Scientists in Oxford have set a record for generating energy from nuclear fusion, which is seen as a potential future source of near limitless power, however the experiment still consumed more energy to create the fusion reaction than the energy released by it, but a sustained fusion event like this is a major advance.
One person who was definitely encouraged was Professor Ian Chapman, chief executive of the UK Atomic Energy Agency who said:
"These landmark results have taken us a huge step closer to conquering one of the biggest scientific and engineering challenges of them all."
About Nuclear Fusion
Fusion power offers the prospect of an almost inexhaustible source of energy for future generations, but it also presents so far unresolved engineering challenges.
The fundamental challenge is to achieve a rate of heat emitted by a fusion plasma that exceeds the rate of energy injected into the plasma.
Today, many countries take part in fusion research to some extent, led by the European Union, the USA, Russia and Japan, with vigorous programmes also under way in China, Brazil, Canada, and Korea. Initially, fusion research in the USA and USSR was linked to atomic weapons development and it remained classified until the cost and complexity of the devices involved increased to the point where international co-operation was the only way forward.
Fusion powers the Sun and stars as hydrogen atoms fuse together to form helium, and matter is converted into energy. Hydrogen, heated to very high temperatures changes from a gas to a plasma in which the negatively charged electrons are separated from the positively charged atomic ions.
Normally, fusion is not possible because the strongly repulsive electrostatic forces between the positively charged nuclei prevent them from getting close enough together to collide and for fusion to occur. However, if the conditions are such that the ions can overcome the electrostatic forces to the extent that they can come within a very close range of each other, then the attractive nuclear force (which binds protons and neutrons together in atomic nuclei) between the nuclei will outweigh the repulsive (electrostatic) force, allowing the nuclei to fuse together. Such conditions can occur when the temperature increases, causing the ions to move faster and eventually reach speeds high enough to bring the ions close enough together. The nuclei can then fuse, causing a release of energy.
Fusion technology
In the Sun, massive gravitational forces create the right conditions for fusion, but on Earth they are much harder to achieve. Fusion fuel – different isotopes of hydrogen – must be heated to extreme temperatures of the order of 50 million degrees Celsius, and must be kept stable under intense pressure, hence dense enough and confined for long enough to allow the nuclei to fuse. The aim of the controlled fusion research program is to achieve 'ignition', which occurs when enough fusion reactions take place for the process to become self-sustaining, with fresh fuel then being added to continue it. Once ignition is achieved, there is net energy yield – about four times as much as with nuclear fission.
Our challenge is to apply the heat to human needs, primarily generating electricity. The energy density of fusion reactions in gas is very much less than for fission reactions in solid fuel, and so the heat yield per reaction is much less. Hence thermonuclear fusion will always have a much lower power density than nuclear fission, this means that a fission reactor can be smaller and potentially cheaper than the old fusion reactors.
Current research based near Oxford is developing fusion energy with a focus on power driver technology using an asymmetric implosion approach. As well as power generation, the company envisages material processing and chemical manufacturing applications.
The latest results from Oxford prove that making fusion energy in this way is at least theoretically feasible.
*The views expressed are the author’s and not ICAEW’s.
