There’s a saying amongst nuclear physicists – ‘it’ll be 50 years before we crack nuclear fusion; and we’ve been saying it for the past 50 years’. This sums up the progress that has been made over the past decades in the search for energy’s Holy Grail. But finally progress is being made. Could controlled nuclear fusion be achievable in our lifetime?
Nuclear fusion is the process which powers the sun. It involves squeezing two hydrogen isotope atoms (deuterium and tritium) together; the result is helium (a harmless gas) and vast amounts of energy. Deuterium and tritium are found in seawater and 2lbs of fusion fuel is capable of producing the same amount of energy as 10,000 tonnes of fossil fuel. There’s plenty of seawater around, so the fuel is essentially free.
But the barriers to nuclear fusion are huge. Huge amounts of energy are needed to squash the hydrogen atoms together and then hold them. In the sun, temperatures of 15 million deg Celsius and immense pressures achieve this, but these are difficult conditions to reproduce on Earth. The hydrogen isotopes must be heated to 100 million deg Celsius, and then confined for the nuclei to fuse. Then the fuel ignites and enough fusion reactions occur for the process to become self-sustaining.
Physicists are following two solutions to the problem of creating sustainable fusion reactions.
Magnetic confinement using strong magnetic fields to contain the hot plasma within a doughnut (toroid) shaped device. A device called a tokamak is where the majority of research and development is being made in this area.
The other solution uses inertial confinement, which compresses a small pellet of fusion fuel to extremely high densities using lasers beams. Under these extreme pressures the hydrogen fuel start a fusion chain reaction, and ignition occurs.
As yet, the plasma energy breakeven point hasn’t been reached. This is where plasmas release at least as much energy as is required to produce them. The Joint European Torus (JET) has managed 70% of input power, but that’s still some way off the mark. There are high hopes for the next generation of tokamak; the ITER (International Thermonuclear Experimental Reactor) is being built at Cadarache in France and scientists hope that it will produce 10 times as much energy as is put into it.
Nuclear fusion has also had its share of false starts. In 1989 there were claims of success with cold fusion experiments – literally fusion at room temperature in a test tube – but these proved to impossible to replicate. So for now the bulk of research is in magnetic confinement and inertial confinement.
Although fusion does produce radioactive waste products these are short-lived compared to those produced by nuclear fission. Fusion offers great potential for practically unlimited, cheap energy – electricity which is literally too cheap to meter – but let’s hope it doesn’t take another 50 years to develop. -MARK LEE