Tuesday, March 18, 2008

David Fleming on Thorium

Introduction: David Fleming has a very different view of thorium that I have taken in Nuclear Green. Fleming poses as an expert on nuclear energy, but it is clear that he is nothing of the kind. Fleming is in fact a nuclear semi-illiterate. I say semi-illiterate because he describes certain nuclear processes, he has no comprehension of the technology by which these things are managed. This leads him into the conceptual in which he tells us that certain things are difficult to accomplish, but he does not give us a clue why this is the case. I will not review Fleming's entire booklett "The Lean Guide to Nuclear Energy." My primary intent is to focuse on his account of thorium.

From: The Lean Guide to Nuclear Energy
By David Fleming

Flemming introduces himself this way:
David Fleming has an MA (History) from Oxford, an MBA from Cranfield and an MSc and PhD (Economics) from Birkbeck College, University of London. He has worked in industry, the financial services and environmental consultancy, and is a former Chairman of the Soil Association. He designed the system of Tradable Energy Quotas (TEQs), (aka Domestic Tradable Quotas and Personal Carbon Allowances), in 1996, and his booklet about them, Energy and the Common Purpose, now in its third edition in this series, was first published 2005. His Lean Logic: The Book of Environmental Manners is forthcoming.

In case we have no doubt where Fleming is coming from he tells us:
"Thank you to Jan Willem Storm van Leeuwen for many months of comments and expert advice. References for his work, and the work he has published jointly with the late Dr Philip Smith, are given on pages 41-42. This booklet is substantially guided by their research, but it builds on it and takes the discussion of energy policy options further. The conclusions I draw, including the concept of “energy bankruptcy”, treatment of the backlog of waste, and the alternative vision of Lean Energy, are my own. All summaries sacrifice detail, some of which may be important. I make no claim that this booklet is beyond challenge in its representation of Storm van Leeuwen and Smith’s exhaustive and careful analysis: the responsibility for the entire contents of this booklet is my own."

Now this Is Fleming's account of thorium.

(b) Thorium
The other way of breeding fuel is to use thorium. Thorium is a metal found in most rocks and soils, and there are some rich ores bearing as much as 10 percent thorium oxide. The relevant isotope is the slightly radioactive thorium-232. It has a half-life three times that of the earth, so that makes it useless as a direct source of energy, but it can be used as the starting-point from which to breed an efficient nuclear fuel. Here’s how:


o Start by irradiating the thorium-232, using a start-up fuel – plutonium 239 will do it. Thorium-232 is slightly fertile, and absorbs a neutron to become thorium-233.
o The thorium-233, with a half-life of 22.2 minutes, decays to protactinium-233.
o The protactinium-233, with a half-life of 27 days, decays into uranium 233.
o The uranium-233 is highly fissile, and can be used not just as nuclear fuel, but as the start-up source of irradiation for a blanket of thorium 232, to keep the whole cycle going indefinitely.


This account is more than a little problematic. There is no mention here of the role that reactors play in the radiation of thorium, of what radioactive particle is involved. Fleming appears to know less than the famous radioactive boy scout. He fails to notice that less conventional neuutron radiation sources have been proposed for use in breeding thorium.

But, as is so often the case with nuclear power, it is not as good as it looks. The two-step sequence of plutonium-breeding is, as we have seen, hard enough. The four-step sequence of thorium-breeding is worse. The uranium-233 which you get at the end of the process is contaminated with uranium-232 and with highly-radioactive thorium-228, both of which are neutron-emitters, reducing its effectiveness as a fuel; it also has the disadvantage that it can be used in nuclear weapons. The comparatively long half-life of protactinium-233 (27 days) makes for problems in the reactor, since substantial quantities linger on for up to a year. Some reactors – including Kakrapar-1 and -2 in India – have both achieved full power using some thorium in their operation, and it may well be that, if there is to be a very long-term future for nuclear fission, it will be thorium that drives it along. And yet, the full thorium breeding cycle, working on a scale which is large-enough and reliable-enough to be commercial, is a long way away.

Fleming tells us that it is hard to breed thorium, but he really does not offer us a clue why a four step breeding processes should be so difficult. He appears to be clueless about how reactors work so he keeps telling us how hard this is and leaves it at that.

And even if that day does come, its contribution, for the foreseeable future, will be tiny, This is because it has to begin with some start up fuel, A source of neutrons to get the hole [sic] thing going. It could come from uranium-235, which is going to be scarce, but there could perhaps be a case for using some in a breeder, even if the process for the first generation of reactors used more energy than it generated. Or, it could come from plutonium, but (a) there isn’t very much of that around either; (b) what there is (especially if we are going to do what Lovelock urges) is going to be busy as the fuel for once- through reactors and/or fast-breeder reactors, as explained above; and (c) it is advisable, wherever there is an alternative, to keep plutonium-239 and uranium-233 – an unpredictable mixture – as separate as possible. The third, and ideal, option is uranium-233, the final fuel produced by the thorium cycle, but the problem here is that it doesn’t exist until the cycle is complete, so it can’t be used to start it.

Fleming does tell us elsewhere why he thinks U235 is going to be scarce. His argument is highly speculative, but I am not going to address that now. It is not clear why enough Pu239 would not be around. First there are two potential sources of Pu239. One is spent nuclear fuel which contains not only Pu239, but also Pu240, Pu241, and AM 242. These are nuclear waste products, which Fleming claims are going to take so much energy to clean up. What Fleming does not understand is that the energy to clean up nuclear waste could come from the very wasteprducts that need to be cleaned up, and that while burning the waste products in a reactor, you can also be generating the neutrons required to breed thorium. Clearly Fleming should have spent not quite as many months talking to Storm van Leeuwen, and spent some time consulting with a real nuclear scientist.

"But let’s suppose that enough uranium-235 or plutonium-239 were made available to provide a full load for one reactor and to keep it going for its lifetime. There is no good foundation for forecasting the rate of growth but, taking account of all the assumptions about technical solutions that are intrinsic to this subject, there is the possibility that by 2075 there could be two thorium-cycle breeder reactors delivering energy to the grid. have to buy-in much of the needed net energy from other sources, at which point, of course, the industry will change from being a net supplier of energy to being a net consumer. And yet, in an energy-strapped society, the non-nuclear energy needed to dispose of the nuclear industry’s legacy will be hard to find. The prospect is opening up of massive stocks of unstable wastes which – since the energy is lacking – are impossible to clear up."

This is the sort of thinking after hanging out of spending many month with Jan Willem Storm van Leeuwen and getting his comments and expert advice. We are going to suppose that (1) the only source of neutrons is going to be U235, or Pu239, (2) that so little Pu239, or U235 would be around that only one thorium breeding reactor could be built, and that (3) no one is going to be smart enough to think of using the U235 and reactor grade plutonium found in nuclear waste in order to breed thorium. Well if David Fleming and Jan Willem Storm van Leeuwen aren't smart enough to think of that, no one else is going to be. Of course Liquid Fluoride Thorium reactors can burn peoples reactor waste to a cinder, while breeding Th232 to produce U233. And the nice thing about the thorium cycles is that it produces very valuable minerals, rather than "reactor waste." This is another thing that Fleming and Storm van Leeuwen dids not understand.

In a post on the Oil Drum on January 4 of this year, Fleming have us his digested take on Thorium:

"And thorium? It is an inelegant technology, lumbering through a decay sequence from thorium 232 to thorium-233 to protactinium-233 – and eventually to uranium 233 – along with a swarm of contaminants including the neutron-emitters uranium-232 and thorium-228. Added complications include the long half-life of the protactinium-233 (27 days), so that it lingers around, causing problems in the reactor, and the awkward fact that uranium-233 can be used in nuclear weapons. Then there is the question of what start-up fuel to use: the best one would be uranium-233, but you only get a supply of that at the end of the first cycle. If plutonium-239 is available, it would seem to be more sensible to use it for the fast-breeder programme than to start the even more uncertain thorium cycle. And the problem of scale is even more decisive in the case of the thorium cycle than in the case of fast-breeders. On the best estimate available at present, and pretending for a moment that the technical difficulties are eventually solved, we could look forward in 2075 to a global fleet of perhaps two thorium-based reactors."

Such scientific language, "ineligent," "lumbering," "a swarm of contaminants." We are told quite inaccurately that U232 and Th228 are "neutron-emitters" and that U232 is a contaminant, actually its presence is viewed as desirable because it contributes to the thorium breeding cycle proliferation resistance. "[T]he best estimate available at present," oh please, whose estimate are we talking about here? Is that the best estimate of doctor objectivity himself? Is that the best estimate of Jan Willem Storm van Leeuwen?

4 comments:

Sovietologist said...

It's a wonder they didn't use U-232 and Th-228 as neutron sources in nuclear weapons, given that they're "neutron emitters."

... seriously, this man has no grounding in nuclear technology at all. But this is about what i'd expect from the Soil Association, which is a profoundly anti-rationalist organization. I'm gladdened that recent events in the UK suggest that the influence of people like Fleming is fading there, at least so far as nuclear power is concerned.

Also, it so happens that the Russians have 130+ metric tons of plutonium, most of which is weapons-grade stuff that the world could do without. About how many MSBRs could be started with that? I don't know, but I bet that it's a lost more that two.

Fifi said...

Charles,

Nice catch. A Helen Caldicott wannabe? Well, may be not Caldicott. He knows how to spell "protactinium" so he's clearly a notch above. But the twit clearly understands precious nothing to the subject but peppers his prose with a few technical terms here and there to spray a varnish of phony credibility with the ignoramuses.

I love the "decay sequence from thorium 232 to thorium-233". If anyone can show a (Z,N) to (Z,N+1) decay mechanism, not only the dude has the Nobel Prize all sewn up, but he's freaking rich. He just invented a mechanism for the spontaneous creation of matter... The "big-picture" minds will wave that off as mere vocabulary quibbling. But as Feynman used to say, nothing is mere, certainly not the difference between decay and neutron capture as it's the whole point of having a breeder.

I don't have anything against amateurs partaking in nuclear chitchat - I'm one - but striking authoritative stands is a bloody dangerous thing to do for amateurs.

Kirk Sorensen said...

Also, it so happens that the Russians have 130+ metric tons of plutonium, most of which is weapons-grade stuff that the world could do without. About how many MSBRs could be started with that? I don't know, but I bet that it's a lost more that two.

Guessing at about 1.3 tonnes/GWe of WgPu for LFTR startup, you could get 100 GWe of thorium-based energy started with that plutonium. If you destroyed it in a liquid-chloride reactor first and bred U233 in the blanket, you could probably get about 200 GWe of LFTRs started.

Sovietologist said...

Well, it sounds like global plutonium stockpiles alone are more than adequate to start 300+ GWe of LFTRs. That's a heck of a lot more than two.

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