A Method for Testing the Diffusion Coefficient of Polymer Films

This project developed and evaluated a method to measure the diffusion of radon through thin polymer films. The system was designed so that the simple, one-dimensional transport model developed by Mosley (1996) could be used. The system uses radium-bearing rock as a high level radon source. The test film is sealed in the system with the high concentration radon gas on one side and an alpha detector sealed on the other side. The activity-versus-time data is collected and fitted using a non-linear least squares method. The system measurements and the three fit coefficients are used to calculate the system efficiency and diffusion coefficient. Three polymer films with published values of the radon diffusion coefficient (polyethylene, polyester, and latex) were tested in duplicate to evaluate the method and determine its comparability to values in published literature. The results show good repeatability (10%) and some comparability to similar published data (20% to 200%).