Comment by areoform | Hacker News Reader

Comment by areoform | Hacker News Reader

Just a quick reminder, we already have practical fusion with tens of thousands of years of runway available to us today. We choose not to do it because it sounds dangerous and it’s not politically expedient.

For those unfamiliar, I am talking about Project PACER. The fusion reactor proposed by Teller after the creation of the thermonuclear weapon. It may sound fanciful but it’s based on a simple precept. We can already induce fusion reactions, albeit in an unstable and explosive fashion. What if we took that warhead, surrounded it with a giant underground chamber made out of steel several feet thick, and let it explode while molten fluoride captured the heat?

Their work conclusively shows that this can be done, and that molten fluoride salts could capture most of the neutrons to prevent embrittlement. A single such facility could power the entire country. Oh and it could be configured to create Tritium in the process.

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

The project was terminated because it was "bound to be controversial" and would "arouse considerable negative responses."

The math is sound. The concepts are sound. We could solve the comparatively minor engineering challenges and build one today while waiting on the the breakthrough needed for controlled, continuous fusion.

It lacks the key advantage of fusion reactors over fission: not contaminating its working fluid with radioactive isotopes. For something like PACER, you have to extract the heat by running the hot fluoride through heat exchangers to run steam turbines. This is difficult and expensive to make safe. Like with conventional fission reactors, you have to be extremely sure your heat exchangers will last 50 years with zero leaks, because you can't touch them once the system has been running. And leaks are extremely dangerous. So every weld has to be triple-inspected and so on.

A second disadvantage is that the parts would undergo constant thermal cycling. Conventional reactors are run at a very steady output level to handle base load, because turning them up and down regularly would cause the moving parts to fatigue and crack over time.

The project was terminated because there were formidable technical issues, it wasn't economically profitable, and there was a real possibility of catastrophic failure that could not be mitigated.

https://books.google.com/books?id=4QsAAAAAMBAJ&pg=PA18#v=one...

> Dropping about two bombs a day would cause the system to reach thermal equilibrium, allowing the continual extraction of about 2 GW of electrical power.

So the idea is to drop 2 nuclear bombs per day to get about as much energy as one gets from a pair of nuclear fission reactors? I seriously doubt that's cost-competitive with fission power.

And, fission is itself not competitive anymore.

Competitive with intermittent sources backed by fossil fuels? No, but those emit carbon emissions. And we lack the ability to add significant amounts of energy storage, so wind and solar will never conceivably break free of it's dependence on fossil fuels during non- production.

It's the most competitive non-intermittent and geographically independent source of carbon-free energy. Because it's the only such source.

And yet, not competitive. So, there is something missing in your model. It is for you to figure out what is wrong.

It's not competitive with a power source containing fossil fuels. And there's no feasible way to run a grid composed of wind and solar without fossil fuels. Ignoring the fact that wind and solar generation is really wind, solar, and fossil fuels, to offset the intermittency is naive.

In areas without hydroelectric and geothermal potential, nuclear is the most competitive carbon-free and non+intermittent option. Because it's the only option. That's why for all your insistence that nuclear is uncompetitive, it produces more electricity than wind and solar combined.i

See, you got the wrong answer again.

Renewables plus local storage, transmission line, and/or ability to burn imported ammonia or hydrogen suffices, and at radically less cost, with no risk of rendering large areas uninhabitable.

Storage at anywhere near significant levels does not yet exist, and might not be achieved in the time necessary to curb the worst effects of climate change. Ammonia and hydrogen storage has been proposed, for decades, yet remains out of reach at the scales necessary to make renewables viable.

Wind and solar is really wind, solar, and fossil fuels. Assuming that we'll be able to replace the last item with energy storage is betting the future of our climate on an engineering breakthrough. No such gamble exists with nuclear, countries like France have successfully produced nearly all their electricity with nuclear power for decades.

You keep repeating this, but you know it is not true.

Some of the heartburn about PACER is that there are failure modes that can only be described as catastrophic.

No shit.

Turns out a daily detonation of a fusion bomb tends to wear on things and when those things fail... you've just detonated a fusion bomb.

We’re facing a catastrophe. I and others have described elsewhere that the path we’re on is much, much worse than even the most dire of predictions the IPCC makes. https://news.ycombinator.com/item?id=30947756

Teller et al anticipated your objection. It’s why the reactor is supposed to dig into sold rock. If there’s a catastrophic failure then it’s yet another subsurface nuclear test. And the more advanced designs considered for Project Plowshare produce minimal residual radioactivity. All of the products dissipate within 6 months.

So, in the worst case scenario, the facility gets buried under tons of rocks, far away from any water. And the residual radioactive products rapidly decay into being harmless with 6 months. Any induced radioactivity from the neutrons produced during the explosion will follow a fairly predictable pattern as well.

This can be done.

In exchange we get a reactor that creates nearly limitless power for entire countries.

The same line of reasoning says that we should build conventional light- or heavy-water reactors. The risk is minimal. And they're (a) tested and (b) much cheaper than PACER.

The advantage of a PACER setup is that you get a lot more bang (heh) per kg of uranium than you do out of a fission reactor. But the cost of uranium is not currently a problem with our fission reactors. We do have a problem with radioactive waste, but even that is way more political than it is technical.

I wonder which two senators are going to be ok with detonating 32 bombs in their state every day? This isn't the 50s, NIMBYs know how to make your life a living hell when trying to do anything nuclear.

Future fission reactors both don't need uranium (thorium reactors) and use less of it while waste that isn't radio active for long (breeder reactors).

Thorium turns out not to be the solution to any problem.

One problem it solves is making reactors that can't produce material for nuclear weapons. That's pretty important if we want to deploy reactors outside the few countries that already have them.

I live near Indian Point, recently shut down. They tried thorium back when it was new. It cost too much then. Nukes of any stripe are not competitive now, and get less so every year. Thorium cannot save them.

Solutions that rely on a steam turbine generally lose to those that do not. A need to fool with fuel and security cost even more. Account for the disaster insurance subsidy and decommissioning cost, and they come out a marked drag on society.

That is, if you manage to complete one before it gets cancelled because renewables are already doing the job more cheaply than it can. We do better not to spend the initial $billions on what will never produce any marketable power. No such money is ever returned.

A nuke that runs only at night costs almost twice as much per kWh.

It's possible the economics have changed since the 50s. The non-proliferation argument certainly has: in the US in the 50s, making plutonium was considered a useful feature of power reactors.

That does happen, but has not in this case.

I suspect worst case scenarios are more about earthquakes either natural or human induced

Or we could chose a number of WAY safer fission reactors for the same cost and same power output (Pick your favorite Gen IV reactor).

We also don't end up creating a literal nuclear weapons manufacturing plant in every nation that wants to use this (since the "fuel" for this reactor is constantly detonating nukes).

Why not Gen III+, these are ready to go whereas most Gen IV reactors are still in the drawing board possibly early prototype phase.

I'm fine with either to be frank. I like that Gen IV reactors should have much cheaper deployment strategies.

Anything is better than the "drop a nuke in the hole" plan. Both Gen III+ and Gen IV reactors can hit the market before all the red tape is cut for prototyping the hole bomb.

> We’re facing a catastrophe. I and others have described elsewhere that the path we’re on is much, much worse than even the most dire of predictions the IPCC makes.

There are a lot of processes we don't fully understand so your claim is hard to substantiate. Also, if that was the case then a lot of people would probably just accept their fate.

Worst case scenario is you blow the doors off of the facility and tons of superheated radioactive fluoride salts are blasted into the air, along with the vaporized particles of all of the workers and the fissile material in all of the bombs in the staging areas.

But surely the payoff would justify a 10-20x overbuild for the containment and research into extremely small payloads, no?

They actually want to detonate a H-Bomb every 45 minutes, all day every day. 32 nuclear explosions every day.

One does have to appreciate how these guys took anti-proliferation concerns with the nuclear industry and said "fuck it, everyone knows we're only doing this to make bombs, so lets make a shit ton of bombs". No more concerns about terrorists getting their hands on some yellowcake and making a dirty bomb. Now they have a full up H-Bomb factory moving so much product that security can get complacent.

And we can expand this out to every nation so everyone gets a nuke factory to keep the lights on. :D

It's so widely impractical.

It would have meant the end of nuclear arms control and non-proliferation efforts, an already difficult process. So yeah, that tends to arouse considerable negative responses.

Isn't the problem that the fuse for a fusion bomb is a fission bomb, and a fission bomb very violently disperses lots of radioactive material? What am I not getting?

It’s a sealed chamber underground. And the amount of fallout can be controlled. Some fusion designs are “cleaner” than others w.r.t. fallout.

From the wiki,

> A typical design called for a 4 m thick steel alloy blast-chamber, 30 m (100 ft) in diameter and 100 m (300 ft) tall,[9] to be embedded in a cavity dug into bedrock in Nevada. Hundreds of 15 m (45 ft) long bolts were to be driven into the surrounding rock to support the cavity. The space between the blast-chamber and the rock cavity walls was to be filled with concrete; then the bolts were to be put under enormous tension to pre-stress the rock, concrete, and blast-chamber. The blast-chamber was then to be partially filled with molten fluoride salts to a depth of 30 m (100 ft), a "waterfall" would be initiated by pumping the salt to the top of the chamber and letting it fall to the bottom. While surrounded by this falling coolant, a 1-kiloton fission bomb would be detonated; this would be repeated every 45 minutes. The fluid would also absorb neutrons to avoid damage to the walls of the cavity.

You can see the general design here, https://nextbigfuture.s3.amazonaws.com/uploads/2016/01/zyrEF...

You control the detonation with either an engineered or natural cavity filled with fluid. You can then use the fluid as a big thermal reservoir to run steam turbines. Per wikipedia:

>"Dropping about two bombs a day would cause the system to reach thermal equilibrium, allowing the continual extraction of about 2 GW of electrical power."

Now... the part you're not getting is that if you can do all that, you can almost certainly just use conventional fission power generation, which is what we really, REALLY need to be doing anyway.

Yes, conventional fission would be much cheaper to operate. But it, also, is no longer economically competitive.

So long as carbon-emitting sources are allowed to be used in the mix. That’s the real problem here.

Carbon sources will have been long since priced out of the market before you could finish building a nuke.

Great information! Project PACER was certainly an attempt to introduce fusion reactors with the technology we currently have Mastery of. In the early 1970s, both LANL and LLNL National Labs had PACER fusion programs. Dr. Ralph Moir was the project leader for this program at LLNL. Inertial Confinement fusion is "controlled fusion" to the very same extent as Magnetic Confinement fusion (the same fuels and fusion reactions are used and the same nuclear waste [stable nonradioactive Helium] is produced.

(more info) What are the reasons that nuclear fusion power generation is not yet realized? https://www.quora.com/What-are-the-reasons-for-nuclear-fusio...

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