- #211
vanesch
Staff Emeritus
Science Advisor
Gold Member
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Phy6explorer said:But it seems that quite a few actinides are found naturally in the Earth. Then don't most actinides share some common components.Why can't they be dumped deep into the Earth, of course, in a depth which is safely above the water -table?
Deep means "below the water table". So deep repositories are necessarily wet, but this is not a bad thing. Because "below the water table" also means "saturated" and hence no oxygen: the environment is chemically reducing. This is a major contributor to stopping the migration of actinides and many other metal ions, which will not be soluble in a reducing water environment. The downside of the wet part is of course the slow corrosion of the stainless steel, and the solution of the glass matrix.
The only repository above the water table I know of is the Yucca Mountain, but it is not considered to be the best of repositories (although it might do its thing).
There is a totally different repository which has been studied, and that was: deep ocean sediments. A very complete study was performed outside of the coast of Hawaii. The idea was to have "penetrator" containers which sink to the bottom and penetrate a few tens of meters into the sediments (which are highly binding also for actinides). The soil there is geologically extremely stable, and the sediments will build up over the years, hence burying the waste deeper and deeper. An eventual leak in the far future would be diluted immediately in the ocean, and no ground water or any people would ever suffer from any increased exposure. Moreover, the technique is very cheap. All considerations of access to the waste for terrorist purposes or whatever are of course totally moot in this context.
However, the project was canceled for unclear political reasons.