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Compact nuclear fusion reactor is 'very likely to work,' studies suggest
11–20 of 373 posts
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#12“Sparc takes advantage of a newer electromagnet technology that uses so-called high temperature superconductors that can produce a much higher magnetic field, Dr. Greenwald said. As a result, the plasma is much smaller.” So, is this ‘just’ a matter of ITER being obsoleted by improvements in magnet tech before it is completed, or is there more in this design than scaling down ITER?
ITER isn't meant to be a practical design, it's for research. So it's not obsolete just because it's using inefficient magnets.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#13“Sparc takes advantage of a newer electromagnet technology that uses so-called high temperature superconductors that can produce a much higher magnetic field, Dr. Greenwald said. As a result, the plasma is much smaller.” So, is this ‘just’ a matter of ITER being obsoleted by improvements in magnet tech before it is completed, or is there more in this design than scaling down ITER?
The arxiv paper describing the design concept is here:
https://arxiv.org/abs/1409.3540
Some additional features (besides the magnets) that jump out at me:
The reactor vessel has joints to allow it to open up for maintenance access (previous tokamak designs have a reactor vessel that cannot be opened up once constructed, so maintenance inside has to be done through small access ports using remote manipulators).
The external current drive for heating the plasma to ignition looks like it is more efficient than previous designs.
The blanket around the reactor vessel is liquid instead of solid, using a fluorine-lithium-beryllium compound.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#14Having read about tokamaks for thirty years, I'd be curious what specific breakthroughs and innovations have occurred since the 1980s, which lead to the optimism described in the article (which is otherwise frustratingly devoid of detail). It's great there are seven-peer reviewed articles about SPARC, but plasma was not my specialty in physics -- would any specialists care to comment on whether there is anything part…
Superconductors recently got much better in a way that has cubic effect on reactor size.
I know essentially nothing about superconductors, but if they all have essentially zero resistance, what makes one better for this application? I thought the main advantage of high-temp superconductors was using liquid nitrogen instead of helium.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#15> If we can overcome the engineering challenges, this machine will perform as we predict If?
Just like the alcubierre drive!
The "Alcubierre drive" isn't an engineering design for a method of propulsion. It's just a nickname for a certain valid solution of the Einstein field equations.
Like, in classical terms, you can get a repulsive force to come out of Newton's law of gravitation if you plug in a negative mass. But that doesn't mean you've designed a hoverboard.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#16Here's the actual summary:
"Although many significant challenges remain, the company said construction would be followed by testing and, if successful, building of a power plant that could use fusion energy to generate electricity, beginning in the next decade."
In other words, "very likely" in this case means "if several roadblocks are overcome, it might be a net-positive power generator in a decade". Even so, this is still exciting given how anemic advancement in the fusion space has been for 50+ years.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#17Earlier quoted context omitted.
Superconductors recently got much better in a way that has cubic effect on reactor size.
I know essentially nothing about superconductors, but if they all have essentially zero resistance, what makes one better for this application? I thought the main advantage of high-temp superconductors was using liquid nitrogen instead of helium.
They still saturate. High-temperature is nice, but a separate consideration.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#18I never quite understood the math behind power densities in a fusion reactor. In the sun, isn't energy production occurring at something like 100-1000 W/m3? So, if you want to build a multiple MW fusion plant, shouldn't these plants be ridiculously huge compared to, say, a wind turbine rated at a couple of MW? Is the density of the plasma so much higher in a fusion reactor? Also, something else I never grokked, how d…
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#19I never quite understood the math behind power densities in a fusion reactor. In the sun, isn't energy production occurring at something like 100-1000 W/m3? So, if you want to build a multiple MW fusion plant, shouldn't these plants be ridiculously huge compared to, say, a wind turbine rated at a couple of MW? Is the density of the plasma so much higher in a fusion reactor? Also, something else I never grokked, how d…
The density is actually lower than the sun in magnetic confinement fusion (MCF) devices because we can’t squeeze plasma together as hard as the sun’s mass can. Inertial confinement fusion (ICF) can squeeze harder than MCF devices, but has serious unaddressed engineering issues.
The trick is in higher temperature plasma. The sun fuses protium (lone protons). We don’t have the confinement necessary on Earth to do this, so we fuse deuterium (1p+1n) and tritium (1p+2n). This reaction is more energetically favorable and is achievable on Earth. Coupled with giant microwave ovens and clever geometry and electromagnetic tricks, we can make plasmas much hotter (faster moving particles) than the sun can.
Once a plasma is fusing, it emits a lot of heat (alpha heating and fast neutrons). A plasma that requires no external heating (no microwave ovens) is said to be “ignited”. We don’t necessarily need or want ignition to have a successful reactor, but it’s a cool thought.
The major trouble with fusion reactors is keeping particles in the bottle long enough to fuse. Since they’re leaving anyway they have to go somewhere. You can tune vessel geometry and magnetic fields to have designated strike points where most of the plasma will exit confinement. These are called divertors. Run some coolant through your divertors and you have a heat source that can boil water and spin a turbine.
Here my knowledge gets shaky because I know that the fastest particles coming out of a D+T reaction are neutrons (they weigh much less than an alpha particle). Since neutrons are electrically neutral I think they are much less likely to become thermalized (they are not likely to bump into another particle on their way out). I’m not sure how neutron thermalization happens in reactor simulations, but I’m under the impression that it does.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#20I never quite understood the math behind power densities in a fusion reactor. In the sun, isn't energy production occurring at something like 100-1000 W/m3? So, if you want to build a multiple MW fusion plant, shouldn't these plants be ridiculously huge compared to, say, a wind turbine rated at a couple of MW? Is the density of the plasma so much higher in a fusion reactor? Also, something else I never grokked, how d…
You boil water from the neutrons/heat it creates.