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This topic is inspired by an observation of Calliban, that fusion (when it is achieved) will be able to produce Tritium in abundance.
Tritium appears to be a useful material for safely delivering heat and small amounts of electricity to billions of Earth citizens, as an alternative to fossil fuel.
The first post in this new topic will be a copy of a post by Calliban in the Fission topic for Tritium production.
(th)
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The following is a quote from the Fission topic devoted to production of Tritium for the home heating and power market.
I note that this post is about consumption of Tritium, so some adjustment is needed, to adapt the post to this new topic.
TH, world lithium mining is over 100,000 tonnes of metal per year.
https://www.reuters.com/markets/commodi … 023-04-21/A 1GWe fusion reactor, will consume ~60kg tritium per year, requiring some 120kg of lithium. If we powered the entire world in this way, it would consume <1% of lithium mined at present. And in a fusion-fission hybrid system, the fusion reaction is providing the neutrons rather than the energy itself. So we don't need anywhere near 1% of present lithium mining to power the world in this way. Lithium is not a limited resource as a nuclear fuel. It is in short supply because idiots need megatonnes of the stuff to produce batteries. But in fusion reactors, a few hundred tonnes a year woukd power the world!
(th)
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I think excess tritium breeding would only work in a fusion-fission hybrid system. A pure fusion system doesn't have enough spare neutrons for this sort of scheme to work. Within a hybrid system, we surround the fusion reaction chamber with rods containing uranium-zirconium alloy. The fast 14-MeV neutrons produced by each fusion reaction will fast-fission the uranium, producing up to five additional neutrons. Some of these will cause secondary fission, but most will be absorbed by uranium-238, which decays into Pu-239. So for each fusion event that takes place, we can expect to generate 10x more power from direct fission and perhaps 4 Pu-239 atoms with which to make nuclear fuel. So for each 17.6MeV of fusion energy we get ~200MeV of direct fission energy yield and enough plutonium to yield 800MeV in downstream reactors.
If plutonium is burned in lithium cooled fast reactors, each fission will yield ~3 neutrons. So four plutonium atoms will yield a total of 12 neutrons, some four of which are used to sustain fission. The other eight are available to support tritium breeding in the lithium coolant. If all of them are absorbed in lithium 6 or lithium 7, we get 8 tritium atoms from each initial fusion event. At least one tritium atom is needed to keep the fusion reaction going. But a maximum of seven additional couod be available for other uses. Due to neutron losses and tritium decay, we can expect lower yields than this. But the overall multiplication could still be substantial.
Last edited by Calliban (2024-01-03 12:40:05)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban re #3
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