“Nuclear fusion breakthrough,” are the world’s headlines today. Eventually we will have free, pollution-free energy. No CO2 emissions, we will be saved. I have lived with the promise of nuclear fusion all my life and it has always been decades away. It’s become something of a bad joke amongst the science community that fusion is always decades away.
Nuclear fusion liberates energy by combining light atoms – isotopes of hydrogen – rather than by using the radioactive decay of large atoms such as uranium and plutonium – nuclear fission. It could have many advantages; the reaction can be switched off (not possible with fission), it uses water as a fuel and produces very little waste. The question is how do you fuse atoms?
Obviously it isn’t easy. Every star in the Universe generates its energy this way but stars are big and places of great pressure and temperature, unlike the Earth. One way is to generate a hot gas of hydrogen isotopes – 100 million degrees or so – and confine it so that the hydrogen nuclei (for it will be ionised) fuse. The heating is done by microwaves and the confinement by a magnetic field, for anything physical would melt. The problem is that the plasma is unstable and so far the reactions are fleeting.
International Thermal Experimental Reactor (ITER)
This is the basis of the major multi-national project to develop fusion, the $22 billion International Thermal Experimental Reactor (ITER) project (China, India, Japan, Korea, Europe, US) which is under construction in France and hopes to start tests in 2035 as part of developing the expertise to build a commercial fusion reactor presumably in the unspecified following decades.
Flash and Burn
Yesterday’s announcement involves a different technique. The US National Ignition Facility focuses a burst from a multitude of high-powered lasers on a grain-sized target that compresses to initiate fusion. The announcement by US Energy Secretary Jennifer Granholm was hailed by the world’s media as a great breakthrough in the developing technique of fusing atoms together, limitless, cheap, green were the adjectives used.
The announcement itself is a puzzle and had the feeling of being some much needed good news to announce. In reality although the experiments referred to took place a few months ago the “breakthrough” results were reported a year ago with the major advance being published in the Journal Nature in 2014. By one analysis 2.05 MJ of energy pumped into the pellet produced 3.15 MJ of energy. This does not include the 322 MJ needed to run the 192 lasers. So the story wasn’t a real breakthrough, just an advance. In any commercial development of this laser technique millions of fuel pellets would be needed for each reactor a year. At present they are tailor-made and cost almost $1 million each.
The US National Ignition Facility.
So why did the story lead some news bulletins? Given the announcement by Granholm it was clearly a story and in the main its coverage was good though some specialist correspondents clearly didn’t know the background and one science editors analysis of the event was puerile. I’ll leave it for an exercise for the reader to decide who I refer to.
But should nuclear fusion be part of the green energy debate? It is certainly not going to rescue us anytime soon. But I suppose linking fusion to green energy and the climate debate will help funds flowing.
Some would disagree with me and point to the many small, private companies that want to develop smaller-scale fusion reactors much sooner. They have acquired significant investment, some 30 firms have raised a total of $2.4 billion and General Fusion of Canada says it hopes for a viable reactor in the 2030s. CEOs of such companies see a payoff within a decade but to me it sounds like a sales pitch to attract further investment. Experts will privately say this is very wishful thinking.
In the mid-1990s I gave an after-dinner speech to a society of nuclear fusion scientists. I wondered out loud if the arrival of the first commercial fusion power would be as far in the future as the first hits of the Beatles were in the past. It took 50 years from the steam engine to trains and the same time between the internal combustion engine and cars. Nuclear fusion is a lot more difficult that such simple thermodynamic engines. Perhaps the desire for this energy coupled with advances in artificial intelligence analysis and control systems will speed up its development and the equations of history will be superseded.
A modern society needs high energy density power production systems. Without energy storage renewables are limited. We need fusion energy which has been promised for so long but I think humans will have walked on Mars long before we get commercial fusion power.