1. Fundamentally, it comes down to biological residence. Plutonium taken in through ingestion (i.e., through the alimentary canal) has a low biological half-time; the body does not readily absorb it. The major hazard from Plutonium is inhalation of Pu, which generally only occurs if it’s a dust (i.e., Pu metal shavings) – but then, the major hazard is lung cancer. (And you’re still far more likely get get a lungful of naturally occurring radon than you are plutonium, which has to be in a fine particle state to get anywhere.)
    Plutonium is not “highly toxic” if ingested, especially compared to other chemically hazardous substances.

    1. @Steve – you are generally correct, but it is worth it to page through the presentations to find out just how much lower the risk is compared to what might have been expected, even from rather substantial doses of inhaled dust. For example, one of the 2008 whole body donations into the autopsy program had this description:
      March: 95-y-old 239PuO2 acute inhalation (Rocky Flats

  2. Rod – first of all, thank you – no, make that THANK YOU!! – for your blog and your work with thorium. I’ve always been a nuclear enthusiast. As a boy here in Alberta, I built the Nautilus, Savannah and nuclear reactor Revell kits because they featured nuclear power. I’m delighted that you’ve been able to continue the blog. You’re giving me a lot of insight into the financial and political issues surrounding energy and nuclear energy.
    Speaking of chemically hazardous substances: through NNadir’s work at DailyKos I found Bernard L. Cohen’s online book, The Nuclear Energy Option. I haven’t finished reading it, but I think it’s great. It should be one of the textbooks for a compulsory course to be taken before running for office or joining in energy discussions. (David MacKay’s online book Sustainable Energy Without the Hot Air would be another text.)
    The chapters on risk in The Nuclear Energy Option really puts hazards in perspective, by including examples and comparisons that, as Cohen says, usually get left out of discussions. Here are the examples for 1990’s power generation and some toxic industrial chemical production (the assumption is that every lethal dose is actually lethally ingested):
    <blockquote>If nuclear power was used to the fullest practical extent in the United States, we would need about 300 power plants of the type now in use. The waste produced each year would then be enough to kill (300 x 50 million =) over 10 billion people. I have authored over 250 scientific papers over the past 35 years presenting tens of thousands of pieces of data, but that “over lO billion” number is the one most frequently quoted. Rarely quoted, however, are the other numbers given along with it11: we produce enough chlorine gas each year to kill 400 trillion people, enough phosgene to kill 20 trillion, enough ammonia and hydrogen cyanide to kill 6 trillion with each, enough barium to kill 100 billion, and enough arsenic trioxide to kill 10 billion. All of these numbers are calculated, as for the radioactive waste, on the assumption that all of it gets into people. I hope these comparisons dissolve the fear that, in generating nuclear electricity, we are producing unprecedented quantities of toxic materials.</blockquote>
    And these numbers don’t even include the caustic soda for making NNadir’s lutefisk! One of the exercises for this chapter (Chapter 11) would be to recalculate these numbers based on current production numbers, and for nuclear fuel cycles that completely burn uranium and thorium, rather than the once through solid fuel use of US reactors in 1990.
    I also have a question, completely off the topic of toxicity. You advocate molten salt breeder reactors (I absolutely agree; reading Cohen in the light of molten salt reactors is very revealing). You say they can be throttled well and provide good load following for grid transients and changes. I presume the reactor and generator designs are the major influences, but how fast could the reactors respond (what slew rate)? Over what dynamic range? What sort of physical limitations influence the engineering? I’d like to know more, especially since Cohen discusses the stresses that grid transients put on solid fuel reactors.

    1. @ Andrew,
      There is a fine blog on the engineering of Liquid Fluoride Thorium Reactors with historical documents and current discussions. My understanding – as a non-engineer- is that the response time is nearly immediate, i.e. seconds, enough time for the thermal difference to flow through the fluid so it becomes denser – increasing power, or less dense decreasing power.
      Kirk does a great job and Rod has had him on the pod casts several times.

  3. No discussion of plutonium toxicity would be complete withoud mentioning Bernard Cohen’s famous challange to Ralph Nader: Cohen offered to eat as much plutonium as Nader would consume in caffine.
    Nader failed to take up the challange.

  4. Looks like shale gas drilling results in uranium being released into the ground water (gasp!). I”’ have mixed feelings if shale drilling is finaly regulated due to some groups hyping the danger from uranium (that being the only thing that will get traction, of course). At least the researcher in the article below clarifies that the main risk is from its chemical toxicity.

  5. Rod,
    Great post. I have a book from Las Alamos that tracked the employees that had Pu uptakes. Many lived to ripe old age.

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