There is obvious excitement within the science community following the successful peer reviewed experiment in nuclear fusion. The creation of more energy ouputting than was inputted is a massive breakthrough. Although it is also important to know that the energy required to power the lasers used far exceeded the energy created in excess.
The National Ignition Facility (NIF) fusion reactor generated a power output of 3.15 megajoules from a laser power output of 2.05 megajoules – a gain of around 150 per cent. However, this is far outweighed by the roughly 300 megajoules drawn from the electrical grid to power the lasers in the first place.
Is that a lot of energy?
No, not really. The difference – 1.1MJ – is about 0.3kWh. It takes about 0.2kWh to boil a full kettle of water.
As Karl Whittle, Professor of Zero Carbon & Nuclear Energy at Liverpool University’s School of Engineering explains:
‘The recent announcement by the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) in the US is the first step in the development of nuclear fusion as an energy source.
It has shown that nuclear fusion, the joining of two atoms releasing energy, is possible as an energy source here on the planet. After all the only other locations where we know it to work are within stars, and this is where the challenges lie, as replicating a star terrestrially is tricky.
Going forward the key challenges are how to sustain a fusion reaction, how to build a fusion reactor that outputs electricity, and where to get the fuel from.
Starting with a sustainable fusion reaction, to achieve this we need to compress isotopes of hydrogen gas to overcome repulsion between the atoms, think of putting two magnets of the same poles to each other they repel each other.
In a star this is done with the help of high temperature and gravity which is not really possible here on the Earth, so we use either inertial confinement which LLNL uses, or magnetic confinement which we use here in the UK at UKAEA, and will be using at ITER in Caderache, France.
Each method faces challenges in both scale up and, possibly more importantly, how they can be built, as successful fusion releases energy effectively as heat, which raises the temperature of the plasma to very high temperatures, ~ 150 million Kelvin, placing a load on the containment greater than the space shuttle had on re-entry into the atmosphere. This heat places a strain on the materials being used to contain the fusion process as we don’t want it to melt, but given the nature of the plasma limits what we can build it out of.
The second major challenge is how to convert this heat to electricity, most power stations heat water to boiling, and then use steam to drive a turbine generating electricity. In a fusion core this approach is likely to be used initially, but it faces a challenge in taking the heat out, and it is linked with generating the fuel, more specifically the tritium required, the final challenge.
In a fusion reactor, the first type of fusion, as used at LLNL, will be fusing two isotopes of hydrogen, deuterium and tritium, as this reaction occurs at a slightly lower temperature than others. Deuterium is naturally found on the planet, wherever there is water there is deuterium, which is stable and harmless, so easy to get. Tritium on the other hand, is found in trace amounts, with an estimated ~20 kg worldwide, forming from cosmic ray bombardment with the atmosphere and some fission reactors, and is radioactive with a half life of ~12 years.
This is the key challenge for running a fusion reactor, in order to fuel the reaction, we need to make tritium, which we can do by capturing the neutrons from the fusion process, and react them with lithium. To make enough tritium we need to capture all of the neutrons, or multiple those caught. The challenge, we still need to cool the reactor to prevent melting, but we also need to collect the neutrons to make the fuel…how to balance this is key to achieving fusion at the large scale, impacting reactor design.
The good news from LLNL shows it is possible to get more energy out from fusion than put in, up till now not achieved, showing that the research being undertaken here at Liverpool in fusion helps the development of fusion as a reliable zero emissions energy source, and brings the day closer when fusion power stations are used commercially.’
Therefore, in time it is expected that nuclear fusion will provide all the energy required for human activity to be sustainable and replace all other forms of energy. The issue though, which is the brontasaurus in the room, is ‘in time’. The science appears to be doing its thing but the problem now moving forward, as explained above, is the technology.
There are two main research approaches aiming to achieve viable nuclear fusion. One uses magnetic fields to contain a plasma, while the other uses lasers. NIF uses the second approach, known as inertial confinement fusion (ICF), where a tiny capsule containing hydrogen fuel is blasted with lasers, causing it to heat up and rapidly expand. Although we have had a grand announcement, science and technology are still a very long way from either approach realising their ultimate aim.
With climate change now rapidly speeding up it appears that we do not have the time.
It is now expected that 10% of all remaining species on the planet will be gone by the end of this century whilst human populations continue to grow. Thus more people, more energy required and ever increasing carbon emissions. Therefore, more climate warming and more pollution across the globe and more shortages. This will lead to more competition for resources, more wars, more refugees and eventually a complete collapse of the planet’s capacity to sustain many life forms including humans.
Unless science and technology unite and are successful very quickly. the fusion gains will be nothing more than an historical entity with no humans around to know it.
The clock ticks….
Jason Cridland
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