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Comment by japanuspus | Hacker News Reader

Only replying to this low-effort response because it is currently the top response.

> The energy density of the plasma is necessarily so low that a useful power plant would be absolutely monstrous.

The size of e.g. the SPARC proposal is so low that you could fit on the order of 10 units of 50 MW within the tower of one 10 MW wind turbine [0].

> ... Rather, it is a jobs program for high neutron flux physicists ...

You do realize that many current effort in fusion power are privately funded, right?

[0]: https://www.cambridge.org/core/journals/journal-of-plasma-ph...

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The power density of the ARC proposal (volume of the magnets and everything inboard of that) is some 40x worse than the volumetric power density of a commercial PWR (volume of the primary reactor vessel + core). This is much better than ITER, but still much worse than existing fission reactors.

I'd characterize as "low effort" the shallow dismissal of very real issues facing fusion.

PWRs are some of the highest power-density energy sources that exist, though (which is why they're so popular on submarines). 40x less than a PWR is not low.

I agree that ITER is an overwrought boondoggle, however.

Fusion and fission plants will be similar outside the nuclear island. So if you take a small fission reactor, and replace it with a much larger, much more complex, fusion reactor, you're going to increase the cost of your power plant.

How’s it fare against a gas turbine power plant? Because that’s what it would actually replace, not a PWR.

Since a fusion or fission reactor is a source of thermal energy, and the power density there does not include the volume of external heat exchangers or turbines, the proper comparison is to the COMBUSTOR of a gas turbine. Gas turbine combustors have thermal power densities of 100 MW/m^3 or higher, some five times the power density of a PWR primary reactor vessel and 2000x the power density of ITER.

Gas turbines also have large advantages in the rest of the plant, though. Fusion plants or PWRs will require at least two sets of heat exchangers (one for transfering heat to the external cooling water, and one for isolating the nuclear coolant from the fluid going through the turbines). Simple cycle gas turbines (without regeneration) don't require any heat exchangers, and combined cycle plants get most of their power from the topping cycle, so the heat exchangers on the bottoming cycle are smaller.

The cost of a simple cycle turbine power plant is around $400/W, maybe 5% of the capital cost of a fission power plant.

$400/kW, I meant

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