I never wanted to write this article. There is already way too much conflation of nuclear energy with nuclear weapons, and even writing with the best of intentions and clearest of language I guarantee that someone will attempt to use this article as proof that nuclear is too dangerous because Bombs!
I ignore these people like I ignore anti-vaxxers, flat-earthers, and similar purposefully ignorant people because the method of producing nuclear weapons is completely separate from the production of electricity from nuclear reactions.
I understand that the thought of nuclear weapons is terrifying. They held and even still hold our world in the grip of fear that we might destroy ourselves with them. And I can’t stop that fear. No one can until either nuclear weapons are themselves removed from our abilities, or we succeed in building a world that Everyone agrees is not worth destroying.
First things first. Only fissile materials can be used to make a nuclear explosive. That basically means that U235 is the easiest to use because it occurs naturally in fairly large quantities. Using anything else like Pu-239 or U-233 really is just showing off.
One difference between making a fission weapon and a fission reactor is how pure the fissionable material you need is. A light water reactor needs between 3-7% of the input uranium to be the fissionable U-235 rather than the non-fissionable U-238, where a weapon needs at least 50% U-235 but the higher the better. But how do you enrich uranium?
This is a warehouse full of operational gas centrifuges. The difficulty with enrichment is that you are trying to separate two things that are chemically identical and only differentiated by a 1% mass difference. So the way you separate them is to make a gas, usually Uranium hexafluoride, and then you spin the gas inside these centrifuges really really fast to take advantage of centripetal force to draw the heavier U-238 to the edge and bottom of the centrifuge while the lighter U-235 gets “floated” to the center and top.
This is not a quick process. Made less so because adding the 6 fluorine atoms to the uranium reduces the mass difference to 0.8%, so it either takes a very long time to purify a single centrifuge, or you cascade it like shown in the picture. Pull the gas with the slightly higher U235 concentration out of the top, and the slightly lower concentration out of the bottom. The top goes on to the next centrifuge in line and the bottom goes back to the beginning to hopefully pull out some more of the stuff that’s left. Each centrifuge increases enrichment by usually less than 0.1%. And even that is only if you are being incredibly aggressive about it.
Now before someone starts going off about breeding plutonium in a reactor to use as a bomb, there is a slight problem with that line of logic. Plutonium-239 is a very good bomb material, Plutonium-240 is Too good of bomb material. The presence of too much Pu-240 can actually cause a plutonium-based bomb to spontaneously explode.
Not ideal in something that is meant to be a strategic deterrent I’m sure you will agree. And Plutonium 240- is made in the same process that breeds Plutonium-239 so if you want to make a bomb that doesn’t get too excited about its job, then you have to centrifuge your material anyways. And since the mass difference is less than 1/3rd that of uranium separation it takes that much longer and costs that much more.
So how do we keep an eye on people who might be trying to develop nuclear weapons with or without a civilian nuclear program? Well here’s where I get to flex my degree credentials. What do nuclear weapons and Olympic fencers have in common?
They both use a really interesting kind of steel called maraging steel. Fencers use it because it is extremely crack resistant, flexible, tough, and strong. Gas centrifuges use it for exactly those same reasons. The efficiency of a centrifuge depends on really only one thing, the speed at which it rotates. Speed it up and the forces get drastically increased, which improves the speed of the process and the efficiency of the separation. Gas centrifuges for nuclear weapons production can rotate at tens to hundreds of thousands of RPM. No one really knows the exact speeds except the people actually designing and operating them because… well Top Secret national defence kinda stuff.
The problem is is that very few materials can withstand those kinds of forces being exerted on them for long periods of time and are also corrosion resistant because the hexafluoride gases used in them are viciously corrosive. So what international organizations do is they monitor countries for their imports of materials that can be used to produce maraging steel. As amazing a material as it is, there aren’t many economic uses for it, so it’s hard to cover up a paper trail for it.
I know nuclear weapons are awful, terrifying, and generally just a bad idea. But trying to lump civilian applications of nuclear energy in with them is counterproductive and ignorant. You can’t put the genie back in the bottle and other such assorted clichés, and being childish by saying that all nuclear is bad because it’s possible to make bombs is neither productive nor true.