The fact is, there is no reasonable expectation of ever getting viable commercial power from a tokamak-style fusion reactor. The density of energy production, in watts per cubic meter, is so low that an impractically large volume of confined plasma would be needed, requiring a reactor many times larger than a fission plant for the same power output. But fission-driven power is itself too expensive to produce to justify deploying on its own merits.
Furthermore, since the power must be extracted by intercepting high-energy neutrons after they have blasted through the plasma focusing apparatus, such a plant would destroy its most expensive parts in a short time, requiring frequent rebuilding -- by robots, because of induced radioactivity at the work site.
There has never been any expectation of practical commercial power resulting from plasma-confinement thermal-neutron fusion projects. Their only plausible budgetary justification is as a jobs program for high-neutron-flux physicists. They are called for by military policy as a population to draw personnel from for weapons work.
Coal has always been cheaper than fission. Solar and wind power costs are much less, and continue falling; and numerous viable energy storage methods, all demanding no fundamental research -- gravity (solid and aqueous), underground and underwater compressed air, LH2, ammonia, methane from captured CO2, even powdered iron -- vie only for which will end up cheapest to deploy and operate.
If a commercial reactor were ever built and made to work, it would take many decades just to break even on the money already spent to date, before bevinning to pay down its own construction -- even presuming it could find a market for its output. In practice, without continued public subsidy as long as it operated, its debt would continue to grow indefinitely.
The only responsible course for the future is to cancel all publicly funded thermal-neutron fusion work, immediately.
I think there is a slim chance that nuclear could remain relevant. The key would be greatly reducing the cost of the non-nuclear side of the power plant. Perhaps the best approach would be replacing large steam turbines with far more compact supercritical CO2 turbines. This would require temperatures somewhat higher than from PWRs. And this (not thorium, not waste destruction, nor really even safety) is perhaps the best argument for molten salt reactors.
Nukes remain potentially relevant for space systems.
For example, in the cloud tops of Venus, an air turbine may be constructed from a very large, balloon-supported polypropylene fabric tube with an air turbine on top as its only moving part, and a no-moving-parts naked atomic pile suspended near the bottom, heating air directly -- by neutrons colliding with atmospheric CO2 -- that rises to drive the turbine. Some of the air would become radioactive, but so what?
In free-fall, a reactor at the end of a long-enough tether would present no risk of environmental contamination or user safety, and so could dispense with both the containment vessel and shielding. Even there, though, pB seems a more atractive goal than thermal neutrons, because destroying your plasma focus apparatus every few months would get tedious.
Nukes are absolutely needed for any deep space missions beyond Mars. Unless you're going with laser propulsion or solar sails.
Moreover, if you can fit a compact reactor (fission or fusion) on a space ship, then you can run nuclear thermal (ISP >800), or nuclear ion engines with extreme efficiency. (>15,000 ISP!) Considering NASA's Kilowatt reactor weights 2tons, assume a dry mass of 10t and a payload of 2%, you end up with a 500t ship (wow, do we even have 498 metric tons of xenon in the world?), but with a delta-v of 500,000 m/s. That gets you to Pluto flyby in 99 days. (I didn't count the Kilowatt reactor fuel weight, I'm not sure how much uranium is needed for a 15,000 Isp burn, I was just interested how much delta-v 15,000 Isp buys you.)
SpaceX starship, if it works, could launch this in about 4 refuelings. (>100-125t to LEO)
Space applications cannot justify any significant use of nuclear power on Earth. To the extent space uses are valuable, the relevant stakeholders can pay for it.
Nuclear reactors would be wonderful for use on Titan, btw. Simple open Brayton cycle systems would be highly effective at quite reasonable core temperature.
Furthermore, since the power must be extracted by intercepting high-energy neutrons after they have blasted through the plasma focusing apparatus, such a plant would destroy its most expensive parts in a short time, requiring frequent rebuilding -- by robots, because of induced radioactivity at the work site.
There has never been any expectation of practical commercial power resulting from plasma-confinement thermal-neutron fusion projects. Their only plausible budgetary justification is as a jobs program for high-neutron-flux physicists. They are called for by military policy as a population to draw personnel from for weapons work.
Coal has always been cheaper than fission. Solar and wind power costs are much less, and continue falling; and numerous viable energy storage methods, all demanding no fundamental research -- gravity (solid and aqueous), underground and underwater compressed air, LH2, ammonia, methane from captured CO2, even powdered iron -- vie only for which will end up cheapest to deploy and operate.
If a commercial reactor were ever built and made to work, it would take many decades just to break even on the money already spent to date, before bevinning to pay down its own construction -- even presuming it could find a market for its output. In practice, without continued public subsidy as long as it operated, its debt would continue to grow indefinitely.
The only responsible course for the future is to cancel all publicly funded thermal-neutron fusion work, immediately.