Physical Insights

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Rethinking nuclear power.

with 8 comments

ABC Unleashed has recently featured an article by environmentalist Geoffrey Russell; Rethinking Nuclear Power.

It’s worth reading.

I like the idea of closing down uranium mines, and using existing stocks of mined uranium efficiently.

Uranium mining is far less environmentally intensive than mining coal, of course, but it’s basically inevitable that all mining is fairly environmentally intensive, and it’s always an appealing prospect if we can mine less material (whilst still maintaining our energy supplies and our standards of living, of course.)

I have to admit, when I first saw Geoff’s claim that we could completely eliminate uranium mining, I was skeptical. So I took a more detailed look.

A nuclear reactor which is efficiently consuming uranium-238 and driving a relatively high efficiency engine (typically, a Brayton-cycle gas turbine) will require approximately one tonne of uranium input for one gigawatt-year of energy output. This high efficiency use of U-238 could be best realized something like an IFR or a liquid-chloride-salt reactor (the latter is essentially the fast-neutron uranium fueled variant of a LFTR). This figure of one tonne of input fertile fuel per gigawatt-year is also comparable for the efficient use of thorium in a LFTR.

There are about one million tonnes of already mined, refined uranium in the world, just sitting around waiting to be put to use, which is termed so-called “depleted uranium”.

According to one source, the exact worldwide inventory of depleted uranium is 1,188,273 tonnes [1].
The total electricity production across the world today is about 19.02 trillion kWh [2].

Therefore, total worldwide stocks of depleted uranium, used efficiently in fast reactors, could provide every bit of worldwide electricity production for about 550 years.

That’s not forever, but it’s a surprisingly long time. And that’s just “depleted uranium” stocks; not including the stocks of HEU and plutonium from the arsenals of the Cold War, and not including the large stockpile of uranium and plutonium that exists in the form of “used” LWR fuel.

I know some thorium proponents aren’t going to like this; but there’s a strong case to be made here that uranium-238 based nuclear energy has a clear advantage over thorium, simply became of these huge stockpiles of already-mined uranium, for which there exists no comparable thorium resource already mined. The 3,200 tonnes of thorium nitrate at NTS is tiny compared to the uranium “waste” stockpile, but they’re both really useful energy resources which can replace the need for more mining.

Any type of breeder or burner reactor utilising 238U, or 232Th, as fuel requires an initial charge of fissile material to “kindle” it; however this requirement for fissile material is quite small; and personally, I think the inventories of HEU and weapons-grade plutonium recovered from the gradual dismantlement of the arsenals of the Cold War are perfectly suited to this purpose – destroying those weapons materials, whilst putting them to a valuable use.

Then again, with the means to completely replace the use of coal and fossil fuels in a way that requires very little or no uranium mining, I really hope the rest of the world keeps buying that iron and copper and bauxite. Alternatively, we’re going to have to start developing a more technologically based economy in this country to make up the reduction in exports of these commodities – perhaps developing and selling reactor technology?

Developing uranium enrichment technology, such as SILEX, is of limited usefulness because the relatively inefficient thermal-neutron fission of 235U, and hence the need for enrichment, will not supply any large portion of world energy demand in a sustainable fashion over the long term. The small amount of 235U in nature is of limited significance, over the long term.

Alternatively, perhaps a shake up of agriculture, using extensive desalination to supply fresh water requirements, might be used to replace Australia’s income from coal and uranium. I’m not sure.

Tip ‘o the hat to Barry at Brave New Climate for pointing out this article.

[1]: http://www.wise-uranium.org/eddat.html
[2]: From the World Factbook, 2008 ed. (jokes about the integrity of CIA’s intelligence aside…)

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8 Responses

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  1. Luke,

    Your article caught my eye because the title is like that of my Dartmouth ILEAD course, Energy Policy and Environmental Choices: Rethinking Nuclear Power. Your readers might enjoy paging through some of the hundreds of PowerPoint graphics and web references in the course, posted at http://rethinkingnuclearpower.googlepages.com.

    Also, I’m a proponent of the LFTR. I don’t think the “already mined” argument for using depleted uranium is strong since very little mining will be required for thorium, and it can even be extracted from existing mine tailings. The LFTR does have the advantage that there will be considerably less long-lived radioactive actinide waste in the LFTR waste stream than, say, the IFR, because six fewer neutron absorptions are required in using Th-232. I think the LFTR thermal neutron flux provides better control ability than in fast neutron reactors. There is an illustrative presentation of the LFTR at http://rethinkingnuclearpower.googlepages.com/aimhigh and more technical details at http://energyfromthorium.com.

    Robert Hargraves

    May 3, 2009 at 6:39 pm

  2. There’s an alternate way to end terrestrial uranium mining and that is to utilize marine uranium.

    The world’s oceans contain more than 4 billion tonnes of uranium in seawater. That’s enough to power our entire planet (electricity, synfuels, and industrial chemicals) for more than 3600 years or over 5000 years if spent fuel is re-utilized. So terrestrial nuclear mining could also be ended by using marine uranium in current the current generation of nuclear power plants without any new breeding technologies.

    http://newpapyrusmagazine.blogspot.com/2008/10/fueling-our-nuclear-future.html

    Marcel F. Williams

    May 3, 2009 at 6:52 pm

  3. Luke, There would be very little difference between the cost of thorium and uranium. A lot of thorium exists in easily accessible forms, so the cost of thorium would competitive with uranium. The LFTR has a big cost advantage with its ability to process core fuel and blanket salts. Fuel has to be extracted from the IFR and processed in a separate production facility. This adds to cost. The LFTR is safer than the IFR. The LFTR would most likely be cheaper to build and set up. A Liquid Chloride Fast Reactor would take some time to develop, but would erase most of the LFTR advantages while operating on the Uranium Fuel cycle. The LCFR is less proliferation resistant than the LFTR, otherwise they are quite similar. The LCFR would have a higher breeding ratio. The LFTR would have a clear economic advantage over the IFR, The LCFR might have some economic advantage over the LFTR, but by the time LCFRs were built the LFTR might have a leg up because it had a large installed base.

    Charles Barton

    May 12, 2009 at 11:29 am

  4. Is the comment system broken?

    uvdiv

    July 26, 2009 at 10:21 am

  5. Yes it is: it discards my comment – gives me a page saying “discarded”. But I can post these comments. Which means something about my comment is making it unpublishable. :(

    uvdiv

    July 26, 2009 at 10:22 am

  6. Oh well. I’ve posted my comment as a blog post.

    http://uvdiv.blogspot.com/2009/07/ive-thought-about-this-and-it-isnt.html

    In short: you should consider the impact of the “starting material” requirements of fissile material.

    uvdiv

    July 26, 2009 at 10:25 am

  7. Given that the biggest uranium mine is actually a copper mine, Olympic Dam, it seems pointless to speculate about the need to close down urnaium mines when they are often getting the uranium almost as a by-product. Where uranium is mined in its own right, the footprint per unit energy is relatively low, and could be smaller yet.

    And the fact that the energy in uranium is nuclear, not chemical, means that in-situ extraction is feasible, with vastly less of the normal envirnomental disruption compared to mechanical ore extraction generally.

    SO I wouldn’t hasten to close uranium mines. None of which takes away from the potential energy you describe, that we have locked up in already-extracted uranium, and indeed already-extracted thorium.

    Note also that CANDU reactors run on unenriched uranium using heavy-water moderation.

    Joffan

    August 4, 2009 at 10:40 pm

  8. I apologise regarding comments not getting posted.

    Sometimes I get really busy and forget to check the software’s log of comments that it won’t post pending manual approval by the blog moderator.

    Luke Weston

    October 3, 2009 at 12:00 pm


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