The Impossible Dream

In 1920, The Observatory journal published an article by Arthur Eddington entitled ‘The internal constitution of the stars’. In his paper, Eddington proposed, for the first time, that stars derive their immense energy from the internal fusion of atomic nuclei (Eddington, 1920). Only under the enormous gravitational pressure within the star’s core can the nuclei come close enough for the strong nuclear force attracting them together overcome the much wider-ranging electrostatic force pushing them apart, allowing them to fuse into a single larger nucleus in an exothermic reaction, releasing the energy which the star radiates (nuclear fusion can be understood as the opposite of nuclear fission, in which energy is released by splitting one large atomic nucleus into two smaller daughter nuclei). Understanding of the process by which this occurs was further developed throughout the 1920s and 1930s by Atkinson and Houtermans (1929) and by Bethe (1939).

It was of course soon realised that if a controlled and sustained fusion reaction could be replicated on Earth, it could provide a nearly-limitless source of low-cost power. Throughout the 1940s and 1950s experimental fusion devices were tested in Britain, France, Germany, the United States and the Soviet Union. In 1968, Soviet scientists developed the tokamak device, which magnetically confines the particles used as fuel in the fusion reaction, and remains the principal type of device used to achieve fusion power in modern experiments (Highfield et al. 2009).

Achieving electricity production by nuclear fusion on a commercial scale could, in short, provide a practically limitless source of low-cost and zero-emissions electricity sufficient to replace all present forms of fossil-fuel, nuclear fission, renewable and other sources of power (Kirk, 2016). Of the two hydrogen isotopes which constitute the only fuel required for fusion reactions (deuterium and tritium), deuterium is easily (and routinely) distilled from any kind of water, while tritium is produced from lithium, of which proven terrestrial reserves are estimated to be sufficient for over 1,000 years of fusion power – furthermore, lithium can be extracted from ocean water, where it is estimated that reserves would be sufficient to meet global fusion energy requirements for six million years (ITER, 2016). The sole emission of deuterium-tritium nuclear fusion is helium, meaning that fusion power could eliminate emissions of CO2 and other GHGs, of any other pollutants associated with fossil-fuel power, and of radioactive waste produced by nuclear fission which remains hazardous for tens of thousands of years (Kirk, 2016). In addition, environmental damage associated with fossil and nuclear fuel extraction would be eliminated due to the straightforward and environmentally benign process of extracting deuterium and tritium from ocean water.

If the eternal supply of bountiful, clean power from ocean water seems too good to be true, it might be. Although research into nuclear fusion has yielded impressive and encouraging results, commercial-scale application remains a very long way away. The record for the longest sustained plasma duration is held by the French Tore Supra tokamak at 6 minutes and 30 seconds (ITER, 2016), while the current record for power output is held by the Joint European Torus (JET) in the UK, at 16.1 MW representing ~70% of input power (Cowley, 2010) – in short, a fusion reaction presently requires more energy to initiate and sustain that it can produce. In the near future, the ITER project (an international collaboration between the European Union, the United States, China, India, Japan, Korea and Russia) aims to produce 500 MW of power from an input of 50 MW, and dramatically increase the duration over which the plasma can be contained and the fusion reaction sustained (ITER, 2016). The most significant challenge in achieving sustained fusion reactions which produce meaningful amounts of power is the magnetic confinement of hydrogen plasma at hundreds of millions of degrees Kelvin – the very short duration of current fusion experiments is in large part due to the difficulty of magnetically containing the plasma over long periods (Kirk, 2016; MIT, 2016). The ITER project hopes to use an advanced combination of magnetic fields operating in tandem to successfully achieve longer confinement durations (ITER, 2016).

So how much store should we really set by the development of fusion power? The UK government’s Atomic Energy Authority (UKAEA) states that ‘nuclear fusion… could play a big part in our sustainable energy future’, and it is the stated aim of the organisation to keep the UK at the very forefront of fusion research globally, and to design the world’s first nuclear fusion power plant in the UK (UKAEA, 2016). However, despite general optimism regarding the prospect of achieving commercial-scale fusion power production within the next century or two, the need to dramatically reduce global GHG emissions while increasing energy supply is far more urgent than that (as I sought to illustrate in my first post to this blog). Nuclear fusion remains very much a matter of continued scientific research, and more generally UK energy policy is increasingly focused on developing new nuclear fission generating capacity in order to reduce GHG emissions while maintaining energy security using established and proven zero-emissions technology (GOV.UK, 2015).  In the short-to-medium term, it undoubtedly makes sense for policy and research focus to concentrate firmly on established means of low-emissions electricity production, such as renewables or nuclear fission.

However, in the longer-term, it is argued that the very continuation of human progress and growth is dependent upon the successful application of fusion power. Lee and Saw (2011) argue that even if the ambitious goal of commercial fusion power by the end of the 21^st century is achieved, during the second half of the century humanity will be plagued by energy shortage, stifling human progress. They further argue that in the total absence of fusion power, chronic shortfalls in global energy supply will ultimately result in ‘a severe downturn unavoidably in the fortunes of Mankind with world population shrinking below 5 billion and eventually even lower’ (p.398). In summary, the urgency of the need to address GHG emissions and increasing demand for energy means that in the short term, the development and application of established means of low-emissions energy production must be prioritised – however, in the longer-term, fusion power should provide the means for continued human population growth and technological progress into the 22^nd century and well beyond.