2. Mechanism of radon release

Radon escapes from a portion of radium trapped in a solid element (such as granite) thanks to its recoil kinetic energy of 86 keV (kiloelectron volts).

The emanation mechanism takes place in three stages: the recoil effect (direct recoil) propels (diffusion) the new element towards a permeable pore (dissolution), which may be air or water.

Radon emanation is a function of :

• water content (emanation is four times stronger if the environment is saturated with water rather than dry):

• radium localization;

• granulometry ;

• soil porosity ;

• temperature ;

• etc.

Only a part of the atoms produced by emanation reaches...