Credit: Justin Randall

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What if we could build a nuclear reactor that offered no possibility of a meltdown, generated its power inexpensively, created no weapons-grade by-products, and burnt up existing high-level waste as well as old nuclear weapon stockpiles? And what if the waste produced by such a reactor was radioactive for a mere few hundred years rather than tens of thousands? It may sound too good to be true, but such a reactor is indeed possible, and a number of teams around the world are now working to make it a reality. What makes this incredible reactor so different is its fuel source: thorium.

Named after Thor, the warlike Norse god of thunder, thorium could ironically prove a potent instrument of peace as well as a tool to soothe the world's changing climate. With the demand for energy on the increase around the world, and the implications of climate change beginning to strike home, governments are increasingly considering nuclear power as a possible alternative to burning fossil fuels.

But nuclear power comes with its own challenges. Public concerns over the risk of meltdown, disposal of long-lived and highly toxic radioactive waste, the generation of weapons grade by-products, and their corresponding proliferation risks, all can make nuclear power a big vote-loser.

A thorium reactor is different. And, on paper at least, this radical new technology could be the key to unlocking a new generation of clean and safe nuclear power. It could prove the circuit-breaker to the two most intractable problems of the 21st century: our insatiable thirst for energy, and the warming of the world's climate.

BY THE END OF this century, the average surface temperature across the globe will have risen by at least 1.4˚C, and perhaps as much as 5.8˚C, according to the United Nations Intergovernmental Panel on Climate Change.

That may not sound like much, but small changes in the global average can mask more dramatic localised disruptions in climate.

Some changes will be global: we can expect sea levels to rise by as much as 0.9 metres, effectively rendering a huge proportion of what is now fertile coastal land uninhabitable, flooding low-lying cities and wiping out a swathe of shallow islands worldwide.

The principal culprit is carbon dioxide, a gas that even in quite small quantities can have a dramatic impact on climate, and has historically been present in the Earth's atmosphere at relatively low concentrations.

That was until human activity, including burning fossil fuels, began raising background levels substantially.

Yet while we're bracing ourselves to deal with climate change, we also face soaring demand for more energy - which means burning more fossil fuels and generating more greenhouse gases.

That demand is forecast to boom this century. Energy consumption worldwide is rising fast, partly because we're using much more of it - for air conditioning and computers, for example. In Australia alone, energy consumption jumped by 46 per cent between the mid-1970s and the mid- 1990s where our population grew by just 30 per cent. And energy use is expected to increase another 14 per cent by the end of this decade, according to the Australian Bureau of Statistics. Then there's China, which, along with other fast-growing nations, is developing a rapacious appetite for power to feed its booming economy.

And fossil fuels won't last forever. Current predictions are that we may reach the point of peak production for oil and natural gas within the next decade - after which production levels will continually decline worldwide.

That's if we haven't hit the 'peak oil' mark already. That means prices will rise, as they have already started to do: cheap oil has become as much a part of history as bell-bottomed trousers and the Concorde.

Even coal, currently the world's favourite source of electricity generation, is in limited supply. The U.S. Department of Energy suggests that at current levels of consumption, the world's coal reserves could last around 285 years. That sounds like breathing room: but it doesn't take into account increased usage resulting from the lack of other fossil fuels, or from an increase in population and energy consumption worldwide.

According to the U.S. Energy Information Administration, as of 2003, coal provided about 40 per cent of the world's electricity - compared to about 20 per cent for natural gas, nuclear power and renewable sources respectively. In Australia, coal contributes even more: around 83 per cent of electricity.

This is because coal is abundant and cheap, especially in Australia. And although a coal-fired power plant can cost as much as A$1 billion (US$744 million) to build, coal has a long history of use in Australia. Coal is also readily portable, much more so than natural gas, for example - which makes it an excellent export product for countries rich in coal, and an economical import for coal-barren lands.

But the official figures on the cost of coal don't tell the whole story. Coal is a killer: a more profligate one than you would expect.

And it maintains a lethal efficacy across its entire lifecycle.

One of the main objections held against nuclear power is its potential to take lives in the event of a reactor meltdown, such as occurred at Chernobyl in 1986. While such threats are real for conventional reactors, the fact remains that nuclear power - over the 55 years since it first generated electricity in 1951 - has caused only a fraction of the deaths coal causes every week.

Take coal mining, which kills more than 10,000 people a year. Admittedly, a startling proportion of these deaths occur in mines in China and the developing world, where safety conditions are reminiscent of the preunionised days of the early 20th century in the United States. But it still kills in wealthy countries; witness the death of 18 miners in West Virginia, USA, earlier this year.

But coal deaths don't just come from mining; they come from burning it. The Earth Policy Institute in Washington DC - a nonprofit research group founded by influential environmental analyst Lester R. Brown - estimates that air pollution from coal-fired power plants causes 23,600 U.S. deaths per year. It's also responsible for 554,000 asthma attacks, 16,200 cases of chronic bronchitis, and 38,200 non-fatal heart attacks annually.

The U.S. health bill from coal use could be up to US$160 billion annually, says the institute.

Coal is also radioactive: most coal is laced with traces of a wide range of other elements, including radioactive isotopes such as uranium and thorium, and their decay products, radium and radon. Some of the lighter radioactive particles, such as radon gas, are shed into the atmosphere during combustion, but the majority remain in the waste product - coal ash.

People can be exposed to its radiation when coal ash is stored or transported from the power plant or used in manufacture of concrete. And there are far less precautions taken to prevent radiation escaping from coal ash than from even low-level nuclear waste. In fact, the Oak Ridge National Laboratory in the U.S. estimates the amount of exposure to radiation from living near a coal-fired power plant could be several times higher than living a comparable distance from a nuclear reactor.

Then there are the deaths that are likely to occur from falling crop yields, more intense flooding and the displacement of coastal communities which are all predicted to ensue from global warming and rising oceans.

There's so much heat already trapped in the atmosphere from a century of greenhouse gases that some of these effects are likely to occur even if all coal-fired power plants were closed tomorrow. Whichever way you look at it, coal is not the smartest form of energy.