Can thorium help save the planet?

Safer, cheaper nuclear power?

IN the latest of our Friday science features, Prof Bob Cywinski of the School of Applied Sciences, University of Huddersfield looks at a different way to produce nuclear power.

IT is impossible to open a newspaper without reading about climate change. What is worse is that we are told that it is our fault because it is the carbon produced by the fuels we burn for transport and for energy generation that is driving global warming.

If this is the case, then prospects are gloomy as the growth in global population stands at 165,000 per day.

Assuming each of these new arrivals uses no more energy on average than current inhabitants of the planet then, just to meet their needs, we will have to build the equivalent of a gigawatt power station somewhere in the world every single day.

All of these new power stations, if fuelled with conventional fuels such as oil, gas or coal, will pump an additional 1,300 million tons of carbon into the atmosphere in just one year!

Surprisingly, even if we resorted to “clean” wind power, the cost of building and servicing the windmills would be an extra 13 million tons of carbon annually, not to mention the additional 80 thousand square miles needed for wind farms each year . . . and we would have to pray that the wind kept blowing!

These are the reasons that the Government has suggested that we simply cannot afford to ignore nuclear power, an energy source with a carbon cost only half that of wind.

The problem is that, whether rationally or irrationally, public perception of nuclear power is coloured by issues of safety, the radiotoxicity of its waste, its links to nuclear weapon proliferation and concerns about its vulnerability to terrorism.

Clearly the nuclear option is very controversial.

But perhaps there is a more acceptable nuclear alternative.

Almost 20 years ago Nobel prize winner and director of CERN, Carlo Rubbia, promoted the energy amplifier concept.

To understand the energy amplifier, let’s start by taking a look at a conventional nuclear reactor. Here the uranium nuclei in the fuel undergo spontaneous fission. In other words, they split into two, releasing two or three fission neutrons and a tremendous amount of energy.

Some of the neutrons are lost, but as long as one fission neutron goes on to split another uranium nucleus, the reactor is said to be critical, there is a chain reaction and the process is self sustaining.

The number of available neutrons must therefore be carefully controlled — too many and the chain reaction is out of control, too few and the chain reaction dies away and the reactor, which is then said to be subcritical, simply stops.

The elegance of the energy amplifier is that it operates in precisely this safe subcritical mode.

The additional neutrons needed to drive the fission process and generate energy are produced by bombarding a metal target within the reactor with high energy particles from a particle accelerator.

Some of the electrical energy produced by the reactor (say 5 pr cent) is used to drive the accelerator. If the accelerator is switched off, like a light bulb, no further neutrons are produced and the reactor also switches off.

The energy amplifier becomes even more attractive when it is considered that it can be fuelled by thorium rather than uranium.

Thorium is four times more plentiful than uranium and, more importantly, only 5,000 tons of thorium can produce all the energy needed by the planet for a whole year.

Although thorium itself doesn’t undergo fission, it can be converted into fissile fuel in an energy amplifier. As thorium is burned, unlike uranium, it produces no plutonium, the highly toxic and potent ingredient of nuclear weapons.

In fact, existing plutonium stocks and other nuclear waste can even be burned as fuel in an energy amplifier, rendering it safe for future generations.

Clearly, the energy amplifier has the potential to fill the gap of carbon-free nuclear power stations with a safer, cheaper and more sustainable form of nuclear power.

The University of Huddersfield, together with scientists from the Universities of Manchester and Cambridge, is currently developing a viable, cost-effective energy amplifier design in a research programme that has already received over £1 milliom in funding, and which is attracting the attention of both industry and government.

Even Carlo Rubbia himself visited the University of Huddersfield a few weeks ago to discuss developments and offer encouragement to research which might just save the planet.