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).
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.