Comment by igiveup
4 days ago
While temperature may be in the stellar ballpark, pressure should be much lower. That is fine because we are not trying to do proton-proton fusion (that one is very slow even in a star) but a much easier deuterium-tritium fusion.
So, deuterium needs to be obtained from sea water through distillation and electrolysis - both energy intensive operations. And tritium comes from nuclear reactors.
I have always wondered - assuming that the confinement problem is solved, how does the cost of the fuel compare to fission (or other generation methods?
The energy cost to extract deuterium from seawater is about 1/238000th (0.00004%) the energy released from fusing that deuterium.
Nuclear fusion breeds its own tritium from lithium.
Running a 1 GW thermal fusion reactor for a year would consume $483,000 of deuterium and $1300 of lithium. At 40% conversion efficiency and 5 cents per kwh, the fusion reactor would produce $175 million of electricity in that same year.
For comparison, fuel is about 5% of the cost of electricity from fission, and about 50% the cost from coal.
The energy needed to separate deuterium is many orders of magnitude less than the energy liberated by fusion of the deuterium.
The fuel cost is small compared to fission, but note that even with fission fuel is a small fraction of the total cost, so this doesn't save much.