“Graph” of the Week: What happens if nuclear waste repository leaks?

Lately, I’ve been spending some time reading through reports on nuclear waste management. What is striking is how conservative the calculations seem to be; for example, the report by Posiva (the Finnish company responsible for the world’s first civilian nuclear waste repository, Onkalo) goes to almost absurd lengths when calculating what might be a possible highest dose for the single worst-affected individual ten thousand years from now.

For example, the calculations assume that the person in effect spends all of his or her days – from birth to death – in the single worst contaminated one square meter plot around the repository; eats nothing but the most contaminated food available, with a diet that maximizes radionuclide intake; and drinks only the most contaminated water and nothing else. The figure – 0.00018 milli-sieverts per year – also assumes that the copper canisters where spent fuel pellets are housed begin to leak after mere 1000 years.

And still, the worst-case figures amount to a dose what one would get from eating about two bananas.

I’m fully prepared to accept that many surprising things could happen, and that we cannot be certain of what happens 10 000 years from now; but given the figures here, and the way they’re achieved, I have some confidence that the likelihood of people receiving doses that can actually pose some real danger, even in the long term (say, more than 10 mSv per year – which might just produce enough cancer cases to be visible in statistical sense) seems remote indeed.

You can read the Posiva Biosphere Assessment report (be warned, it’s 192 pages of rather technical text) in English here:

http://www.posiva.fi/files/1230/POSIVA_2010-03web.pdf

As always, corrections and comments are highly appreciated. You’re also free to distribute the image as you see fit – just provide a link to this page.

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About J. M. Korhonen

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13 Responses to “Graph” of the Week: What happens if nuclear waste repository leaks?

  1. Mika says:

    But if the canisters start leaking after a 1000 years, what about people of 3012AD?

    • This is the maximum dose rate anyone received in about 30 simulation scenarios that were summarized to the report above. For many cases (but not for this one, case PD-BC), graphs of dose over time were also included; most show that doses begin to grow from zero quite soon after the canisters are breached, then stabilize for very slow growth and eventual decay over thousands of years. So I’d guess the possible extra dose for the most affected person in about 3012 AD would be about zero, for the most affected person in about 3100 AD perhaps one and a half banana.

      The reason why there’s no such graphs for this one case is probably because it’s from older assessment and its results were included only as comparison. All the other cases result to lower doses, usually by a factor of 10-100. And using more realistic assumptions for e.g. food consumption, the doses would be far lower still.

      It’s worth noting that all the scenarios assume that one canister (at least) is faulty and has a hole in it that lets water in immediately after emplacement. (This is rather unlikely to actually happen, because the bentonite clay by itself should keep the water out pretty nicely.) In these calculations, the faulty canister is always considered to be the first canister, installed in 2020.

  2. jmdesp says:

    10 mSv per year has never been visible in the statistical sense, we have difficulties seeing something in the statistical sense even for the Chernobyl emergency workers, cf http://www.ncbi.nlm.nih.gov/pubmed/14762668 “Solid cancer incidence among the Chernobyl emergency workers residing in Russia: estimation of radiation risks”
    Their mean external radiation dose is estimated to be 0.13 Gy, but the results do not allow to exclude the null hypothesis.
    And also http://www.ncbi.nlm.nih.gov/pubmed/16628547 Estimates of the cancer burden in Europe from radioactive fallout from the Chernobyl accident
    “It is unlikely that the cancer burden from the largest radiological accident to date could be detected by monitoring national cancer statistics. Indeed, results of analyses of time trends in cancer incidence and mortality in Europe do not, at present, indicate any increase in cancer rates — other than of thyroid cancer in the most contaminated regions — that can be clearly attributed to radiation from the Chernobyl accident.”

    • That’s probably true (although I do recall hearing from some papers that claim evidence for very slightly elevated disease burden in around 10 mSv prolonged doses; can’t comment on their quality) but I wanted to be extra super duper conservative here.

      (EDIT: Certainly, 10 mSv per year would not be acceptable to regulators. The regulatory limit for the dose of the most exposed person is 0.1 mSv per year.)

  3. UPDATE: Recent Twitter exchange pointed out that Posiva’s reports have been criticized by, who would guess it, Greenpeace. This is true, and you can read the critique for yourself here:

    http://www.greenpeace.org/finland/Global/finland/Ydinvoima/Reports/Safety%20of%20spent%20nuclear%20disposal,%20no%20layot.pdf

    HOWEVER, I’ve still yet to see a single criticism detailing any significant flaws in the actual dose scenarios detailed above. For example, the above critique spends considerable verbiage in exposing what it considers flaws in Posiva’s assumptions and even in its assumed mentality. According to the critique, flaws in assumptions include the overlooking of potential corrosion of copper canisters – so that they do not last the entire 100 000 years – and a “piping erosion problem” where the bentonite clay is washed away faster than predicted.

    But, as can be seen from the case above, those assumptions are already factored in to the case. As noted above, it assumes that copper canisters spring a leak after mere 1000 years (design lifetime: 100 000 years), and that water is in free contact with the fuel (meaning no bentonite clay barrier) immediately after that.

    No matter: the maximum dose is still about two bananas.

    It is highly instructive to note how anti-nuclear activists seek to discredit the science here. They may well know that even using highly pessimistic assumptions about e.g. the copper canister and the bentonite clay, there is an overwhelming probability that any doses caused to the environment or to the public will be negligible. Perhaps for that reason, or perhaps simply because they themselves honestly believe that any leakage results to immediately horrendous effects, they completely ignore the crucial question: “so what?”

    What would happen if a waste repository springs a leak?

    What would be the effects of the leak to humans or to the environment?

    Even if you search through the voluminous material provided by the anti-nuclear brigade, you most likely will not find a single statement answering these questions. Cleverly, anti-nuclear activists simply state it’s possible that nuclear waste can leak – which is not in doubt, anything is possible – and rely on innuendo and human imagination (fertilized by perceptions of nuclear waste as something unthinkably horrible) to fill in the gaps in the narrative.

    Whether you go along with this manipulation is, of course, up to you.

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  6. Do you think people even 500 years from now are just going to leave the “waste” sitting there unless they’re all cavemen from an asteroid strike?

    • Probably not, but who knows. It’s only prudent to prepare in case plans for waste-burning reactors or other technological solutions do not materialize, and there is nevertheless a need for disposing some potentially dangerous waste even then. So it’s not like the effort is going to be wasted.

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  8. Ikemeister says:

    What seems so striking to me is this over-the-top safeguarding being demanded when chemical wastes that are many times more toxic and threatening to all manner of lifeforms are ignored, rather are served with yawns.

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