[ludsan]

I think this is a safe bet. Between Commonwealth Fusion's Arc/Sparc, or General Fusion's spinning glob of hot metal, or TAE systems, or any of the others, I think you have a better than average chance of settling this bet within 20 years.

[pfdietz]

ARC has a power density 40x worse than a LWR's primary reactor vessel.

General Fusion abandoned their first scheme because of at least three showstoppers (vaporization of the liquid metal wall, Richtmyer-Meshkov instability turning the implosion into jets of metal, and stochastic magnetic field lines in the spheromak causing unacceptable loss of energy via electrons to the metal). The new scheme has extremely serious engineering problems (the central pillar will be in a radiation/thermal environment orders of magnitude worse than the walls of ITER, and subject to extreme JxB forces). And they've never produced a neutron, as far as I know.

Rostoker et al. were told 20+ years ago that their p-11B concept couldn't work, for at least eight different reasons.

https://www.researchgate.net/publication/235032059_Comments_...

If I had to bet on any current private fusion effort I'd choose either Zap Energy or Helion.

[nathanathan]

Why is the power density of the ARC/SPARC reactor problematic?

[pfdietz]

Lower power density implies larger size, which implies higher cost. Since the parts outside the reactors themselves (the turbines, generators, heat sink, etc.) will be similar, this means a fusion power plant will cost more to build that a fission power plant.

The other problem is that size is also related to reliability. A fusion reactor will have many more parts than a fission reactor. It will also be much more complex, and operate at higher radiation and thermal stresses. This is particularly important because it is very difficult to repair something that is so radioactive that hands-on access is not possible.