We definitely don't "know" that yet. There is for example no experiment that has ever actually tried to extract any energy from the fusion reaction - it's assum

We definitely don't "know" that yet. There is for example no experiment that has ever actually tried to extract any energy from the fusion reaction - it's assumed that the lithium blanket idea will work, but this remains more or less purely theoretical. It's sound science, but we're nowhere near sound engineering there.