Quote:
Originally Posted by Steve Jordan
Isn't that because France is shipping all of its waste to the former Soviet Union?
(Oops... actually wasn't going to get into this discussion.)
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No, actually. They're reprocessing a bunch, and vitrifying the (very small amount) that's left over. For political reasons, they're doing small-billet vitrification and dry storage, which is much more expensive (and actually a bit less safe) than the method they originally intended -- large-billet vitrification.
Vitrification of nuclear waste basically involves carefully mixing the waste into molten leaded glass (it's basically lead-crystal like fancy wine glasses). Then you cast the glass into billets. The "small" billets the French are using are cylinders 1.5 meters long and .5 meters in diameter (roughly speaking, I'm working from memory here). They store these billets in a secure dry facility. As cast, they're minimally radioactive, and stable over quite long time-scales. The secure dry storage is overkill even for the small billets, but it makes the public feel safer, so that's what they do. Note that maintaining that dry storage, and providing security for it(!) is a major fraction of their reprocessing cost -- the original big-billet plan would be much cheaper.
The original plan was to take the small billets and cast them inside much larger billets of leaded glass. These larger billets would each be about the size of a large railroad box-car. The reasons for doing this are pretty straight-forward:
- The resulting billets are stable for 20,000+ years. (Really! The French nuclear agency did some super-careful research on ancient Egyptian glass that's over 5K years old in order to learn about the long-term stability of glass. From there, it's cube-square-law on the dimensions with leaching rates and such as measured. Very solid data!)
- Reduced security risk. These things are SO big and heavy that you need truly substantial heavy equipment to move them. And that's going to be noticed! It's not something that can be stolen in secret.
- Radioactivity reaching the outside of the billet is reduced to essentially zero.
- The physical size of the billets and their strength makes them extremely robust. There's not even any need for dry storage -- just bury them below the frost-line and you're fine.
- If you need the material back for some reason, you can get it (at some substantial cost and effort).
Long-term storage of high-level waste really doesn't need to be a problem at all (from an engineering standpoint). And, by volume, there really isn't that much high-level waste. Especially if you reprocess first. Low-level nuclear waste is even less of a problem -- the definition of low-level (in the US, at least) is less radioactive than the bricks in my house! As for the mid-level stuff... I guess I don't know anything about that. Maybe HarryT can jump in on that part.
Really, the whole nuclear waste thing needn't be an issue in terms of engineering and science. Politics, on the other hand, is a whole different story.
Xenophon