1 Modeling Tritium Removal from Metal Surfaces

2 A program was written to numerically model the diffusion of tritons throughout a metal bulk. The program uses Fick’s diffusion equation to follow the time evolution of a concentration profile. It has been used to accurately model how particles will flow out of a system with a concentration of zero at the surface. It has also been used to model how a change in diffusion constant, such as the one between the metal oxide layer and the metal bulk, affects the diffusion of particles. Using this model for the concentration profiles within a substance, the outgassing rate of tritons from a surface as a function of time has also been modeled. The outgassing rate model accurately models the outgassing rate from experiments at longer times, but at earlier times it is less accurate. This is believed to be due to the fact that only diffusion through the solid is accounted for in the outgassing rate model, and surface equations are ignored. This would suggest that at earlier times, the removal of tritons is governed by surface equations, while at later times it is governed by diffusion. Work on a more complex program to model the removal of tritons from the surface of the metal has been started, and will be used in conjunction with the diffusion model.