The significant issue is that DT fusion reactors are very large compared to fission reactors. If we look at gross nuclear power output per unit volume, comparing a fusion reactor to a PWR primary reactor vessel, the comparison is stark. ITER, for example, has a power density 400x worse than a PWR; the 2014 ARC design is 40x worse.
This large size has devastating implications. The nuclear island of a fission power plant is maybe 12% of the cost of the plant. Increase that cost by an order of magnitude and you've doubled the cost of the plant. Commercial nuclear power is already not competitive; double the capex and it becomes ludicrously uncompetitive.
If someone presents you a fusion proposal, the first thing you should ask is "what's the volumetric power density of your reactor?"
If you look at the arguments purporting to show DT fusion could have a chance they do things like assume they can build everything for 2x the cost of materials. Yeah, good luck with that, especially when that cost estimation technique would give wildly low results if you applied it to fission power plants, which are much less complex.
As I see it, there's only a couple of ways fusion might make it. The first is an approach that makes minimizing reactor size the primary goal. This would involve very small plasma configurations and one where all plasma-facing surfaces are covered with thick layers of flowing liquid lithium so areal power density can be very high, at least an order of magnitude higher than most concepts. Among DT efforts, only Zap looks like it might have a chance here (but there are parts on one end of the reactor that are still exposed to neutrons, unshielded.) The experience with liquid sodium in fission reactors should give one pause about making this work, though.
The other approach would be to avoid non-nuclear parts than fission power plants have by exploiting direct conversion of plasma energy to work, so the apples-to-apples comparison of heat sources does not apply. Helion is the front runner here, using more advanced fuels that put most of their energy into the plasma, not into neutrons. I consider Helion the least dubious of all current fusion efforts.
This large size has devastating implications. The nuclear island of a fission power plant is maybe 12% of the cost of the plant. Increase that cost by an order of magnitude and you've doubled the cost of the plant. Commercial nuclear power is already not competitive; double the capex and it becomes ludicrously uncompetitive.
If someone presents you a fusion proposal, the first thing you should ask is "what's the volumetric power density of your reactor?"
If you look at the arguments purporting to show DT fusion could have a chance they do things like assume they can build everything for 2x the cost of materials. Yeah, good luck with that, especially when that cost estimation technique would give wildly low results if you applied it to fission power plants, which are much less complex.
As I see it, there's only a couple of ways fusion might make it. The first is an approach that makes minimizing reactor size the primary goal. This would involve very small plasma configurations and one where all plasma-facing surfaces are covered with thick layers of flowing liquid lithium so areal power density can be very high, at least an order of magnitude higher than most concepts. Among DT efforts, only Zap looks like it might have a chance here (but there are parts on one end of the reactor that are still exposed to neutrons, unshielded.) The experience with liquid sodium in fission reactors should give one pause about making this work, though.
The other approach would be to avoid non-nuclear parts than fission power plants have by exploiting direct conversion of plasma energy to work, so the apples-to-apples comparison of heat sources does not apply. Helion is the front runner here, using more advanced fuels that put most of their energy into the plasma, not into neutrons. I consider Helion the least dubious of all current fusion efforts.