Scientists have been working on developing nuclear fusion power generation since the early 1950s. The main problem has always been that more energy has been required to produce the reaction than is produced.

Scientists at the National Ignition Facility in California believe that their latest experiments will overcome the problem.

Their technique uses lasers to concentrate isotopes of hydrogen. The pressures and densities achieved are close to what occurs in the sun. At these densities. mass becomes energy in the form of heat which can be used to drive a turbine.

A demonstration reactor is expected to begin testing later this year and to be in operation within two years. If successful, the scientsist believe that they could have a power plant delivering electricity to the grid within ten years. Electricity produced in this way would be economical, carbon free and effectively limitless.

However, other scientists are more sceptical.

Michael Moyer, writing in Scientific American, sees the major problem as being in the need to convert energy from the neutrons into heat that drives a turbine. The conversion occurs in a region surrounding the fusion core called the "blanket". The blanket is also used to manufacture tritium which is needed to fuel the reaction. Inside the blanket, channels of lithium capture neutrons to produce helium and tritium. The tritium must then be collected and fed back into the core reaction.

The National Ignition Facility is not testing blanket designs. Some scientists believe that it could take 30 or more years to understand the issues in blanket design sufficiently to permit construction of full-scale power plants.