1 December 2010

Thorium: The Future of Nuclear Power?

The race to produce a commercially viable thorium-based nuclear reactor is heating up with claims that a private company in China is planning to make a prototype capable of producing electricity for less than 10 US cents per kilowatt hour – making its technology cost competitive against conventional sources of power

It won’t be alone. At the same time, the Chinese National Academy of Sciences announced an initiative last year to develop thorium molten-salt reactor technology.The research will be led by Dr Jiang Mianheng, an electrical engineering graduate of Drexel University. One of the key purposes of that initiative, according to Wenhui News, is to secure the global intellectual property rights behind thorium reactor technology.

“The scientific goal is to develop a new generation of nuclear energy systems [and to achieve commercial] use in about 20 years. We intend to complete the technological research needed for this system and to assert intellectual property rights to this technology,” stated the Academy.

The advantage of using thorium over uranium-only-fuelled light water reactors (LWRs) is that the raw material is found in vast quantities around the world. The International Atomic Energy Agency (IAEA) suggests that it is between three and four times more abundant than uranium and also much more efficient in the fuel cycle, being potentially between 100 and 300 times more fuel efficient than a standard light-water reactor in terms of material usage. It also generates less waste as a result of this efficiency.

In addition, once started, the reactors work at low pressure, minimising the risk of catastrophic accidents, such as Windscale in 1957, Three Mile Island in 1979, Chernobyl in 1986, and Fukushima in 2011 – a key consideration in the wake of current anti-nuclear sentiment.

Most of the waste will have a much shorter half-life, requiring storage for just a couple of hundred years instead of the thousands of years that standard nuclear waste needs to be stored for. This fact alone could drastically slash the costs associated with nuclear power.

Finally, the main reason why thorium was rejected by the US and elsewhere in the 1970s has become one of its most attractive features: the claim that it cannot be used to generate weapons-grade material.

That claim is disputed by the US Institute for Energy and Environmental Research (IEER). It argues that thorium-232, the base material, converts into uranium-233 during the course of the thorium fuel cycle, which, it says, “is as effective as plutonium-239 for making nuclear bombs”.

Oak Ridge rejection

Thorium was investigated in the 1950s and 1960s, particularly by the US military. It also requires some fissile uranium to kick-start the process – typically either uranium-235 or plutonium-239. The centre of US research was the Oak Ridge National Laboratory where an experimental ‘molten salt reactor’ was built as part of a feasibility study.

Molten salt reactors use salts in liquid form at high temperatures into which thorium is dissolved along with a small amount of fissile material, to get the reaction started. The molten salt works as a coolant for the reaction, which maintains a low pressure even at high temperatures. The most promising form of molten salt reactor are liquid fluoride thorium reactors (LFTRs).

However, whilst operating an experimental reactor for four years without incident, the programme was nevertheless discontinued in 1976.

But, the technology never went away. In recent years, development efforts have mushroomed as governments around the world have sought stable sources of power insulated from the vagaries of fossil fuel prices.

For India and China especially, a lack of indigenous reserves of uranium combined with relatively abundant supplies of thorium make the material a logical choice. Indeed, China has a stockpile of thorium as a by-product of the extraction of rare earth elements, a global trade monopolised by Chinese miners.

And in the US, there is a groundswell of support in the scientific community behind renewed research into thorium. Scientific campaigners such as NASA’s James Hanson lobbied President Obama when he was elected calling for a big research campaign behind thorium. “LFTRs are 100-300 times more fuel efficient than light-water reactors. In addition to solving the nuclear waste problem, they can operate for several centuries using only uranium and thorium that has already been mined,” he wrote in an open letter to the incoming President.

Furthermore, the decades-worth of highly radioactive nuclear material accumulated by the US nuclear industry could be used as the fissile material in the thorium reactors, claims Hanson, helping to reduce the US stockpile of radioactive waste at the same time.

However, plans to destroy those stocks are nevertheless going ahead and US thorium research efforts remain modest compared to developments elsewhere in the world – especially China and India.

China’s developments are potentially the most exciting, given the resources that its government is devoting to throrium. For years, the ‘Holy Grail’ of thorium nuclear power research has been the molten-salt reactor, particularly LFTRs, and last year’s announcement indicated that China had joined the race to develop viable LFTR technology in earnest.

In truth, research into the technology has been burning away slowly in the background for decades. For example, China North Nuclear Fuel, a subsidiary of China National Nuclear Corporation (CNNC) was formed in 1998 to research the thorium fuel cycle. It runs a fuel fabrication plant at Baotou in Inner Mongolia.

China urgently needs power diversification. In a bid to keep up with booming demand for electricity as the country has grown so fast economically, provincial authorities have generally built fossil-fuel-fired power stations – especially coal. Now the country is paying the price in terms of heavy pollution, especially in its fast growing cities.

Although a nuclear power since the 1960s, the pace of nuclear development has been slow until recently. Today, China has 14 nuclear power reactors in operation, generating 10.2 GWe capacity, with more than 25 under construction or about to start construction, according to the World Nuclear Association, taking total output to around 40 GWe capacity. Another 40 are rumoured to start construction, which will provide a further 70 or 80 GWe in total by 2020. That may sound impressive, but in 2009 output of nuclear electricity accounted for just 1.9% of total generation in China.

India’s thorium plans

For 50 years, India was the world’s only source of serious major research into thorium – and for good reason. While it has no significant reserves of uranium and its nuclear programme was hampered for decades because the country remained outside the Nuclear Non-Proliferation Treaty (which made it difficult to acquire enough enriched uranium), it nevertheless has significant reserves of thorium – containing as much as one-quarter of the global total.

It also has an ambitious nuclear development programme as it bids to catch up economically. India’s government, for example, intends to have 20,000 megawatts electrical (MWe) nuclear capacity online by 2020, ramping up to 63,000 MWe by 2032, according to the World Nuclear Association. By 2050, nuclear will supply one-quarter of all its electricity needs.

That, at least, is the plan. At present, the total output of India’s nuclear power stations stands at about 4,385 MWe and if every nation on Earth were to attempt a similar growth in conventional nuclear, the world would run out of uranium-232 within 100 years. That is why India’s plan relies on the development of viable thorium-based reactors.

Whilst still a non-signatory to the Non-Proliferation Treaty, India’s nuclear ambitions were opened up following the Nuclear Suppliers’ Group agreement, signed in September 2008. Civil nuclear cooperation agreements have been signed with the US, Russia, France, UK, South Korea and Canada, as well as Argentina, Kazakhstan, Mongolia and Namibia – potential suppliers of uranium.

But, it is in thorium development that India excels. A 300 MW prototype thorium-based advanced heavy-water reactor (AHWR) – the Kalpakkam fast-breeder reactor near Tamil Nadu – is expected to be completed late this year and go operational in 2013, according to Indian press reports, with five more under construction. The new thorium reactor is a fast-breeder reactor and uses a plutonium core rather than an accelerator to produce neutrons.

According to the World Nuclear Association, it will be “fuelled with uranium-plutonium oxide (the reactor-grade plutonium being from its existing pressurised heavy water reactors (PHWRs)). It will have a blanket with thorium and uranium to breed fissile uranium-233 and plutonium respectively, taking the thorium programme to stage two… Six more such 500 MWe fast reactors have been announced for construction, four of them in parallel by 2017. Two will be at Kalpakkam, two at another site”.

The Kalpakkam reactor project will usher in the second stage of India’s three-part plan to achieve energy independence based on thorium by 2025, which was described by Ratan Kumar Sinha, Director of Bhabha Atomic Research Centre, when he spoke to IEEE Spectrum magazine two years ago: “In the first stage, pressurised heavy water reactors – similar to those used in advanced industrial countries – burn uranium.

In the second stage, fast-breeder reactors, which other countries have tried to commercialise without success, will burn plutonium derived from standard power reactors to stretch fuel efficiency. In the key third stage, on which India’s long-term nuclear energy supply depends, power reactors will run on thorium and uranium-233.”

France, Japan and Russia are the other major centres of thorium reactor research. The Laboratoire de Physique Subatomique et de Cosmologie in Genoble has already developed a fluid core thorium cycle reactor that could be commercialised, while researchers in the Czech Republic plan to construct a molten-salt reactor by 2013. In Japan, miniFuji is under development – although Dr Kazuo Furukawa needs to raise US$300 million to bring it to fruition. Meanwhile, Russia’s Kurchatov Institute in Moscow is working with US company Thorium Power on its otherwise conventional VVER-1000 reactor that has been modified to take mixed fuels using a combination of enriched uranium, plutonium and thorium.

Of course, while the hype around thorium has almost reached fever pitch, it will be at least a decade – probably two – before the technology is viable. Even the Chinese Academy of Sciences will be giving it two decades before a new generation of nuclear energy systems will be developed. Unless, that is, turmoil in the Middle East forces the pace of development of ‘alternative’ energy.

Copyright © 2010 Resources Magazine

Technology, Thought leadership