Saturday, May 22, 2010

Mr. President, Close the Cycle

In response to the vapid republican presidential orders I've been hearing: "Mr. President, Do your Job", "Mr. President, Finish the Dang Fence", I've been thinking: Why aren't the republicans telling him to do something, oh, I dunno, useful?

For example, we have a political monster that rears its ugly head from time to time: storage of nuclear waste.  It's an artificial problem, really; Part of Carter's various obsessions as President was the prevention of nuclear weapons proliferation.  In his zeal in this regard, he made probably the most disastrous move for the United States' energy economy that any president has, ever.

On April 7, 1977, President Jimmy Carter banned the reprocessing of commercial reactor spent nuclear fuel.

Reprocessing is a neat trick. When you burn low-enriched uranium (95% 238-U, 5% 235-U) in a light water reactor, two major things happen:

  1. About half of the 235-U fissions, producing a melange of mid-periodic isotopes called "fission products"

    1. 90% of fission products decay to background radiation within a year
    2. 97% decay to background in 10 years
    3. 100% decays to background in 300 years.

  2. 238-U breeds to 239-Pu

    1. 239-Pu is an excellent reactor fuel
    2. 239-Pu is no more weaponizable than the 235-U that is normally present in nuclear fuel
    3. 239-Pu burned in a light water reactor is more valuable as energy than as weapons.
The fission products end up causing problems: they absorb neutrons that could be put towards fission, fouling up your reactivity controls, and eventually turning off your reactor.  As a result, you can only fission about 1% of your input mass - the rest becomes spent fuel.

Reprocessing is the act of removing the fission products from your fuel pellets, and recasting them into new fuel elements.  There's no need to remove the 239-Pu - in fact, you wouldn't want to.  239-Pu is an excellent fuel for light water reactors.

If we permit reprocessing, three things happen:
  1. The cost of running a nuclear plant goes marginally down; you can re-fission the same fuel over a hundred times.  
  2. The sustainability of nuclear power goes up - from 6 years at full burn to over 600
  3. Long-term storage of nuclear waste ceases to be an issue, as all of your input fuel eventually becomes fission products - most of which can be sold as industrial materials after just 1 year.
So, when I say, "Mr. President, close the Cycle", I mean permit reprocessing.  Close the loop; help get us off of foreign energy.

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