EVALUATION OF DIFFUSION PARAMETERS OF RADON IN POROUS MATERIAL BY FLOW-THROUGH DIFFUSION EXPERIMENT

The effectiveness of a material in reducing the fluence rate of Rn fro m soil was assessed in this study by using a flow-through diffusion ex periment to evaluate the diffusion parameters-apparent diffusion coeff icient and capacity factor-of radon (Rn) in a porous material. The dif fusion process would be required to have already reached a steady stat e so that an accurate estimate of the diffusion parameters could be ob tained. An improved method based on the nonlinear least-squares and Ma rquardt's method (NLSM method) was proposed to provide more reliable a nalyses of experimental data than the graphical method. The NLSM metho d was confirmed by the experimental results to be capable of estimatin g the diffusion parameters, even if the process was transient. This me thod was also demonstrated to correlate sufficiently with the results by the conventional method while the process had already reached stead y-state. Natural mordenite was employed in this study as a testing mat erial because it has more effective sorption for noble gas than any ot her earthen material.