Emanation and mobility of radon

Radon escape from clilTerenl types of rocks. 

I rcciucncy distribution of Rn in air at two locations as a function of elevation above ground. 

It is obvious from the data of Tables ll-VIII to I l-XII that the emanation power varies widely. As a rule, the finer the particle size the greater the emanation power. However, when samples are severely weathered or damaged, as in the case of radioactive ores, further comminution of a specimen has little effect on the emanation power. In both cases it is believed that Ra has migrated from the original site of its parent in the crystal lattice and has adsorbed on the surfaces of microfractures facilitating Rn escape. When certain samples are pulverised in the laboratory they may even emit less Rn than the whole lump. This can happen when U and its decay products are associated with minerals that do not pulverise as easily, i.e., are less friable. Starik and Melikova (1957) found that a whole lump of ore had an emanation power of 46% 

Emanation power (%) of uranium ores in air at ambient temperature 

Starik and Melikova, 1957 Ores with seeondary minerals (1), 30 65  

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