Nuclear Fusion is Irrelevant

Click for a larger image. News stories last week heralded a major breakthrough in fusion research. Links to the stories can be found below.

Friends, last week we were subjected to a press campaign on behalf of the teams of scientists and engineers who are carrying out nuclear fusion research.

Here are links to some of the stories that reached the press.

  • BBC Story
    • If nuclear fusion can be successfully recreated on Earth it holds out the potential of virtually unlimited supplies of low-carbon, low-radiation energy.”
  • Guardian Story #1
    • Prof Ian Chapman, the chief executive of the UK Atomic Energy Authority said “It’s clear we must make significant changes to address the effects of climate change, and fusion offers so much potential.”
  • Guardian Story#2 (from last year)
    • The race to give nuclear fusion a role in the climate emergency

The journalists add little to these stories – they mainly consist of snippets from press releases spun together to seem ‘newsy’. All these stories are colossally misleading.

Floating in the background of these stories is the idea that this research is somehow relevant to our climate crisis. The aim of this article is to explain to you that this is absolutely not true.

Even with the most optimistic assumptions conceivable, research into nuclear fusion is irrelevant to the climate crisis.

Allow me to explain how I have come to this conclusion.

Research into a practical fusion reactor for electricity generation can be split into two strands: an ‘old’ government-backed one and a ‘new’ privately-financed one.

The state of fusion research: #1 government-backed projects

The ‘old’ strand consists of research funded by many governments at JET in the UK and the colossal new ITER facility being constructed in France.

In this strand, ITER will begin operation in 2025, and after 10 years of ‘background’ experiments they will begin energy-generating experiments with tritium in 2035, experiments which are limited by design to just 4000 hours. If I understand correctly, operation beyond this limit will make ITER too radioactive to dismantle.

The key operating parameter for fusion reactors is called Q: the ratio of the heat produced to the energy input. And the aim is that by 2045 ITER will have achieved a Q of 10 – producing 500 MW of power for 400 seconds with only 50 MW of input energy to the plasma.

However ITER will only generate heat, not electricity. Also, it will not create any tritium but will instead only consume it. Following on from ITER, a DEMO reactor is planned which will have a Q value in the range 30-50, and which will generate electrical power, and be able to breed tritium in the reactor.

So on this ITER-proposed time-line we might expect the first actual electricity generation – may be 100 MW of electrical power – in maybe 2050.

And then assuming that these reactors take 10 years to build and that the design will evolve a little, it will be perhaps 2070 before there are ten or so operating around the world.

You may consider that research into a technology which will not yield results for 50 years may or may not be a good idea. I am neutral.

But it is definitely irrelevant to our climate crisis: we simply do not have 50 years in which to eliminate carbon dioxide emissions from electricity generation in the UK.

And this is on the ITER-proposed timeline which I consider frankly optimistic. If one considers some of the technical problems, this optimism seems – to put it politely – unjustified.

Here are three of the issues I keep at the top of my file in case I meet some fusion scientists at the folk club.

  • Q is the ratio of heat energy injected into the plasma to the heat energy released. But in order to be effective we have to generate net ELECTRICAL energy. So we really need to take account of the fact that thermodynamics limits the electrical generation to ~30% of the thermal energy produced. Additionally we need to include the considerable amounts of energy used to operate the complex machinery of a reactor. So we really need to consider a wider definition of Q, one that includes the ratio of input to output energies involving the entire reactor. Sabine Hossenfelder has commented on this issue. But basically, Q needs to be a lot bigger than 10.
  • Materials. The inside of the reactor is an extraordinarily hostile place with colossal fluxes of neutrons passing through every part of the structure. After operation has begun, no human can ever enter the environment again – and it is not clear to me that a working lifetime of say 35 years at 90% availability is realistic. Time will tell.
  • Tritium. The reactor consumes tritium – possibly the most expensive substance on Earth – and for each nucleus of tritium destroyed a single neutron is produced. The neutrons so produced must be captured to produce the heat for electrical generation. But the neutrons are also needed to react with lithium to produce more tritium. Since some neutrons are inevitably lost – so the plan is for extra neutrons to be ‘bred’ by bombarding suitable materials with neutrons, which then produce a shower of further neutrons – 2 or 3 for every incident neutron. And these neutrons can then in principle be used to produce tritium. But aside from being technically difficult, this breeding process also produces long-lived radioactive waste – something fusion reactors claim not to do.

If short, when one considers some of these technical problems, optimism that this research path will produce significant power on the grid in 2070 seems to me to be unjustified.

But what about this new ‘breakthrough’?

The breakthrough was not a breakthrough. It was undertaken because the walls of the previous reactor were found to absorb some of the fuel! So this ‘breakthrough’ represented a repeat of a previous experiment, but with new materials in place.

You can relive the press conference here.

Starting with a much larger amount of energy, they managed to produce 59 megajoules (MJ) of energy from fusion in about 8 seconds.

59 MJ is about 16.4 kWh of energy, which is sufficient to heat water for around 500 cups of tea, more than a cup of tea each for all the scientists and engineers working on the project.

For comparison, the 12 solar panels on my house will produce this easily in a day during the summer. To generate the energy in 5 seconds rather than 12 hours would require more panels: a field of panels roughly 200 m x 250 m, which would cost a little under 1 million pounds.

So the breakthrough is modest in absolute terms. But as I mentioned above, after billions more in funding, and another 20 years of research, the scientists expect to extend this generating ‘burn’ from 5 seconds to 400 seconds at a much higher power level.

In my opinion, JET and ITER are a complete waste of money and should be shut down immediately. The resources should be transferred to building out solar and wind energy projects alongside battery storage.

The state of fusion research: #2 privately-backed projects

The ‘new’ strand of fusion research consists of activities carried out primarily by privately-funded companies.

What? If the massive resources of governments can only promise fusion by 2070, how can private companies hope to make progress?

The answer is that JET and ITER were planned before a technical key advance was made, and they are committed to proceeding without incorporating that advance! Its a multi-billion pound version of “I’ve started so I’ll finish“. It is utter madness, and doubly guarantees the irrelevance of ITER.

The technical advance is the achievement of superconducting wire which can create magnetic fields twice as large as was previously possible. It turns out that the volume of plasma required to achieve fusion scales like the fourth power of the magnetic field. So doubling the magnetic field makes the final reactor potentially 16 times smaller!

This also makes it dramatically cheaper requiring amounts on the order of $100 million rather than billions of dollars. Critically, reactors can exploit the concept of Small Modular Reactors (SMRs) which can be mass-produced in a factory and shipped to a site. Potentially the first reactors could be built in years rather than decades, and the technology iterated to produce advances.

I have written about this previously. With some qualifications, I think this activity is generally not crazy  (it is certainly much less crazy than JET and ITER) but success is far from guaranteed.

A key unresolved question with this technology concerns its potential timeline for delivery of a working power plant.

The reactors face exactly similar problems to those in the much larger ITER reactor, and these are not problems that can be solved in months. So let’s suppose that the first demonstration of Q>1 is achieved in just 5 years (2027), and that all the technical problems with respect to electricity generation required only a further 10 years (2037). Given the difficulties in planning, let’s optimistically assume that the first production plant could get built just 5 years after that in 2042.

The ‘S’ in SMR means reactors would be small, with a thermal output of perhaps 150 MW and an electrical output of perhaps 50 MW. This is small on the scale of typical thermal generation plant. For example Hinckley C is designed to output 3,200 MW of electrical power i.e. more than 60 times larger than a hypothetical SMR fusion reactor.

So if we assume a rapid roll out and no technical or societal problems, then perhaps these reactors might generate significant power onto the grid in perhaps 2050. Nominally this is 20 years ahead of ITER.


With optimistic assumptions concerning technical progress, we might hope for fusion reactors to begin to make a significant contribution to the grid somewhere between 2050 and 2070, depending on which route is taken.

That is already too late to make any contribution to our climate crisis.

We need to deploy low-carbon technologies now. And if we have a choice between reducing carbon dioxide emissions now, or in 30 – 50 years, there is no question about what we should do.


We also need to consider the likely cost of the electricity produced by a fusion reactor.

Like conventional fission-based nuclear power, the running costs should be low. Deuterium is cheap and the reactor should generate a surplus of tritium.

The majority of the cost of conventional nuclear power is the cost of the capital used to construct the reactor. If I recall correctly, it amounts to around 95% of the cost of the electricity.

It is hard to imagine that a fusion reactor would be cheaper than a fission reactor – it would be at the limit of manageable engineering complexity. So we might imagine that the costs of fusion-generated electricity would be similar to the cost of nuclear power – which is already most expensive power on the grid.

In contrast, the cost of renewable energy (solar and wind) has fallen dramatically in recent years. Solar and wind are now the cheapest ways to make electricity ever. And their cost – along with the cost of battery storage – is still falling.

So it seems that after waiting all these years, the fusion-based electricity would in all likelihood be extraordinarily expensive.


The idea of generating electricity from nuclear fusion has been seen as technological fix for climate change. It is not.

Even the most optimistic assumptions possible indicate that fusion will not make make any significant contribution to electricity supplies before 2050.

This is too late to help in out in our climate crisis which is happening now.

Additionally the cost of the electricity might be expected to exceed the cost of conventional nuclear power stations – the most expensive electricity currently on the UK grid.

If as an alternative, we invested in renewable generation from wind, solar and tidal resources, together with ever cheaper storage, we could begin to address our climate crisis now in the knowledge that the technology we were deploying would likely only ever get better. And cheaper.



2 Responses to “Nuclear Fusion is Irrelevant”

  1. daveburton Says:

    I agree with you that the folks hyping nuclear fusion as a remedy for “the climate crisis” are blowing smoke. It’s complete nonsense. But that’s no different from everyone else hyping their remedies for “the climate crisis.” They’re all grifters.

    That’s because the “climate crisis” is a political fiction. There is no actual climate crisis. It’s all smoke and mirrors. The evidence is compelling that manmade climate change is modest and benign, CO2 emissions are beneficial, rather than harmful, and the social cost of carbon is negative.

    Our CO2 emissions are affecting the Earth’s climate… but for the better, not for the worse. The benefits are measurable by satellites. Here are some articles and peer-reviewed papers about it:

    Here’s a NASA video about it:

    CO2 emissions are environmentally very beneficial, and the are also very beneficial for agriculture. Here’s a National Geographic article about it (which they’ve since removed):


    ‍‍‍‍‍‍ Images taken between 1982 and 2002 revealed extensive regreening throughout the Sahel, according to a new study in the journal Biogeosciences.
    ‍‍‍‍‍‍ The study suggests huge increases in vegetation in areas including central Chad and western Sudan. …
    ‍‍‍‍‍‍ In the eastern Sahara area of southwestern Egypt and northern Sudan, new trees—such as acacias—are flourishing, according to Stefan Kröpelin, a climate scientist at the University of Cologne’s Africa Research Unit in Germany.
    ‍‍‍‍‍‍ “Shrubs are coming up and growing into big shrubs. This is completely different from having a bit more tiny grass,” said Kröpelin, who has studied the region for two decades. …
    ‍‍‍‍‍‍ “Before, there was not a single scorpion, not a single blade of grass,” he said.
    ‍‍‍‍‍‍ “Now you have people grazing their camels in areas which may not have been used for hundreds or even thousands of years. You see birds, ostriches, gazelles coming back, even sorts of amphibians coming back,” he said.
    ‍‍‍‍‍‍ “The trend has continued for more than 20 years. It is indisputable.”

    Here’s a New Scientist article about it:

    Rising CO2 levels boost agricultural productivity, and make crops more resistant to drought. That has helped make large scale drought-triggered famines a fading memory, for the first time in human history.

    It is impossible to overstate the importance of that. Ending famine is a VERY Big Deal, comparable to ending war and disease. Compare:

    ● Covid-19 has killed 0.133% of world population, so far.

    ● 1918 flu pandemic killed about 2% of world population.

    ● WWII killed 2.7% of world population.

    ● But the global drought & famine of 1876-78 killed an estimated 3.7% of world population.

    • protonsforbreakfast Says:


      Hi. I trust you are well. That’s a very long post and I will sift through the links in the next day or two.

      It is certainly clear that around 25% of CO2 emissions are absorbed in plant growth. And yet the warming arising from the residual 50% of CO2 emissions that remain in the atmosphere is certainly affecting where those plants can be grown. Famine is not just about how many plants are growing but about which ones are growing, and where.

      We have discussed sea level change previously, and I agree that evidence for acceleration of sea level change is not strong.

      But the temperature changes, the loss of arctic sea ice, and the drift in climate extremes are all real also. It seems to me that trying to arrest the main driver for these changes would be a smart thing to do.

      Best wishes


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