I'm not a specialist but here is what I think I know (I'm talking with the point of view of a Frenchman, who consumes most of his electricity from (fission) nuclear power plants):

1/ Uranium is not a renewable (quite the opposite), needs to be mined and treated (which is expensive and very polluting), and not present at the required concentrations in most of the world (this creates geopolitical issues).

2/ Fission nuclear plants require a well functioning [state|government], and no war. A (conventional) strike on a nuclear power plant can have devastating and lasting consequences. Even a random terrorist group can do that.

3/ I've read that "Ultimately, researchers hope to adopt the protium–boron-11 reaction, because it does not directly produce neutrons, although side reactions can" (that's a wikipedia quote, but I've read that already from other sources).

So fusion doesn't seem the best option on the short term, because of the complexity and cost of research, but definitely seems to be the very best option in the middle and long term. And we made the short term catastrophic choice already with coal and oil, it'll be good to learn from that.

Or maybe I'm totally wrong.

> Neutrons make hardware radioactive

True, but two caveats:

1. Neutron bombardment due to fusion makes hardware radioactive for less than 10 years, which isn't great but does not compare to fission waste;

2. Some fusion processes don't emit neutrons (aneutronic fusion). As I understand it, these processes aren't as efficient, but there is the possibility of a tradeoff between generation of ratioactive waste vs. efficiency.

> we know how to build and operate them at 95%+ efficiency. Fission can provide all the power we need.

I am not sure what do you mean by 95%+ efficency here. But if you are talking about the entire process of getting the energy/power from the nuclear reactor this is not possible. You are still limited by carnot cycle. Even the most advanced reactors like HTGRs [1] operate with efficiency about 45%.

If you have some other definition of efficiency than the standard then it would be good if you define that.

[1] https://en.wikipedia.org/wiki/High-temperature_gas-cooled_re...

You posted this same comment[0] nearly word for word a month ago. Why is that? Not sure why, but “many on hacker news fantasize about fusion (not fission)” stuck in my head.

[0] https://news.ycombinator.com/item?id=41677250

Thats least of your problem imo. Neutron corrosion is bigger problem. There is trick to use Lithium shielding, with create Tritium needed for Fussion. But not sure how effective it is, especially for long term reactor lifetime. Those reactors are very expensive, not sure if its worth to shut it down every year and replace entire Li shielding...

> Many on Hacker News fantasize about fusion (not fission) reactors. These fusion reactors will be an intense source of fast neutrons. All the hardware in a fusion reactor will become radioactive. Not to mention the gamma rays.

My personal ideology about fusion aside, it should be mentioned there is an easy fix for these radiation problems. What you do is put the fusion reactor in space, and collect the energy with specialized fusion energy collectors on Earth (or in space). They'll have the problem that they aren't able to collect energy if the fusion reaction is below the horizon, so this design is imperfect, but having the fusion reaction take place in space means you don't have to deal with a radioactive casing by not including it in your fusion reaction space station design because you don't need any. Just a bit of hydrogen, a tiny bit of helium, and a some time.

Exactly. We should be working on making nuclear reactors cost $1/watt to construct. I can't see a technological reason why they couldn't be that cheap to build.

> Hacker News is hostile to fission and defeatist (unable to contemplate innovation in fission technology) but this attitude will gradually change.

Lots of us like fission and think the fears are overestimated.

Nevertheless, the observation is that new developments in fission tend to result in the cost increasing, not decreasing.

And I say that as someone with a similar mindset regarding fusion, though for different reasons: you can pick aneutronic fusion reactions… but look at what weapons can proliferate with transmutation from the neutrons you can also choose, and ask which governments will turn them down.

The radioactivity generated from neutron activation is low-level, so you don't need to worry about accidents releasing lots of radioactivity, or about how to store waste for a long time. There are a lot of people worrying about those two things for fission reactors.

Also, the fuel for fusion reactors is much more plentiful. If we went all in on fission we might run out of easily minable uranium ore in a century or so, so it would be nice to have fusion reactors ready to take over then.

The only hard part of dealing with nuclear waste is the social aspect. If not for that, you can simply and safely dump it into the ocean. Water is excellent shielding and the amount of uranium/etc already dissolved in sea water is absurd. Put it in a stainless steel vessel first if you want most of it to decay before coming into contact with the water, but that's not even necessary.

Fission is "simple" but it seems every designer in the XX century made it as much complicated as possible for not so great reasons (and don't even get me started on the "let's not use breeding reactors" stuff)

Cooling that requires pumps, as an example, should be a non-starter in new projects.