Monitoring Radioactive Aerosol By Gamma Spectrometry

The definition of aerosol in the books is: any substance particles, can be solid or liquid form, suspended in the gas medium(usually refers to the air) formed with uniform properties of colloidal system; simple explanation, the aerosol is suspended in the air particles.For aerosol of the concept, people may not too familiar with, but aerosols in our life but can be seen everywhere, such as cooking to produce smoke;clean room produce dust; early in the morning air in the mist, these all belong to the aerosol of a, so you can say aerosol completely filled with the living environment of human beings, so monitoring of aerosol is absolutely necessary.If the particles suspended in a gas medium, itself radioactive aerosol system, then formation will be radioactive, we call this aerosol for radioactive aerosol.Radioactive aerosol in the current social environment,there are two most widely distributed, the greatest harm, is natural uranium, thorium Department of radiology in the decay daughter to form the aerosol and the nuclear power plant in the fission product leakage formation of aerosols, they are in radiation protection focus on the object.From the beginning of human consciousness to the hazards of radioactive aerosols, the radioactive aerosol monitoring method isconstantly updated. But previous aerosol monitoring are dependent on aerosol alpha or beta radioactivity to, is aerosol particles in the air collected into the filter, in by alpha and beta detector probe membrane emission of alpha and beta counting in order to complete the monitoring.But as we all know, alpha ray energy is relatively high, penetrating poor,often in the detection process of formation energy spectrum broadening,beta ray more needless to say, are generally continuous spectrum, the radioactive aerosol monitor is very adverse, so the traditional radioactive aerosol monitoring measurement methods are mostly used to excess alarm, unable to distinguish radionuclides in aerosol. In order to solve this problem, this paper research.The most important natural radioactive aerosols formed by the decay bodies in the natural uranium and thorium radioactive systems are also the major natural background. Due to aerosol particles are natural uranium, thorium Department of radiology in the decay daughter, then they must obey the uranium and thorium Department of radiology in certain decay law, this paper, from the aspects of the. The theoretical analysis of the motion law of decay in the air, some conclusion is gotten,and to promote, according to the aerosol collection to the membrane process is a combination of air movement equations, gives the aerosol particles in the membrane motion law.Artificial radioactive aerosol monitoring is mainly concerned withthe fission product aerosols produced by nuclear power plant leakage,then these fission products are the source of aerosol monitoring. This paper first analyzes the fission products in the disclosure process of nuclear power plant, also according to the 2011 Fukushima nuclear power plant accident, the surrounding environment monitoring data gives the fission product aerosol source. It is proved that they are mostly with gamma radiation, so the use of gamma radiation monitoring is feasible.Aerosol monitoring is generally divided into online and non online type two, non online measurement is generally aerosol samples were collected and sent to the laboratory for analysis and measurement, the results obtained are generally very accurate, but due to the sample sent to laboratory process has time difference. This time difference is difficult to control, so it is not conducive to the short half-life of the radionuclide measurement. In order to improve this problem, then puts forward the online aerosol monitoring, it is to design a monitoring system, can at the same time sampling and measurement of radioactive aerosols, simply say that while collecting edge detection. Considering the experimental accuracy problem, this is online measurement, reference to foreign monitoring device assembled a set of online monitoring system, which is divided into three parts: aerosol sampling system, aerosol detection system, air circulation loop. The mechanical structure of the three parts together reasonably.The scintillator probe for the sodium iodide crystal and lanthanum bromide crystal, in order to understand the probe the nature of, this paper in energy resolution, steady peak method and cost are the two were compared. At the same time, more detailed introduction to the each part of the monitoring system, to have a visual understanding of the monitoring system.To demonstrate the excellent performance monitoring method of gamma spectrum, in order to verify the earlier in this article on the air, the membrane uranium, thorium Department of radiology in the decay daughter body motion state theoretical analysis, this paper first introduced the a radioactive aerosol monitoring method-218 Po radon measuring method, and experimental analysis, and a preliminary understanding of the characteristics of alpha radioactivity monitoring.; and then through the analog calculation gamma spectrum method and other radioactive detection method detection limits are compared. It is proved that the method detection limit of gamma spectrum. This paper also measured60 Co, 137 Cs and 133 Ba three radionuclide mixed source of measuring the energy spectrum, and the energy spectrum test the gamma spectrum method to distinguish radionuclide ability. The results show that gamma spectrum method can effectively identify the spectrum of the main peaks,and accurately calculate the radiation source in the nuclear activity, so that the aerosol monitoring and have the capacity for nuclideidentification, which is compared to the innovation of traditional radioactive aerosol monitor.