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AI for real-time fusion plasma behavior prediction and manipulation

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Re: AI for real-time fusion plasma behavior prediction and manipulation

#31

Neutrons make hardware radioactive. Many on Hacker News fantasize about fusion (not fission) reactors. These fusion reactors will be an intense source of fast neutrons. All the hardware in a fusion reactor will become radioactive. Not to mention the gamma rays. If you have to deal with radioactive materials, why not just use fission? After 70 years of working with fission reactors, we know how to build and operate th…

Fission is "simple" but it seems every designer in the XX century made it as much complicated as possible for not so great reasons (and don't even get me started on the "let's not use breeding reactors" stuff) Cooling that requires pumps, as an example, should be a non-starter in new projects.

The designs are complicated, well, because in practice it's not as simple as "put these rocks next to each other and they get hot". When you put the rocks next to each other, they not only get hot, but also emit some nasty radiation that has to be shielded. And if the rocks get a liiiitle bit too close together, they might explode, which leads to huge headaches for everyone involved, so you'd better make sure that doesn't happen...

Re: AI for real-time fusion plasma behavior prediction and manipulation

#32
post #9

>Nuclear power plants are largely considered as one of the most reliable sources of energy. Inside the plants, reactors use fission to heat water into steam, which is then used to spin turbines and produce carbon-free electricity. However, nuclear fission produces nuclear waste, which requires great amounts of regulation for safe storage and disposal. This is an odd angle to highlight. The risk of long-lived nuclear…

It is not true that coal is more radioactive than spent nuclear fuel. It's very much the opposite: SNF is 10^11 times more radioactive than coal per kilogram, or 10^6 times more radioactive per energy unit.

Per the EPA, US coal has, at the high end, 10^3 Becquerel/kg of natural radioactivity [0].

Spent nuclear fuel has 3 million Curies/tonne (33 MWd/kg burnup fuel, at the age of 1 year) [1], which is equal to 10^14 Bq/kg. Since 33 MWd/kg is an energy density a factor of 10^5 greater than that of coal, the normalized ratio of [radioactivity]/[energy] is 10^6.

The graph in [1] depicts the decay of SNF activity on a log-log scale. It reaches the same radioactivity level as coal (again, normalized by energy output) at about 1 million years.

I'm fairly confident I know the origin of this social media-popular pseudofact. It's this poorly-titled Scientific American [2] article from 2007, which is about the (negligible) amount of radioactivity that nuclear plants release into the environment in the course of routine operation. It is *not* about spent fuel. It's a fair—but nuanced and easy to grossly misunderstand—point that coal power plants throw up all their pollution into the environment in routine operation, while nuclear plants, by default, contain theirs.

[0] https://www.epa.gov/radiation/tenorm-coal-combustion-residua... ("TENORM: Coal Combustion Residuals")

[1] https://www.researchgate.net/figure/n-situ-radioactivity-for... ("Impact of High Burnup on PWR Spent Fuel Characteristics" (2005))

[2] https://www.scientificamerican.com/article/coal-ash-is-more-... ("Coal Ash Is More Radioactive Than Nuclear Waste [sic]" (2007)

Re: AI for real-time fusion plasma behavior prediction and manipulation

#33

Neutrons make hardware radioactive. Many on Hacker News fantasize about fusion (not fission) reactors. These fusion reactors will be an intense source of fast neutrons. All the hardware in a fusion reactor will become radioactive. Not to mention the gamma rays. If you have to deal with radioactive materials, why not just use fission? After 70 years of working with fission reactors, we know how to build and operate th…

> Neutrons make hardware radioactive

True, but two caveats:

1. Neutron bombardment due to fusion makes hardware radioactive for less than 10 years, which isn't great but does not compare to fission waste;

2. Some fusion processes don't emit neutrons (aneutronic fusion). As I understand it, these processes aren't as efficient, but there is the possibility of a tradeoff between generation of ratioactive waste vs. efficiency.

Re: AI for real-time fusion plasma behavior prediction and manipulation

#34

TIL: it's not just buzzwords. https://en.wikipedia.org/wiki/Fusion_power#Machine_learning

My advisor also worked on this ML project for estimating electron density and temperature within tokomaks: https://www.cs.wm.edu/~ppeers/showPublication.php?id=Ozturk:...

Technically that counts as "AI in nuclear fusion", but it isn't any sort of breakthrough. In almost every case the effects of AI are marginal. Not zero exactly, but nowhere near the breathless hype.

Re: AI for real-time fusion plasma behavior prediction and manipulation

#35

TIL: it's not just buzzwords. https://en.wikipedia.org/wiki/Fusion_power#Machine_learning

When I used to work in grid computing almost 20 years ago, we were already running fusion experiments, realtime streaming the data to the grid, which would rapidly analyze it and compute some new parameters for the next run (I think they had a 20 minute downtime). I don't think it was considered machine learning at the time, though (and was certainly not deep learning as we practice it today).

Re: AI for real-time fusion plasma behavior prediction and manipulation

#36

Neutrons make hardware radioactive. Many on Hacker News fantasize about fusion (not fission) reactors. These fusion reactors will be an intense source of fast neutrons. All the hardware in a fusion reactor will become radioactive. Not to mention the gamma rays. If you have to deal with radioactive materials, why not just use fission? After 70 years of working with fission reactors, we know how to build and operate th…

The only hard part of dealing with nuclear waste is the social aspect. If not for that, you can simply and safely dump it into the ocean. Water is excellent shielding and the amount of uranium/etc already dissolved in sea water is absurd. Put it in a stainless steel vessel first if you want most of it to decay before coming into contact with the water, but that's not even necessary.

Re: AI for real-time fusion plasma behavior prediction and manipulation

#37
> Nuclear power plants are largely considered as one of the most reliable sources of energy.

Reliable how?

I mean we first have the issue is we've never built one so how we can judge reliability?

I assume the author is alluding to the apparent abundance of fuel for nuclear fusion. This is and isn't true. Obviously hydrogen (particularly protium) is abundant. Deuterium is relatively abundant, even at ~150ppm. Tritium needs to be produced in a nuclear reactor.

Current hydrogen fusion models revolve around dueterium-tritium ("D-T") fusion. This is because you need to neutrons to sustain the reaction but that presents two huge problems:

1. Because everything is at such high temperature, you eject fast neutrons. This is an energy loss for the system and there's not really a lot you can do about it; and

2. Those free fast neutrons destroy your containment vessel and reactor (as do free Helium nuclei aka alpha particles).

And then after you do all that you boil water and turn a turbine just like you do in a coal or natural gas plant.

So "reliable" is an interesting and questionable claim.

There are other variants like so-called aneutronic fusion (eg Helium-3, which is far from abundant) and those aren't really "neutron free". They're really just "fewer neutrons".

So what about containment? Magnetic fields can contain charged particles and you have various designs (eg tokamak, stellarator) and that's what the AI is for here I guess.

But the core problem is to make this work you superheat the plasma so you're dealing with a turbulent fluid. That's inherently problematic. Any imperfection or failure in your containment field is going to be a problem.

Stars deal with this by being large and thus using sheer size (ie neutrons can't go that far without hitting another nucleus) and gravity.

It increasingly seems to me that commercial nuclear fusion power generator is a pipe dream, something we simply want to be true. I'm not convinced it'll ever be commercially viable.

I'd love to be proven wrong and certainly won't stop anyone from trying.

In a way AI is the new blockchain. Go back a few years and you had a gold rush of startups attaching every idea to "blockchain" to build hype. That's what AI is now. I don't think it fundamentally changes any of the inherent problems in nuclear fusion.

Re: AI for real-time fusion plasma behavior prediction and manipulation

#38

TIL: it's not just buzzwords. https://en.wikipedia.org/wiki/Fusion_power#Machine_learning

Yeah machine learning is more or less just very complex application of control theory techniques and notably it is usually done by people without formal control theory backgrounds.

Super useful for control applications but obviously you really want to know control theory so that you aren't just using ML to throw darts at a wall.

Re: AI for real-time fusion plasma behavior prediction and manipulation

#39

Neutrons make hardware radioactive. Many on Hacker News fantasize about fusion (not fission) reactors. These fusion reactors will be an intense source of fast neutrons. All the hardware in a fusion reactor will become radioactive. Not to mention the gamma rays. If you have to deal with radioactive materials, why not just use fission? After 70 years of working with fission reactors, we know how to build and operate th…

> Neutrons make hardware radioactive True, but two caveats: 1. Neutron bombardment due to fusion makes hardware radioactive for less than 10 years, which isn't great but does not compare to fission waste; 2. Some fusion processes don't emit neutrons (aneutronic fusion). As I understand it, these processes aren't as efficient, but there is the possibility of a tradeoff between generation of ratioactive waste vs. effic…

Aneutronic fusion is even harder than regular fusion so it's not a realistic solution in any near-term scenario.

Re: AI for real-time fusion plasma behavior prediction and manipulation

#40
post #37

> Nuclear power plants are largely considered as one of the most reliable sources of energy. Reliable how? I mean we first have the issue is we've never built one so how we can judge reliability? I assume the author is alluding to the apparent abundance of fuel for nuclear fusion. This is and isn't true. Obviously hydrogen (particularly protium) is abundant. Deuterium is relatively abundant, even at ~150ppm. Tritium…

Nuclear as in fission power plants :-)
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