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Proliferation warnings on nuclear "wonder-fuel"

06 December 2012
​The element thorium, which many regard as a potential nuclear “wonder-fuel”, could be a greater nuclear weapons proliferation threat than previously thought, scientists have warned.

Writing in a Comment piece in the new issue of the journal, Nature, nuclear energy specialists from four British universities, including Colin Boxall, The Lloyd's Register Educational Trust Chair at Lancaster University, suggest that, although thorium has been promoted as a superior fuel for future nuclear energy generation, it should not be regarded as inherently proliferation resistant.

Professor Boxall said:

“Proponents of thorium advocate that it is a low proliferation risk alternative to uranium. This work demonstrates that this is not the case. However we are not suggesting that thorium is not explored as a potential nuclear fuel but it needs to be explored with the same vigilance towards proliferation risks as uranium based fuels.”

The piece highlights ways in which small quantities of uranium-233, a material usable in nuclear weapons, could be produced covertly from thorium, by chemically separating another isotope, protactinium-233, during its formation.

The chemical processes that are needed for protactinium separation could possibly be undertaken using standard lab equipment, potentially allowing it to happen in secret, and beyond the oversight of organisations such as the International Atomic Energy Agency (IAEA), the paper says.

The authors note that, from previous experiments to separate protactinium-233, it is feasible that just 1.6 tonnes of thorium metal would be enough to produce 8kg of uranium-233, which is the minimum amount required for a nuclear weapon. Using the process identified in their paper, they add that this could be done “in less than a year.”


Thorium is widely seen as an alternative nuclear fuel source to uranium. It is thought to be three to four times more naturally abundant, with substantial deposits spread around the world. Some countries, including the United States and the United Kingdom, are exploring its potential use as fuel in civil nuclear energy programmes.


The researchers are: Dr Stephen F. Ashley and Dr. Geoffrey T. Parks from the University of Cambridge; Professor William J. Nuttall from the Open University; Professor Colin Boxall from Lancaster University; Professor Robin W. Grimes from Imperial College London.

Professor Boxall is Director of Energy Lancaster which brings together Lancaster University’s world leading expertise in a wide range of energy related areas covering the demand and supply of energy. By combining cutting edge research in these areas with expertise across Lancaster and beyond, Energy Lancaster is working in partnership with global organisations in the development and management of secure and sustainable energy supplies in support of the world’s energy needs
Image An early, thorium-based molten salt reactor, pictured in the 1960s. Image credit: Oak Ridge National Laboratory.