I'm rooting for LPP Fusion https://lppfusion.com/ it is a "garage" startup but their approach of using plama instability instead of trying to stabilize it (and the fact they're very close already to net gain https://lppfusion.com/investing-in-lppfusion/our-plan-to-net...) sure sounds great. Garage sized 5MW aneutronic pb11 fusion reactor with direct-to-electricity conversion sure sounds like something we all can use :)
Compact nuclear fusion reactor is 'very likely to work,' studies suggest
361–370 of 373 posts
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#362What are the decommissioning costs? Who will pay for the cost overruns? Just one of the big problems with nuclear is that it is very centralized and takes individual control away from the consumers, who foot the bill through increased taxes and fees, and who could otherwise be using their money to finance options that give them individual control over their energy costs.
This reactor prototype has gotten private investment, because it is both comparatively affordable (hundreds of millions instead of tens of billions of dollars) and it will likely be profitable to license the technology to commercial plant operators. It is unlikely that commercial reactors would require public funding. Decommissioning costs should be negligible because the reactors won't generate radioactive fission b…
Yeah no thanks... at those prices this is still centralized and the costs of corruption and “few decades” decommissioning after a mere 10 years of usefulness will still be passed along through government subsidies and taxation. I’d rather just install solar and have control of these costs myself.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#363Earlier quoted context omitted.
> Gaseous tritium being significantly lighter than air tends to end up in the upper atmosphere That's not how it works. A low molecular weight gas anywhere below the homopause remains well-mixed, and does not separate by molecular weight. On Earth, that's anywhere below 100 km altitude. https://en.wikipedia.org/wiki/Homosphere
Yes, but not what I am referring to. 100 miles is a long way up. A large release of Tritium would first quickly gain altitude while in a high concentration before mixing with other atmospheric gasses. For the same reason as hot air from a fire initially rises as a column. After that it’s going to keep mixing with other atmospheric gasses and spreading through literally billions of cubic miles of atmosphere around the…
The quantity of tritium we're talking about here is about 100 kg. That will rapidly be mixed into air within a short distance of the plant. It's not going to form some coherent blob that can penetrate 100 km of atmosphere.
Once in the troposphere, hydrogen of any kind will be oxidized to water within a couple of years, and then rain out. Of more concern would be accident processes that would cause it to be oxidized immediately. For example, any fire or exposure of hot materials to air would cause associated tritium to react.
This is all unrealistic anyway, since the plant will not have 100 kg of tritium on hand at any time. That's about the amount consumed in a year, but the reactor could not afford to have any substantial amount sitting around, decaying, or else the breeding ratio will be too low.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#364What are the decommissioning costs? Who will pay for the cost overruns? Just one of the big problems with nuclear is that it is very centralized and takes individual control away from the consumers, who foot the bill through increased taxes and fees, and who could otherwise be using their money to finance options that give them individual control over their energy costs.
This reactor prototype has gotten private investment, because it is both comparatively affordable (hundreds of millions instead of tens of billions of dollars) and it will likely be profitable to license the technology to commercial plant operators. It is unlikely that commercial reactors would require public funding. Decommissioning costs should be negligible because the reactors won't generate radioactive fission b…
So you say the chamber has a 10 year lifespan but has been bombarded with radiation for a few decades. Do you see any contradiction there? How does that work.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#365Earlier quoted context omitted.
Yes, but not what I am referring to. 100 miles is a long way up. A large release of Tritium would first quickly gain altitude while in a high concentration before mixing with other atmospheric gasses. For the same reason as hot air from a fire initially rises as a column. After that it’s going to keep mixing with other atmospheric gasses and spreading through literally billions of cubic miles of atmosphere around the…
The quantity of tritium we're talking about here is about 100 kg. That will rapidly be mixed into air within a short distance of the plant. It's not going to form some coherent blob that can penetrate 100 km of atmosphere. Once in the troposphere, hydrogen of any kind will be oxidized to water within a couple of years, and then rain out. Of more concern would be accident processes that would cause it to be oxidized i…
I think we have mostly been talking past each other as I don’t disagree.
Anyway, for a more detailed description of what I was expecting. A least initially it’s going to act just like hot air. Hydrogen’s is 7% the density of air so Tritium is presumably 21% the density of air. Which is similar to air at 2000f without the particulate matter of smoke.
About 100kg should be roughly 500 cubic meters depending on temperature, but a more reasonable limit of ~10kg is still close to 50 cubic meters of gas. If we are talking a sudden release from say a pressurized tank rupturing outside that’s going to from an invisible but mushroom shaped blob and rise. Where a detonations mushroom cloud stops rising as the temperature cools, this thing only slows as it mixes with air which isn’t that fast. The troposphere is only ~8miles up so it’s likely to reach the stratosphere mostly intact.
If we’re talking a venting pipe or something that releases gas more slowly then you get much faster mixing. However, baring the slowest of leaks we are still likely talking going up hundreds of feet at a minimum and more likely miles before it dispersed enough to act like the rest of the atmosphere.
In the absolute worst case, you still get a lot of vertical mixing of the atmosphere from thermals and rapid dispersion from the wind which doesn’t slow down. Within days you’re talking thousands of cubic miles of atmosphere. So, a short term evacuation of those down wind might happen, but they should be able to return in days.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#366Earlier quoted context omitted.
It’s not that simple. Fission’s primary form of shielding is generally large pools of water or other coolant which don’t directly become radioactive. Fusion on the other hand needs to maintain a near vacuum so your pressure vessel is under heavy neutron bombardment. However, small amounts of radioactive materials get dissolved in the fission’s water which the goes on to contaminate the primary coolant loop which incr…
In ARC the containment is not under vacuum, the reactor chamber is surrounded by molten salt of fluoride and lithium, and so the neutrons produced travel into molten salt where they collide and produce tritium. It would help to actually watch the presentations. They’ve solved a lot engineering problems from Routine maintenance to blanket Renewal.
ARC reactors due use high temperature plasma in a near vacuum. “The confinement time for a particle in plasma varies with the square of the linear size, and power density varies with the fourth power of the magnetic field,[2] so doubling the magnetic field offers the performance of a machine 4 times larger.”
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#367Earlier quoted context omitted.
Radionuclides are major contribution to growth of cancer rate. Quote: Radioactive fallout from nuclear weapons tests probably caused 17,000 cancer deaths in the United States in the latter half of the 20th century http://news.bbc.co.uk/2/hi/americas/1849471.stm
"probably" 17000 in 70 years against 700 000 000 total cancer death. Pack it up, boys. And if anything, that shows how bad nuclear weapons are, not the power plants.
The 17000 is US numbers and the US is a long way from 10 million cancer deaths per year. The point stands fine without using misleading numbers.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#368Earlier quoted context omitted.
And what do they do with gamma radiation? As I said at thermonuclear temperatures it contains majority of the energy of the system.
It is absorbed by the FLiBe salt blanket in the ARC design and converted to heat. The hot salt is circulated out and the heat is used for power generation before the salt is recirculated.
Thanks for explaining. Good luck with removing all this gamma radiation from the system before it vaporizes the chamber but not fast enough as to cool the plasma and stop the reaction. I doubt that this sweet spot exists. Thermonuclear bombs exist only because plasma is surrounded by a thick layer of uranium which absorbs and re-emits gamma radiation thus not letting the plasma to cool. And this layer doesn't have to exist for too long. Less than a millisecond is fine to make a big enough bang.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#369Earlier quoted context omitted.
> Anyone could have said similar things about computers in 1953, and been just as correct. Many people could say similar things about software in 2020 and be just as correct. :) The good Admiral may be describing some timeless aspects of engineering, possibly related to the recently discussed observation that reality has a surprising amount of detail: https://news.ycombinator.com/item?id=16184255 . Though, as you say…
I, for one, never have corrosion problems on my software projects.
You jest, but... compatibility is the corrosion of software. The environment and dependencies underlying your software are slowly oxidizing/transforming all the time and unless you pick only the stainless steel of interfaces/system calls, your software will cease to function more quickly than lots of iron objects rust through.
Re: Compact nuclear fusion reactor is 'very likely to work,' studies suggest
#370I wish these people the best, and I really hope they get a working fusion plant soon. That said, I can't resist sharing Admiral Rickover on academic reactors vs practical reactors: Important decisions about the future development of atomic power must frequently be made by people who do not necessarily have an intimate knowledge of the technical aspects of reactors. These people are, nonetheless, interested in what a…
This point is worth noting:
> (3) It is requiring an immense amount of development on apparently trivial items. Corrosion, in particular, is a problem.
The design has molten fluoride salt circulating in a strong magnetic field. Molten salts, unlike molten metals, have low (but not zero) conductivity.
But the motion will still induce a voltage drop across the salt. If the walls are metal, there is the possibility of galvanic corrosion due to this potential. And there's the possibility that radiation could enhance this corrosion.