Methods of study radioactive-gas diffusion in solids. IX. Desorption method

The desorption method is considered for examining the diffusion of a gas or vapor in a solid. Two forms of diffusion apparatus have been devised for determining diffusion coefficients from measurements on the radioactivity in the gas or in a solid (under vacuum or in an inert atmosphere). The effects of the initial concentration profile on the kinetic curves are discussed, as are those of the diffusion mechanisms (bulk diffusion, kinetic mode of outgassing, and so on) and those from radioactive decay. A general solutions obtained to the equations for dissociative diffusion subject to the boundary conditions of the desorption method. Gas-release curves have been computed from the diffusion model with retention time. The methods have been tested on the diffusion of radon-222 in low-density polyethylene.