The Science Show | 15 April 2006
Robyn Williams: As concern about global warming grows, the race is on to find reliable alternative sources of power to replace greenhouse gas emitting fossil fuels. Nuclear power generation is clean but is thought by many not to be a safe option. Would public perception change if a system was available that would never have a meltdown, and which burnt old radioactive waste as part of the power generation process?
Wilson da Silva: When it comes to discussing energy, the word “nuclear” is about as popular as the word “paedophilia”: not something you bring up in polite conversation. And certainly not something you advocate as a solution to our growing energy demand.
And yet, if it wasn’t for nuclear processes, we wouldn’t even be here: all of the elements of the Periodic Table were created inside the nuclear furnace of a star. Everything from carbon and oxygen, to iron and calcium – essential ingredients for life – were made in the heart of a star.
Even solar power – the pin-up child of alternative energy – is really just nuclear power from a great distance. All life on Earth depends on the nuclear energy generated inside the Sun’s core, where about 5 million tonnes of matter is converted into energy every second.
We know climate change is happening, and we know that human activity is greatly contributing to a warming planet. Just this month, the United Nations said that the 6th mass extinction event in the Earth’s history had already begun, this time thanks to global warming. And just this week, a study in the journal Conservation Biology stated that global warming will become a leading cause of extinction from the tropical Andes to South Africa, with thousands of species of plants and animals likely to be wiped out in a matter of decades.
This comes at a time when the world’s demand for more energy is ravenous, a time our civilisation uses more energy now than at any time in human history. Energy demand in advanced economies has risen 10% since 1990, and a whopping 59% since 1967. And yet, many of the most populous nations on Earth have yet to reach the peak consumption levels we have in the industrialised world. When they do, they will have similar energy requirements.
Where is all this energy going to come from? Coal is by far the cheapest and most abundant energy source, but also one of the biggest contributors to greenhouse gases, particularly carbon dioxide. And carbon dioxide stays a long time in the atmosphere: it’s estimated that 56 per cent of all of the CO2 ever generated by our burning of fossil fuels is still in the atmosphere. It’s estimated that this is responsible, directly or indirectly, for 80 per cent of all global warming. Surely, we cannot afford to build another 544 coal-fired power stations, as China alone is planning to do over the next two decades.
Which is why, in the face a mass extinction event boosted – if not largely created – by human activity, it’s perhaps time to consider any form of power generation that does not make global warming worse. In an ideal world, we would all rely on solar or wind energy – but these are unreliable for baseload power: the backbone of any electricity network. When we get up in the morning and turn on the lights, we expect the power to be there: if it isn’t, we don’t shrug and say, ‘Oh well, no wind today.’ Without dependable on-call energy, our factories and offices would grind to halt, our economies suffer, and our cities become dysfunctional.
The cleanest form of baseload energy is hydroelectric power – but most of the world’s easy-to-dam rivers are already tapped. Besides, flooding valleys to create dams has a negative impact on biodiversity, and would require the movement or destruction of existing human, animal and plant communities in the path of any new development.
Which leaves nuclear power. Nuclear reactors have generated billions of gigawatts of baseload power whilst emitting no greenhouse gases. Despite the public concern over safety and radioactive waste, nuclear energy has an exemplary safety record: in the 55-year history of nuclear power generation, fewer people have died from its use than are killed every week by coal. Mining coal kills more than 10,000 people a year.
But burning it is the worst: The Earth Policy Institute in Washington DC estimates that air pollution from coal-fired power plants accounts for 23,600 U.S. deaths annually. As well an estimated 554,000 asthma attacks, 16,200 cases of chronic bronchitis, and 38,200 non-fatal heart attacks each year. We worry a lot about nuclear waste buried deep underground, but not about the coal waste we breathe in the air, or the radioactivity of coal ash that’s left over from burning this very nasty fossil fuel.
So even conventional nuclear power looks good in comparison with coal. But what if we could generate nuclear power with a reactor that would never suffer a meltdown, produced no weapons-grade by-products, and even burnt up old radioactive waste as part of the process? Such thorium-fuelled reactors are theoretically possible, with the most attractive candidates being Accelerator-Driven Systems.
Conventional reactors have uranium or plutonium in the core, and are effectively an atom bomb trying to blow up: the extraordinary heat created is used to drive a turbine and generate power. But an Accelerator-Driven thorium System is different: no matter how much thorium you put in the core, it can never blow up. They make lousy atom bombs. But attach an accelerator to the core, cook it up to criticality, and you have a nuclear power source.
This completely changes the physics of nuclear reactions. It means that a fraction of the waste is generated, and all of it is radioactive for only 500 years (a lot better than the 10,000 years of conventional reactors). More importantly, it burns old nuclear waste in the process. Imagine destroying old nuclear weapons stockpiles, as well as other intractable radioactive waste, while generating power. And, more importantly, not spewing out tonnes of greenhouse gases, as other forms of baseload energy generation do.
Accelerator-Driven thorium systems look very attractive to a world desperate for more energy, but needing to dramatically reduce its greenhouse emissions. A lot of the basic science of these reactors has already been done in Russia, India and Germany, and while there’s no full-scale prototype in operation, they look safer as an alternative to today’s conventional reactors.
Despite the promise of thorium – and the fact that Australia has the world’s largest reserves of thorium – there is only one scientist in the whole country involved in researching the technology: and he is funded by the Germans!
Whatever energy choices we make, it’s clear we have the scientific know-how to quench our thirst for more energy without making the planet an unpleasant place to live, or bringing on a mass extinction event. We can generate most of our electricity from sources other than fossil fuels. But we need to turn to science for the answer: so many decisions about energy are made not based on the best scientific advice, but on whether an option is the least expensive, the most convenient, or the least politically offensive.
These days, the world is too complex, the decisions too important and the implications too far-reaching for us not to listen to the best scientific advice available. And there are a range of technologies out there – like Accelerator-Driven thorium systems – that look really promising, and should be investigated. While we still have time.