Neil DeGrasse Tyson Reveals Why Iran's Centrifuges Are So Dangerous

[00:00:00]If you want to make a bomb, you have centrifuges.

[00:00:05]It's that simple. [music] The centrifuges invented to create weaponsgrade U235 can centrifuge so fast that the molecules themselves are experiencing nearly a million G's. That's what you need. In this video, astrophysicist Neil Degrasse Tyson talks about what goes into the process of enriching uranium.

[00:00:30]Why don't we watch this video together?

[00:00:32]I'm going to have some thoughts to add as we go, and then I want to know what you think about it in the comments. You might have heard something on the uranium enrichment program in Iran and the centrifuges.

[00:00:44]So, let me just put some of that in context in case you were wondering what's going on. So uranium, one of [music] the elements on the famed periodic table, it has 92 [music] protons in it. And the number of protons in an element defines the element.

[00:01:04][music] Uranium is traditionally considered the heaviest natural element. We look around the universe. Do we see anything heavier than that? No. No, not [music] not really. We, however, are not content with what nature gives us. We want more.

[00:01:20]So, in particle accelerators, we bombard the nuclei of elements and we can make heavier elements than uranium. And we've done so. Last I checked, we're up to [music] 118.

[00:01:34]That's 26 more elements than the universe gave us. So frankly, I think that's badass [music] for humans with our primate brain being able to come up with that kind of advance on something birthed in the universe. Anyhow, when you find uranium in nature, typically it's uranium ore, it comes in completely mixed in three varieties. There's uranium 234, uranium 235, uranium 238. Oh, by the way, these versions of uranium are called isotopes.

[00:02:14]Anytime you vary the number of neutrons in an in an atom, it's an isotope. They all have 92 protons, but all the rest of that number comes from neutrons. It's got way more than 92 neutrons. Oh my gosh, they're crammed into the nucleus.

[00:02:30]So many of these big elements are unstable for that reason. Okay? There's a lot going on in the nucleus and the nucleus wants to spontaneously break apart into lighter elements. Neutrons, by the way, go wherever they want. If you were a proton, there's only so [snorts] close you can get to the nucleus because the nucleus is positively charged and you're positively charged. You'll you'll repel. So neutrons since they are neutral they are offered no resistance walking straight into the nucleus of atoms. [music] So here is uranium 235 and it's hit by a neutron. What happens is the nucleus splits into two parts two lighter atoms. If you measure the mass of those two lighter atoms, it is less than the mass of the original 235. Where did the mass go? [music] Ask Albert. Hey Einstein, where did the mass go? E= MC².

[00:03:34]Energy is the mass time the speed of light squared, which is just a constant in that equation. So energy and mass are equivalent. And if you lose mass, you gain energy for having done so. Anything that's radioactive emits energy. So that's not what's interesting about [music] uranium 235. If you split it, the splitting creates two or more new neutrons. If I have a a collection of uranium 235 atoms and I split one of them with a neutron, two neutrons pop out the other side. They hit two other atoms. Now we're up to four, then eight, then 16. This doubles fast [music] and you get what we named back at the birth of atomic energy a chain reaction.

[00:04:29]And each one of those reactions releases energy. And [music] given the kind of thinking that goes on in warfare, this wasn't simply a physics experiment that you write up in the journal. It was immediately weaponized to create a bomb. So [music] it turns out uranium 234 doesn't behave. You can split it, but it doesn't shoot out extra neutrons on the other side. So you'll get the energy from splitting one of them, but you're not going to create a chain reaction.

[00:04:59]Same problem with uranium 238. It's only the 235 that has [music] this property.

[00:05:05]If you get enough uranium in one place at the same time and start the reaction, you light the fuse. Now, I guess for myself, I understood that uranium 235 was special in some way, but until he explained it here, I didn't fully grasp why. And that makes so much sense. Now, in the second half of the video here, he he starts to explain what it actually means to enrich uranium. If you want to make a bomb, you want to isolate the uranium 235 from the uranium 234 and 238. Most of the uranium ore is uranium 238.

[00:05:41]Not useful for you. About no more than 1% of the uranium that is mined [music] is uranium 235.

[00:05:50]So you want to enrich that. You want just the uranium 235. Well, how are you going to do it? These atoms [music] are mixed together completely.

[00:05:58]How are you going to pull out the one that's in between the other two? Use a centrifuge.

[00:06:04]Well, centrifuges don't work on solid matter. You have to turn the matter into a fluid. It's a homogeneous [music] substance that takes the shape of its container. So, liquid is fluid.

[00:06:14]So is gas. The study in physics of fluid dynamics is the study of objects moving through gas and liquid. The same formulas apply in both cases. Back to uranium. [music] One way to do this is to turn it into a liquid, but turns out it's easier to turn it into a gas. Once you gasify the uranium, you now centrifuge it. You spin it. the centrifugal forces will separate out the U238 from the U234 leaving the U235 in between those two. So these centrifuges are complex bits of engineering to siphon out the uranium 235 in between the 234 and 238.

[00:07:05][music] Now, if you pull it out when it's enriched by 5%. [music] That would mean what you've pulled out is 5% [music] uranium 235. That's good enough for nuclear power plants.

[00:07:20]Sure. [music] Want to make energy from fision? Go right ahead. Up the purity to 20% or more. That's enough to power [music] sort of nuclear propulsion in for example nuclear [music] submarines for the Navy. And the value of that is it can stay underwater for much longer periods of time before [music] refueling. But to make a bomb, it has to be so purified that at least 90% [music] of the uranium that's extracted is composed of uranium 235. So [music] it all depends on your goal.

[00:07:58]>> So that's fascinating to me because I have read these articles. I've heard these pundits talking about the degree to which it is acceptable for Iran to have enriched their uranium whether it's 60% or right and and I was sort of like oh okay so I guess more is worse or better but but this makes it so much clearer. We don't think of just living on earth as a centrifuge. But in a way, it is. On Earth, you live in a centrifuge of 1g. That's why your Italian salad dressing settles out.

[00:08:34]Okay? The denser material goes to the bottom, the lighter goes to the top.

[00:08:38]That would be the vinegar, which is denser than the oil. You just centrifuge it by just setting it down in Earth's gravity at 1g. [music] If it was 2g, that that process would happen faster. Now back to uranium.

[00:08:50]What's the mass difference between U234 and U235?

[00:08:56]It's one neutron. Yes, they have different mass, but it's a tiny fraction difference. [music] So for a centrifuge to be able to separate them and distinguish the two, it's got to be really high G. And in fact, [music] the centrifuges invented to create weapons U235 can centrifuge so fast that the molecules themselves are experiencing nearly a million G's. [snorts] That's what you need to separate out these three isotopes so that you can isolate the U235 in the middle. There are details I'm not sharing because for they differ for different centrifuges but [music] the detail doesn't change the basic idea that I'm sharing with you. If you want to make a bomb you have centrifuges.

[00:09:50]It's that simple. So something as simple in concept as a centriuge which medical [music] professionals use to separate platelets from your plasma in your blood. When taken to its extreme limits, who would have thought that a centrifuge can actually influence the balance of geopolitical [music] power in the world?

[00:10:17]That's a bit of a cosmic perspective [music] on this. What's up with that?

[00:10:23]>> I think it's fascinating. Neil deGrasse Tyson of course does is careful here not to take a political side especially as it pertains to the situation that's continuing to unfold in Iran. But uh you know understanding the actual science of it I think is absolutely fascinating and the idea that we as a country might be all right with a hostile uh country like Iran hostile to us anyway. uh having uh enrichment facilities as long as they didn't enrich it past a certain point makes a lot more sense when you understand the actual physics of it. Um, let me know what you think in the comments.