Eli5: How are Nuclear Weapons different from Nuclear Power Plants?
In: Physics
Nuclear fuel rods are basically the same thing as the coils on an electric stovetop, just instead of being heated by electricity, they more or less heat up all on their own. And keep releasing heat for a *long* time, just less and less over time. Very different from a nuclear explosion, which you probably understand creates a violent explosion.
Now, nuclear waste is not fuel that is “completely done”, it’s simply all the fuel rods that can’t release enough heat to continue being viable in making commercial scale power. They still heat up. A lot. And they stay hot for *many, many* years. It’s just one little extra “fuck you” nuclear waste has for us in the challenge of keeping it safely contained.
Fun fact: this “heats up all on its own” thing is the major contributing factor to why Earth’s core is still molten today. Radioactive elements in the Earth’s interior are decaying and heating it up, just like spent nuclear fuel rods do to their containers. This indirectly powers all geothermal processes like volcanoes, earthquakes (via plate tectonics), geothermal vents, and the dynamo that creates the global magnetic field. In a way, you could say these are all “nuclear-powered” phenomena.
What is the difference between a stick of dynamite and a gasoline engine? Both are using chemical reactions to create energy. You can’t really make a gasoline engine explode violently unless you completely disassemble it into component pieces and reassemble the component parts into something more explosive. You can’t run an engine on TNT either, without chemically breaking it down and re-configuring it.
Nuclear power plants and nuclear reactors have the same sort of relationship. They both generate energy from the same nuclear source, but you can’t make a nuclear power plant work as a bomb, and you can’t make a nuclear bomb work as an effective power plant.
Nuclear power plants are designed to release nuclear energy in a very slow, controlled manner. This produces useful heat, which can be used to generate electricity. A nuclear bomb is designed to produce nuclear energy extremely quickly, the fast release of energy results in an explosion.
nuclear power is 2 oxen yoked to a plow used by a farmer to grow crops
nuclear weapons are 10,000 oxen stampeding across a field, obliterating everything in their path
One is like driving your car using the petrol in the tank.
The other is like pouring the petrol out and setting fire to it.
They use the same energy source, but release it in different ways at very different speeds.
My reactor uses 5% enriched fuel.
A bomb uses 99% enriched fuel.
My reactor has an automatic shutdown system and is designed to minimize reactivity.
A bomb doesn’t stop once started.
Nuclear materials get “angry”*.
The stuff in a nuke would just punch you in the face, while the stuff in a power plant will talk about it instead.
The energy released is useful, either for making things disappear, or for boiling water to spin a fan to make power.
*Note; I am not qualified in this field, but that won’t stop me.
They differ in (i) the amount of power produced and (ii) the speed at which it is produced (I am using the word power in a general way).
I am really making it sound easy and simple here, risking to sound wrong even. The attempt is to point to the process not explain it faithfully….
When a nuclear reaction begins, each neutron from an atom knocks three more neutrons from other three atoms, releasing heat in the process. Each of these three neutrons knock 3 new ones each releasing three times more heat. And those 9 neutrons then end up knocking 27 neutrons, releasing even more heat. Thus, it becomes an ever-intensifying chain reaction releasing catastrophic amounts of heat. That’s nuclear bomb (based on fission). Since the release happens VERY fast and a tremendous amount of heat escapes, the result is devastation.
In nuclear power plants, the same principle applies. One neutron knocks out three more, releasing heat in the process. However, this time control rods are interspersed that absorb 2-3 excess neutrons, thus leaving only 1-2 more neutrons to go their merry way knocking out more neutrons. Heat does get released, but it is less in amount, and it is produced slowly, in a controlled fashion. So this is a controlled chain reaction. And it can be controlled depending on how many free neutrons you want knocking around. This is how nuclear power plants generate heat.
Nuclear bombs have an uncontrolled nuclear reaction where it is forced to go “critical” nuclear reactors have inhibitors which stop the reaction from being out of control and going “critical”.
A nuclear power plant is nothing more than a steam factory. It takes something that’s hot (the nuclear material) and uses it to heat up water into steam and then the steam spins a turbine that creates electricity. You can do this with anything that is hot and can heat up water into steam. You could burn things, like oil or coal or trash or wood. We just like to use nuclear material because we can keep it hot for a LONG LONG LONG time without needing to replace it, unlike the other materials.
A nuclear explosion is a very (very) tightly controlled runaway reaction of a small amount of material using explosives to compact and crush the material in a very specific manner. You cannot just accidentally have a nuclear explosion. It needs to be done in a very particular way to have the desired effects.
A nuclear power plant we put in radioactive rods. These rods do not explode. They just generate a ton of heat. The heat causes water to turn to steam, just like in a gas or coal power plant. The steam then rises, and turns a turbine, which then creates electricity. The steam is then cooled back into water, and then ran back through the system again and again, creating more and more electricity.
In a nuclear weapon, we use weapons grade radioactive material, uranium or plutonium, and we surround it with another type of conventional explosive, usually in a ball shape (for the first stage). Then, when the outer conventional explosion happens it pushes the highly radioactive material in on itself, and causes the radioactive material to explode. It’s a lot more complicated than this because it actually involves a bit of fission and fusion to make modern day nuclear weapons, but that’s the simplified version.
So in a nutshell: Nuclear Power Plants heat up water, and have no explosions. Nuclear bombs use explosives to compress radioactive material so it causes a big explosion.
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