Hesitant, spatially limited return to the surface
No water flows through the underground clay rock layer. Atoms trapped in this structure move only very slowly, hesitantly and in all directions. Radioactive atoms in a waste container will move in the same way as ordinary atoms. They should not travel any further than those of our ancestor Lucy, who has not moved for the past two or three million years. Any atoms that did rise to the surface would follow very variable routes and arrive at very different times.