NUMERICAL-ANALYSIS OF THROUGH DIFFUSION EXPERIMENTAL RESULTS

Good estimation of the diffusion coefficient by graphical methods requires that the diffusion process approach a steady state. However, it may take several years to complete the diffusion experiment if the sample is fairly thick. A numerical technique using the Nonlinear Chi-Square and Newton's (NCSN) method is proposed in this study to quickly determine the diffusion coefficient and the capacity factor from all experimental data. Comparisons of the results of the NCSN method to those of the conventional graphical method are presented for the cases of Cs-137+ and THO diffusion through cement. The data plotting work required by the graphical method is usually cumbersome and may be inaccurate in some cases. The NCSN method is reliable and it offers error estimates of the fitting parameters by analyzing experimental data from each stage of the diffusion process. Furthermore, this study can interpret the dead-end pores phenomenon in the transient region. It can also judge if the diffusion experiments have been performed sufficiently long to achieve a steady state.