Theoretical study of high radon emanation

Radon emanation coefficients larger than 0.6 have been reported; such large values were unexpected. This led the authors to study how the maximum possible radon emanation coefficient (hereafter referred to as 'maximum radon emanation probability') could be determined. Theoretical calculations were repeated in which the grain configuration was changed in order to get the maximum radon emanation probability. Two types of grains were targeted. The first type consisted of two components mixed together; one component was a large amount of mother grains including no radium and the other component was a small amount of very fine grains including radium. For this type, the maximum radon emanation probability was obtained as 0.75. The second type consisted of only one grain component including radium. For this type, the maximum radon emanation probability was 0.625. In both types, the high coefficients were attributed to the extremely small size of the radium-bearing grains. This finding hinted at a possible countermeasure to suppress radon emanation, i.e., sintering at a rather low temperature, which may best be fitted to industries which process naturally occurring radioactive materials (NORM).