Discussion Of Control Indexes And Standard Method For Radon Exhalation Rate Of Building Materials

Half human dose caused by the natural radiation comes from radon and its progeny inindoor, inhaling of radon and its progeny play a major role in the development of lungcancer. Building materials mingle with coal ash and waste powder that contains theamounts of radium above of standards have been widely used in the civil building in therecent year, which leads to the rise of radon in indoor. In view of the relationship betweenradon exhalation rate and concentration of radon indoor, accurate determination andcontrol of radon exhalation rate are directly related to the concentration of indoor radon forcontrol and protection.The study of radon exhalation rate from materials surfaces just limit to the directmeasurement concentration of radon exhalation rate in wall surface or separate measuringradon exhalation rate value through building materials samples at home and abroad. Thedirect measurement results of the wall surface can’t let people to make right choice inbuilding materials of low radon exhalation rate value according to the measurement results,so that evaluation method presents an obvious hysteretic nature in protection of radon, andit is trouble to take direct measurements for radon exhalation rate from indoor buildingmaterials surface due to the adornment on real building walls; The measurement ofbuilding materials alone are not representative actual radon exhalation rate from buildingwalls.In this paper, the study and comparison the radon concentration distribution in actualbuilding walls and building materials sample, combining with theoretical modes had beenestablished for the inherent radon exhalation rate in the building materials, we find that thepretreatment model which exposed one side or two sides of building materials after sealedis able to simulate the actual state of walls with limited thick and infinity extension.Comparison of different methods for measurement radon exhalation rate, find that activated carbon box method is the most suitable method for inherent radon exhalation rateof the building materials. Based on the two points above, a reliable and predictable methodfor evaluation and determine the radon concentration from building materials has beendeveloped in this paper. The state of radon exhalation rate from walls with limited thickand infinity extension simulate by different pretreatment for building materials, then radonexhalation rate from that are measured with the charcoal canister-gamma spectroscopymethod for calculating radon inherent exhalation rate, at last radon exhalation rate frombuilding surfaces of any thick which made with that building materials. Through thatradon exhalation rate from building surface is able to evaluate accurately, someexperiments have been conduct based on that.Experiment results shows that the deviation between radon exhalation rate frompretreatment building surface by calculated with radon inherent exhalation rate and theactual measured value of building surface is less than10%, the method for radonexhalation rate from pretreatment building surface by calculated with radon inherentexhalation rate is reliable. Radon inherent exhalation rate is a suitable index for evaluationof radon exhalation rate form building materials surface based on it can reflect the actualvalue of the radon exhalation rate without influence by the building material, It issuggested that radon inherent exhalation rate can be introduced into the national standards[Limit of radionuclides in building materials](GB6566-2001) for more application.