Hotline to fusion

Commercial fusion power, a source of abundant and relatively clean energy, could be a reality within the next 25 years, according to a team of UK and Japanese researchers.

Until now successful nuclear fusion, which replicates the atomic reaction in the sun, was not expected to be available on a large scale until 2050.

But following tests of a high-powered laser in Osaka, a prototype reactor could be built in eight years’ time for less than £1bn, said Dr Peter Norreys, UK team leader for the project, based at the Rutherford Appleton Laboratory.

‘Our test demonstrated a laser that could generate temperatures of eight million degreess C. We require 100 million degrees C to produce a fusion reaction that generates more energy than we put in. We simply need to have a longer laser pulse than our experiment to achieve this,’ he said.

The GEKKO XII system in the prototype reactor would be a petawatt laser. A petawatt is a million billion watts and the laser would be used to bombard fuel pellets to produce energy in a process known as inertial confinement fusion.

For a full-scale reactor a yet more powerful laser would be required. Norreys is confident this could be developed within 10-15 years, and a commercial reactor could be built another 10 years after that.

If successful, inertial confinement fusion offers an alternative to Tokamak fusion being developed by the Joint European Torus (JET) programme.

Tokamak suffers from being unable to sustain the fusion process. It uses a plasma that is controlled within a magnetic field and fed with deuterium tritium fuel. But as soon as the plasma contacts the reactor’s interior wall the process stops. A commercial- scale reactor of this type is not expected to be built until 2050.Instead inertial confinement fusion does not aim to sustain a plasma. It generates energy by firing 10 frozen pellets of deuterium tritium fuel every second into a vacuum chamber.

Each pellet is hit by two lasers. The first compresses the pellet because it raises its temperature so rapidly. Then the second laser causes the fusion of the pellet’s atoms, which generates at least 50 times more energy than the lasers originally fired into the pellet.

What is left of the pellet’s atoms is absorbed by the interior wall of the reactor. Norreys claimed the theory was sound and there were no insurmountable engineering obstacles.

While the inertial confinement team aims to persuade governments to fund their prototype reactor the Tokamak researchers are developing their next-generation power plant, called Iter. It has already been designed, and the project’s partner organisations are deciding where to build it. Their goal is to sustain fusion for five to 10 minutes.

Robert Aker, a scientist working on JET, said the inertial confinement researchers’ claims about the prototype were over-confident. ‘Their big problem is how do they use energy from what is essentially a number of hand grenades going off inside their reactor? Inertial confinement was never originally intended as an energy source. It had military applications.’