The uncertainty evaluation of calibration instrument is an important step to evaluate the performance of instrument. The
radon chamber is a standard instrument used to calibrate the radon monitors. Because the radioactivity decay and
statistical fluctuation of radioactivity measurement, the uncertainty evaluation of radioactivity measurement instrument
is different from the general instrument, the uncertainty evaluation of radon chamber should trace to the national
reference radium source. In this paper, the two different uncertainty evaluation model of radon concentration based the
radon source and radon monitor is described. The uncertainty of different input variables include radon concentration,
radioactivity statistical fluctuation, the temperature and humidity is evaluated in evaluation standard Type A or Type B.
According to the contribution of different factor to the uncertainty of radon concentration, the expanded and relativity
expanded uncertainty of radon chamber is calculated and discussed in detail. Through comparison, the uncertainty
evaluation of radon concentration based on radon monitor is better than the model based on radon source.
KEYWORDS: Radon, Fuzzy logic, Control systems, Systems modeling, Calibration, Affine motion model, Complex systems, Data modeling, MATLAB, Process control
As a kind of radioactive gas, radon has the characteristics of radioactive decay and statistical fluctuation. The radon
concentration is always in a dynamic changing process, it is difficult to implement the accurate control. In order to make
the radon chamber keep a stability radon concentration, a fuzzy radon replenishment control model based on Takagi-Sugeno model is proposed. According to the idea of Takagi-Sugeno model, a two-dimensional fuzzy controller include
two inputs and single output is designed. The input variables of this fuzzy controller is E and EC, E is the deviation
between the actual concentration and expected radon concentration, EC is the change rate of radon concentration. the
output variable of controller is U that used to control the valve of radon source. The fuzzy control rule of radon
concentration is build by reasoning machine. The accurate control output variable is obtained by anti-fuzzy method and
be used to control the valve state radon source. A radon chamber control system is developed by Labview based on the
fuzzy control model. The experimental results show that the fuzzy control method improve the robustness of dynamic
radon replenishment.
As a standard instrument to calibrate the radon monitors, radon chamber is in urgent need with the deepening study on Radon and its progeny. According to the requirement of calibrating the radon monitors and radon detectors, the multifunctional and automatic controlled radon chamber is designed and constructed. By the reason of radon decay, the radon concentration in the chamber is continuously changing. The radon concentration must keep stability and homogeneity in order to calibrate the radon monitors and bio-culture. The supply and control of radon in the chamber is a critical problem in the design of Radon chamber. The paper introduced the mathematic model of dynamic radon replenishment according to the law of radon decay, three time parameters to replenish radon is discussed. The related automatic monitor and control system is developed by this mathematic model, the expected radon concentration can keep stability and homogeneity controlled by the system. The structure of radon chamber and the design flow system is presented in detail. The main performance parameter of the radon chamber such as airproof, stability and radon concentration certification is discussed. The research result can be used to calibrate the radon monitors, biological test on radiation environment and radiation medicine test.
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