Diffusion of Radon Gas from Uranium Mill Tailings

A finite element model is presented which predicts radon diffusion in an n layer composite. The basis functions are obtained from an exact solution to the differential equation for a homogeneous layer. Thus the model gives the exact solution for n homogeneous layers and, by using many small layers, will give good results for any nonhomogeneous composite. The model can account for diffusion into the soil below the tailings, a finite radon concentration in the ambient and a radon source in each layer and the underlying base soil. In addition to the general matrix equation, closed form solutions are presented for some important special cases.