this post was submitted on 10 Feb 2024
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In this context, the "energy that they put in" only counts the heating of the plasma. It does not include the energy needed to run the rest of the reactor, like the magnets that trap the plasma. If you count those other energy needs, about an order of magnitude improvement is still required. Possibly more, if we have to extract the energy (an incredibly hard problem that's barely been scratched so far).
So yeah, it's nice to see the progress, but the road ahead is still a very long one.
I feel like the big scary problem is capturing the heat. The proposed method I've seen involves a beryllium "blanket" that captures the heat to send it off to a boiler. The problem is beryllium is quite expensive and quite limited in availability. And in fact we may only have enough beryllium (in the world) for a dozen or so reactors. But it's worse, because these blankets absorb high energy neutrons, and become radioactive over time. And that means two problems, you need to replace the blanket and you need to dispose of radioactive waste.
When you put all that together, I just think "shouldn't we stick with fission power?"
Someone please correct me if I'm wrong, but isn't the problem that Uranium has a half-life of a couple hundred million years, while the half life of beryllium is less than a second?
Only Beryllium-10 has a long half-life for beta decay. Adding another neutron drops that back down to a few seconds and additional neutrons drop it back to a fraction of a second. So as long as that specific type of Beryllium isn't used, it would be fine, right?
Edit: https://www.thoughtco.com/beryllium-isotopes-603868
Those quick half-lives decay right away, losing a neutron, right? So that Berillium-11 just decays back into Berillium-10.
The problem is that the blanket is constantly absorbing neutrons from the fusion reactions, that's it's job. So despite using simple berillium 5 to build your blanket, you end up with these heavy isotopes over time, and because the heavier ones quickly decay into lighter ones, you basically end up with a whole lot of berillium-10.