention and control of Radioactive pollution"went into effect on October 1, 2003At present, there are a variety of methods of measuring Radon, but each method has its own limitations. Considering the actual situation in the laboratory, active carbon cartridge method is used to measure the concentration of the indoor Radon. Active carbon cartridge method is passive and cumulative type. It has many advantages such as easy to operate, flexible, low cost, high sensitivity and easy to find a weak anomaly. So it can be deployed in many points. Activated carbon cartridge method is used to collect Radon in indoor air and then calculate the radon concentration in indoor air by measuring the release of radon daughters decay characteristic peaks ofγ(214Pb: 242keV, 295keV, 352keV; 214Bi: 609keV) with NaI (Tl) detectors or HPGe detectors.The experiment is located at a room which is vacant and closed all the year round. It can be ignored the factor which affect the concentration of the radon such as gas, water and smoking. Put the fresh active carbon cartridges into the room and number the cartridges and then wait for 1-6 days. After collection, record the temperature and humidity, and then record the quality change. After 3 hours, measure again and the time for every cartridge is 1 hour. Through the research, the following conclusions can be drawn:1. When the active carbon cartridge absorb the indoor Radon, it also absorb water vapor in the air. After 3 days, the adsorption will come to the summit. Water quantity is related to the variety of the activated carbon, the dosage of the activated carbon and the humidity of the air2. With the NaI(Tl) detectors and the HPGe detectors, radon and its daughters will come to the balance after 3 hours. The conclusion coincides with the theoretical calculation.3. With the NaI(Tl) detectors and the HPGe detectors measurement of Radon daughters, the time that active carbon cartridges absorb the indoor Radon is 3 days. If the time is longer, it would waste time and reduce the efficiency of collection and detection.4. Through NaI (Tl) detectors and HPGe detectors measure the Radon of the same house, the results are almost equal. Considering the routine maintenance, the cost and other things, we choose the NaI (Tl) detectors.
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