-Sputtering of shielding and every other part of the reactor from fast neutrons. If your reactor is becoming brittle as it’s in operation, and requires constant maintenance, it won’t be operating enough to be cost effective.
-Breeding blankets. If we’re not breeding tritium in the blanket (and no one has been able to sustain a reaction that way yet) then we’re just using fission a lot. Expense becomes an issue, as does radiological issues.
-The plasma diverter is very much an unsolved problem. I can get into more detail here, but in short this is the part of the reactor that “skims” some of the hot plasma off to do the work. The dynamics of very hot, magnetically constrained plasmas still escapes us, and when you throw a rock into that stream, the complexity increases. Current divertes wouldn’t last a day in an operating plant. Disassembling your whole plant every day and reassembling it is a non-starter.
-Containment of plasma at sufficient energies is still something measured in seconds, or fractions of seconds. The usual metaphor is trying to uniformly squeeze a balloon; it will just “squirt” out. For s research reactor a second or two of fusion is an achievement. For power generation it’s nothing.
-Neutron activation of otherwise inert materials means you’re going to have serious radioactive waste. It’s unclear just how dirty D-T fusion would be from soup to nuts, but “pretty dirty” seems like a good bet.
-Tritium penetration.
-Most of the energy produced is in the form of neutrons, and we don’t know how to use that as a source of power. Those neutrons, in addition to destroying the reactor itself and activating materials, represent a loss.
-What we really need is aneutronic fusion through alternative cycles to D-T, like p-p, but that’s a much hotter plasma and no one has a clue how to make it work yet.
-Coolant for a constantly running reactor is a boring, but unsolved problem.
There’s more, but these are the ones most poeple on HN probably are aware of when they dismiss this article.
-Sputtering of shielding and every other part of the reactor from fast neutrons. If your reactor is becoming brittle as it’s in operation, and requires constant maintenance, it won’t be operating enough to be cost effective.
-Breeding blankets. If we’re not breeding tritium in the blanket (and no one has been able to sustain a reaction that way yet) then we’re just using fission a lot. Expense becomes an issue, as does radiological issues.
-The plasma diverter is very much an unsolved problem. I can get into more detail here, but in short this is the part of the reactor that “skims” some of the hot plasma off to do the work. The dynamics of very hot, magnetically constrained plasmas still escapes us, and when you throw a rock into that stream, the complexity increases. Current divertes wouldn’t last a day in an operating plant. Disassembling your whole plant every day and reassembling it is a non-starter.
-Containment of plasma at sufficient energies is still something measured in seconds, or fractions of seconds. The usual metaphor is trying to uniformly squeeze a balloon; it will just “squirt” out. For s research reactor a second or two of fusion is an achievement. For power generation it’s nothing.
-Neutron activation of otherwise inert materials means you’re going to have serious radioactive waste. It’s unclear just how dirty D-T fusion would be from soup to nuts, but “pretty dirty” seems like a good bet.
-Tritium penetration.
-Most of the energy produced is in the form of neutrons, and we don’t know how to use that as a source of power. Those neutrons, in addition to destroying the reactor itself and activating materials, represent a loss.
-What we really need is aneutronic fusion through alternative cycles to D-T, like p-p, but that’s a much hotter plasma and no one has a clue how to make it work yet.
-Coolant for a constantly running reactor is a boring, but unsolved problem.
There’s more, but these are the ones most poeple on HN probably are aware of when they dismiss this article.
Some further reading https://thebulletin.org/fusion-reactors-not-what-they’re-cra...