Recent events in Fukushima, Japan, have once more brought the safety of nuclear reactors under global scrutiny. The Fukushima plant is uranium based, which is the most common type of reactor worldwide.
There is, however, an alternative technology based on the element thorium. Thorium nuclear reactors have several critical advantages over other types, including: safety; reduced waste output; consumption of existing nuclear waste; energy efficiency; cost-effectiveness; plus, the relative abundance of the fuel source.
Examining the advantages in greater detail, safety is the most prominent issue. In an appropriately designed thorium reactor, there is no possibility of a meltdown. Without priming, thorium cannot sustain a nuclear chain reaction, so fission terminates by default. Consequently, there would be no threat of incidents such as those that occurred at Fukushima, Chernobyl, and Three Mile Island. All research to date indicate that the safety of thorium as a nuclear fuel is intrinsic and not in doubt.
Although thorium waste can produce a dangerous level of radioactivity for hundreds of years, this is a considerable reduction from uranium waste, for which it is in the tens of thousands of years. Thorium reactor waste is also virtually impossible to turn into plutonium, so there are no concerns that some nations might attempt to produce weapons-grade material from it. Furthermore, one of the overriding benefits of thorium reactors is that they can make efficient use of, and burn up, existing high-level radioactive waste, and decommissioned nuclear weapon stockpiles.
The energy potential of thorium is not merely significantly better than uranium, it is better by a vast degree. One tonne of thorium can produce as much energy as 200 tonnes of uranium. It has been calculated that the amount of energy used by the average American during their lifetime could be provided from just 8 tablespoons of thorium.
Thorium is at least 4-5 times more abundant in the Earth's crust than all isotopes of uranium combined. It also comes out of the ground as almost 100% pure, usable isotope (thorium-232), which does not require enrichment. Conversely, natural uranium contains only 0.7% fissionable uranium-235, and preparation requires isotopic separation.
Thorium is present on most continents, and due to the ease and cost-effectiveness of extraction in its required form, many countries already have large supplies. For example, there is enough in the United States alone to power the country at its current energy level for over 1,000 years. India is currently thought to have the largest easily accessible deposits and, globally, thorium is abundant enough to satisfy planetary demand well beyond the next millennium.
The direct monetary cost-effectiveness of thorium itself is predominantly based upon the abundance of the element, the natural state in which it is found, the energy potential it contains, and the potential consumption of other nuclear waste. There is a clear financial case for thorium being used to generate safe, clean, inexpensive power in the long term.
More significantly, the cost of constructing a 1-gigawatt thorium plant could be less than a quarter of the equivalent uranium plant, which would cost about $1.1 billion (US). The key reason it would be so much cheaper is that expensive safety features to prevent meltdown are not required, due to the lack of meltdown potential with thorium reactors. The implications in relation to the economics of nuclear power are, therefore, substantial.
Indirect cost advantages have also been put forward. In the US, for example, medical costs from breathing coal pollutants have been estimated at up to $160 billion annually.
So if thorium-based reactors are so much better from all of these perspectives, the intelligent question is: why aren’t they more widespread already?
Whether or not the advantages are considered compelling in themselves, there are disadvantages and arguments as to why the thorium energy route has not been exploited. Continuing with the cost issue, there is the current short-term problem of funding the building of thorium-based power plants at a time of global austerity. This does not preclude, however, a gradual shift towards replacing ageing uranium reactors with thorium reactors, particularly if new and more costly uranium plants would otherwise be constructed. Of course, the uranium fuel cycle technology is proven and well established, and, although thorium-based technology is advanced, there are still aspects that require further research.
Ultimately, the financial cost of nuclear energy is governed by the cost of building and decommissioning reactors, not the fuel used to power them. A ten-fold increase in the cost of the fuel itself, for example, would only translate to an increase in the cost of nuclear energy output of a small fraction of a penny per kWh.
A separate disadvantage for the UK specifically is that no significant thorium deposits have yet been identified, although the incentive to look for thorium has not been strong. This may explain why countries with abundant supplies of thorium have, or are planning to progress the technology, whereas the UK has not. Incentives to explore for natural deposits of thorium within the UK aside, issues relating to imports are comparable for both thorium and uranium.
It should also be noted that a thorium-based programme requires process instigation by a neutron source, such as waste from a uranium reactor. Although this might explain why a uranium energy initiative would have been required initially, this does not in itself justify a continued uranium programme. A second thorium reactor could activate a third thorium reactor, and so on.
Perhaps the key argument for why we have uranium rather than thorium plants centres on the development of nuclear weapons. It is much harder to retrieve weapons-grade material from thorium liquid-fuel cycle MSRs (Molten Salt Reactors) than it is from uranium (U-233) or plutonium (Pu-239) plants.
The weapons argument is double-edged. Historically, the race for nuclear supremacy among leading nations governed policy. The specific requirement for uranium plants within each major nation was justified from a defence perspective alone. Beyond that, there were subsequent political difficulties preventing other nations from developing their own programmes. The control of uranium shipment worldwide was regulated on a basis of ensuring other countries could use uranium for power needs, but not weapons development. The demand for thorium was potentially negated by the race for uranium and plutonium development.
This raises the question of whether the safety and wellbeing of members of the public has been jeopardised and overridden by leading governments for decades. The argument centres on whether the national defence and nuclear weapons deterrent was in the public interest to a greater degree than the threat of nuclear incidents from a technology with demonstrated relative safety issues. The argument becomes increasingly hard to justify as the disadvantages of using uranium or plutonium for nuclear energy are weighed against the advantages of thorium.
Perhaps conventional thinking up until now has been centred on the status quo. The effort required to switch to thorium has not seemed worth it while abundant uranium is available and uranium plants are widespread.
It’s not that thorium hasn’t already been examined. The US, for example, ran a Molten-Salt Reactor (MSR) programme between 1964 and 1969. Most of the initial test reactors were closed down due to a lack of funding, and the MSR program was discontinued in 1976. The following year, a Light-Water Reactor (LWR) at the Shippingport Atomic Power Station, Pennsylvania, was used to establish a thorium-based fuel cycle. Decommissioned five years later, the significant safety and efficiency advantages of MSRs have since been recognised.
Canada has over 50 years’ experience with thorium-based fuels. Designs of reactors in Canada allow thorium to be used as a fuel source.
But it is only in recent years that the race for thorium has begun. India leads the way with the first thorium-based Advanced Heavy Water Reactor (AHWR) at the Kakrapar plant in the west of the country. Motivated by a desire to become energy-independent, combined with restricted availability of uranium, the nation is exploiting large natural deposits of thorium within its borders.
Last month it was confirmed that China has initiated a project to develop MSR technology. Russia has plans to establish a programme, and Norway has considered thorium as a potential key source of energy.
The dash for thorium, however, should not be interpreted as a commodity investment opportunity. Because of its abundance, ease of extraction, and reserve levels, its price is unlikely to become volatile. Investment opportunities are more likely to come from the growth of private organisations specialising in particular areas of technological advancement related to thorium. In 2010, the founder of Microsoft, Bill Gates, announced that he would be investing in thorium-based technology as a ‘miracle’ that would help solve global energy problems relating to CO2 emissions and world poverty.
Renewable sources of energy, like wind, wave/tidal and solar power, may provide a long-term solution in the future, but the technology is not yet viable for the majority of energy production. The interim solution for the coming years and decades would appear to be best-served by a switch to thorium-based power production.
Bullet point box for thorium (Th):
Radioactive chemical element
Discovered in 1828
Named after Thor, the Norse god of thunder
Atomic number: 90
Out of the 90, four are valence electrons
Occurs naturally in the isotope Th-232
Half-life of approximately 14.05 billion years
Decays slowly by emitting an alpha particle
Professor Carlo Rubbia, from the European Organization for
Nuclear Research (Cern), is one of the leading global experts on
thorium. On Tuesday, he gave a short interview
to the BBC World Service's One Planet, which can be heard