Posted by Laurence Watson

Negotiations about Iran's nuclear plans

By U.S. Department of State from United States [Public domain], via Wikimedia Commons

The recent agreement between six world powers and Iran has, according to President Obama; “cut off Iran’s most likely paths to a bomb”The agreement includes many commitments to cease enrichment of uranium above concentrations of 5%, dismantling or halting construction of additional centrifuges and a pledge to not construct a reprocessing facility. Iran will continue to enrich uranium to concentrations of 3.5% to keep its stocks at a constant level as it is consumed in the civilian nuclear power program.  

However, much of the discussion about the deal has missed one key question: the extent to which we are made prisoners by the proliferation risks of existing fuel cycles. Could a programme of nuclear R&D, aimed at developing proliferation-resistant nuclear energy, prevent future nuclear crises?

What if we said that no enrichment facilities would be necessary if Iran was planning on producing nuclear energy with a thorium fuel cycle?

Thorium sits two places down the periodic table from uranium, and while very little of naturally occurring uranium is the U235 necessary for use in a reactor, almost all of naturally occurring thorium is Th232, which is the isotope suitable for use as a nuclear fuel. . Because of this, there is no need for any enrichment of thorium fuel and no need for centrifuges of any kind. The lack of any need for these facilities would certainly change the game in terms of detecting rogue nuclear programmes.

However, there is a “but”: thorium fuels need a “fissile driver” to provide the initial neutrons to start the thorium chain reaction. This can be uranium-233, uranium-235 or plutonium, although for anti-proliferation purposes we should certainly discount the last two.

So that leaves us with U233. Handily, uranium-233 is produced by thorium fuels in a reactor (in a thorium fuel cycle, it is actually uranium-233 that fissions). The rub is that the world has very little U233 available and if we want to develop proliferation-resistant fuel cycles, we’ll need a lot more of it. Currently the only way to make it is to kickstart thorium fuel with…U-235 or plutonium, and then reprocess it (although Accelerator-Driven Systems could help).

Proliferation resistance

While U233 is recognised as a proliferation risk by the IAEA, it is far less suitable for making weapons than highly enriched U235 or Pu239. Indeed, only two nuclear tests have involved U233; the USA’s ‘Operation Teapot’and one 0.2kt experimental design in India’s Pokran-II tests. No nuclear weapons in existence are made with U233. Sadly uranium-235 and plutonium have a well-proven track record of making functioning bombs.

U232 is produced in smaller amounts alongside the U233, which is a hard gamma ray emitter. This gives the material a strong and easily detectable radiation signature. The material has to be handled very carefully, and fuel fabrication for example has to be done remotely with sophisticated equipment. These increased difficulties have long been cited as  properties that would hinder weapons proliferation.

Hans Blix, the former head of the International Atomic Energy Agency has recently called for the development of nuclear energy from thorium, citing a lower risk of weapons proliferation from reactors as well as benefits including reduced waste. He wrote in the Guardian newspaper that the commitments were “constitute substantial bars to any bombmaking” without curtailing the civilian power program. I’m sure he would agree that if Iran was pursuing thorium-fuelled reactors, the barriers to a weapons program would be even higher.

Of course, how any future international thorium fuel programme would obtain and distribute the “fissile drivers” would be very sensitive, needing just the kind of increased transparency and oversight that has just been agreed. What is certain is that proven thorium fuels, started with U233, would give the international community new diplomatic options in future nuclear disputes.

The nuclear club is expanding

Thirty-one of the world’s countries currently use nuclear power to generate over 11% of global electricity. Over forty-five countries are considering embarking down the nuclear route, with the front-runners after Iran and UAE including Lithuania, Turkey and Belarus. It is important to stress that thorium is not a magic bullet to weapons proliferation– but it can be a part of the solution to future international proliferation disputes, alongside appropriate regulatory regimes and oversight mechanisms. Given the pressing need for low-carbon energy it seems only prudent to support a more proliferation-resistant route for nuclear energy.

The MegaTons to MegaWatts program which saw almost 20,000 Russian warheads dismantled and used as fuel in American nuclear power plants has recently come to an end, providing almost 10% of US electricity for 15 years. A similar amount of warheads remain in existence. In 1953, Eisenhower’s ‘Atoms for Peace’ speech carefully tried to open the eyes of the world to the positive benefits of nuclear energy, after the horrors of the nuclear bomb had become clear. He urged that “the miraculous inventiveness of man shall not be dedicated to his death, but consecrated to his life”. Perhaps it is time for that speech to be revisited, starting with a massive push to develop proliferation-resistant nuclear energy.


  1. G.R.L. Cowan says:

    Separation of uranium isotopes and reprocessing of neutron-irradiated uranium are the only known ways to the Bomb. CANDU reactors require neither, and — like all varieties of power reactor — have never been implicated in any known instance of nuclear weapon proliferation.

    An industrial infrastructure that can make piston-in-cylinder car engines can inevitably make bullet-in-barrel guns. There is no way to break the thermodynamic link between the two. And yet the chance that car proliferation will cause gun proliferation seems to be zero, and this is accurately analogous to the chance that nuclear power proliferation will cause nuclear weapon proliferation.

    Those who promote nuclear power variants that don’t yet exist on the grounds that they are proliferation-resistant must not fail to acknowledge that existing variants have been perfectly so.

  2. Barrie Lee says:

    But North Korea did go down that route and Iran is suspected of wanting to do so, hiding behind nuclear technology for energy production.

    Two methods were published last year of producing bombs from thorium reactors. I’m a scientist but nuclear is not my field. What I would really like to know is how easy is it to produce bombs from thorium compared with from uranium?

    It seems that intelligence services can detect uranium bomb making equipment as it is so specialised. Is it just as easy to detect equipment for making bombs from thorium?

    Can the thorium fuels be adulterated, or can the reactors be designed for “export” to make them even more difficult to make bombs with? Is any research going into this last point?

    The reason I ask this is that every time I try to persuade someone in authority to back thorium they always quote this proliferation “problem” as an excuse to do nothing, and I see MSRs and thorium MSRs in particular as the best chance of avoiding the utter catastrophe of going through the climate change tipping point. But I’m fairly sure now that we have VERY little time left to avoid that tipping point.

    So we have to solve these problems quickly – or (more politically sensitive) only allow thorium reactors in those (many) countries that can be trusted or that already have the bomb. These would of course include most of the major carbon and methane emitters such as America and China, amongst others.

  3. Robert Steinhaus says:

    I hold the view that if you widely publish to the world the “fact” that Thorium reactors present a reduced proliferation risk on the grounds that U-233 is unsuitable for weapons you should at some point verify that belief by checking with actual weapons designers. Arguments based on technical suppositions, worries, and personal non-weapons industrial experience does not have the same weight.

    I would invite you to consider the following recently declassified document that discloses the opinion of Senior LLNL weapons designers regarding their opinion on the suitability of U-233 for weapons:

    W.K. Woods “LLNL interest in U-233” – DUN-677

    From DUN-677 (Extended quote from Senior LLNL weapons designers in context without omissions)

    “U-233 has been shown to be highly satisfactory as a weapons material; however, it has substantial technical advantage over plutonium only in certain environments, and the probability of such environments being encountered is quite low. LRL is quick to point out that conditions are subject to change and reappraisal, but as of today, they have no plans for developing weapons systems using U-233.

    The statement was made that if today’s weapons were based upon U-233, LRL would have no interest in switching to plutonium.”

    I would only ask that you give some consideration to the opinions of Senior weapons designers recorded in DUN-677. I would hope that in the end those that have a keen interest in better Thorium nuclear try to release to the public the best and most accurate information that we possess.

  4. Boris says:

    Charles, I’m not seeing the video, just a blank space below your post’s text where antoher paragraph, or a youtube vid might go. Is there any way to remedy this situation?

  5. Robin Gould says:

    In my humble opinion and as a 4-year long newbie advocate of Thorium fuelled MSR technology, the general public is very unaware that any sensible solution to the climate change problem even exists.

    Scientists, academics and money controllers would do well to come out of the ‘long grass’ and actually participate for the common good. Far more Facebook, Twitter and other media-centric publicity is essential, to produce a groundswell that national governmebnts will listen too and act upon.

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