Uncertainty evaluation of calibration radon chamber

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.