Terrestrial fusion energy over-rated compared to fission

[S12RPG]

Don't get me wrong, I'm a big fan of science and am glad that we are researching fusion energy. But I disagree with the sentiment that terrestrial fusion energy power is a utopian energy source that is unequivocally superior to fission.

In terms of fuel, both fission and fusion fuel is refined from prevalent materials (water or uranium ore), so let's assume fuel for both is trivial.

In terms of cost, I'll be generous to fusion and say that in the future we may be able to use LK-99 or some other cool tech to make fission and fusion capital costs and operating costs per MW identical. Given the immense increased complexity of fusion reactors, I think this is quite the concession to fusion!

The common assumptions is that fusion would have advantages when it comes to radioactive safety or nuclear waste. The risk of nuclear meltdown with fission is remote with literally a handful of accidents in older plants caused by human error. Perhaps that is enough to make fission politically infeasible, but I think this is irrational. Though fusion requires power to maintain the reaction, and thus a run-away reaction is not a risk, I can certainly see how human error with a highly sophisticated facility that requires radioactive fuel (tritium) can lead to environmental disasters.

When it comes to nuclear waste, I don't see why fusion would be waste free! The most accessible type of fusion is D-T fusion which generates significant neutron flux. Again, the tritium fuel is radioactive and we're going to end up with a neutron-embrittled and radioactive reactor casing that we need to periodically replace, see discussions about DEMO reactor https://iopscience.iop.org/article/10.1 ... 326/ac62f7

4.2. Fusion versus GEN-IV fission
Recent calculations [15] considered activation waste volumes holistically when comparing waste from fusion to GEN IV fission. Under the current UK regulatory waste classifications system, they found that the European sodium-cooled fast reactor (ESFR) has a lower fraction of ILW or HLW in the structural components (i.e. ignoring fuel) compared to the latest concepts for the European DEMO. Considering DEMO's much larger size (the equivalent containment vessel and interior of DEMO is massive and could be as much as ten times as large as ESBWR—see figure 3). This suggests a significantly greater waste burden from fusion in comparison to fission reactors developed on the same timescales. DEMO may produce as much as 10 000 t of solid waste from in-vessel components alone [16], compared to around only 2000 t from ESFR [15] plus an estimated 300 t of spent fuel produced during ESFR's lifetime [17] resulting in ∼2500 t of waste (HLW, ILW). While ESFR produces four times less waste, it will generate much longer-lived actinide waste.

Some may say that we'll get to aneutronic fusion, and that'd be awesome, but my guess is that there will still be unwanted side fusion reactions that generate those pesky neutrons and lead to radioactive waste.

Meanwhile, fission of course also generates nuclear waste. However, fission is a mature technology, now with 4th generation plants being built with decreased cost and more safety advances, and countries do have experience in dealing with the nuclear waste. Even if fusion and fission generate the same amount of nuclear waste that requires storage (note the above reference suggests fusion generates more waste), fusion has the same political cost of convincing people that nuclear waste can be managed safely.

So, even with these generous assumptions to fusion, fission still looks like a better deal. What am I missing? If people are saying fusion energy can solve all our problems, what can it truly do that fission cannot? If we are not willing to ramp up fission energy production now, why are we assuming that we would be willing to ramp up fusion once a commercially viable fusion plant is available? And even if we could solve the political problems, why would we bother with increased complexity of fusion over more proven fission for terrestrial power production?

As an aside, fusion engines/generators on spaceships would be sick! There you'd get the full benefit from the increased energy density and higher temperatures from fusion.

[Jub]

Don't get me wrong, I'm a big fan of science and am glad that we are researching fusion energy. But I disagree with the sentiment that terrestrial fusion energy power is a utopian energy source that is unequivocally superior to fission.

In terms of fuel, both fission and fusion fuel is refined from prevalent materials (water or uranium ore), so let's assume fuel for both is trivial.

That's a poor assumption. At current use rates, we have ~90 years of proven mineral reserves of Uranium and less than that in proven Thorium.

https://www.world-nuclear.org/informati ... 20minerals.

We can likely discover more but fissionable material is at best an interim step in meeting our clean energy needs. We must either find ways to become vastly more efficient so true renewables can power comfortable healthy lifestyles or make some breakthrough in fusion power.

[S12RPG]

Hmm all right, I'll grant that long term, there is more fusion fuel on Earth than fission fuel. But I don't think the concerns for future high price or scarcity of uranium is currently the reason we are not currently ramping up fission. Governments have a hard time thinking in 10 year increments, let alone 90. I'll table the discussion of throium, as I want to compare currently in use fission reactors (Gen 3 with some Gen 4) with theoretical future fusion.

So my question still remains, why is there a common belief that fusion power will be wildly accepted and bring us utopian abundance once it becomes commercially available, if fission right now can provide that level of power density and reliability, but we aren't doing it.

[Jub]

Waste material generally isn't the cause of public concern for fission plants, it's possible accidents and meltdowns as well as the materials needed to run the plant. None of these are issues in fusion which can't have run-away reactions and don't rely on bringing in materials that many NIMBYs associate with danger. Unless there is heavy lobbying against fusion combined with a Chernobyl level incident those same people won't have the same illogical fear that stalls the current nuclear industry.

[S12RPG]

I disagree that people aren't afraid of nuclear waste. In fact, I think people's fear of nuclear accidents is primarily about the release of nuclear waste. For example, Three Mile Island didn't have anything explode, but it did have an undesired release of radioactive noble gases into the environment. People didn't die in a mushroom cloud in Fukushima, but there was a release of nuclear waste into the ocean. Like I said before, a large complex, high power facility that is performing nuclear reactions, has tanks of radioactive tritium on site, and constantly generates radioactive spent reactor casings components, that is run by humans who can mistakes, could definitely have an accident that releases radioactive material into the environment.

What I'm getting at is the same kind of people who are terrified of nuclear accidents and/or release of nuclear waste from fission plants will have the same fears when fusion plants are actually up and running. Why would we assume otherwise?

[bilateralrope]

One other advantage that fusion plants could have is different construction requirements to fission. Making a mix of fusion and fission plants quicker to get to producing the same power output than going 100% either way.

Which matters when one thing humanity needs to do is replace CO2 producing power plants as quickly as possible.

[S12RPG]

The construction requirements would be different only in that fusion powerplant requirements are more burdensome. You're still going to need radiation safety measures and the standard power plant steam turbines, cooling towers, etc. But instead of a concrete box with fuel cells and graphite rods, with fusion you need some engineering miracle to generate sufficient pressure and temperature to fuse D-T. Perhaps other than security to prevent theft of the uranium/plutonium in a fission plant, fusion powerplant construction requirements are flat out more difficult.

If humanity/society/governments/private industry etc truly felt that we needed to embrace nuclear power to replace CO2 producing power plants, there's no point to wait for fusion. Rather than a hypothetical mix of fission and fusion, just build all fission plants now and replace CO2 plants cheaper and sooner!

[Jub]

The construction requirements would be different only in that fusion powerplant requirements are more burdensome. You're still going to need radiation safety measures and the standard power plant steam turbines, cooling towers, etc. But instead of a concrete box with fuel cells and graphite rods, with fusion you need some engineering miracle to generate sufficient pressure and temperature to fuse D-T. Perhaps other than security to prevent theft of the uranium/plutonium in a fission plant, fusion powerplant construction requirements are flat out more difficult.

We can look at what causes a lack of nuclear fission plants and a lot of it is due to constantly shifting regulations during construction. Fusion bypasses the need for the same level of inbuilt redundancy as it doesn't pose the same risks. So while they may be in some ways more difficult to build they could actually prove cheaper to build per MW generated.

https://progress.institute/nuclear-powe ... ion-costs/

If humanity/society/governments/private industry etc truly felt that we needed to embrace nuclear power to replace CO2 producing power plants, there's no point to wait for fusion. Rather than a hypothetical mix of fission and fusion, just build all fission plants now and replace CO2 plants cheaper and sooner!

Let's say we end up ramping up the number of reactors by 5x over the next decade. That means our 90 years of proven reserves goes to a mere 18 years (assuming we found more reserves over that span otherwise we're down to 16 years) unless we can keep discovering accessible sources of fissile material and can extract it in a way that allows the plants using it to run carbon neutral. Fission fuel is simply too rare to run the world on.

[S12RPG]

We can look at what causes a lack of nuclear fission plants and a lot of it is due to constantly shifting regulations during construction. Fusion bypasses the need for the same level of inbuilt redundancy as it doesn't pose the same risks. So while they may be in some ways more difficult to build they could actually prove cheaper to build per MW generated.

https://progress.institute/nuclear-powe ... ion-costs/

Very cool article that I will bookmark for future discussions, but I guess I will come back to what I said above.

I think that once people start conducting the environmental impact studies to build commercial fusion reactors, the same concerns about possible radioactive waste leaks are going to come up and there will be the same constantly shifting regulations that have lead to the current hesitancy to build fission plants.

The limited uranium thing reminds of "peak oil", which ended up being solved with tech like deep sea mining. If we move to a uranium economy, I can see similar tech being developed to find more uranium. Regardless, based on my understanding of human nature, I don't think possible future uranium scarcity is an actual reason people today are not building fission plants today, but I could be wrong.

[Jub]

I think that once people start conducting the environmental impact studies to build commercial fusion reactors, the same concerns about possible radioactive waste leaks are going to come up and there will be the same constantly shifting regulations that have lead to the current hesitancy to build fission plants.

Fusion is being hailed as clean free energy even by news agencies that would scaremonger about fission plants. While it may hold that as the technology rolls public perception sours and regulators continue to change standards at an unreasonable rate, we don't know that it will happen. What we do know is that fission plants DO face these issues.

The limited uranium thing reminds of "peak oil", which ended up being solved with tech like deep sea mining. If we move to a uranium economy, I can see similar tech being developed to find more uranium. Regardless, based on my understanding of human nature, I don't think possible future uranium scarcity is an actual reason people today are not building fission plants today, but I could be wrong.

With peak oil we knew where a lot of these alternative reserves were already it just wasn't clear how easily we could extract them and if it could be done profitably. Also, unlike with oil, it takes more effort to explore a site that mines for ore, and most sites that seem promising never get mined due to various factors. It's just flat harder to get more fissile material than it is to find more oil deposits.

[S12RPG]

It's just flat harder to get more fissile material than it is to find more oil deposits.

Perhaps, but again, I don't think this is the reason we are not currently building fission plants. And we are clearly demand rather than supply limited for uranium, from the article you linked above.

This reaction started in 2003 with a strong upward movement in world uranium prices that continued into 2007 (the spot market price increased by a factor of 13 between early 2003 and mid-2007), but went into a downward correction, accentuated by the Fukushima accident in 2011. Since the accident, uranium prices have fallen to one of the lowest inflation-adjusted levels ever experienced.

Fusion is being hailed as clean free energy even by news agencies that would scaremonger about fission plants. While it may hold that as the technology rolls public perception sours and regulators continue to change standards at an unreasonable rate, we don't know that it will happen. What we do know is that fission plants DO face these issues.

Your argument that fusion may not suffer from the same public perception problem that currently affects fission seems wildly optimistic. The fission PR issue didn't come from nowhere. I'd surmise that there were many factors including conflating atomic energy with atomic weapons, environmentalist concerns about nuclear waste, fossil fuels and green energy companies trying to undermine competition, Hollywood playing up the radiation being a mysterious invisible killer and pretending the nuclear plants are bombs in disguise, etc.

All those arguments could apply for fusion tech too! Easy to imagine local newscasters explaining fission versus fusion by comparing thermonuclear weapon yields. I think you are underrating the nuclear waste issue and the remote but still present risk of environmental disaster with a waste leak. Superconducting magnets, radiation, a blue glowy Tony Stark fusion reactor gone wrong would make an awesome Hollywood movie. And competitive power plants corps would be motivated to undermine fusion just as much as they undermine fission.

Currently fusion energy is fuzzy future tech, is not well understood, and there's no plan to build them in anyone's backyard. So, there's no real motivation by any of the above groups to fearmonger about them. The motivations will change once FusionCorp is contracted to build a reactor near some city or politically sensitive area.

Which brings me back to the point of this thread, I don't see why we are so optimistic that fusion will be embraced if fission is not currently.

[Jub]

Perhaps, but again, I don't think this is the reason we are not currently building fission plants. And we are clearly demand rather than supply limited for uranium, from the article you linked above.

The price of fuel doesn't matter if we don't have enough to meet long-term increased demand.

[quoteWhich brings me back to the point of this thread, I don't see why we are so optimistic that fusion will be embraced if fission is not currently.[/quote]
If fusion works it's the ONLY long-term energy source we've got that isn't driven by the sun. Fossil fuels and fissile materials aren't unlimited and we may be in the last century or two of having easy access to either depending on just how reckless we are with our reserves. If fusion doesn't work we won't have many generations left to either sort battery tech and go entirely renewable or figure out fusion and accept that we have no other options.

Fusion is also BY FAR the best option for powering anything that needs to move rapidly through space. Mirrors and solar panels can work for fixed habitats all the way out past Pluto but it'll be tough to make them work for anything that needs to move around at any kind of velocity. So we either beam energy to them and accept that we have giant lanes where you'll get cooked if you fly through them or figure out better long-term energy supplies for those trips.

[S12RPG]

I'm not disagreeing with you that fission fuel is limited LONG-TERM. I'm saying I disagree that long-term scarcity would dissuade CURRENT exploitation of this resource. If you like to continue this argument, please name one other industry where this mindset is the reason that people are not pursuing something that would be profitable short-term. I'd actually argue that current and projected fuel costs over the ROI period of the power plant are all that matters for investors, and that it would be unusual to consider projected future scarcity beyond that ROI period when deciding to build a power plant. Of course, uranium costs would go up if more people started building plants, but your source stated that uranium mine production increased with demand and many closed down recently when demand dropped, so I think it is a reasonable analysis that we are demand limited rather than supply limited with fission fuel.

Numerous economists have studied resource trends to determine which measures should best reflect resource scarcity (Tilton, J. On Borrowed Time? Assessing the threat of mineral depletion, Resources for the Future, Washington DC 2002). Their consensus view is that costs and prices, properly adjusted for inflation, provide a better early warning system for long-run resource scarcity than do physical measures such as resource quantities.

Not to appeal to authority too much, but that seems to be what nuclear NGOs say as well. This references has an interesting story about how at one point we thought we had 30 years of copper left, it's an interesting read!

Fossil fuels and fissile materials aren't unlimited and we may be in the last century or two of having easy access to either depending on just how reckless we are with our reserves

I agree with this take on fossil fuels, but by this logic, why are we still building fossil fuel plants? Even putting aside global warming and the need to limit CO2 production, nations and corporations are still actively building new plants and looking for new fossil fuel resources. Some nations are winding down fossil fuel production, but it's clearly below what international guidelines recommend, and it's not because these countries are switching to fission power.

Perhaps I could have clarified in my title, but I'm not necessarily denying that fusion is an objectively better option on the tech tree for long term survival of humanity. Absolutely agree that fusion tech will be a major advancement in future spacecraft power generation and propulsion. What I'm interested in discussing is, why are we optimistic that commercial fusion for terrestrial energy production will be embraced if commercial fission energy is not currently embraced?.

I'm arguing against the claim that when commercial fusion is viable, humanity will promptly switch its terrestrial energy production needs to fusion. My main counter-claim is that has not happened with fission, and that fusion has at least the same economic/human incentives drawbacks as fission does. One might say you need to give it some time for advanced and safe fusion reactors to be developed, but the first fission power plant was made in the 1950s, with multiple refinements since then, and it has not been fully embraced. I would imagine at best, a similar scenario for fusion plays out - a very slow, limited adoption fraught with public hysteria, legal challenges, excessive regulatory confusion, and multiple other roadblocks.

[His Divine Shadow]

Fissile materials are basically unlimited for all intents and purposes though. The idea that they're limited to a century or less is a talking point based on a lot of shady reasoning like only counting current existing mines. Like we can't prospect and open new mines if we want to... or use reprocessing and breeders or other techniques.

[Jub]

Fissile materials are basically unlimited for all intents and purposes though. The idea that they're limited to a century or less is a talking point based on a lot of shady reasoning like only counting current existing mines. Like we can't prospect and open new mines if we want to... or use reprocessing and breeders or other techniques.

I'll have to do more digging then. Most of the sources I've looked at express concerns about the long-term viability of fission due to fuel scarcity and that breeding and recycling are bandaid solutions.

[Jub]

I looked a little more and it feels like the fission is unlimited crowd is really banking on seawater extraction being viable. I don't think they're wrong about it being possible or about it being more efficient than osmosis but I do have questions about the ecological impact of filtering that much seawater year over year. Their world energy estimates also seem optimistic especially if drier coastal regions are forced to switch to desalinization as rainfall and snowpack patterns change.

I'll admit that it is still more viable short term than I expected it to be once breeder reactors are factored in but fusion, if it ever works at scale, is still what we should be aiming for long term.

[His Divine Shadow]

For actually literally unlimited fission, sure seawater extraction would be very useful.

But for say many additional centuries of fuel. We'll get to that simply by prospecting and opening new mines. And that's before taking into account reprocessing all the of the current waste. Or more effectively, feeding it into breeders. Lots of open paths forward and many of them are very simple and not just done because of economical reasons, once uranium goes up in price, opening new mines become viable.