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I agree with all this. People make two big mistakes when evaluating fusion: 1. The fuel is free to cheap, depending on the fuel; and 2. Stars can do it so sur
by jmyeet 2y ago
I agree with all this. People make two big mistakes when evaluating fusion:
1. The fuel is free to cheap, depending on the fuel; and
2. Stars can do it so surely we can.
So let's consider a mythical plant that costs $30B to build, has a lifetime of 30 years, costs $3B/year in maintenance and produces 1000MW of power. And the fuel. is free. Is the electricty free? Not even close. That's ~8.8GWh per year. No plant runs at full capacity 24x7 so let's call it 4TWh. That's about $1/kWh. That's ludicrously uneconomical. Of course you can throw in vastly different numbers and vastly different results but the main point is that fuel cost is a non-issue.
And as the article points out, in a D-T reactor, you still need to produce tritium because it's basically not naturally occurring in a way that can be gathered. That means a fission breeder reactor. That fuel isn't free.
Second, "the Sun does it" misses the point. As the article correctly points out, damage from neutrons ("neutron embrittlement") is a huge problem. Beyond that, it's a huge problem because every high-speed electron that escapes the plasma is energy loss from the system.
Stars use gravity for containment.
- jcarrano 2y agoAlso, the power density of the sun is extremely low. A rotting orange produces more power per unit mass.
- pfdietz 2y ago> And as the article points out, in a D-T reactor, you still need to produce tritium because it's basically not naturally occurring in a way that can be gathered. That means a fission breeder reactor. That fuel isn't free. It doesn't require a fission breeder reactor. All DT schemes imagine a blanket where they breed their own tritium, and produce enough to start additional DT reactors. Some imagine a startup phase where they run just on DD for a few months, with Q < 1, to make enough tritium to start up. If fission had to be used to make all the T then DT fusion would be a complete nonstarter economically.