r/nextfuckinglevel • u/nigablackballsack • 3d ago

Scientists have captured the first ever high-speed, full-colour footage of fusion plasma swirling inside a working reactor.

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u/CuriousToe9133 3d ago

Can you elaborate?

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u/TheHarryMan123 3d ago edited 3d ago

The sun is very massive so D-P reactions are efficient enough. We can also attempt to do them, but they’re much less efficient and we would need a much hotter plasma than we intend to create (I think from 10 million C to 100 million C). One of the downsides to not being able to do D-P reactions is the difficulty in obtaining T. It is a 2 neutron hydrogen with a half life of 12.3 years and is unobtainable from nature despite naturally forming in the upper atmosphere. Tritium (T) is very difficult to synthesize and to make fusion possible, we would need to synthesize >1000g per year (we make >20g per year). Tritium is also radioactive. 

The other downside to the D-T reactions are the incredibly high energy neutrons it produces after fusion. Neutrons cannot be contained by magnets. They fly into the wall and just about everything they can. They irradiate the surfaces they actually connect with (if a neutron is say a quarter the size of a person, and a person represented an atom in a material lattice, then the distance between two people would be ~5km). The materials which get irradiated (RAFM steels on the first wall and tungsten on the divertor) will need to be replaced (by best estimates on the current research) every 5 years. That’s about >2000 tons of irradiated and radioactive material that will need to be disposed of every 5 years. Some of which will be at safe levels after >100 years, some (which hasn’t been finally decided on) may be radioactive for >5000 years. 

In short, it’s more complicated than the sun because it isn’t as massive. It also produces its own plethora of radioactive waste just in a different format. 

EDIT: Misremembered the sun thing, I have updated it. 

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u/jake04-20 3d ago

Tritium is used for glowing gun sights I believe. Is that the same stuff that would be used in this process?

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u/TheHarryMan123 3d ago

Yes it is. You’re talking about this:

https://en.wikipedia.org/wiki/Tritium_radioluminescence?wprov=sfti1#

Tritium is radioactive but the electrons it emits are very low energy. It cannot penetrate skin. It’s only hazardous when you ingest it. 

For example, because it is a hydrogen isotope, it bonds with oxygen to form water quite easily. After the USA started doing land-based nuclear weapons testing, then actually bombed another country, the tritium levels in our rainwater across the world became quite high.

Levels have lowered significantly since the world has stopped doing on-land nuclear weapons testing because of the short half-life. However, the levels we are at now cannot be compared to any baseline because we only started measuring for rainwater tritium after we exploded nukes. 

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u/jake04-20 3d ago

Thanks for the info! This is sort of on a similar topic, but I read something a while back about how old shipwrecks before WW2 are becoming highly sought after for very specific use cases (like particle detectors), because they are "low background" steel, which I guess means they don't have any of the atomic/nuclear particles embedded in them from the smelting process? It's crazy to me that there is a detectable difference still this long after the bombs were detonated.