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Comment by nickik | Hacker News Reader

I still don't understand why people want fusion.

Like fisson already does basically what you need and is easier in every way.

Yes, the energy density of fusion is higher but the energy density of fission is already so absurdly high compared to chemical.

There are only a small number of cases where I can think of this making sense, and even then it would likely not be worth it.

The problem with nuclear power is the lab to operations process, regulation and engineering cost. Fission will likely not improve on either of those compared to fission reactors now being developed.

If we can't can't get a Molten Salt reactor with a CO2 Brayton Cycles turbine into commercial deployment, I have little hope for Fusion.

And if we do, then its hard to see how Fusion reactors beats it on price.

That said, I want fusion for crazy rocket concepts.

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It is, of course, the regulatory cost they want to attack. Fusion can’t continue melting down. Unlike fission. The fact that it’s much harder to get to work at all is considered kind of an advantage here because it means the reactor can’t accidentally keep producing energy when you don’t want it to. Second, if you get really good at fusion there are some reactions that don’t produce neutrons means you don’t get all this activated material. And that lack of neutrons also makes it proliferation-resistant (and can allow more compact ways of generating electricity than a typical thermal cycle). But even with the low hanging fruit type of fusion with tritium & deuterium, you don’t get these long lived transuranic isotopes. Also, fusion has some important very long term applications in human spaceflight (& interstellar travel). And the fusion fuel infrastructure is much less susceptible to being diverted to making weapons.

But overall I agree with you. Fusion makes fission look really easy, and there are advanced fission designs and processes which address most of the above issues.

If we built a fission reactor with the low power density of a fusion reactor it would be so big it couldn't melt down, just from its own thermal inertia.

Arguably a fusion reactor has a much higher chance of harming the population around as a breach in containment could release highly radioactive gases.

> But even with the low hanging fruit type of fusion with tritium & deuterium, you don’t get these long lived transuranic isotopes.

You don't get these in a good fission cycle either.

> Also, fusion has some important very long term applications in human spaceflight (& interstellar travel).

Yes but and fission has a lot of applications in human spaceflight too. And not some theoretical interstellar travel, but rather in things that are actually useful and that we need now.

Mars surface power most importantly. Nuclear Electric Propulsion second most importantly.

Its all fine to dream of interstellar travel, but by any logical view to world, Mars is a closer term thing then interstellar space travel.

Also, if we just want to send interstellar probes. Lasers driven by fission are much more likely to be a good solution in the next 100 years.

There are several advantages:

A fusion reactor doesn't create create long-lived radioactive waste (or any kind of pollution).

A fusion reactor cannot be used to create nuclear weapons.

A fusion reactor doesn't require any form of mining for it's fuel.

A fusion reactor cannot meltdown in any way.

Due to these inherent safety features, the costs associated with the regulation and engineering a fusion power plant could be much lower than a fission plant.

It will be easy to use neutrons from DT fusion to get weapon-grade plutonium. This may be easier to police, i.e. "there should be no uranium nowhere near a fusion plant", but that's a much subtler statement.

And of course mining for lithium as a fuel is still necessary, so you should perhaps say "no additional mining" or something.

The need for lithium is a valid point. The amount required for fuel is very small though. A 1 GW plant would use more on initial filling than a 30 year lifetime of refilling and even that first filling would be on the order of a metric ton (unverified ballpark, dependent on reactor size, blanket thickness, and plumbing overhead). 80,000 metric tons of lithium are mined each year. We consume about 18 TW.

So I estimate that converting all electricity sources to fusion would use about 1/4 of a year’s worth of lithium, but would be enough to make 30 year plants, which would still have most of their lithium left over for recycling/reuse afterwards.

And enriching lithium is necessary. A single ARC reactor would use a good fraction of all the 6Li produced for the US thermonuclear weapons program.

The tritium produced in a fusion reactor program would make it much easier to engineer high yield fission bombs, via boosting.

> And of course mining for lithium as a fuel is still necessary, so you should perhaps say "no additional mining" or something.

True, but the quantity of lithium required to breed tritium for power generation is ridiculously low. Operating a DEMO-like reactor for 30 years would consume 2 tons of lithium, which is nothing compared to the annual consumption for battery manufacturing (around 30000 tons).

The blanket of DEMO, if using PbLi eutectic, would require 52 tonnes of 6Li. In addition to the raw lithium itself, building even a single reactor like DEMO would require maturing a new 6Li separation technology (the old one caused unacceptable mercury pollution) and industrializing it.

https://www.sciencedirect.com/science/article/pii/S092037961...

You can not actually police that sort of thing. Thorium is literally everywhere in the earth core.

You could basically dig hole right next to your fusion reactor and mine Thorium right out of it, expose it to neutrons and create Uranium-233.

I suspect a reactor that uses FLiBe can produce pollution: the BeF2 in the solution is toxic, and presumably would have to be replaced periodically. https://en.wikipedia.org/wiki/Beryllium_fluoride#Safety

If the Be is not recycled then Be consumption becomes unacceptable. A single ARC reactor (2014 paper) would use 40% of the world's annual production of the element.

> A fusion reactor doesn't create create long-lived radioactive waste (or any kind of pollution).

It can create things that take 100 years, a closed cycle thorium breeder takes 200-300 years.

And the waste from that process is actually quite useful to extract isotopes for medical, nuclear batteries and other applications.

> A fusion reactor cannot be used to create nuclear weapons.

That is just flat wrong. Most fusion reactors that are considered today absolutely can be used to create nuclear weapons.

I would argue starting a nuclear weapons program if you have control over a fusion reactor is far easier compared to when you have a thorium breeder.

While it is possible in theory, in practice nobody would ever do it. Your whole workforce would suffer from to much radiation and because of certain other parts of the material, it would be incredibly easy to track in terms of proliferation.

This is a buggy-men, and would still be with fusion.

> A fusion reactor doesn't require any form of mining for it's fuel.

Thorium is incredibly common. Its already a waste in rare earth mining, so likely you wouldn't even need a single new mine. Every country has enough thorium in the ground to power itself.

> A fusion reactor cannot meltdown in any way.

A fusion reactor is actually more likely to release dangerous gases into the air.

> Due to these inherent safety features, the costs associated with the regulation and engineering a fusion power plant could be much lower than a fission plant.

That's a nice fantsay to have as we don't yet have fusion reactors so one can just make assertion. But as I explained above, a fusion reactor would need at least as much or more regulation as the fission reactors I describe above.

And if you follow the industry you will know that those reactors have a very hard time clearing the regulation.

Fission has a few unavoidable issues: long radioactive isotope half-life, weapons proliferation, and the runaway scenario. Fusion has none of these issues plus the fuel being abundant. It's the answer to the question "how do we meet the growing energy demands of humans over the next thousand years?".

The only real danger is that of a tritium leak, but the short half-life makes the prospect of a leak less concerning.

Since the reactors would ostensibly be continuously operating, the danger is the same. 10+ year half life is about as dangerous as 10000 years because you are always generating the waste.

Er, no. If you generate the same volume of waste per year, but for a fusion reactor the waste stops being a problem within a century and for a fission reactor it takes 10,000 years, at any point in time after the first 100 years, waste from a given fusion reactor will be less prevalent than waste from a given fission reactor.

It also doesn't matter that no specific nuclear reactor will have a lifetime of 10,000 years. The problem is that per megawatt of energy generated, fission theoretically creates (much) longer-lived waste than fusion. Over a longer-than-one-hundred-year timeframe, equivalent amounts of energy generation result in vastly different waste carrying costs. Fusion's waste carrying costs are much lower.

And obviously that number is even more in favor of fusion if it only takes 10 years. (ITER claims 100 years though: https://www.iter.org/sci/Fusion)

The danger is not the same between fusion and fission.

Firstly, 10 years worth of energy is inside a fission reactor and is capable of releasing most of that energy in an instant if not properly controlled. This cannot happen in a fusion reactor. A year's worth of fuel is in a gas tank on the wall and needs absurd conditions to ignite. It cannot happen spontaneously.

Secondly, the exhaust is helium-4: a stable isotape of a valuable element.

Thirdly, the neutron bombardment in a fusion reactor activate the materials they hit. If they hit lithium then they make tritium: a much needed isotape for fuel in first generation fusion reactors. The other materials they hit are chosen to have half-lives of less than 100 years. So you have a nuclear site that no one's allowed to touch for a while then you can recycle the materials. It's nothing like the transuranium nuclear waste from fission plants.

If you had a half life of 5 minutes you'd only need to store the waste for a couple hours before burying it somewhere and there's a certain (smallish) amount of high-grade waste at any given moment, no matter how long you run the reactor.

10 years isn't 5 minutes, but it means you just need to keep it secure for a few decades before burying and forgetting it rather than many human lifetimes.

Any leaks will be (to some extent) self-cleaning, insofar as they'll decay substantially within a human lifetime, so if you stop the leak you can wait a couple decades and it will have cleaned itself up. That's much better than the long-life stuff fission produces.

Why is the runaway scenario unavoidable for nuclear fission? Pressurized water reactors for example have negative void and temperature coefficients, and from what I've read about potential future reactors designs (e.g. high temperature gas reactors and some of the molten salt reactors) passive/inherent safety is a major selling point.

All of those solutions involve better ways at keeping neutron multiplication factor below 1. Fission reactors need fuel that naturally have an eta above 1. Fission reactors are also designed to have large quantities of fuel inside of them. So if the control systems fail, even if those control systems are built-in chemically, then you have a disaster that lasts for timescales that humans would prefer not to be on the table.

What's a scenario where passive safety systems, say those of a HTGR with TRISO fuel, fail and cause it to go prompt critical? I'm genuinely curious about this, as everything I've read suggests this is essentially impossible due to the design of the reactor, fuel, and coolant.

I don’t have an answer. Not knowing failure modes doesn’t mean they don’t exist. HBO’s Chernobyl series highlighted how dangerous surpressing information about fission reactors is. No one knew how the design could fail until it did and then it was painfully obvious. I’m not saying that HTGRs can meltdown nearly as readily as RBMKs, but the risk of the unknown needs to be given respect when the stakes are high.

It’s difficult to be sure of safety in complicated systems when the only people with enough technical expertise to fully vet the systems have an interest in their success. I’m not saying it can’t be done, but I think it slows policy down significantly.

How could someone demonstrate the safety of these systems if their very association with those systems is a sufficient reason for you to doubt them? If the research and experiments of nuclear engineers, scientists, and regulators from around the world cannot be trusted to develop or assess the safety of fission reactors, why does this change with fusion? I also have not seen evidence that anyone is attempting to suppress information about nuclear safety. Overall nuclear power has an outstanding safety record and ranks among the lowest deaths per TWh of any energy source (and this includes Chernobyl)[1][2].

For the record the HBO series on Chernobyl, while a good show, greatly exaggerated parts of the story. There was no threat of a megaton-level thermonuclear explosion that would destroy Kiev or make huge parts of Europe uninhabitable from the melted core coming in contact with water. The soviets did know about the RBMK's propensity to have a runaway reaction, and the rest of the world never allowed those types of reactors to be built.

[1] https://www.statista.com/statistics/494425/death-rate-worldw...

[2] https://ourworldindata.org/grapher/death-rates-from-energy-p...

Assuming all that is true, reality is extremely unpredictable. Imagine a country is at war and they accidentally drop bombs on the reactor that crack the fuel and change the chemistry enough. A volcano erupts under the plant. Imagine a nuclear weapon going off nearby and causing a meltdown (for example, if the attacker was using a "low yield" neutron bomb). Imagine an astronomical phenomenon that happens to pass through the plant.

Low probabilities, but man they would suck.

We keep finding new ways to make fission safer and reducing risk of runaway scenario but I'm pretty sure we'll never reach zero risk. Sure we might reach it on paper but human error can always happen. Chernobyl operators thought their reactor design had zero risk of exploding, current reactors are much safer but I'm pretty sure the risk isn't zero.

With modern reactor designs the inherent safety mechanisms mean that humans are not in the loop to reduce reactivity or remove decay heat.

Here's an example from Argonne National Laboratory:

> In the first test, with the normal safety systems intentionally disabled and the reactor operating at full power, Planchon's team cut all electricity to the pumps that drive coolant through the core, the heart of the reactor where the nuclear chain reaction takes place. In the second test, they cut the power to the secondary coolant pump, so no heat was removed from the primary system.

"In both tests," Planchon says, "the temperature went up briefly, then the passive safety mechanisms kicked in, and it began to cool naturally. Within ten minutes, the temperature had stabilized near normal operating levels, and the reactor had shut itself down without intervention by human operators or emergency safety systems."

https://www.ne.anl.gov/About/hn/logos-winter02-psr.shtml

There is obviously a difference between:

- There are many passive systems that work in concert to prevent the fission material from having a runaway chain reaction that continues on its own,

and

- It is literally impossible within our understanding of physics for the reaction to continue without the continued application of power to the reaction chamber.

No matter how 'safe' the former gets, it's just asymptotically approaching the latter. There will always be more assumptions and caveats involved in preventing a self-sustaining reaction from continuing.

In particular, re. that article, a lot seems to be resting on the sodium cooling pool being present while there's something else going wrong. So what if an earthquake breaks it open and dumps it out. Or a bomb.

Their risk isn't zero but even the 60s the inventor of PWR said this was not very safe design and designing inherent safely systems are far better.

Of course you never have zero risk. That literally impossible and not a standard you would use for literally anything else in human existence.

The fact is, you can design nuclear power plants that are so safe that the chain of events you had to come up with to get any radiation outside of the reactor safety boundary is so ridiculous that the probability of them happening is barley measurable.

Sure if you have human error and 3 black swan events on the same day, the risk is not zero.

But even if you come up with these crazy events the damage from those events would be a far smaller then Chernobyl and Chernobyl was also far less damaging then in popular imagination.

The risk that somebody dies during the construction of the reactor confinement building is probably 100000x higher, but nobody seeks to prevent ever building large structures.

> Chernobyl operators thought their reactor design had zero risk of exploding, current reactors are much safer but I'm pretty sure the risk isn't zero.

This is where we are with nuclear. Any debate goes back to Chernobyl. Again, in no other area do we go and say 'well the soviet thought this in the 60s so therefore we can never moved past it'.

There is fundamental physics and chemistry involved and just because some soviet operators didn't know that does mean its unknowable.

Humanity should be living in the nuclear age. Climate change would not even be a thing if everybody had done what the French have done in the 70s. And we would be much better in terms of space exploration if the whole world were not so reluctant about using anything nuclear.

- no radioactive waste

- no nuclear meltdowns / runaway processes

- more abundant fuel (on earth and the rest of the solar system)

- less pre-processing of fuel

- fuel cannot be used to easily make weapons

Should we use fission right up until we have viable fusion? Of course, we should definitely be building more fission reactors. But I can't think of a single reason we'd continue using fission once we get to fusion.

- there is waste, it's just shorter lived than fission waste and lower in quantity. The expectation is that fusion reactors will have to be regulated in almost exactly the same way as fission reactors because they are nuclear sites, with nuclear waste, and proliferation concerns.

- there is lot's of pre processing of the fuel to breed the Tritium in a molten salt blanket that surrounds the reactor and separating from the salt and then feeding it into the chamber

- there is plenty of fission and fusion fuel. Yes, there is more hydrogen around.

- tritium is used in nuclear weapons as a booster, to dramatically lower the amount of necessary fissile material - each fusion reactor is a fast neutron source, which means it can be used to make weapons grade materials. Conveniently, it has a breeding blanket for tritium, in which other fertile fuels can be place to make weapons material: proliferation concerns are a real problem for fusion

- tritium is used in nuclear weapons as a booster

It is, but tritium is not put into bombs. Lithium is.

- proliferation concerns are a real problem for fusion

Unless all fissile materials are banned. It is very easy to check for the existence of fissile materials. If there were no legitimate, safe reasons to have any fissile materials in use on the planet, then a global ban on fissile materials is on the table. A treaty where every nation checks on the other is reasonable. It is hard to build a secret fusion reactor, just as its hard to build a secret uranium centrifuge.

It is, but tritium is not put into bombs. Lithium is.

Both are put into bombs.

The main concern when it comes to tritium supply, regards tritium used for boosting of fission charges. Both applications are crucially important, but fusion boosting appears to require significantly larger quantities of tritium. Tritium and deuterium for boosting are supplied to the weapon from an external reservoir (gas bottle) as part of the arming process of the weapon.

Since about 5.5% of existing tritium decays every year, the tritium assigned to each weapon must be regularly replenished. This is done by removing the weapon’s tritium reservoir and exchanging it with a newly refilled reservoir (5). Figure 1.3 shows what may be such a reservoir.

From Norwegian Defence Research Establishment report "Tritium production":

https://publications.ffi.no/nb/item/asset/dspace:6780/20-013...

Also see this Savannah River Site page about tritium supply for weapons:

https://www.srs.gov/general/programs/dp/index.htm

And for a deeper dive, this fascinating blog post:

"U.S. Tritium Production for the Nuclear Weapons Stockpile – Not Like the Old Days of the Cold War"

https://lynceans.org/all-posts/u-s-tritium-production-for-th...

You are both correct :) Tritium is used for boosting fission bombs, lithium (lithium 6/7 deuterides) as fusion fuel in thermonuclear bombs.

So interesting story about this.

We originally didn't know Lithium-7 would be useful in thermonuclear weapons. It was assumed that it would be inert and that only the Lithium-6 would react with neutrons from the fission primary and breed tritium for the fusion secondary.

Then we tested a bomb [0] and the yield on it was accidentally 2.5x greater than anticipated. So large, in fact, that it is still the largest bomb ever detonated by the USA. It turns out that Lithium-7 will also breed tritium if the neutrons are powerful enough, and emits an additional neutron to continue the reaction. Reactions that we might never have discovered (or probably not until later) if it hadn't been for this mistake.

The end result was a lot more fuel for the bomb, and the explosion was so large that many of the measuring instruments were vaporized. The large yield also contributed to a radiological disaster [1], which was then the inspiration for the original Godzilla [2].

Anyways, that's how a math/chemistry mistake lead to the most famous kaiju movie (series) of all time.

[0] https://en.wikipedia.org/wiki/Castle_Bravo

[1] https://en.wikipedia.org/wiki/Daigo_Fukury%C5%AB_Maru

[2] https://en.wikipedia.org/wiki/Godzilla_(1954_film)

> more abundant fuel (on earth and the rest of the solar system)

This is by far the most important reason in the long term. Between stars and even at our own outer planets where solar panels aren't reasonable fusion is the only long-term large scale energy source.

It's the difference between being stuck as a Kardashev I or II civilization or approaching III.

> Should we use fission right up until we have viable fusion? Of course, we should definitely be building more fission reactors. But I can't think of a single reason we'd continue using fission once we get to fusion.

The power density and relative simplicity of fission (including mere thermocoupled) is still worthwhile for robotic probes or initial sources of power in distant places, but we'll be able to make our own fissionables indefinitely once we have solid fusion power.

> no radioactive waste

It can create things that take 100 years, a closed cycle thorium breeder takes 200-300 years.

And the waste from that process is actually quite useful to extract isotopes for medical, nuclear batteries and other applications.

> no nuclear meltdowns / runaway processes

Neither can a properly designed fission reactor. And in a molten salt reactor all dangerous gases are chemically bound in the salt and if removed from the reactor would freeze instantly not realising them into the air. So even if some basically unforeseeable chain of event lead to a runaway process, it would not release gases into the air and would stay contained on the reactor site.

A fusion reactor is actually more likely to release dangerous gases into the air in case of an accident.

> more abundant fuel (on earth and the rest of the solar system)

Thorium is incredibly common on most rocky planets. Its already a waste in rare earth mining, so likely you wouldn't even need a single new mine. Every country has enough thorium in the ground to power itself. Mars has plenty of Thorium as well.

Fission does not have any practical issues in regards to fuel availability.

> - less pre-processing of fuel

Depending on the fusion reactor you still need some preprocessing. Depending on fission reactor you need more or less.

If you have a continuously refundable thorium breeder you actually need very little pre-processing other then devolving the metallic thorium into salt.

While that might be an advantage, I don't see it as some gigantic advantage that it worth the additional complexity of fusion.

> fuel cannot be used to easily make weapons

Most fusion reactors that are considered today absolutely can be used to create nuclear weapons.

I would argue starting a nuclear weapons program if you have control over a fusion reactor is far easier compared to when you have a thorium breeder.

With neither is it easy in any way.

Practically is mostly a non problem. This is a buggy-men, and would still be with fusion.

Well, the cost is the reason why you might not want to do fusion if fission works. That said, I'm not anti-fusion. I'm just miffed that we rush into fusion when we have so much improvement on fission that could solve the exact problems fusion is trying to solve.

People want fusion because fission reactors leave long-lived radioactive waste, can melt down dangerously, and use the same fissile materials as nuclear weapons, making combating nuclear proliferation difficult.

That's why there are extremely high regulatory costs associated with fission reactors.

(I'm not saying we should wait for fusion reactors, but there's a lot of good reasons to develop them, and once fusion reactors are available there's a lot of good reasons to stop building fission reactors at that point.)

The issue is that the current fusion choices (deuterium) produce neutrons during fusion, that hit your containment vessels, and ... create long-lived radioactive isotopes while slowly embrittling the containment vessel. When you replace it, it is in fact, a long lived radioactive husk that you need to safely contain for a long time. There are other fusion options that do not, but they are MUCH harder to fuse than deuterium (what we are still trying to achieve)

While true, it's still better than fission in terms of waste. (And much less liable to Fukushima-style meltdowns, and less likely to lead to nuclear weapon proliferation.)

Well, actually, a nice source of a large number of neutrons is a HUGE proliferation thread: weaponizable Pu-239 is produced out of easily-available U-238 by neutron capture. Only generation 2 (or 3) fusion, when we move past deuterium, will be proliferation-safe.

It's a threat comparable to fission reactors only if fusion reactor containment vessels are built out of uranium, which they aren't.

To put it another way: operating a nuclear reactor today is expensive due to regulatory constraints meant to prevent nuclear weapon proliferation. If the fuel for your reactor can't be mistaken for nuclear bomb parts, and the components of your reactor can't be mistaken for nuclear bomb parts, it's a lot cheaper to build and operate. And it's a lot safer for someone to sign off on "Yep that's a whole bunch of lithium for a fusion reactor" than looking at a bunch of uranium and being like... Well...

> operating a nuclear reactor today is expensive due to regulatory constraints meant to prevent nuclear weapon proliferation

The way I read that, you seem to imply that this cost dominates all others. If you do mean that, i'd like to see a citation please.

Here you go: https://www.americanactionforum.org/research/putting-nuclear...

"These figures have profound implications for the industry’s bottom-line. Based on a review of per-plant profitability, there are at least six plants nationwide where regulatory burdens exceed profit margins."

Regardless, as I mentioned, the entire process is safer from a proliferation perspective.

Those regulatory burdens described there exceed profit margins on operations. Those margins ignore the sunk capital cost of the plants.

For new nuclear construction, these regulatory costs would be a small compared to the cost of actually building the plants. Of course, new nuclear plants would be outrageously unprofitable.

You can't ignore operating costs because of sunk capital costs. That's the sunk cost fallacy! You can sometimes ignore sunk costs if operating revenue is good. But if it's negative, that's the problem.

I wasn't ignoring operating costs. I was pointing out you can't ignore capital and financing costs.

This is exactly my point, a properly designed molten salt thorium fission reactor is really terrible to build nuclear weapons (no nation would ever do it) and a Fukushima-style meltdown is literally impossible.

The waste from a closed cycle breeder reactor only has to be stored less then 300 years and you can put it back into a mine before that if you want.

People want fusion because of mental inertia. Fusion was long sold as the future, so the idea that's it's desirable has become a social default. But it's a fossil belief, perhaps true decades ago, but with little to justify it now.

Fusion has long seemed unattainable, but now we seem to be approaching the point where we can actually build a useful reactor. Why wouldn't we use fusion if we could? It's a lot better than the coal and gas we're still using. Wind and solar will be a big part of the power grid going forward, but the installation costs are substantial and we'll need a lot more battery storage to fully transition to renewables.

Even assuming SPARC (or one of its competitors) works, it'll be awhile before the technology becomes mature and we can assess whether it's actually cheaper/better than fission or wind/solar/batteries. But from where we stand now it looks promising. Why the pessimism?

> now we seem to be approaching the point where we can actually build a useful reactor.

I think not. Reaching ignition in a fusion reactor would be akin to what fission achieved in 1942. There would then be enormous engineering obstacles to overcome, particularly to produce a design that could be competitive with other sources of energy. Fusion has grave disadvantages (low power density, complexity, reliability, difficulty of testing components) that must be overcome. I see nothing from existing efforts that suggest they will be able to surmount these obstacles.

Fusion is much less likely to have accidents that poison the local landscape for the next 10,000 years.

As odd as this may sound, this is not an impediment to current nuclear fission deployment. The risks are small, and many populations are very willing to accept them. See France, as well as most places in the US that already have nuclear reactors nearby. Or for that matter, many many sites in the UK.

I am skeptical of this, assuming you need some sort of public support in order to build a nuclear power plant (I'm guessing voters are involved somewhere, even if it's electing their state governor).

Most people are scared of nuclear power, so it seems politically problematic (at least in the United States).

I went to school in Pittsburgh where there are nuclear power plants nearby and people still felt more comfortable with coal being shipped over from Virginia.

Current sites that would welcome new nuclear, as evidenced by enthusiastic local support matched by a new construction project:

* Vogtle, Georgia

* VC Summer, South Carolina

* a cluster of small towns in the west that are the first customers for small modular reactors

* Wylfa, UK

* Hinkley, UK

The greater challenge with nuclear is getting the funding to construct, followed by actual engineering, procurement, and construction.

The funding problem is because of the safety problem. There are high regulatory costs associated with building new (fission) nuclear power plants, because:

* If you don't regulate the materials and fuels used for fission nuclear power plants, most countries could easily build nuclear weapons, and

* If you build fission power plants badly, or maintain them poorly, everyone and everything around them dies in a large radius, and in an even larger radius gets severely sickened. And this radius is poisoned effectively forever.

If there weren't safety problems inherent to fission nuclear reactors, they would be much cheaper to build as well as being much cheaper to operate — and thus easier to fund. That's part of why fusion reactors are interesting: theoretically they should work just as well if not better than fission reactors at converting fuels to energy; the fuel is more prevalent and cheaper; and there should be lower costs associated with building and operating them since the risks are lower.

We just don't know how to build them yet, and figuring that out is expensive.

> The funding problem is because of the safety problem.

I have yet to see convincing evidence of this. It seems like an excuse. Perhaps it's code for "the regulators won't let us get away with screw ups", which is what happened at Flamanville.

The chance of that happening with the fission reactors currently being built is almost vanishingly small.

And even the largest nuclear accidents ever did not lead to anything close to that.

This is just fear mongering nonsense. And btw, even with Fusion you still produce huge amounts of high energy particles that can be just as dangerous and can be used to do bad stuff as well.

Fusion is not magic.

On the other hand, they will almost certainly have tritium leaks far larger than from fission plants. A single 1 GW(e) DT fusion reactor would burn enough tritium each year to contaminate 2 months of flow of the entire Mississippi River above the legal limit for drinking water. Leaking even a small fraction of that could have serious consequences.

I guess people are increasingly frustrated with the failure of the current nuclear reactors to cost scale in the modern economy, so they look forward for a fundamental shift in technology. That is, there is no hope in fission, it has not stood the test of time so far, and it there is no reason it will in the near future. If we want nuclear we can only hope for fusion.

Note that this is me projecting. I don’t have a horse in this race. I’d be perfectly happy with nuclear free Earth; with renewables being our primary method of generating energy; a future which as of now looks the most likely. And if people develop fusion at some point in the future... cool.

Yes, it's magical thinking born of frustration, not something that one should truly expect.

Fusion could be a great equalizer in terms of global access to large amounts of energy: if you have moderately good access to the ocean, you have a nearly inexhaustible source of the hydrogen isotopes available in seawater and required as fuel for a fusion reactor.

Contrast this with both fossil fuels and fission materials. Those resources are the foundation of modern geopolitics. Seawater is not, and way more people have access to it.

Literally every country in the world has enough thorium in the ground for 100s of years.

Go look up how much thorium is in the earth.

You can literally go in-front of your house, dig a whole and in theory you can have enough thorium for a year.

Thorium is literally waste material that comes out of rare earth mining, its not a limited resource in any way.

I imagine that the popular view of fusion will be better, because of the impossibility of meltdown and the much easier to manage spent materials. If that translates into less NIMBYism, the regulatory costs should be much lower.

If the inputs can then ever be scaled, it could present a gateway to powerplant "mass production", which would be truly revolutionary. Especially for those crazy rocket concepts!

If a fission reactor had a power density as low as a fusion reactor, it would also be impossible to melt down, just because the thermal inertia of the core would be so large. Of course, it would also be uneconomical, because of the cost of that larger core (just as a fusion reactor would be uneconomical.)

re: regulation. This is the problem with fission. but not necessarily so with fusion. The reason is that unlike fission, where it's impossible to a small company to get a handle on fuel and build a fission plant in a less-regulated country, with fusion that becomes a lot more approachable.

But I am just as skeptical as you about the future of fusion and fission in the US and Europe.

> I still don't understand why people want fusion.

> That said, I want fusion for crazy rocket concepts.

There you go, you answered it yourself. Fusion rockets would open up the Solar System the way the steam engine opened up the oceans.

Also on Earth, fusion would be cool. It's less dirty than fission, and the fuel is FAR more plentiful.

The question is why wouldn't you want fusion. More options are always better I think.

I'm not saying I don't want it. It just seems as humanity we totally fucked up. We found a revolutionary new energy source and we totally fucked up the deployment of it.

We should live in a nuclear age already, fission powered space craft, trains, ships, power stations, remote electricity. There is no fundamental reason why fission should not be used an all of those.

Yet we almost don't use it at all, and phasing it out at the same time as we face climate change.

At the same time huge money is spent on Fusion that is much less likely to actually help. With the money spent on ITER you could literally run a matcher competitive competition to build 3-4 new fission reactors and likely multible new powerful turbines.

A molten salt reactor with a brayton turbine would likely be far more revolutionary then whatever ITER can ever be.

In general I just feel like fission is disliked and future has this 'wow the future could be magical', and I'm saying, the present could be magical, we don't need to wait for some magical technology. All that is required is some engineering and a general acceptance that fission is good among politicians, regulators and people.

If some start ups want to work on it, I'm not against it. The point is more that even if this magical technology break-threw happens, deploying it in the real world will run against many of the same problems as fission does.

The problem, in my view, is mostly regulatory capture and this incessant drive to let markets do their thing.

As it stands, fossil fuels should be taxed so high that building, maintaining, and running nuclear power plants is cheap in comparison. Yet we have continued investment into fossil fuels even though we're now fully aware of the damage they're doing. And people say "oh, well we don't have nuclear, because it's so expensive." You know what else is expensive? Entire cities being under 6ft of ocean and having to relocate hundreds of millions of people.

In other words, the known externalities are not imbued in the price, because yay capitalism. I think a little market tampering is warranted when planetary survival is at stake. And obviously, the ramp-up should be gradual, ie, we should have been starting this 20 years ago, when it was also painfully obvious that digging up huge amounts of carbon and burning it is a bad idea. Oops.

Recently I've been seeing people comment that raising a building 6 feet using jackstands OR filling the first story in with cement isn't "actually" that difficult or uncommon 100 years ago.

https://en.wikipedia.org/wiki/Raising_of_Chicago

https://en.wikipedia.org/wiki/Regrading_in_Seattle

https://en.wikipedia.org/wiki/Seattle_Underground

https://www.asce.org/project/galveston-seawall-and-grade-rai...

Feeding them all, that's what I worry about.

I'm having trouble determining the connection between my comment and yours. Can you help me out?

I was responding to your off-hand comment "You know what else is expensive? Entire cities being under 6ft of ocean and having to relocate hundreds of millions of people."

6ft of water seems somewhat manageable, relatively speaking, so long as you're willing to move up a story or go full neo-Venice.

Oh, interesting. I didn't connect those two.

I think my hesitation would not be that 6ft of water is not manageable in the single case, ie, one building. But several thousand of them at the same time? A whole city? Good luck coordinating that in any reasonable amount of time, especially when roads are all flooded.

Abandonment is a much more viable option at some point along that particular path.

I wouldn't want it because it would be far too expensive.

From my point of view, fusion is incredibly important for long term space exploration... but I would agree, not much else. Even the "not so long" term space exploration can be done with fission.

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