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Nuclear Power – Cure For Global Warming?
Dr Duncan Copp
June 2005
Global warming has begun and we may now face one of the greatest dilemmas in human history. Our use of fossil fuels, notably gas and coal, is blamed for the rising levels of greenhouse gases (carbon dioxide and methane) in the atmosphere. These gases are considered responsible for the observed increase in global temperature over the last century. But this is just the beginning. Developing countries, like China, are on the brink of dramatically increasing their use of fossil fuels with the inevitable surge in their economic progress. Meanwhile, the developed world continues with its insatiable appetite for these fuels. Is it time to reconsider nuclear power?
Limited measures are in place to curb the production of greenhouses gases, and while the UK government considers itself on course to satisfy the international Kyoto Treaty (drawn up in 1997) on emissions, it's doubtful it will meet its own more stringent target.
'The threat of climate change may soon dwarf problems associated with nuclear power.'
In a society where most seem unwilling to compromise living standards in favour of a cleaner environment, nuclear power, which has been steadily declining for 30 years or so, may be set to make a return, welcome or not. Recently, the Prime Minister told reporters that nuclear power would be considered in the battle against global warming. 'There can't be debate on climate change without serious consideration of it,' he declared. If climate scientists are right, cabinet ministers have little time for procrastination: the threat of climate change may soon dwarf any problems associated with nuclear power.
So what is nuclear power? What are the pros and cons, and how does it measure up to other forms of fuel?
Nothing new under the Sun
Nuclear energy is nothing new – it's billions of years old; as old as the stars; the very reason the Sun shines. It's the one natural source of energy ubiquitous in the Universe. Nuclear energy comes from the natural fission (splitting) and fusion (joining) of nuclei. Both processes produce heat.
'Sustaining the fission of uranium is key to the process in producing power.'
Nuclear power is harnessed from the splitting of radioactive elements such as uranium and plutonium – a process known as nuclear fission. Uranium, the most widely used nuclear 'fuel' for this process, is a metal found naturally within Earth's crust as an ore, uranium oxide. Uranium is naturally radioactive. Periodically, uranium atoms will split apart, discarding subatomic particles (neutrons) from the nucleus, and creating new elements in the process. Nuclear power takes the natural process a step further. The idea is to make uranium atoms unstable by absorbing neutrons and thereby inducing fission.
'The heat energy released by uranium fission in turn heats gases that heat water which produces steam that drives turbines to produce electricity.'
Sustaining the fission of uranium is key to the process in producing power. Fortunately, when a uranium atom splits, it spits out more neutrons. If other uranium atoms absorb the ejected neutrons then they too will split, releasing more neutrons and so more heat energy. This is the famous chain reaction.
For a nuclear power station the trick is to keep the fission going, as left to its own devices the chain reaction fizzles out. So nuclear reactors use a 'moderator', which can be graphite or water, to promote the chain reaction. The heat energy released by uranium fission in turn heats gases that heat water which produces steam that drives turbines to produce electricity.
Reasons to be cheerful
What advantages does nuclear power have over fossil fuels? First, uranium oxide (U3O8) is about as abundant as tin in Earth's crust. Furthermore, a little uranium goes a long way. The amount of energy produced by the fission of a uranium atom may be very small, but there are billions of atoms to split in just one uranium fuel pellet less than a centimetre in size. In fact, one uranium pellet can produce as much energy as 800 kilogrammes of coal or 530 litres of oil. Current estimates suggest there is enough uranium contained within the world's oceans to provide an almost limitless supply of power (though technologies have to be developed to extract it first).
'Uranium oxide is about as abundant as tin in Earth's crust.'
Second, with regards to emissions, nuclear power is very clean compared to coal and gas. Nuclear fuel does come with its own waste problems, but emissions are practically zero. By comparison, a typical coal-fired power station emits some 11 million tonnes of carbon dioxide, one million tonnes of ash, 29,000 tonnes of nitrous oxide, 16,000 tonnes of sulphur dioxide, and produces 21,000 tonnes of sludge each year. And it's interesting to note that a coal-fired power station emits more radioactive material than a nuclear power station, as uranium is in coal and once burnt is released into the atmosphere via ash and dust.
'One uranium pellet can produce as much energy as 800 kilogrammes of coal or 530 litres of oil.'
While the initial outlay for a nuclear power plant is greater than that for a fossil fuel power station, its long-term costs are not dissimilar. And, the power plant lifetime and reliability of a nuclear station is greater. Also, it's calculated that nuclear power could sustain world demand for electricity. Currently, nuclear power supplies around 20% of the world's electricity.
Lesser of two evils
Of course, a major concern with nuclear power is its safety record. I distinctly remember 26 April 1986. In the midst of revising for my O-levels came news of Chernobyl. Reactor number four of the aging Ukrainian power station exploded during a routine shutdown, conducted in order to see how long the plant's turbines could run without power. Also disabled were the automatic shutdown mechanisms. After a series of human errors, the fuel elements in the reactor ruptured, emitting a vast surge of heat energy and producing enough steam to blow the top off the reactor, killing 31 people on the site. Soon after, a cloud of radioactive gas wafted over Europe. That week, my form room at school reverberated with conversations of how many hundreds of thousands would die, and the inevitable emergence of two-headed sheep in Wales. It was a disturbing time.
'Worldwide, the deaths associated with fossil fuel extraction run into thousands.'
But how does nuclear power measure up against fatalities associated with fossil fuels? While the number of post-disaster deaths expected from Chernobyl was in the tens of thousands, almost 20 year on, the actual figure has been put at 14. Furthermore, a United Nations report on the tragedy states that radiation from Chernobyl caused no measurable increase in birth defects and no increased incidence of leukaemia, contrary to concerns.
Chernobyl received a vast amount of press attention. Less well publicised is the fact that each year worldwide the deaths associated with fossil fuel extraction run into thousands. Is this a fair comparison? Many will argue the potential for nuclear power to harm is much greater than fossil fuels – but surely it depends how you look at it.
'The side effects of nuclear power are far more controllable and predictable than global warming.'
August 2003 was one of the hottest on record. In Europe that month the heat caused tens of thousands of premature deaths. In France alone, 14,800 people died from heat exhaustion; that's an average of one every three seconds and 19 times the death toll from the SARS pandemic.
The total cost of that European heat wave was estimated at £8 billion. If such temperatures are the result of global warming brought about by burning fossil fuels, then perhaps nuclear power is the lesser of two evils, especially as continuing developments in technology mean accidents are far less likely. And ultimately, the side effects of nuclear power are far more controllable and predictable than global warming.
Dirty work
Perhaps the biggest stumbling block for nuclear power is the unavoidable waste produced. The uranium pellets contained within the reactor are efficient for three years or so, after which they no longer have enough radioactive energy to produce heat.
'The issue then is what to do with the waste?'
The spent fuel pellets contain by-product elements, such as caesium and strontium, generated by the fission process. Both caesium and strontium are radioactive and emit atomic particles capable of effectively shredding the nuclei in cells of living things. This radioactive waste, though a small amount compared with waste generated by fossil fuels, is particularly nasty. Furthermore, the by-products are still very hot (1000°C plus) when they emerge from the reactor and consequently difficult to deal with.
As with all radioactive elements, the amount of radioactivity (the number of nuclear particles emitted) decays with time. For example, the radioactivity of strontium halves every 28.8 years – 28.8 years being called its 'half-life'. But the radioactivity of strontium is initially so high that it's typically hundreds of years before the waste decays enough to become harmless.
'Plutonium is much prized for far more destructive purposes – atomic weapons.'
The issue then is what to do with the waste? To date, the best solution has been to bury the waste in geologically sound storage sites and let it fester there until someone comes up with a better method over the next few hundred years.
There is however, a more sinister concern regarding nuclear waste, one which has perhaps loomed larger in recent years. It revolves around plutonium. Plutonium is formed as a by-product when a type of uranium (uranium238) absorbs a neutron but doesn't fission. Plutonium is radioactive and is often extracted from spent fuel, recycled, and used as nuclear fuel in the station's reactor. But plutonium is much prized for far more destructive purposes – atomic weapons. The notion that plutonium could be illegally bought and sold as a terror commodity is now a major issue in the case against nuclear power.
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