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It will be easy to use neutrons from DT fusion to get weapon-grade plutonium. This may be easier to police, i.e. "there should be no uranium nowhere near a fusi

It will be easy to use neutrons from DT fusion to get weapon-grade plutonium. This may be easier to police, i.e. "there should be no uranium nowhere near a fusion plant", but that's a much subtler statement. And of course mining for lithium as a fuel is still necessary, so you should perhaps say "no additional mining" or something.

willis936 6y ago
The need for lithium is a valid point. The amount required for fuel is very small though. A 1 GW plant would use more on initial filling than a 30 year lifetime of refilling and even that first filling would be on the order of a metric ton (unverified ballpark, dependent on reactor size, blanket thickness, and plumbing overhead). 80,000 metric tons of lithium are mined each year. We consume about 18 TW. So I estimate that converting all electricity sources to fusion would use about 1/4 of a year’s worth of lithium, but would be enough to make 30 year plants, which would still have most of their lithium left over for recycling/reuse afterwards.
pfdietz 6y ago
And enriching lithium is necessary. A single ARC reactor would use a good fraction of all the 6Li produced for the US thermonuclear weapons program. The tritium produced in a fusion reactor program would make it much easier to engineer high yield fission bombs, via boosting.
rnhmjoj 6y ago
> And of course mining for lithium as a fuel is still necessary, so you should perhaps say "no additional mining" or something. True, but the quantity of lithium required to breed tritium for power generation is ridiculously low. Operating a DEMO-like reactor for 30 years would consume 2 tons of lithium, which is nothing compared to the annual consumption for battery manufacturing (around 30000 tons).
- pfdietz 6y ago
  The blanket of DEMO, if using PbLi eutectic, would require 52 tonnes of 6Li. In addition to the raw lithium itself, building even a single reactor like DEMO would require maturing a new 6Li separation technology (the old one caused unacceptable mercury pollution) and industrializing it. https://www.sciencedirect.com/science/article/pii/S092037961930835X https://www.sciencedirect.com/science/article/pii/S092037961...
nickik 6y ago
You can not actually police that sort of thing. Thorium is literally everywhere in the earth core. You could basically dig hole right next to your fusion reactor and mine Thorium right out of it, expose it to neutrons and create Uranium-233.

willis936 6y ago

The need for lithium is a valid point. The amount required for fuel is very small though. A 1 GW plant would use more on initial filling than a 30 year lifetime of refilling and even that first filling would be on the order of a metric ton (unverified ballpark, dependent on reactor size, blanket thickness, and plumbing overhead). 80,000 metric tons of lithium are mined each year. We consume about 18 TW. So I estimate that converting all electricity sources to fusion would use about 1/4 of a year’s worth of lithium, but would be enough to make 30 year plants, which would still have most of their lithium left over for recycling/reuse afterwards.

pfdietz 6y ago

And enriching lithium is necessary. A single ARC reactor would use a good fraction of all the 6Li produced for the US thermonuclear weapons program. The tritium produced in a fusion reactor program would make it much easier to engineer high yield fission bombs, via boosting.

rnhmjoj 6y ago

> And of course mining for lithium as a fuel is still necessary, so you should perhaps say "no additional mining" or something. True, but the quantity of lithium required to breed tritium for power generation is ridiculously low. Operating a DEMO-like reactor for 30 years would consume 2 tons of lithium, which is nothing compared to the annual consumption for battery manufacturing (around 30000 tons).

pfdietz 6y ago
The blanket of DEMO, if using PbLi eutectic, would require 52 tonnes of 6Li. In addition to the raw lithium itself, building even a single reactor like DEMO would require maturing a new 6Li separation technology (the old one caused unacceptable mercury pollution) and industrializing it. https://www.sciencedirect.com/science/article/pii/S092037961930835X https://www.sciencedirect.com/science/article/pii/S092037961...

nickik 6y ago

You can not actually police that sort of thing. Thorium is literally everywhere in the earth core. You could basically dig hole right next to your fusion reactor and mine Thorium right out of it, expose it to neutrons and create Uranium-233.