The call for thorium power is not without precedent worldwide. India has pursued thorium technology for decades. And China is revisiting a molten salt reactor design mothballed by the USA in the 70’s. Recently, several companies have sought to commercialise thorium energy, including an Australian-Czech alliance.

One critical difference is that thorium, in its natural state, is resistant to fission. This is the process whereby the atomic nucleus splits apart, thus releasing energy that can then be harnessed to generate electricity.

Uranium can undergo fission relatively easily, but for thorium to undergo fission – and be useful in a nuclear power plant – it must first be converted into a usable form. This is done via a process known as “breeding”, where the thorium absorbs a neutron, thus transmuting into a heavier element that can later undergo fission.

Thorium was first studied as an energy source during the Manhattan project, but uranium proved much easier to work with. During the post-war commercialisation of nuclear energy this dominance was reinforced. Engineers identified myriad paths to design reactors based on uranium, while the added complexities of thorium meant that alternatives didn’t get much of a look in.

Today, advocates of thorium typically point to a variety of advantages over uranium. These include fail-safe reactor operation, because most thorium reactor designs are incapable of an explosion or meltdown, as was seen at Chernobyl or Fukushima. Another is resistance to weapons proliferation, because thorium reactors create byproducts that make the fuel unsuitable for use in nuclear weapons.

Other advantages include greater abundance of natural reserves of thorium, less radioactive waste and higher utilisation of fuel in thorium reactors. Thorium is often cast as “good nuclear”, while uranium gets to carry the can as “bad nuclear”.

Not so different

While compelling at first glance, the details reveal a somewhat more murky picture. The molten salt architecture which gives certain thorium reactors high intrinsic safety equally applies to proposed fourth-generation designs using uranium. It is also true that nuclear physics technicalities make thorium much less attractive for weapons production, but it is by no means impossible; the USA and USSR each tested a thorium-based atomic bomb in 1955.

Other perceived advantages similarly diminish under scrutiny. There is plenty of uranium ore in the world and hence the fourfold abundance advantage of thorium is a moot point. Producing less long-lived radioactive waste is certainly beneficial, but the vexed question remains of how to deal with it.

IF

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