Sunday, 1 April 2018

Nuclear fusion

Fusion seem like the ultimate technical fix for energy, supplying vast amounts of energy from fusing isotopes of hydrogen at very high temperatures -100 million degrees or so.  That’s what happens in the sun, but on earth, artificial fusion always seems to be decades away. And that may still be the case even if the current high-cost test programmes work. Here is a good simple up-tempo introduction:

Oddly it doesn’t mention ITER- the largest project, a giant Tokomak with magnetic firing and containment of the hot plasma. Construction is underway in France, but it won’t be ready until the late 2020s. It is claimed that 10 times more energy will be produced than consumed - it’s rated at 500MW. However, that will only be for 1-hour maximum runs: its not designed to be power plant, just to do better than the previous smaller JET test rig at Culham in the UK, which managed 16MW in 30-40 second bursts. Moreover, there is some doubt as to the claim of ‘10 times more out than in’ for the complete ITER system: it may not even reach 1.6 times: And there are a host of other issues:

Ten years on from the start of testing ITER with tritium fuel and maybe we might have some results and answers, and, if all goes well, proposals for another much larger, but still very pre-commercial, DEMO prototype, to be built maybe in the 2040s or even later: 2050 seem to be the current best guess: It’s always possible there will be break throughs there or elsewhere- the USA’s laser-fired pellet compression ‘ignition’ system has its fans and the UK’s MAST spherical Tokomak and ST40 derivative may yet come up with something, and there are several others including in China and Russia- see below.  

However, we are probably not looking at anything that can help us with our urgent climate change, air pollution and energy security problems before the second half of the century at the earliest. And even if fusion ever works, and proves to be economic, there would still be radiation contamination and safety risks to deal with:  The neutron flux will irradiate the reactors internal equipment, materials and systems, which will affect operations and have to be regularly stripped out and stored somewhere for a century or so. So it’s not waste free. And there are accidental tritium escape risks…. as well as potential long-term shortages of lithium to make tritium- since we may well use a lot of it in Electric Vehicles and backup household/commercial Li Ion batteries. 

So fusion sounds like a long shot, with some risks. That’s not the impression you get from the gushy mainstream media coverage, e.g. the Independent ran an article with the headline ‘One giant leap for mankind: £13bn ITER project makes breakthrough in quest for nuclear fusion, a solution to climate change and an age of clean, unlimited energy’. That was in 2103 before work even started on it:   The Guardian, in 2016, when construction work had started, was a bit more measured: After 60 years, is nuclear fusion finally poised to deliver’, but it was  still pretty gung ho: The left has always had a soft spot for fusion, but right wing UK newspapers have of late also taken up the cause, with for example, the the Express fearing that, given China’s progress in the field, the UK could loose its Culham/JET lead:

JET, the Joint European Torus, may survive as a test bed, even after the UK leaves the EU and Euratom, but UK national hopes rest with for the MAST project at Culham and derivatives like the ST40, said to be running by 2030: and There was also talk of the UK hosting the proposed EU ‘Hiper’ laser fired fusion project: But that seems to have disappeared- and the UK is only one small player, with, in addition to the big international ITER programme, many other projects being underway around the world.

Some of them are evidently making progress e.g. in the USA, where an MIT Tokomak managed to sustain a plasma for a 2 second, although the project then ran out of money: S.Korea has done better with a 70 second burn:  Germany also has astellarator’ system which some see as a better design than ITER: It has reportedly managed to produce net power output:  So has the big laser fusion system in the USA- at the Lawrence Livermore National Ignition Facility:  Some see its ‘inertial confinement’ approach, with tiny fuel pellets being compressed to fuse with multiple focused laser beams, as winning over Tokomak magnetic constriction plasma systems like ITER. We shall see, with Google even entering the field, offering advanced electronics:
Russia is also a significant player –it invented to Tokomak design. But China may yet beat them all:

As can be seen it’s all still in flux, with many projects at various scales and stages of development, but as yet little idea if any of them will lead to economic, commercial scale plants. Although to try to improve the economic potential, some look to mini-fusion reactor designs: and In 2014, Lockheed even bravely said ‘Prototype in 5 years, defence products in 10, clean power for the world in 20 years’.

These ideas all seems long shots. But, in a even longer shot, some still hanker after cold fusion! Meanwhile, as a shortcut, some look to fission-fusion hybrids: And there could well be some cross-overs, with tritium fuel for fusion systems being produced in fission reactors, including old heavy water moderated plants: So while some see fusion plants as a replacement for fission plants, they may actually coexist..

The fusion field certainly attracts a wide range of views with some saying it could be done faster: But for good or ill, this quote from the UK Atomic Energy Authority may put it all in perspective:  fusion ‘has the potential to supply 20% of the world’s electricity by the year 2100’. Renewables already supply more than that now globally, including hydro. We don’t need to wait for artificial fusion: renewables offer us a way to limit climate change now, using the fusion reactor we already have in the sky, supplying more energy to the earth than we could ever need. If artificial fusion ever does become viable, it might have a role in powering spacecraft or planetary bases far from the sun- to mine helium 3 or whatever, to run the fusion reactors! But maybe not on earth..

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