7 ms·
"Non Radioactive Fuel" is technically correct. But. The fusion produces neutrons.[1] That means that at least some parts of the infrastructure can't avoid bec
by fghorow 6y ago
"Non Radioactive Fuel" is technically correct.
But.
The fusion produces neutrons.[1] That means that at least some parts of the infrastructure can't avoid becoming radioactive. Decommissioning -- at the very least -- is still a problem.
Any actual nuclear physicists want to chime in here?
[1]Yes, the concept of "Aneutronic fusion" exists: <https://en.wikipedia.org/wiki/Aneutronic_fusion https://en.wikipedia.org/wiki/Aneutronic_fusion>. But read the parts about the required conditions being much more extreme than D-T fusion.
- Retric 6y agoDeuterium is a stable isotope, but Tritium’s half life is only 12.32 years making it quite radioactive. There is significant effort put into using lithium blankets to create tritium at which point arguably the fuels are lithium and deuterium. But that’s also going to require irradiate the relevant equipment.
- pleasedontbanme 6y agoTritium is worth $30,000 a gram.
- Retric 6y agoYea, though only about 400grams are used worldwide mostly for self illuminating signs. Which adds up to 12 million dollars per year of demand resulting in such high prices. At scale it’s significantly cheaper to produce.
- sergeykish 6y agoLithium carbonate Li2CO3 is worth $6.75/kg https://www.fastmarkets.com/commodities/industrial-minerals/lithium-price-spotlight https://www.fastmarkets.com/commodities/industrial-minerals/...
- fghorow 6y agoQuite right. I stand corrected w.r.t. my inaccurate statement about Tritium.
- pfdietz 6y agoTritium is in the fuel, and it's quite radioactive. A 1 GW(e) reactor would burn enough tritium in a year that, if that quantity were to be released into the environment, it could contaminate 2 months worth of the flow of the Mississippi River above the legal limit for drinking water. Tritium containment at a fusion reactor will have to be damned near perfect. This will be a major problem, as tritium permeates through all sorts of things (for example, plastic seals on containment penetrations cannot be used).
- Retric 6y agoGaseous tritium being significantly lighter than air tends to end up in the upper atmosphere not contaminate the local environment. As it’s beta decay you could have a glass glass jar of the stuff on your desk for years without issue. Unlike fission power plants there isn’t going to be years worth of the stuff on site. For one thing 5% of the stuff decays sitting around so you want a tight loop of production to consumption. Further, the reactor is holding low density plasma so there is very little inside at any one time.
- pfdietz 6y ago> 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 https://en.wikipedia.org/wiki/Homosphere
- Retric 6y agoYes, 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 globe because unlike fallout it can stay in the atmosphere. As a beta emitter it’s blocked by just a few feet of atmosphere thus rendering the bulk of it harmless. Eventually, some will combine with oxygen and end up as water, but again most of that just ends up in the ocean.