DIY Nuclear Reactors After the End

[Minuteman37]

In This thread we discuss possible means of generating power after the end via nuclear energy, as well as how it would look, and the feasibility/resource requirements of such an endeavor.


I'm only a layman on the topic myself, but I seem to recall something about thorium molten salt reactors being feasible with TL6 technology.

[johndallman]

What kind of size of communities and economies are you envisaging in your AtE setting?

There is a significant technical gap, in that only two, small, molten salt reactors have ever been operated, and the last one was shut down in the early 1970s. Neither of them used thorium. While the physics and the theoretical engineering look sound, a significant engineering and development programme would be required in today's world to make thorium molten salt reactors into a practical technology.

Even if that had been done Before the End, making thorium fluoride for fuel requires industrial-scale fluorine production, which is one of the more tricky and dangerous chemical industry processes. You also need a supply of enriched uranium or plutonium to start your thorium-based fuel cycle, because it works by running a nuclear reactor on one of those fuels to supply neutrons to transform thorium-232 into uranium-233.

The most plausible way to have nuclear power AtE is to have a nuclear plant that was shutdown and mothballed before the catastrophe, plus a surviving cadre of operators, and a surviving supply of ready-fabricated fuel within transportation distance.

[Minuteman37]

Originally Posted by johndallman

What kind of size of communities and economies are you envisaging in your AtE setting?

There is a significant technical gap, in that only two, small, molten salt reactors have ever been operated, and the last one was shut down in the early 1970s. Neither of them used thorium. While the physics and the theoretical engineering look sound, a significant engineering and development programme would be required in today's world to make thorium molten salt reactors into a practical technology.

Even if that had been done Before the End, making thorium fluoride for fuel requires industrial-scale fluorine production, which is one of the more tricky and dangerous chemical industry processes. You also need a supply of enriched uranium or plutonium to start your thorium-based fuel cycle, because it works by running a nuclear reactor on one of those fuels to supply neutrons to transform thorium-232 into uranium-233.

The most plausible way to have nuclear power AtE is to have a nuclear plant that was shutdown and mothballed before the catastrophe, plus a surviving cadre of operators, and a surviving supply of ready-fabricated fuel within transportation distance.

Then what is the next most plausible way to have nuclear power AtE?

As for the scale of the settlement I'm not sure on exact numbers, but obviously it's large enough that scavenging solar panels and burning phonebooks for warmth isn't cutting it.

[malloyd]

Originally Posted by Minuteman37

As for the scale of the settlement I'm not sure on exact numbers, but obviously it's large enough that scavenging solar panels and burning phonebooks for warmth isn't cutting it.

Even a smallish nuclear reactor is a fairly major industrial project, and one that demands a lot of rather exotic materials and equipment. Yes you probably can build one with TL6, or maybe even TL5 technologies assuming you know how, and are more tolerant of risks and fatal accidents than modern societies. But that's with a full scale TL5 economy. If you can build an automobile factory or a battlecruiser, sure you might be able to build a nuclear reactor too, but none of those are projects for a "settlement".

Edit: If you want a settlement to have locally produced electric power, I really recommend either hydroelectric, or (wood or coal fired) steam engines, both of which are scalable all the way down to projects individual hobbyists or off-grid fanatics, can and do put together themselves with parts well within the reach of a small machine shop. Even getting nuclear fuel is hard - there's a reason we haven't had a terrorist movement or even small civil war deploy a nuclear or radiological attack yet.

[Minuteman37]

Well sure, we're not working within a full economy but there's still a lot of pre end TL8 tech and material around that doesn't need to be made from scratch that certainly lessens the infrastructure requirements.

[PTTG]

I think it kind of depends on how much you value your workers.

You might be able to get away with a big pile of mixed radioactives and having slaves keep it stacked so it stays critical.

[johndallman]

Originally Posted by Minuteman37

Then what is the next most plausible way to have nuclear power AtE?

I'm guessing you won't be satisfied with "Find a nuclear reactor manufacturing facility that had all the parts ready to assemble?"

Originally Posted by malloyd

Even a smallish nuclear reactor is a fairly major industrial project, and one that demands a lot of rather exotic materials and equipment. Yes you probably can build one with TL6, or maybe even TL5 technologies assuming you know how, and are more tolerant of risks and fatal accidents than modern societies. But that's with a full scale TL5 economy. If you can build an automobile factory or a battlecruiser, sure you might be able to build a nuclear reactor too, but none of those are projects for a "settlement".

The easiest nuclear reactor to build is a graphite- or heavy water-moderated design, because they don't require enriching uranium. That's a definitely TL7 industrial process. It's also kind of heavily regulated, because the same plant that enriches uranium for fuel can enrich it a bit more, for bombs. Oh, and it needs industrial-scale fluorine production, again.

Making sufficiently pure graphite that you can use unenriched uranium needs a pretty good chemical industry. So does making heavy water. You need either of these in quantities of tens of tons, which you aren't going to manage in a surviving high-school science lab. Late TL5-grade industrial plant can do it, but it's industrial plant, because the minimum quantities to make a working reactor are rather large.

These materials aren't generally found lying around in adequate quantities. This is because in these quantities, they don't have any uses except making nuclear reactors, and that's quite strictly controlled on safety and bomb-making grounds.

If you want a settlement to have locally produced electric power, I really recommend either hydroelectric, or (wood or coal fired) steam engines, both of which are scalable all the way down to projects individual hobbyists or off-grid fanatics, can and do put together themselves with parts well within the reach of a small machine shop.

This is vastly more practical than a DIY nuclear reactor.

Originally Posted by PTTG

You might be able to get away with a big pile of mixed radioactives and having slaves keep it stacked so it stays critical.

With the wrong radioactives, it doesn't go critical. With the right ones, it melts down, and gives you a new mini-apocalypse. Making and operating a controllable nuclear reactor is harder than this.

[cptbutton]

Originally Posted by PTTG

I think it kind of depends on how much you value your workers.

You might be able to get away with a big pile of mixed radioactives and having slaves keep it stacked so it stays critical.

SM Stirling wrote a story with this premise, where scavenged plutonium pits from unused nuclear weapons were used to create steam power.

[Ulzgoroth]

Originally Posted by johndallman

With the wrong radioactives, it doesn't go critical. With the right ones, it melts down, and gives you a new mini-apocalypse. Making and operating a controllable nuclear reactor is harder than this.

Though you don't actually have to achieve criticality to produce usable power. A safely sub-critical reactor pile would require a lot more mass and especially a lot more fissionable material than a proper reactor of the same power, but is a much easier engineering task if you somehow have enough material for it. (Essentially a giant RTG.)

[AlexanderHowl]

I really do not think that it is possible without external help unless you have a TL7 society with a minimum of 50 million people or a TL6 society with 100 million people. Even if you had people who understood the science, which is not going to happen in an AtE scenario, nuclear power is the hallmark of a developed TL7 society (nuclear weapons are much easier). Thorium can be used in place of uranium (you can use particle accelerators for the neutron bombardment), it is much more common, but it requires a much more advanced technology (it is really a TL8 technology, though TL7 examples exist).