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My view on nuclear fusion, in a nutshell

Alternative Energy
Nowadays few businesses would invest in conventional nuclear power stations. In the US subsidies of 100%, or more, fail to attract private investment for a nuclear fission power station, the classic form of nuclear energy.  There are good economic reasons why this is so aside from the strong emotional stigma.
There is another form of nuclear energy, thermonuclear fusion, the one that powers the stars. Fusion, the sticking together of high energy light atoms such as hydrogen, is a nuclear reaction distinct from fission, where heavy atoms, such as uranium, break apart even at room temperature.
Fusion energy production has been pursued since the WWII years in excellent national labs and universities all over the world, but it has so far resisted a clear indication of its potential.
What’s magnetic confinement fusion
There are two ways to burn hot nuclear fusion fuel: make it react very quickly before the burning gas flies away, the way an H bomb works, or use a magnetic field to insulate the plasma from the reactor walls.
With the bomb method the micro-explosion repetition rate has to be high to produce relevant electric power and this poses huge unsolved problems.
A giant laser fusion experiment in the US, the National Ignition Facility, has demonstrated how difficult and expensive is to produce a micro-explosion once a day. Imagine hundreds of times a second for years.
Even with a budget provided by the military for weapon development, laser fusion is further away from pointing to a credible commercial reactor than magnetic fusion.
From the inception of fusion energy research most efforts have been devoted to magnetic confinement of steady state hot plasmas.
After 70 years of trying, almost everybody in the field has concentrated on one favorite scheme which goes under the name of TOKAMAK, a Russian invention.
This kind of tests indicate that the minimum size of a potential reactor core will be large, the size of a large building.
ITER, a TOKAMAK presently under construction to demonstrate the feasibility of fusion at almost real size, is of this magnitude, so expensive that its construction is requiring the financial contribution of all developed nations on earth.
The doughnut shaped reactor core is 30 meter in diameter, 20 m high. It’s an extremely complex device, much more sophisticated than an equivalently powerful nuclear fission reactor and roughly 10 times the volume.
It can’t be factory manufactured because a single unit is too large, its core weights more than 100 thousand ton, just the floor of ITER uses 200 thousand cubic meter of concrete.
This is where the most obvious drawback of nuclear fusion resides. The unavoidable large size of a fusion reactor makes it impossible to be factory mass produced.
The present panorama of the competition is characterized by a large industrial production of comparatively small generators: gas turbines of 50-100 MW, efficient wind mills of a few MW, photovoltaic solar panels of less than 1 kW. This generators can be transported by truck and the speed of their industrial development has been inversely proportional to the power of an individual module.
The cost of electricity for photovoltaics and wind, the $/kWh, originates mainly from the cost of capital invested in the generator and its ancillary equipment, just as it’s the case for fusion the fuel is free.
Natural gas power stations burn inexpensive fuel and have the lowest generator capital cost of all, but are CO2 polluters, nowadays a serious drawback.
Because of its large size and complexity it’s very hard to imagine that a TOKAMAK fusion reactor could be less expensive than a conventional fission reactor and detailed estimates put the cost of the kWh to more than 12 ¢, just for the capital cost, and before knowing all the details of a working reactor.
On the other side electricity commercialized from unsubsidized photovoltaic and wind generators is presently sold at prices between 2 and 7 ¢/kWh and there is room for more savings. These sources are intermittent, fusion is not, but for a renewables dominated electrical production the additional cost of energy storage would entail a fraction of the cost of energy production.
This is a purely economic consideration: renewables are already less expensive than this still hypothetical new source of energy.
There is a second very relevant drawback linked to the large size of the fusion reactor: its development time.
ITER will experiment with real fusion fuel not earlier than 2035 and will realistically carry on the experiments in the following 5 to 10 years. It implies that this experimental phase, not a prototype reactor since ITER will be incapable of producing energy in steady state, will have taken roughly 50 years.
To make a dent in the world electricity production one should implement thousands of 1 GW size reactors. How long of an experimentation phase should one consider to reach this goal from when ITER will have answered the initial round of questions? Is 100 years. i.e. a couple of experimental phases, a realistic prediction?
To summarize on top of a pletora of unresolved, even unknown, design issues of technical nature, magnetic fusion poses a couple of problems linked to the huge size of the TOKAMAK reactor core: a large kWh cost and a very long development time.
Why the reactor has to be large
Why a magnetic fusion reactor has to be big, physically very large?
Thermonuclear fuel has been proven to explode in the H bomb, but it can burn also non explosively, think of the sun.
For any fuel to burn in steady state the energy released in the volume of the burning matter equals the energy escaping from it, heat produced equals heat lost.
The rate at which energy si produced goes with the density of the fuel, the number of atomic nuclei per cubic cm: the power density increases with the density of the reacting particles.
The plasma in a reactor is a gas of atomic constituents roughly in thermal equilibrium, its kinetic energy content is characterized by a pressure.
If the TOKAMAK plasma has to be contained by a magnetic field the field pressure has to be substantially higher than the plasma pressure.
The magnetic pressure produced by the external superconducting magnets at the plasma location is limited to less than 200 atmospheres by the electromechanical strength of the magnets.
Improvements are foreseeable on the magnets front, and they would be helpful, but the magnet materials are themselves subject to hard to bend laws of nature, these improvements will be marginal.
Like in an ordinary gas the plasma pressure is proportional to particle temperature and density.
In reactor relevant cases the fusion temperature has to be in the region of hundreds of millions of deg C hence, because of the pressure limit, the particle density turns out to be pretty low, of the order of 1020 particle per m3. This is orders of magnitude less than the molecular density of the air we breathe, 1026 per m3.
To summarize: the magnets mechanical strength limits the burning plasma power density to the one of a very rarefied nuclear fuel.
The energy escaping the burning mass, the other side of the reactor power balance equation mentioned above, is dictated by plasma turbulent motions and the size of the device.
Turbulence has been experimentally demonstrated to be present at a decisive level in all magnetically confined plasmas of thermonuclear interest, just like with water in a canal.
The analogy is very close, for a given incline the water flow in a canal is constrained by an irreducible turbulent drag, with negligible dependence on the canal construction details.
This is the case also for energy confinement in a thermonuclear plasma, it’s dominated by unavoidable turbulent fluid motions.
But the ratio of volume (energy production) to surface (losses) of any geometric solid of a given shape always increases with the volume size and a reacting core size large enough to reach a power breakeven always exists. The sun, without a magnetic field, is certainly large enough.
In summary: the tokamak reactor size has to be very large, the size required to maintain the large core temperature needed for the plasma to fuse.
Bottom line
For now the competition has won, the present day renewables are considerably less expensive than a potential nuclear fusion reactor.
My work in fusion coincided  with the Reagan electric sector deregulation, when something similar happened between natural gas and coal fired power stations.
The development of large aviation jet engines made possible efficient, inexpensive, factory produced, electricity generators which proved to be impossible to beat and coal power plant investors went bankrupt to allow for the american industry to take advantage of the newer, less expensive, technology.
It was then too early for the wind and photovoltaic revolution but now they are here to make nuclear fusion obsolete before it has been proven to work.
Cassandra’s legacy by pep

21 Comments on "My view on nuclear fusion, in a nutshell"

  1. dissident on Wed, 21st Mar 2018 7:18 am 

    That is only the case in stupid America where nuclear power has been demonized by Hollywood inspired hysterics. America dropped the ball on nuclear power. Carter actually killed any chance it would have of developing a nuclear reprocessing industry to burn “waste” in fast neutron breeder reactors.

    But corporate America sponsors global warming deniers so that it thinks burning coal, oil or natural gas is perfectly fine.

    Alternatives are a side show.

  2. BobInget on Wed, 21st Mar 2018 10:16 am 

    OUR fusion reactor (SUN) is already big enough
    to power this planet with tech already in hand.

    I’m not against pure science. That’s how we managed to get solar hand-jobs.

  3. dave thompson on Wed, 21st Mar 2018 10:41 am 

    George Carlin summed it all up, to paraphrase;We build these multi million-billion dollar machines and what do we do with them? Boil water, that’s right boil water.

  4. Duncan Idaho on Wed, 21st Mar 2018 11:03 am 


  5. Go Speed Racer on Wed, 21st Mar 2018 11:13 am 

    The best nuclear reaction is a tire-fire.
    All those hydrocarbons reacting with the
    atmosphere producing big clouds of black
    thermo-nuclear smoke.

  6. Go Speed Racer on Wed, 21st Mar 2018 11:15 am 

    Duncan Idaho, see how that curve is sort
    of accelerating faster & faster, CO2 buildup,
    as time goes by?

    Thats cause of me. And my woodstove and
    all the crap we burned up in my backyard.

    Otherwise it would be flat as a ruler.

  7. MASTERMIND on Wed, 21st Mar 2018 11:42 am 

    Mark Anthony Conditt Photos: Pictures of the Austin Bomber

    On the blog, Mark Conditt of Pflugerville, Texas, railed against gay marriage and advocated against the release of a terrorist, calling it “plain dumb.” He advocated against abortion, writing, “First, if a women does not want a baby, or is incapable of taking care of one, she should not participate in activities that were made for that reason. He defined himself in 2012 as conservative.

  8. Antius on Wed, 21st Mar 2018 1:31 pm 

    In a nut shell, a Tokamak would have piss-poor power density. We have spent 60 years developing something that will produce expensive electric power that no one can afford.

    This doesn’t automatically mean that all fusion is waste of time. There are other approaches, i.e inertial confinement.

  9. dave thompson on Wed, 21st Mar 2018 3:17 pm 

    In my tire fire I like some supplements added in for an extra umpf. Things like old running shoes and wads of plastic bags make for a great addition.

  10. JH Wyoming on Wed, 21st Mar 2018 3:38 pm 

    “Boil water, that’s right boil water.”

    Funny yes, but water heated turns to steam which is an expanding force. That expansion is what turns turbines and produces electrical energy.

    It takes a lot of energy to boil water. Ever watch a pot of water on the stove? Come on, come on, boil!

  11. dave thompson on Wed, 21st Mar 2018 4:23 pm 

    “Boil water, that’s right boil water.”

    Yes the irony of it all is sometimes missed.

  12. Outcast_Searcher on Wed, 21st Mar 2018 5:05 pm 

    Earth to mastermindless. Do you have any concept of a topic of conversation?

  13. MASTERMIND on Wed, 21st Mar 2018 6:00 pm 

    Here’s What We Know About The Austin Package Bomber (He was a Millenial Conservative Survivalist Doomer!)

  14. dave thompson on Wed, 21st Mar 2018 7:15 pm 

    It is fascinating to hear the MSM change the “terrorist” narrative to the “shooter” or the “Austin Package Bomber” when a white male is involved instead of some guy named Akkbbar who is called a “terrorist” doing the same thing, namely bombing or spraying bullets into a crowd.

  15. Alpha Male 3000 on Thu, 22nd Mar 2018 3:28 am 

    Tom Whipple was interviewed on the James Howard Kunstler podcast recently.
    He’s still going on about Rossi’s e-cat and all the other dumb ass free energy magic ideas. He really is pathetic.
    Whipple is a flake.

  16. Anonymouse1 on Thu, 22nd Mar 2018 4:14 am 

    dave, that is because you simply don’t understand how modern, professional corporate media in amerika operates. uS media are honor bound to provide context, balance, and not to over-sensationalize events. But the most important thing, is to maintain not just the semblance, but the reality of balanced reporting.

    Thus, all white(ish) dudes, become ‘lone gunmen’, survivalists, neo-nazis, skinheads, mentally disturbed etc. And they almost always act(ed) alone.YMMV. They are seldom, if ever, inspired by Jesus or Yahweh. However, it is perfectly ok to blame this groups actions as being inspired by, computer games, internet porn or, their shitty job and a-hole bosses. All amerikans, and the amerikan media know that no patriotic amerikan would ever go on a shooting rampage just because Allah said so. Nor does this group ever want to get revenge against amerika.

    In order to maintain balanced reporting, all muslim, or even vaguely muslamic types, by contrast, are all blood-crazed Al-qaeda(tm) operatives. Part of a shadowy global cabal of evil, inspired by Al-Bigidadi, the ghost of Saddam Hussein, Vladimir Putin, and Bernie Sanders. This group is, by default, nearly always inspired by something called ‘radical Islam’. That this groups only purpose is to bring death to amerika, and that they plot ceaselessly to achieve this goal, is a widely known and self-evident fact. This group, is always trying to punish amerika for the crime of being amerika, OR possibly, is upset about Syria.

    Besides, It would be unfair, to characterize white, christian(ish) dudes with fully automatic weapons that go on murderous rampages, as ‘terrorists’. If characterized in this manner too often, people might start to get ‘terrorist’ confused with amerikan police and or uS troops. Can’t have that.

  17. Davy on Thu, 22nd Mar 2018 5:43 am 

    “amerika, uS”

    Weasel, does this mean you hate the US a really really lots. Will you ever demonstrate real intelligence?

  18. fmr-paultard on Thu, 22nd Mar 2018 5:51 am 

    Anontard I swear of obsessing about a particular religion but your stupidity provided a window into your sick anti American mind

  19. fmr-paultard on Thu, 22nd Mar 2018 6:03 am 

    Anontard I’m a tard and a blue Republican who switched party to vote for president Paul.
    I’m deep into analysis of media. I’m currently a libtard.
    I read you and juantard like a compass because I know I’m a tard. I know myself therefore I know you

  20. Survival Acres on Thu, 22nd Mar 2018 7:59 pm 

    Stop calling them “renewables”. They’re not and never will be. They still require fossil fuel. If you don’t know this – you’re not worth reading.

  21. dave thompson on Fri, 23rd Mar 2018 10:40 am 

    Anonymouse1, Thanks for the strait forward explanation now I get it.

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