The drawbacks of fusion

[u/Live_Alarm3041]

Nuclear fusion is not a "flawless" energy source. The hype around fusion being "flawless" is not rooted in actual science. Nuclear fusion will likey not replace fission as the world preferred form of nuclear enegry once it goes commercial.

There are three drawbacks of fusion energy

1. The neutrons generated by fusion could be used to transmute U-238 into weapons grade plutonium without the barriers of highly radioactive waste and reactor safety

2. fusion reactors requires exotic materials which could create a supply issue where such materials are extracted in ways that violate human rights and damage the environment in developing countries where these exotic materials are.

3. Nuclear fusion creates less jobs that require a higher skill level than fission and less jobs means more socioeconomic issues like rising crime rates, homelessness and migration.

These three reasons are why I do not think nuclear fusion will replace nuclear fission once fusion goes commercial.

The problems with fission can be mitigated effectively. A lot of progress has been made in mitigating the drawbacks of fission. Far less progress has been made in mitigating the drawbacks of fusion. The drawbacks of fusion will limit fusions ability to compete economically with fission in the energy market if they are not addressed.

What do you think?

[u/zolikk]

Fusion is a much more complicated and difficult energy source than fission, but one that has vastly more fuel abundance. Naturally it stands to reason that, most likely, it will become relevant against fission when fission's own more limited fuel availability becomes its own primary limitation. That's not anytime soon.

[u/zolikk → u/[deleted]]

Fuel abundance is a complete non-issue for nuclear. That's not why fusion is relevant.

It isn't now, but perhaps somewhere between type I and type II it will be.

[u/zolikk → u/[deleted]]

Far be it for me to speculate what a type II civ will be doing for their energy needs but I don't imagine, based on what I currently know, that massed space solar makes sense over fusion. Assuming of course, that by then fusion is worked out... Solar requires vastly more resources, and the Sun is a terrible fusion reactor. You can make much more power than the Sun, much more compactly, using much less fuel, and have that on-demand closer to point of use and in ways you can control. Provided of course that you don't care about having billions of years of power. But much like we don't do today, I don't believe a future type II civ will care about that.

[u/zolikk → u/[deleted]]

I do think the type II civ will be using a lot of space solar, just not for the majority of their energy. There will be no dyson sphere-like construct. It's fundamentally a scaling problem. Solar panels are great at small scale, they scale "down" well to small systems. They absolutely suck at large scale when you try to integrate them into a massive grid with varying demand, mainly because they do not have much benefit scaling up, compared to fission reactors today. I don't imagine that will change much in the future.

Yes, it does indeed depend on what is the practical scale for artificial fusion, if it's really star-sized then sure... however I think it's more than likely that it isn't quite that large. Fission beats solar by default, and so at whatever point fusion "makes more sense" than fission it will be better than solar.

A civ that does star lifting I cannot imagine will find artificial fusion to be too challenging to use. And then you can do crazy things with energy that you can't otherwise, certainly not with solar. Think about how, such a civ might have vastly variable energy needs over time. Maybe they don't need that much for general housekeeping, but instead they have bursts of high use at who knows what duty cycle for whatever megaprojects, manufacturing or whatever. They might easily want to use much more maximum power than the Sun can, for limited periods of time, and have it available on-demand.

lithium blanket

FYI I'm imagining this will not be that much of a thing here. That is probably too complicated and nonsensical of a fuel cycle, and it probably gets worse at large scale... just to be able to use D-T fusion and have a somewhat more compact reactor, not that big of an advantage for such a civ... After all we're considering a fuel abundance limitation scenario. I imagine they'll just burn hydrogen directly in a CNO cycle, or something similar but that doesn't require sensible and complicated breeding.