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Comment by dazbradbury | Hacker News Reader

Are the various "small" nuclear reactor projects seen as a way to tide over the gap until fusion (which has a similar number of startups and organisations working on it) takes over? Or a bet that fusion won't be feasible in the end? Or are they seen as filling different gaps and co-existing longer term?

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Neither? Fusion is not feasible right now, and we need power now. It doesn’t really matter whether fusion eventually becomes viable. Fission is fine for the long term; fusion would also be fine, if it eventually worked.

Fusion isn't proven yet, so government can't really plan for it. Even if it does arrive, nobody knows when that might be. It could easily be in 100 years for all we know. Small nuclear reactors are seen as a way to get the benefits of fission at lower cost.

I think all of these projects are coming together primarily to replace the existing nuclear plants. As the older plants reach the end of their operational life, there's still a desire for fission power; building a new plant with the old designs doesn't work for a lot of reasons, so hopefully new designs that take into account 40-60 years of operational, construction, and regulatory experience will make it possible to fill the void. I'm sure all the teams are also hoping to broaden the market for fission power too; if they can show the ability to build reactors in reasonable timelines and with reasonable budgets and operability, it could happen. If not, these are likely to be the last generation of fission plants (aside from naval applications)

It's always been a problem that the current way we do reactors involves lots of one-off designs, with gigantic powerplants that require too much red tape to get finished in a reasonable time frame.

Now instead of that have a small modular core that is certified to high heaven and can be mass produced. It would cut down maintenance, deployment, construction, everything. I truly think this is a fantastic way towards a net zero future.

Metaculus indicates that the first fusion plant may not be online until the 2040s[1]. We shouldn't be not building lower carbon energy infrastructure now with the idea that fusion will save us.

[1] https://www.metaculus.com/questions/363/will-a-fusion-based-...

I think small reactors are proven to be feasible now, and can be producing energy in short term.

Fusion is a longer-term bet – it's probably coming, but there's no certainty on the timeline.

None of the above. Smaller nuclear reactor projects are an effort to reduce the capital requirements to get started. There are inherent economies of scale in the physics which promote building larger reactors. Military propulsion reactors are < 1/10 the size of commercial power reactors today, and they are safe enough that we operate them with enlistees. But they are far too expensive for commercial operation.

There's not really that level of central planning going on here (and IMO that's a good thing).

Even if fusion is feasible, it will not solve the problems people keep hoping it will.

1. Proliferation. A thorium reactor already has no proliferation risks

2. Costs. LOL. At least 2000 years to recoup the R&D, and then OpEx still exists

3. Fuel availability. Thorium. Reactor.

4. Waste. Where do you think all those neutrons will go? The container. which will slowly become radioactive as you transmute it thus... IT will also become brittle and need replacement. It is ... nuclear waste. Radioactive and in need of storage. Also: a thorium reactor can use existing nuclear waste to for a while it'll REDUCE amount of waste we have to deal with

The one and only thing fusion does have going for it: at least IN THEORY it might be possible to do on a space ship by collecting interstellar gas. Not much heavy isotopes there but plenty oh H and some He

There's already a reactor that can do this (CANDU reactor), and has been operational for decades, no research required. That there is little new investment in building them tells me that no one really cares about reducing the amount of nuclear waste, and that it's all very political.

Yep. Ontario's power reactors can (and have!) run on plain uranium, partially depleted uranium "waste" from American power reactors, and my favourite: a mix of depleted uranium and ex-Soviet warhead plutonium [1]. A thorium breeding cycle is also possible, in theory with CANDU and it's actually being done with India's heavy water pressurized reactors using thorium, which are an indirect derivative.

[1] https://www.cbc.ca/news/canada/russian-plutonium-one-step-cl...

Thorium reactors still have proliferation risks. See this explanation written by physicist and HN commenter acidburnNSA:

https://whatisnuclear.com/thorium-myths.html#myth3

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