an autodidact meets a dilettante…

‘Rise above yourself and grasp the world’ Archimedes – attribution

Archive for the ‘nuclear power’ Category

Exploring the future of nuclear fusion

leave a comment »

Canto: So, with Christmas cookery and indulgence behind us, it’s time to focus on another topic we know little about, nuclear fusion – or I should say human-engineered nuclear fusion. Ignition has recently been achieved for the first time, so where do we go from here?

Jacinta: Well I listened to Dr Becky the astrophysicist on this and other topics, and she puts the ignition thing into perspective. So it occurred back on December 5 at the National Ignition Facility in California. As Dr Becky explains it, it involves ‘taking 4 atoms of hydrogen and forcing them together to make helium’, which is slightly lighter than the four hydrogens, and this mass difference can, and in this case has, produced energy according to special relativity. Of course fusion occurs in stars (not just involving hydrogen into helium) and it can potentially produce huge volumes of clean energy. But there’s a big but, and that’s about the high temperatures and densities needed for ignition. Those conditions are needed to overcome the forces that keep atoms apart. 

Canto: Yes they used high-powered lasers, which together focus on heavy hydrogen isotopes – deuterium and tritium – to produce helium. And this has been achieved before a number of times, but ignition specifically occurs when the energy output is greater than the input, potentially creating a self-sustaining cycle of fusion reactions. And the difficulties in getting to that output – that is, in creating the most effective input – have been astronomical, apparently. They’ve involved configuring the set of nearly 200 lasers in the right way, using ultra-complex computational analysis, recently guided by machine learning. And this has finally led to the recent breakthrough, in which an energy input of 2.05 megajoules produced an output of 3.15 megajoules…

Jacinta: 1.1 megajoules means ignition, though it’s nothing earth-shattering energy-wise. It’s apparently equivalent to about 0.3 kilowatt-hours (kWh) – enough energy for about two hours of TV watching according to Dr Becky. And also this was about the energy delivered to the particles to create the reaction, it didn’t include the amount of energy required to power the lasers themselves – approximately 300 megajoules. So, good proof-of-concept stuff, but scaling up will be a long and winding road, wethinks. 

Canto: Another favourite broadcaster of ours, theoretical physicist Sabine Hossenfelder, also covers this story, and provides much the same figures (400 megajoules for the lasers). She also points out that, though it’s a breakthrough, it’s hardly surprising given how close experimenters have been getting to ignition in recent attempts. And she is probably even more emphatic about the long road ahead – we need to ramp up the output more than a hundred-fold to achieve anything like nuclear fusion energy at economically viable levels. 

Jacinta: I’m interested in the further detail Dr Hossenfelder supplies. For example the NIF lasers were fired at a tiny golden cylinder of isotopes. There must be a good reason for the use of gold here. She also describes the isotopes as ‘a tiny coated pellet’. What’s the coating and why? She further explains ‘the lasers heat the pellet until it becomes a plasma, which in turn produces x-rays that attempt to escape in all directions’. This method of arriving at fusion is called ‘inertial confinement’. Another competing method is magnetic confinement, which uses tokamaks and stellarators. A tokamak – the word comes from a Russian acronym meaning ‘toroidal chamber with magnetic coils’ – uses magnetism to confine plasma in a torus – a doughnut shape. A stellarator…

Canto: Here’s the difference apparently:

In the tokamak, the rotational transform of a helical magnetic field is formed by a toroidal field generated by external coils together with a poloidal field generated by the plasma current. In the stellarator, the twisting field is produced entirely by external non-axisymmetric coils. 

Jacinta: Ah, right, we’ll get back to that shortly. The Joint European Torus (JET) holds the record for toroidal systems at 0.7, which presumably means they’re a little over two thirds of the way to ignition. 

Canto: A poloidal field (such as the geomagnetic field at the Earth’s surface) is a magnetic field with radial and tangential components. Radial fields are generated from a central point and weaken as they move outward.

Jacinta: PBS also reports this, citing precisely 192 lasers, and a 1mm pellet of deuterium and tritium fuel inside a gold cannister:

When the lasers hit the canister, they produce X-rays that heat and compress the fuel pellet to about 20 times the density of lead and to more than 5 million degrees Fahrenheit (3 million Celsius) – about 100 times hotter than the surface of the Sun. If you can maintain these conditions for a long enough time, the fuel will fuse and release energy.

Canto:  So the question is, does nuclear fusion have a realistic future as a fuel?

Jacinta: Well, did the internet have a realistic future 50 years ago? We’ve had a breakthrough recently, and the only way is up. 

Canto: Yeah the future looks interesting after I’m dead. Still, it’s worth following the progress. Back in February The Guardian reported that JET had smashed its own world record, producing ’59 megajoules of energy over five seconds (11 megawatts of power)’. Whatever that means, it wasn’t ignition – it might’ve been the .7 you mentioned earlier. Creating a mini-star for five seconds was what one experimenter called it, which I think was in some ways better than the current effort, in that it created more energy in absolutes terms, but less energy than the input. 

Jacinta: Perhaps, but what they call ‘gain’ is an important measure. This recent experiment created a gain of about 1.5 – remember just over 3 megajoules of energy was put out from just over 2 megajoules of input. It’s a start but a much bigger gain is required, and the cost and efficiency of the lasers – or alternative technologies – needs to be much reduced. 

Canto: Apparently deuterium and tritium are both needed for effective fusion, but tritium is quite rare, unlike deuterium, which abounds in ocean waters. Tritium is also a byproduct of the fusion process, so the hope is that it can be harvested along the way. 

Jacinta: Of course the costs are enormous, but the benefits could easily outweigh them – if only we could come together, like bonobos, and combine our wits and resources. Here’s an interesting quote from the International Atomic Energy Agency:

In theory, with just a few grams of these reactants [deuterium and tritium], it is possible to produce a terajoule of energy, which is approximately the energy one person in a developed country needs over sixty years.

Canto: Really? Who will be that lucky person? But you’re right – collaboration on a grand scale is what this kind of project requires, and that requires a thoroughly human bonoboism married to a fully bonoboesque humanism….

References

https://www.pbs.org/newshour/science/what-a-breakthrough-in-nuclear-fusion-technology-means-for-the-future-of-clean-energy

https://www.theguardian.com/commentisfree/2022/dec/13/carbon-free-energy-fusion-reaction-scientists

https://www.iaea.org/bulletin/what-is-fusion-and-why-is-it-so-difficult-to-achieve

https://www.bbc.com/news/science-environment-60312633

Written by stewart henderson

December 29, 2022 at 6:26 pm

more on nuclear fusion: towards ignition!

leave a comment »

 

I recently wrote about and tried to get a handle on the nuclear fusion facility, ITER, being built in southern France, but I barely mentioned the importance of magnets, and I didn’t mention another essential feature or factor in nuclear fusion – called ignition. That’s because I’m still a learner after all these years. But some news broke recently regarding a completely different experimental fusion facility in the USA, which uses lasers rather than magnets to control and focus the energy, which, as previously described, needs to be – a lot.

The National Ignition Facility (NIF) at the Lawrence Livermore National Lab in California is designed, it seems, to try and achieve exactly that – ignition. The term is kind of self-explanatory, as when you ignite something you get a burst of energy, seemingly more than you put into the igniting, like when you strike a match. But ignition in nuclear fusion is a really difficult thing to achieve, which is presumably why they had to build a whole national facility around it. They’ve been trying to achieve it for decades.

I did write that to achieve fusion – ignition? –  required temps of around 150,000,000 celsius, and obviously to sustain such temperatures requires a fair amount of energy, ten times that at the sun’s centre. Did I get that figure wrong? Pressure comes into it too (there’s a direct proportionality between temperature and pressure at any given volume).

I’ve found a great video explainer of the ignition breakthrough, presented by Anton Petrov, and a recent New Scientist podcast (no 81) also discusses it. So basically the possibilities of nuclear fusion as an energy technology have been on the cards since the development of the H-bomb in the late forties and early fifties. The energy required to set off an H-bomb, and for subsequent neutron bomb technology, was derived from nuclear fission. So that’s a lot of energy to make more energy. Since then, the aim, the holy grail, has been to find a way to create ignition, an energy output that is greater than, and preferably much greater than, the energy input. This is, of course,, essential for real-use thermonuclear energy. A number of technologies for creating thermonuclear fusion have proved successful, except insofar as the input-output ratio is concerned. Out of all these experiments chasing this elusive ignition, two models seemed most promising. Firstly, the toroidal fusion reactor (eg ITER), which is a magnetic confinement reactor, in which super-heated plasma is spun very quickly around a magnetically confined chamber, to create higher-than-the-centre-of-the-sun energy/temperatures. A number of these reactors, or tokamaks, have been built around the world and have successfully created fusion, but not ignition.

The second model is very different. It’s called inertial confinement fusion, and  it uses tiny hydrogen pellets. The idea came from observation of the H-bomb: a small enough hydrogen pellet would require a minimum energy of 1.6 megajoules (million joules) of energy to initiate an explosion – essentially, an ignition. This energy could be provided by lasers. Now this process is complicated – it’s not  simply a matter of fusioning hydrogen into helium because, as described in my previous post about ITER, there are isotopes involved. These isotopes (deuterium and tritium) are used to overcome the electrostatic repulsion which would normally occur when using proteum, the common form of hydrogen. This repulsive force between protons is known as the Coulomb force. The attractive force between protons and neutrons, called the nuclear force, acts against the electrostatic repulsion force, and this helps in overcoming the Coulomb barrier, and facilitating a fusion energy greater than that inside our sun, where plasma particles may not fuse at all over long periods. We’re basically looking at creating a more efficient kind of fusion, which requires the kinds of temperatures and pressures found inside much larger stars than our sun.

The key to the elusive status or point known as ignition is a concept called the Lawson criterion. Wikipedia describes it thus:

The Lawson criterion ….compares the rate of energy being generated by fusion reactions within the fusion fuel to the rate of energy losses to the environment. When the rate of production is higher than the rate of loss, and enough of that energy is captured by the system, the system is said to be ignited.

We haven’t achieved ignition yet, but it seems another baby step has been taken. One of the researchers at the NIF has described it as a ‘Wright brothers moment’, which has led to a bit of head-scratching. Basically, what was achieved at the NIF was a ‘momentary’ ignition – very momentary, and still only releasing some 70% to 80% of the energy input. Yet this was the most significant achievement in 60 years of work – a proof of concept achievement, which is built on previous experiments yielding increasing levels of energy. The process involved almost 200 super-amplified lasers confining and directing energy at a tiny hydrogen pellet for a period of 3 nanoseconds. That’s 3 billionths of a second. This required excruciating accuracy, coordination and timing, with everything – the lasers, the amplifiers, the pellet, the hohlraum chamber (holding the pellet) and so forth, being executed precisely. The precision level has improved markedly in recent times, leading to this breakthrough moment (after all, the ‘Wright brothers moment’ wasn’t exactly the first commercial passenger flight). The 1.3 megajoules released in this most recent ignition experiment was some 25 times what the facility could muster only three years ago. So there doesn’t seem far to go.

And yet. The energy input required is enormous. The lasers would need to fire more or less constantly – machine-gun-like – to produce the output required for human use (the current record of 1.3 megajoules has been described as ‘just enough to boil a kettle’. So we’re talking orders of magnitude, not just for the laser energy but for the hydrogen pellets, which need to be produced en masse at a teeny fraction of current costs. And so on.

This not to minimise the achievement. The publicity already being generated augurs well for the future of a technology that has for so long failed to live up to expectations. Those at ITER and other labs around the world will receive a great fillip from this, not to mention some small mountains of cash. Looking forward to it.

References

movements in nuclear fusion: ITER

Major Breakthrough in Nuclear Fusion After Decades of Research (Anton Petrov video)

https://en.wikipedia.org/wiki/Lawson_criterion

https://podcasts.google.com/feed/aHR0cHM6Ly9mZWVkcy5idXp6c3Byb3V0LmNvbS84MTQwMzUucnNz/episode/QnV6enNwcm91dC05MDU0NjU3?hl=en-AU&ved=2ahUKEwiasaDm3NryAhUGeH0KHVAaDZMQjrkEegQIBRAI&ep=6

Episode #841

 

Written by stewart henderson

August 31, 2021 at 5:19 pm

movements in nuclear fusion: ITER

with one comment

the world’s biggest clean energy project? ITER in southern France

Geographical, the magazine of the UK’s Royal Geographical Society, had an article in its April 2021 edition entitled ‘Caging a Star’, all about the International Thermonuclear Experimental Reactor (ITER) project in Provence, France. Thermonuclear fusion has of course been talked up as an ultimate solution to our energy needs for decades, to the extent that it’s become something of a joke, but in the meantime, practical movements are underway. In fact, they’ve been under way for a long time. An international contract was signed in 1986 to implement research on fusion, though it took another twenty years to agree on the site for ITER. The project now involves 35 countries – largely WEIRD ones (Western Educated Industrial Rich Democracies), producing 85% of global GDP. It’s a long-term project, certainly, but it’s being taken seriously, and construction is happening, big-time.

With the IPCC having recently come out with its 2021 report, nations are looking to their targets and feeling concerned – some more than others (wake up Australia). Boštjan Videmšek, the author of the Geographical article, assesses the current situation in stark terms:

70% of all CO2 emissions pumped into the atmosphere are created through energy consumption; 80% of all the energy we consume is derived from fossil fuels. The EU has formally pledged to start producing half of its electric energy from renewable resources by 2030. By 2050, the bloc’s members are planning to hoist themselves into a fully carbon-neutral society. But, given current trends, this seems like wishful thinking. Renewable energy resources simply won’t be enough for the task.

The ITER project came out of the closet, so to speak, in late July 2020, when the heart of the project, the tokamak, began to be assembled onsite – though construction of various elements of the program have been going on for years. A tokamak is a toroidal or doughnut-shaped chamber, controlled by huge, powerful magnets, in which hydrogen plasma is manipulated to produce energy according to Einstein’s mass-energy equation. We all know, I hope, that fusion is constantly happening in the sun, and in all suns throughout the universe, and that its energy is essential to our existence, but ITER’s scientists are hoping to improve on the sun’s processes. Hydrogen collisions inside the sun don’t always result in fusion – the fusion process is quite slow. Recognising this, researchers looked to isotopes of hydrogen to speed up the process. Hydrogen’s most common form, consisting simply of a proton and an electron, is called protium. However, there are two other isotopes, deuterium and tritium, containing an additional one and two neutrons respectively. The best form of fusion reaction for producing energy is DT fusion, using deuterium and tritium. This produces more energy, at a lower temperature. The problem is with the tritium, a highly radioactive and unstable isotope, which is both rare and expensive, at about US$30,000 per gram. The rarity, though, is related to low demand, and there is potential for ITER to produce its own supply of the isotope.

Of course, none of this is expected to be ready in the near future. ITER is essentially a proof-of-concept project for future power plants, and is expected to spend a decade in testing, finalising in around 2035. Those future power plants are already ready and waiting, at least in terms of design. The key to achieving fusion is a sufficiently high temperature (150,000,000 degrees celsius!) and high particle density, for an optimum fusion rate. Containment of the volatile plasma will also, of course, be an issue. ITER’s experiments will also be about capturing and utilising the energy produced. As Videmšek describes it:

The idea is that heat will build up along the sides of the tokamak, where it will be captured by the cooling water circling the reactor. As in a normal power station, the heat will be used to produce steam and – by way of turbines and alternators – electricity. The water will eventually be released with the help of vast cooling towers. These have already been put in place…

The science itself, as researchers told Videmšek, is straightforward enough, but the infrastructure, the international nature of the project, the politics and the funding can all provide obstacles. The siting in Provence has helped, as France has successfully embraced nuclear fission technology for decades, and the project is a boon for the Provençal economy. And of course there’s the global warming issue. The IPCC has just released its 6th Assessment Report and, among other findings, has confirmed what we here in Australia have experienced regarding extreme weather events:

Human-induced climate change is already affecting many weather and climate extremes in every region across the globe. Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones, and, in particular, their attribution to human influence, has strengthened since the Fifth Assessment Report (AR5).

The report argues that, ‘unless deep reductions in carbon dioxide (CO2) and other greenhouse gas emissions occur in the coming decades’, this scenario of extreme weather events will continue into the foreseeable future. These deep reductions, it seems, are a matter of political will, not to mention recognition of the crisis, which is clearly not universal. The way that many nations, including some of the most powerful and impactful on climate, have dealt with the clear and present threat of the SARS-CoV-2 virus, doesn’t provide much cause for optimism. If the ITER project, mostly funded by EU nations, goes off without a hitch over the next few decades, it may just put another nail in the coffin of our self-destructive exploitation of fossil fuels. Better late than never I suppose…

References

Boštjan Videmšek, ‘Caging a star’, in Geographical, April 2021

https://www.ipcc.ch/report/ar6/wg1/#SPM

 

Written by stewart henderson

August 15, 2021 at 7:19 pm

giving nuclear energy a chance, please

leave a comment »

Compared with nuclear power, natural gas kills 38 times as many people per kilowatt-hour of electricity generated, biomass 63 times as many, petroleum 243 times as many and coal 387 times as many – perhaps a million deaths a year.

Steven Pinker, ‘The Environment’,  Chapter 10 of Enlightenment now. 

an unfortunate slow-down

I’ve written about nuclear energy before, here and here. It comes to mind again due to my reading of Pinker’s new book, so I’ve decided to venture into the field again, despite not having improved my paltry readership over the years.

Clearly the spectre of radiation hangs over the nuclear industry, and many green polemicists have done their best to darken that spectre, but if facts count for what I wish they would count for, Australia could solve all its considerable energy woes with a few nuclear power plants.

Take the case of France, a nation with almost three times our population. Thanks largely to its nuclear power program, which was boosted after the seventies oil crisis in order to deliver national energy security, it’s the world’s largest net exporter of electricity, because once the plants are built and paid for, electricity generation is cheap. In fact, some 17% of this electricity comes from recycled nuclear fuel. It currently earns 3 billion euros annually from exported electricity, and that’s not factoring in its exports from reactor technology and fuel products and services.

Australia has far more land than France, and given its small population, it would stand to gain substantially from exporting nuclear-derived electricity to the world, after finally putting an end to its frankly ridiculous domestic energy woes. I recognise though, that such a far-reaching project is beyond the imaginations, let alone the negotiating skills of today’s adversarial pollies. We need more entrepreneurs and non-partisan public intellectuals to get behind such projects, accompanied by realistic schemes and hard data.

There’s also the problem of winning over the public. The facts on nuclear energy should speak for themselves, but the largely human tragedies of Fukushima and Chernobyl, together with the perceived and perhaps actual connection between nuclear energy and weapons, and also the general fear of radiation and its relation to storage, leakage and accidents, have created polarised outlooks that impede progress in the field. This is well illustrated by a three-part set of videos on the subject, including an intro and two others, ‘nuclear energy is awesome’ and ‘nuclear energy is terrible’, suggesting that its authors have found little common ground.

As the negative part of the videos points out, weapons technology has been developed in five countries – India, Pakistan, Israel, South Africa and North Korea – through reactor technology. As the current debate over Iran illustrates, it’s hard to distinguish between nuclear energy technology and covert weapons technology. There’s also the waste problem. Radioactive and toxic chemical materials such as plutonium remain a problem for tens of thousands of years. A stable and remote underground environment, such as exists right here in South Australia’s north, would be one of the safest bets for burial, but beware of apoplectic rage when anyone suggests such an idea, even though, as one of the world’s largest exporters of uranium, we’re deeply involved in the industry and would likely get plenty of help from nations grateful for our raw material.

Of course, there have been accidents.

To put the nuclear energy scare in perspective, it’s worth noting that if you mention the word Tohoku outside of Japan you’re likely to get little back but an unknowing shrug. Mention Fukushima and you’ll likely get a more animated response. The Tohoku earthquake and tsunami killed approximately 16,000, with over 6,000 injured and 2,500 still missing. Almost 250,000 were left homeless. The Fukushima meltdowns resulting from this disaster killed nobody – though there are ongoing tests regarding radiation and cancer incidence, which suggest that increased risks are small.

I’ve written in one of my earlier posts about the obvious inappropriateness of building nuclear plants in earthquake-prone areas, and about the boys’ club mentality of Japan’s nuclear oversight system, but what about the accident itself and the associated radiation spill? As the most recent serious nuclear incident, and therefore the most relevant to the future of a developing industry, it’s worth taking a close look at it.

The Fukushima facility, one of the world’s largest, was made up of six boiling water reactors, of which three were in use at the time of the earthquake. The oldest of these was built in 1967, the other two in the early seventies. The seawall protecting the plant was ten metres high. The largest tsunami wave to hit the plant was 13 metres (a 2008 in-house study suggesting that the plant was unprotected from waves above 10.2 metres was dismissed, as purveying ‘unrealistic’ concerns). There were failures of the emergency cooling system, including piping and valve problems that hadn’t been monitored sufficiently. A number of hydrogen-air explosions occurred in the days after the tsunami, further damaging the plant. Clearly, there were maintenance problems in the lead-up to the failure, communication problems during the crisis, and a general culture of complacency throughout, deadly to such high-risk geographical locations. However, none of this should necessarily act as a complete brake on the industry. The lessons to learn would seem to be obvious. More openness, more active monitoring, sensible placement of nuclear plants, and ongoing research towards improved and safer facilities.

As far as I can see, there’s much more to be said about the positives of nuclear energy. In spite of the recent massive pause, or reversal, in our reliance on it, nuclear is by a huge distance the safest – and greenest – form of energy in terms of lives lost, health problems and any other indicator we can think of. There is plenty of data to back this up, but it involves far more than workplace safety. The damage from global carbon emissions is, of course difficult to calculate and the subject of endless debate, but there’s no doubt that nuclear has the smallest carbon footprint of any current energy technology. More importantly, it’s the only non-fossil fuel technology capable of providing reliable electricity on a global scale, at a time when the battle against global warming is very far from being won. The Trump debacle won’t last of course, but there is a greater threat from increased industrialisation in China, India, and the developing countries of the world – though any casting of blame would be unfair term considering the carbon being pumped out by the fully industrialised west.

The critics of nuclear point to the past, and to the radiation hazards of storage. They’re not interested in acknowledging modern developments which have made nuclear power increasingly safe and cheap, due to streamlining and standardisation of design, the plausibility of cheaper thorium reactors, and a host of innovations that have led to gen-III and gen-IV systems waiting to be brought online. Sadly, we may have to wait a while to see them. France, Germany, Japan and the USA are reducing their reliance on nuclear, and turning back to dirty energy, due only to its largely undeserved public reputation. It’s likely we’ll have to wait until the climate crisis deepens before we return to seeing the sense of nuclear energy. It will be interesting to see just how long it takes.

Written by stewart henderson

June 27, 2018 at 8:48 pm