Nejistota stanovení objemové aktivity radonu v pobytových místnostech a na pracovištích

Abstract

Radon is a radioactive gas that is a produced from the decay of radium; a main source of which is the geological bedrock. Radon from soil gases can penetrate buildings in a number of different ways, posing a serious health risk to the resident population. Compared to other natural radiation sources, radon can be managed and health risks reduced. Quality assurance and control of radon measurements therefore represents an important element of radon risk assessment and management. This Ph.D. thesis analyses possible sources of uncertainty in the measurement of radon in residential rooms and work places. Three computational approaches were used to evaluate and interpret the uncertainty associated with the measurement of radon: an analytical approach (according the international handbook JCGM 101:2008 GUM); a simulation approach (the Monte-Carlo method); and a probabilistic approach (the binomial distribution). These approaches are applied to the integral radon concentration detector (A system for integral dosimetry RM-1), which is recommended by the Czech State Office for Nuclear Safety for the measurement of radon. The calculated combined relative uncertainty for a common radon volume activity level for fully charged electret ion chamber detectors is 7-11,5 per cent for the analytical approach and 5-12 per cent for the simulation approach. Thus, there is only a small difference between these computational approaches (<3 %). The results of the probabilistic approach are ∼90,7–92 per cent confident that a set of two electret ion chamber detectors is suitable for estimation of the radon concentration within the interval of ±20 % of the reference value. In addition, the probabilistic approach highlights the negative impact of a higher absolute humidity (above 9,1g m−3) on the quality assurance of radon measurements. The main benefit of the Ph.D. thesis consists on an application of the GUM international methodology to uncertainty of radon volume activity measurement of the Czech made system for integral dosimetry RM-1. The both measured and simulated results confirm that the analyzed RM-1 system is robust and suitable for estimation of radon concentration in residential rooms and workplaces.