Theoretical evaluation of the 222Rn emanation coefficient for coal fly ash.

The release of 222Rn, from individual material grains in which it is formed, may be largely a diffusion process. This paper presents an analytical model purporting to describe the physical process of the release of 222Rn atoms from a 226Ra-bearing material grain. The solution of the diffusion equation for a spherical grain permits us to calculate theoretically the diffusion and emanation coefficient. Using this analysis to interpret experimental release data is explained.