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So, the apocalypse has occurred, and for about 150 years humanity spent its time wallowing in misery, sorrow, and so on.

So moving on, in the northwest of Nevada there’s an abandoned nuclear reactor, that suffered minimal deterioration. A group of skinless mutants, humans that have transformed into necrotic (but radiation-immune) creatures. They decide to settle the abandoned plant, and to run it.

My question is, in a post-apocalyptic world, would it be possible for the group of mutants to run the plant?

Background Info

  • They have access to refined-uranium, from some Caravan-traders who mined it, so that isn’t a problem
  • As I said, they don’t have to worry about radiation towards themselves.
  • The main thing they lack is the ability to use heavy machinery. Everything has to be done with manpower.
  • If you think this is completely impossible, maybe provide alternatives
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    $\begingroup$ "They have access to refined-uranium" - refined (just chemically) uranium, or enriched uranium (isotopically)? $\endgroup$ – Alexander Sep 11 '20 at 16:31
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    $\begingroup$ I'm certain this has been asked before, but I can't find it. The answer is complex nuclear plants need both trained people and resources (a lot more than just uranium) to operate. If your story provides them, they can. If your story doesn't provide them, they can't. Also: This question asks how long a nuclear reactor will keep running post-apocalypse. This question asks what happens to the spent fuel pool w/o maintenance. $\endgroup$ – JBH Sep 11 '20 at 16:34
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    $\begingroup$ @Alexander Graphite would be easier to come by in a post-apocalyptic society than heavy water. $\endgroup$ – stix Sep 11 '20 at 18:00
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    $\begingroup$ Nuclear fuel, and knowledge of how to run the plant etc. are red herrings. The real stumbling block is that nuclear power plants cannot vary their output to follow the load; the are "base load" power generation facilities. This means that a nuclear power plant cannot run by itself, isolated from the grid; it needs the grid, and it needs a dispatcher to command the more nimble parts of the grid (the hydroelectric plants, the natural gas fired plants, the solar plants, the aeolian plants) to smooth out the variations of the load. Isolated from the grid the nuclear plant will shut down. $\endgroup$ – AlexP Sep 11 '20 at 19:30
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    $\begingroup$ @JBH Were you thinking of Can Average Joe reboot the nuclear power plant? $\endgroup$ – Andrew Grimm Sep 12 '20 at 5:21
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They can't restart a shutdown nuclear power plant because it requires an external electricity source to run the cooling systems, control systems, and so forth necessary for the startup process. They also have no resupply for consumables and equipment that breaks or wears out.

(Aside from that, after 150 years, even if the structure has undergone minimal deterioration, as you have said, much the equipment within would have failed naturally because of aging: the plasticizers in plastic and rubber components would have evaporated, making them brittle and crumbly, lubricants would have congealed or polymerized, electronic systems would be nonfunctional (common electrolytic capacitors have a rated lifetime of a few decades at most), there would be corrosion because of moisture, and so forth. Even if those are overcome, some sources indicate the shafts of the turbines are so heavy that they will bend by themselves if left in the same position for too long, rendering them unusable.)

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Short answer no, long answer probably no, but...

Any reactor of our current designs not actively managed by humans, even when shut down, will eventually suffer an accident, either from the spent fuel pool running dry or the reactor itself from decay heat. The Fukushima accident didn't happen with active reactors; they were shut down but still hot due to decay heat.

If, at any point in that 150 years, the core becomes uncovered, it will likely meltdown and, depending on whether an ignition source is present, explode due to hydrogen formation when its fuel's zirconium cladding gets too hot.

So more than likely the bigger problem is there won't be any abandoned reactors for your mutants to find.

However, if they somehow have no problems with radiation, and possess the appropriate knowledge, building a new reactor would be almost trivial.

The first reactors, called uranium piles, were little more than their names suggest: A pile of uranium and graphite as a moderator. The first was assembled and run without any shielding under the stands of the football field at the University of Chicago.

All your mutants will need to do is gather up enough natural uranium, form it into fuel rods (which might be difficult, since uranium is an extremely dense and hard metal), and assemble it with an appropriate moderator.

So what is an appropriate moderator? Well for natural uranium that would be heavy water or graphite. Heavy water is extremely difficult to produce and requires modern industry and technology, so you'd be stuck with graphite, which is also somewhat difficult to produce, but far easier than heavy water, and could conceivably be done by any society that has the technology to process uranium ore.

This ultimately means building the core becomes the easy part. The hard part? Getting a turbine and creating the cooling and heat exchange system.

Turbines require extremely balanced blades and very precise engineering. They're one of the most expensive parts of any power plant, nuclear plants included. This means they'll probably be out of reach for your post apocalyptic society. However, this is where your abandoned nuclear plant comes in.

Modern civilian reactors in the United States broadly fall into two categories: Pressurized water reactors and boiling water reactors.

In a PWR, the water is kept under extreme pressure and its heat is exchanged with a second isolated cooling loop to produce steam. This steam then drives the turbine. Unfortunately, the technology required for a PWR is almost certainly beyond your mutants, but all hope isn't lost.

In a BWR, the water is converted directly to steam in the core, then used to drive the turbine. This steam is weakly radioactive, and so makes the turbine slightly radioactive, which is one reason BWRs have fallen out of favor (but they still exist, and indeed Fukushima's reactors were all the BWR design). However, this direct conversion attribute of the BWR means it will be more within reach of your mutant nuclear engineers.

Let's go with the following scenario: Your mutants stumble across an abandoned nuclear plant that was never completed. Let's say it has its turbine and electrical infrastructure in place, but the boiling water core was never completed.

The reactor pressure vessel for the original reactor is on site in the reactor room, but was never completed. It has no fuel or control rod infrastructure, but the piping is hooked up. For all intents and purposes, it is a large, empty metal basin capable of holding water. The concrete containment structure also hasn't been completed, but that won't matter to your radiation resistant mutants.

Your mutants happen to have a bookworm among them who has spent her life studying artifacts and books from the past, and has a very good understanding of engineering principles, but no ability to actually create any of the technology she knows about. She correctly deduces the plant's purpose and technology, and has enough of an understanding of nuclear physics to at least, in theory, understand how to build a rudimentary uranium pile.

Realizing how precious and valuable this lost technology is, your mutants establish a colony at the plant and decide to complete it, presumably to generate power for society and attempt to help reestablish civilization.

They know that they can't simply build out the boiling water reactor, since it was designed for enriched uranium and light water as a moderator, and enriched uranium is well beyond the capabilities of what's left of human civilization.

However, they have access to large amounts natural uranium, perhaps because it's renowned as a very hard and dense metal that makes glass glow a pleasing shade of green. Let's also assume that they have a source of relatively pure graphite, and cadmium, which is renowned for its ability to create yellow pigments. The toxicity of uranium and cadmium as heavy metals is a moot point, as the harsh conditions of the apocalypse has forced the evolution of an extremely high tolerance for them, along with the radiation that a nuclear core would emit.

The mutants are able to gather enough of the raw materials, and their craftsmen are able to build uranium rods and flat cadmium plates. They also purchase large blocks of pure graphite and drill holes through the center of them while also cutting them into perfect cubes.

Inside the abandoned reactor pressure vessel, they stack the graphite blocks into a much larger block, leaving grooves between some sides of the blocks. Between some of the graphite blocks they slide the cadmium "control plates" into place to prevent the reactor from going critical. Lastly they slide the uranium rods into the channels they cut into some of the graphite. The rods are designed to be slightly narrower than the channels in the graphite blocks, and thus allow cooling water to flow around them.

They flood their contraption in the reactor pressure vessel and tie chains to the control plates.

The reactor vessel's cap is lowered into place from above using pulleys and levers, as well as manpower from the strongest mutants in the group.

Ahead of time, they had the forethought to cut a small window in the side of the reactor pressure vessel. The window is made from sapphire glass they found at an abandoned laboratory and is capable of handling extremely high heat and pressures, but they won't have to worry about pressure too much in their reactor design.

Very carefully, and extremely slowly, they withdraw some of the cadmium plates. One of them peers into the reactor through the window and notices a faint blue glow in the water below. This Cherenkov radiation is an indicator that they have successfully achieved criticality. The water acts as a fine shield at lower powers, but even at high power the mutants' great resistance to radiation means that they will be fine with people in close proximity to the operating reactor.

They then slowly draw the control plates further, carefully monitoring the brightness of the blue glow of the reactor. Soon the water begins to churn and heats into steam, and the steam system of the plant pressurizes. The turbines roar to life as they consume the steam. Your mutants have managed to make the plant generate electricity.

However, 150 years is a long time, and nuclear power plants are extremely complex machines. Without proper lubrication, the turbines are unable to spin at full power, and the relatively crude reactor design is not very efficient at generating steam.

The plant is unable to generate anywhere near its original 1 gigawatt-electricity design, but it doesn't matter. There isn't enough civilization to consume that much energy anyway. Your mutants are satisfied with a few hundred megawatts of electricity, and the fact that the plant works at all is a marvel of the region and causes the mutant settlement to grow rapidly. A new city is formed around the abandoned plant.

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  • $\begingroup$ Minor disagreement--while it will Fukushima for some years if not cooled in time the radioactivity decays to the point it doesn't destroy itself if not cooled. $\endgroup$ – Loren Pechtel Sep 12 '20 at 3:53
  • $\begingroup$ Instead of having to rely on finding working turbines, why not go back a level in complexity and simply construct a good old steam engine? Sure, it's inefficient, but it is something that in theory can be built completely by hand and a reasonable sketch of how to do so is found in any high-school physics textbook. Also instead of taking the detour via electricity it might be a good idea to use the mechanical energy directly, as apart from maybe running a few lights, most of the energy will likely be used mechanically anyway, for pumping water or running heavy manufacturing equipment. $\endgroup$ – mlk Sep 12 '20 at 13:31
  • $\begingroup$ Although it's a nice idea, the serious issue is that measuring neutron flux visually by Cerenkov radiation isn't viable. In my experience, you won't see a glow until your plant is producing at least few hundred watts. In order to get this power, you are either running some weird source driven sub-critical plant (unlikely), or you would have taken it critical already. Controlling a reactor is NOT simply like pushing the pedal of an internal combustion engine. If you can't accurately measure flux, it is easy to take it prompt critical, meaning everyone is going to have a very bad day. $\endgroup$ – MadScientist Sep 14 '20 at 9:54
  • $\begingroup$ mlk I was trying to keep with OP's desire to use an existing plant. MadScientist CP-1 ran just fine eyeballing it. There are a lot of factors going into whether or not they could easily go prompt critical. TRIGA reactors self regulate and are sent prompt critical as a matter of course for experiments all the time. @LorenPechtel Fukushima already destroyed itself, so I'm not sure what your point is there? The spent fuel pool will be the biggest concern, but the reactor itself can still overheat if uncovered even decades later. $\endgroup$ – stix Sep 14 '20 at 16:25
  • $\begingroup$ @stix The point is that if you can cool it long enough eventually it will survive without cooling. $\endgroup$ – Loren Pechtel Sep 14 '20 at 17:52
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It depends on what kind of reactor

  1. A full scale fission reactor. No, even with trained personnel, the maintenance needed to operate one of these in the best of conditions requires complex supply chains that just don't exist anymore.
  2. A research (university) reactor. Maybe, if they had stocked a large number of spare parts and materials. You say you have refined uranium, but do you have enriched? This could pose a problem.
  3. A large Radioisotope Thermoelectric Generator (RTG). If instead they just find an abandoned factory that made RTG's for the space program, then it's pretty simple. Alternatively they could also maintain lots of small RTG's. This is probably a pretty good solution as they might also have access and materials in order to produce more of them.
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    $\begingroup$ RTGs are not viable, power output is quite small, very limited number in existence, and they degrade over time due to half-life of the radioactive source, and degradation of the thermocouple materials due to their radiation exposure - Pu-238 is is such short supply NASA has to ration it, and the only other likely radiation source used for RTGs that would be viable after 150 years would be Am-241, but it's power density is lower and it's radiation is more damaging. Power would limited to hundreds of watts at best. $\endgroup$ – Gary Walker Sep 11 '20 at 21:01
  • $\begingroup$ @GaryWalker Note that the OP does not state a minimum power requirement, additionally the procurement of new radioactive materials seems to be somewhat hand waved in the OP, so please don't be too quick to judge. $\endgroup$ – Mathaddict Sep 14 '20 at 20:25
  • $\begingroup$ OP does want to start up a nuke plant that is sure to be hundreds of megewatts, I suspect the intention was to have a significant power source. All of the materials suitable for RTGs are only available from running a nuclear reactor or particle accelerator.. $\endgroup$ – Gary Walker Sep 15 '20 at 11:55
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To get it operational, assuming all the parts are good or spares are on hand, and there's fuel available, this could be easier than you might of thought:

  • There have only been 4 reactors approved for construction since 1977, and 2 of them the builder went bankrupt. There's 102 nuke plants in USA, so you have a 97% chance of working with 1970's tech.
    • This tech is real easy to work with - repairing your VW Beetle by the side of the road with a screwdriver and duct-tape kind of easy.
  • They'd need to understand about the complications of things, especially cooling. For example: that you need to cool the core for like 3 days after shutting it off, even in an emergency. But I'm assuming there are manuals and they can read.
  • It's really easy to run a reactor if you don't care about radiation. You can just walk onto the core, and reach down and move the rods by hand if you need to. You also don't need to care about the rest of the world, you can just irradiate it, which is much easier than running a plant safely.
  • This also means you can bypass any faulty circuits or "non-essential" things. You need the core, cooling, and a turbine, everything else "safety systems" or "remote control" is nice but can be kludged out.
  • This "move rods by hand" approach can be used to simplify the startup process. If you turn off all the safety protocols (or just rip everything non-essential out), I believe you can cold start a reactor by filling up the coolant, swimming / wading in (or walking on the core), inserting the fuel rods, and partially removing the control rods until you feel heat. Then once the power starts you can start using your control systems from the control room. This would kill a normal human, good thing these guys are immune to radiation.
  • They will be unable to manufacture spare parts, so after enough breakages, they'll have to salvage one reactor for parts to fix another, eventually diminishing returns until the last reactor stops.
  • You said refined uranium is available. But, is it really going to be long term? It's really hard to make, and it's a lot of processing from what you mine, no way some miners can refine it in the field. The centrifuges are intense:
    enter image description here

There might be an easier way, looking through stats on Nevadas power generation, there is a lot of solar generation in Nevada whose maintenance requirements is basically a good dusting. This might be easier.

Should also mention that there's also no nuclear power plant in Nevada, and I can't find any proposals to build one.

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  • $\begingroup$ “ Should also mention that there's also no nuclear power plant in Nevada, and I can't find any proposals to build one.” Obviously my world takes place in one where there was one $\endgroup$ – DT Cooper Sep 11 '20 at 17:29
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    $\begingroup$ "It's really easy to run a reactor if you don't care about radiation." - is it? If the radiation gets out of the core, it's only because something has been physically destroyed. If you're irradiating the surrounding area, it's because the power plant is already broken. Safety systems protect people by protecting the core, but even if you don't care about protecting people, you still need them to keep the core itself safe. A meltdown is bad news even if you're immune to radiation. $\endgroup$ – Nuclear Hoagie Sep 11 '20 at 18:35
  • $\begingroup$ Most US reactors are PWR reactors, meaning they are meant to run pressurized at ~2200psi. You can't go swimming in that, and trying to start up at a lower pressure, with an open containment will probably lead to a Chernobyl-type event. $\endgroup$ – IronEagle Sep 12 '20 at 2:01
  • $\begingroup$ Also, look at solar panel decay rates - most are only rated at 80% of the initial capacity after 20 years. 150 years later.... $\endgroup$ – IronEagle Sep 12 '20 at 2:03
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Others have already brought up the problems of not being able to start the plant up (requires megawatts of electricity) and cooling (when shut down the power goes to 3%, not 0%) but there's another related problem also--refueling. Obviously the plant isn't operating during refueling operations and thus there's no power for the machinery that deals with the spent fuel. While you call them radiation-immune I think you must be talking about ordinary levels of radioactivity. The spent fuel rods come out so hot that an ordinary human will have a hard time picking them up--because they'll die in the process. There's simply no such thing as truly radiation-immune so while they might not get cancer from it there's no way to protect against your brain shutting down because the nerves aren't transmitting impulses correctly due to the radiation flux.

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  • $\begingroup$ Maybe the mutants could extrapolate the technology of hand-operated cranes to come up with some low-tech materials handling. $\endgroup$ – Gary Walker Sep 12 '20 at 15:04
  • $\begingroup$ @GaryWalker It's not just the lifting, but you need remote operation. That's going to be pretty hard without electricity. $\endgroup$ – Loren Pechtel Sep 12 '20 at 18:08
  • $\begingroup$ Thus the term extrapolate. $\endgroup$ – Gary Walker Sep 14 '20 at 12:18
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A nuclear power plant is just a big steam engine: pressurized steam used to push a rotor within a stator to generate an electric field. The only thing 'nuclear' about it is that nuclear fission is used to provide the heat that boils the water to produce steam. The main problems with running such a plant are:

  • Controlling the rate of reaction so that the heat generated doesn't become excessive and melt the core (leading to a runaway melt down)
  • Maintaining the chamber, piping, and other components so they can handle the extremely high pressures the pile generates
  • Coping with waste: spent fuel rods, radioactive water from the pile, irradiated parts, etc.

Anyone with an 19th century understanding of mechanics could run a nuclear power plant, as long as they got the gist of point #1. Maintaining and repairing it would be more challenging, because most of the components use high-strength alloy steel machined to exacting tolerances. If something breaks, your mutants likely wouldn't have the technical knowledge or industrial base to replace it; they'd have to scavenge from other plants. But note that many of the components for such a plant are large: multi-ton pipes or generators that would produce a Stonehenge-like challenge for movement and installation. Radiation and waste would be a separate problem. They can't just pile spent rods in a corner: spent rods have significant fissionable material remaining, and could still melt down and poison the entire water table.

It's also worth noting that most nuclear power plants — unlike traditional steam engines — are operated remotely, with the mechanical aspects governed by a computer-driven console. This isn't a matter of pulling the right levers or turning the right pressure valves; your mutants would have to piece out how to use the dials, buttons, and command structures of the electronic system. That might pose a bootstrapping problem, since the console itself likely draws power from the plant, meaning they might have to start the plant running before they can begin to figure out how the console works. But, you know... details, details...

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  • $\begingroup$ Waste disposal just about amounts to "piling the rods in the corner". Though that corner needs to be managed carefully, and use some water filled pool for cooling. You're spot on about spare parts though. $\endgroup$ – John O Sep 11 '20 at 16:26
  • $\begingroup$ I beg to disagree with "Anyone with an 18th century understanding..." If this were correct, Chernobyl team was supposedly more backwards than 18th century. $\endgroup$ – Alexander Sep 11 '20 at 16:35
  • $\begingroup$ @Alexander: Well, I probably should have said '19th century'; 18th is a little early. But that aside, being able to 'run' something does not mean it can be run without risk. Chernobyl had design flaws in the reactor itself, which made the margin for error smaller for those running it, and there's reason to believe those people were not well-trained for the task. but that doesn't mean that competent amateur couldn't effectively run a well-designed system. $\endgroup$ – Ted Wrigley Sep 11 '20 at 17:05
  • $\begingroup$ @Ted Wrigley this brings up the question - how can you train people to operate nuclear plant while restricting their knowledge only to mechanical and thermodynamical aspects, leaving nuclear physics and electronic instruments out? $\endgroup$ – Alexander Sep 11 '20 at 17:12
  • $\begingroup$ @Ted Wrigley or maybe you presume that nuclear plant may (at least in theory) run like a car? Many people know how to drive a car, but not so many know how to fix one. $\endgroup$ – Alexander Sep 11 '20 at 17:15
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Viable Post-Apocalyptic Power Systems

Hydroelectric. Existing systems will have to be rebuilt, the power generation equipment and related systems require regular maintenance. Some parts may well be salvageable. A small head (say 5 meters or so) with sufficient water flow can generate 10 or 100 kw (or more). If you have an existing lake nearby, you can even use it as a reservoir fairly simply.

Many small dams will not last 150 years without maintenance, they are generally designed for a lifespan of 50 years (surprisingly low to most people). Though the dam may last 150 years without maintenance, they would likely be unsafe. Though the Hoover dam might last 1000's of year, it is built more like the pyramids than typical dams.

Wind power Very similar to hydroelectric in terms of technology level. Not as power dense, but can be sited without having running water available.

Geothermal Much more limited availability for low-tech civilization, but there are a few sites that are natural locations. Geothermal breaks down over time too, so they would also have to be built.

Steam Power Burning stuff is an excellent low-tech power source. Most likely wood as the easy to find coal, oil, and gas deposits are long-gone - assuming there are any forests left, since people like to stay warm and cook their food. Without high-tech pollution control equipment this will be dirty, but that is unlikely to matter for quite some time due to limited usage. Since high-pressure boilers are necessary for high-efficiency, you would prefer to have engineering expertise. The Purdue Boilermakers have that name for reason. Not as efficient as internal combustion engines, but steam power is considerably simpler.

Alternative Nuclear Collect and focus sunlight. Solar panels not enough tech available to manufacture. But focus some mirrors on a central tower and you could get enough energy to be useful. This will be more challenging, and will not work very well (tracking mirrors requires more tech), and does not work at night (molten salt heat reservoirs will not be an option).

All electric power systems will be downtime for maintenance. The reason electricity is available 24x7 is the large number of generation plants. Coal power plants are only available 68% of the time, nuclear over 90%, but with a single power plant there will be downtime, and the electric grid is a high-tech long-forgotten memory.

Don't use electric systems at all Transmission of mechanical power via belts, gears, shafts is effective and even lower tech. Electricity wins because it is so easily controlled and flexible, but older factories relied on mechanical power transmission systems

Hopefully, you will be able to find some old books that describe engineering principles somewhere. Books can easily last hundred of years - assuming you don't burn them to stay warm.

Mutants are not required for any of the systems above. However, a mutation for high-intelligence would certainly be a large bonus in any of the restarting civilization scenarios. None of the systems above would be easy, you won't have any industrial base, so no machine tools, even a flat surface plate could be hard to find (needed for making tools). There will be many challenges for restarting electric power in any form.

For a story you probably need to consider the justification for electric power at all. Electricity is not about basic needs (water, food, clothing, shelter), but about providing improvements to those necessities and only later for the luxuries. Electric power was introduced to a world that already had quite a bit of industry in place but the advantages in lighting were a key element in early adoption.

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A thought here: Everybody (myself included) has taken the question literally--one reactor. However, reactors often come in groups. One reactor can provide the power needed by the other reactors.

This does not avoid the initial startup problem or the refueling problem, however.

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