Chernobyl Episode 2 - Please Remain Calm - Nuclear Engineer Reacts 

"you'd think that a hospital near a nuclear reactor would have a radiation specialty.... but if RBMK reactors don't explode then why have it?" Now you're getting into the soviet mindset!

I really love the story of General Pikalov, the man who drove the truck in to get the dosimeter reading. He had survived the WWII battles of Moscow and Leningrad, and he became an expert in cleaning up hazardous waste. He actually handled the decommissioning of some WWI German gas weapons and he helped clean up a few toxic spills in Cuba over the years. When he arrived at Chernobyl, he made his young driver get out and stay behind while he drove himself the rest of the way in. He got there the afternoon after the explosion and knew it was BAD, despite what they were saying. He is recorded as telling his driver, “You have yet to become a father.” His officers also organized two young soldiers to go with him in the truck, but he wouldn’t let them go, either. Pikalov was the man who mapped the more dangerous areas, found most of the ejected core fragments, helped get the robots, etc. His officers went on record as saying he slept two hours every night and worked the rest of the time. He went partially blind from radiation exposure by the time he was finished. This is a horrific tragedy for so many, but it also shows us how heroic some people can be.

Regarding the "Bullet" analogy : Remember that he's faced with explaining the situation to politicians of which most have absolutely no understanding of nuclear physics at all. But most of them are veterans of ww2. So that bullet analogy is actually a quite clever idea to make at least the rough concept of the physics and graveness of the situation ascertainable to them.

Starts second video with "Good corrections". Basically "forget my ego, we're after truth". Instant subscribe.

“You’ve made lava.” At minute 23: I’ve worked with a ton of Russian guys; that reaction and “deadpan” incredulity is spot-on old Russian guy.

I think the issue you're missing with the "bullet" analogy, is that, no, he wouldn't have had more time. Remember, he was describing this to people who where already trying to downplay the entire incident. He was purposely trying to scare them into action.

The section at 14:15 with the smoke plumage was not "added for dramatic effect". When the reactor hall exploded, it lit a huge portion of the tar roof on fire as well as the thousands of pounds of other flammable items like wire shrouds, insulation materials in the walls, wood interior sections, etc. which caused a giant plume of smoke.

The podcast about this series actually talks about how the flashlights actually went out in real life. The screenwriter knew people may not believe it, but it happened.

So I've listened to the podcast that accompanies each episode, and the thing that's clear to me is that they were more making an adaptation of the book Voices from Chernobyl, which is a collection of primary accounts of the accident. What this means is that there is a bunch of stuff in the show which isn't scientifically accurate, but which *is* what the people believed at the time. This includes the belief that being near radiation patients could be harmful, and the stuff about her baby in later episodes. Like, that nurse is smart, but not 100% well informed, which is true about just about every part played in the story. So, from a sense of being 100% scientifically accurate, it's not going to be that, but being accurate to how those people reacted to the situation and their rationale behind it, that's accurate.

The issue with the fuel getting into the bubbler tanks was a "real" concern. In that, at that time, the scientists were concerned about it. However, the movie mangles their concern into one about steam. The concern was that the fuel mixing with the water/steam would allow the water/steam to moderate the neutrons and the whole mass would reach criticality. This is definitely a 'worst case' scenario type of thinking, and its not clear how probable the scientists thought it might actually happen. Its very reminiscent of the early concerns with the Trinity test. There was some very early data that suggested the temperature required for nitrogen to fuse would be less than the temperature of a fission bomb, and that the energy released by nitrogen fusing would be enough to sustain further fusing. Thus, the trinity test could ignite the world's atmosphere. This concern is often written about in the history of the atomic bomb, however, it could be looked as 'silly', because we know now (and we knew well before the test), that the fusing temperature was orders of magnitude greater than the atomic bomb. We tell the story, because it gives us an indication of the fears that existed at the time. In this show, we see the fears of scientists with very little time on their hands, however the movie again did decide to explain the concern as a steam explosion and not one of a criticality. Source: www.theguardian.com/environment/2005/apr/25/energy.ukraine

About the "don't touch them, you'll get sick" thing. It was a real misconception at the time that people who had been irradiated were dangerous to be around. We know now that individuals with radiation poisoning are not dangerous to others, but back then there was a great deal of misinformation coupled with fear and lack of knowledge on the subject.

With regards to the sand thing: I work with graphite frequently, often using it as a spacing material to ceramitize Carbon-Silicon Carbide composites. This involves bringing it to over 1000 C (over 1800 F). You can get the stuff to ridiculous temperatures and it'll essentially remain unchanged provided you're doing so in either a vacuum or inerted environment with something like purging with argon and keeping it under positive pressure within a vessel throughout the process. (Feeding argon through it the entire time.) Once you introduce oxygen, even at really low levels, the graphite will actively degrade at elevated temperature. At 600C in the presence of low levels of oxygen, degradation becomes very apparent. In the case of Chernobyl, (according to a quick search), it looks like the core was between 2200C at the initial, down to 1600C 4 days later. At those temperatures and exposed to atmospheric O2 levels, it would have gone to a white ash that was probably starting to coat the area. (The heat from the core throwing it up in the air.) The best I can figure is that dumping the sand on it would have been an attempt to both smother it and to prevent the remaining contaminated ash from flying around. (I'd assume it would also weigh down some of the other fission products being released from the exposed core as well.) There'd still be superheated graphite and other fun things underneath, but as long as it isn't actively decomposing in O2 and the ash allowed to fly up in the atmosphere, it's one less thing to have to worry about at that moment. Doping it with boron was obviously to have something absorbing the radiation. (Better than nothing.)

The mission of three "divers" into the basement levels of the reactor was largely based on wrong assumptions and missing information. For instance the whole reason why they were equipped with diving gear in the first place was the estimated total amount of water present in the basement. Unknown to Sherbina and Legasov, the firefighters had already begun with pumping water out of the basement during their initial firefighting efforts. In the chaos of the aftermath with the firefighters all being hospitalized, this important piece of information was not communicated to the plants staff or authorities. Hence the divers encountered only knee-high water levels in the basement instead of it being totally flooded. This made things a lot easier to them than expected. One of them, former engineer Oleksiy Ananenko, confirmed in an interview that he was actually not a volunteer but was more or less ordered to go down there. He did it not because of some herioc intentions but because he considered it a natural part of his job. While they were told it was to be dangerous, they were not told that it was considered a suicide mission. Nobody told them about the true extend of the danger they were heading into, and consequently Ananenko was not even afraid. Pointing to the scenes in Chernobyl , he said that they had diving suits but no oxygen as shown in the series and they were progessing through the basement at a lot faster pace than shown. They had two dosimeters with them but not the time to spent much attention on them. He did not even remember what the readings were.

20:20 A graphite fire is usually defined like a class D fire - a metal fire. Metal fires require sand ("dry powder") to smother and prevent access by oxygen and to some degree cool - but you still have heat from any nuclear reaction.

The General that drove the truck is Vladimir Pikalov, veteran of the battles of Moscow, Stalingrad, and Kursk. At the time of Chernobyl he had been in charge of the Soviet nuclear and chemical protection troops for 18 years. He was awarded a hero of the Soviet Union for his role in the containment. He died in 2003.

I highly, highly recommend listening to the podcasts that accompany each episode. The screenwriter provides a lot of insight into the choices made in the show that touch on several of your points. Each podcast episode acts as an excellent companion to listen to after watching its respective counterpart.

At 29 minutes: Yup, intense radiation can cause batteries to fail. This was one of the main reasons the robots brought in to clear debris from the roof of Reactors 3 and 4 failed. The problem then became that by the time the batteries died the robots were so radioactive that no-one wanted to change their batteries! They didn't just try a couple of robots. Approximately 60 were used, mostly built in the Soviet Union. It was found that the more advanced the design of the robot the more likely its electronics would be adversely affected by the intense radiation.

You have a really honest and non-degrading way of making me feel like an idiot. I appreciate that, it's the little things. Subbed

My co worker lived “near” Chernobyl, she was an evacuee. She is approximately my age, 60ish. She has 2 children, I think one born in Ukraine, the other in the US. I know that she does not want to talk about Chernobyl, she alway say that she’s had a lifetime worth of it, she’s done, and she’ll politely change the subject. She’s a very nice person, so everyone respects her wishes.

About the firefighters gear. You USED to be able to essentially just go into the basement of the hospital, and see them inside the one room, but it’s since been walled-off with sand/concrete to protect people

I heard somewhere that even the 15,000 roentgen measurement wasn't accurate, the dosimeter they used for THAT measurement maxed out at 15,000 similar to how the other one maxed out at 3 roentgen. So in truth the measurement could have been even higher

It's a shame that Legasov didn't get more credit for what he did. I've seen many documentaries and did some research and the guy is barely mentioned. An unsung hero, he deserves more appreciation.

At 11:57 when Lyudmilla was told to "Get away from them" it was because the man and the baby were actually contaminated (not just radiated). The man and the baby went to watch the fire from the bridge (see Episode one). They were covered with radioactive ashes the other kids watching the fire actually played with the ashes as if it was snow. The tour guide at Cherynobyl told me that everyone who went to watch the fire from the bridge died soon after the exposure. They call it the Bridge of Death.

20:30 The sand is not to "cool" the mass, it is to smother the mass and deny it oxygen to burn with. The graphite is very similar to coal and burns with air in the same way. By covering the graphite with sand it will act like a fire blanket and smother the flames out.

Remember, 15000 roentgens is the max reading on that particular meter. The true number was even higher then that.

We in the West expect that the females working in hospitals in Soviet controlled areas were nurses. In fact it was very common in the USSR for women to be doctors and there were a number of male nurses. I am not sure how they were in this show but I was expecting that the women in the hospital were mostly doctors. There was an odd relationship between doctor and nurse different from the west but they tended to have many more female doctors at that time than we had in the west.

Something I personally find interesting is that yes, while the science might not be 100% valid, especially in the meeting scene, we must remember that they are not just saying things for the sake of science, they are trying to convince the board of soviet directors to give them the resources and funds to contain the accident. We already know they can be cheap and not take these things seriously, so providing a worst-case or even inflated estimate for the explosion and effect of it might be something they intentionally did to get the resources to contain the disaster. Or at least that is how I like to explain it in my head-cannon of the show.

The bullet comment is also to shock the committee into action, they were dismissive about the situation and he had to get them to move.

In a podcast about the series, Craig Mazin said that the divers flashlights did fail, and they did not have backups. The divers knew the building well enough to find the gate, however it may have been a simpler layout than described in the film. Criag added the backup flashlights, because it would have been too difficult to film them finding the gate in complete darkness.

About the thermal steam explosion: It doesn't really matter wether this would have happened or not. The point is, the scientists back then believed it would happen, so it is valid to include it in the show.

I show the series to my environmental science class for high school seniors. I used to show a documentary but the series does a great job of showing the human dimension and that really is what resonates with students since they can relate. Your commentary helps me better understand some of the nuclear science behind it and relay that to my students. My area is more biology so your expertise has been awesome to learn from.

I was an engineer at Rolls Royce and knew quite a few engineers in the nuclear division (Rolls Royce & associates.) At the time of the accident it was believed that there may have been deuterium enriched heavy water stored under the reactor . One of the purposes of the reactor complex was to provide power for heavy water production for the soviet H-bomb program. There was a theory that if the heavy water and the super heated remains of the core were to come into contact that you could have a possible "raw thermonuclear event ." this would have produced the 1-2 megaton blast that could have spread the radioactive contamination over the majority of the soviet union and Europe. The chances of this happening was considered to be very slight by western engineers.

So, as far as the explosion size (looking at 25:00 ish), I think the biggest thing is that if you do a back of the envelope orders of magnitude energy relation, and remember that the water could cause the surface of the molten corium to experience an acceleration in the nuclear reaction as well as the thermal steam explosion, you can get some big numbers. I agree that the presentation of a steam explosion of a couple megatons is fairly ludicrous, but dropping hot corium into a large reservoir of water has the potential to release a HUGE amount of energy, way more than a nuclear bomb, which doesn't contain nearly as much fissile material and what fissile material is present loses criticality as it blows itself apart, meaning you don't burn it all. I think expecting a nuclear detonation from a cave of water is not wholly realistic, but having a large steam explosion in the kiloton range and then a huge nuclear release of energy could cause all manner of problems, so much it would be almost impossible to estimate without detailed maps of the structures and areas to look at pressure waves and melting/burning that would happen in the seconds, minutes, and hours after such an event. tl;dr: as a steam explosion, ur initial reaction that thats waaaay too big is totally reasonable, but considering all of the physics going on, having a number in the megaton range to report to superiors is not as ridiculous as it initially seems. To be 100% real, the fact that corium falling into a pool of water could be comparable to a hydrogen bomb shows exactly how dire this situation really was, and heightens my understanding of the threat level. Ultimately, I think the soviet scientists who constructed the number during the crisis were fairly justified, especially if you are trying to communicate to those who are not literate in the physics of whats involved, because it would have been a potentially planet altering catastrophe in so many different ways had they been unable to stop it. And the show portraying the recommendation accurately speaks as a credit to the research and diligence of the show. Great video, love to hear your insight from one who is involved in this stuff!

I was part of an NBC (Nuclear, Biological, Chemical) detection and decontamination team. We still do the washdown and then stirp down by degrees with the mask being the last item removed. As I said all while being washed down.

The biggest fear all these characters had was cancer from radiation. So I love the paradox of nearly every character being a chain smoker in this mini series. But then we see smokers in real life do the same, complain about the danger of something while inhaling.

Slight correction: You can't go down to the hospital basement anymore. It got burried recently, preventing people from entering.

One of the best series I’ve seen in a long time. A true horror story. The helicopter scene was one of my favorites.

My boss’ father-in-law was a liquidator on the roof. He is still alive today. Somewhat surprised.

Something that might be worth pointing out, too. Just after 19:00 when Pikalov says that the radiation dose near the reactor is 15,000 Roentgen rather than 3.6, he's still wrong. Even though that's high enough to be well off of REMM's chart, it just reflects the highest value that the dosimeter he used was capable of measuring. No dosimeter they'd used so far was capable of actually obtaining an accurate reading, since there aren't too many situations where that kind of measurement would be needed. Also, the "several megaton explosion" bit seems to be based off of an assertion by Vassili Nesterenko, a physicist who played a role in the disaster response. It's not immediately clear how he came up with the numbers involved. He may have gotten that yield based on the idea of all the corium falling into the water at once, which would have been essentially impossible, or he may have even been considering that a second criticality event might occur. That would have definitely been stretching the bounds of plausibility to their breaking point. Either way, the idea of a steam explosion that size occurring at Chernobyl wasn't realistic, but it did apparently come up at least in retrospect. The more likely possibility of a modest explosion was still a real threat and, in order to make the danger more tangible, I can see someone throwing out an implausible worst case scenario in a meeting. Then, of course, dialing it down to, "Even if that doesn't happen, [realistic amount of material] reaching the water would cause [realistic terrible thing]".

I've been to Pripyat. The radiation in the air there is background normal levels, but my geiger counter went nuts when I put it in places where rain water washed down off buildings, near the robots used to lear the graphite, or near the firemen's clothes which are still in the basement of the hospital. The city itlself now is almost totally overgrown with full-on forests in the streets, and I mean in all the streets except in the very centre.

As far as the flashlights were concerned, I heard somewhere that the radiation was either interacting with the electrolytes in the batteries and reducing their lifespan, or that the radiation was ionizing the air around the batteries and shorting/draining them. I know jack about nuclear or electrical engineering though so take that with a bucket of salt.

I love that you acknowledge people’s corrections and also acknowledge your own mistakes. 👏🏽👏🏽👏🏽👏🏽

i love at 20:07 as while he is explaining the use of boron and sand, Legasov and Shershvina seemingly look at him like "well he knows what he is talking about"

loving your explanations. I don't know much about radiation. but what I do know is fire. in the first episode they reported a fire in the roof after the explosion hence why firefighters were called. now if firefighting operations had to stop because of safety or no more firefighters due to radiation hazard. A building fire would still be burning unchecked. all the flammable materials on the roof, building insulation, building contents, etc would still be alight and burning regardless of what is happening at the core (which i know nothing about), i think the smoke plume is more to signify that there is still a building fire going on separate to the disaster that is happening with the core. also that back aggressive smoke plume usually comes from unburnt products of combustion from man made materials such as plastics. wood generally burns "cleaner"

I’m an artist and not a scientist at all but I love learning about all of this, it’s so super interesting please do more videos!!!

Oh yes ye boi delivered on part 2 and brought back the chart :) congrats on your success with part one, that scene walking in the water was anxiety inducing, crazy to think those men survived and lived into I believe the early to mid 2000's

The “bullet” analogy is a great analogy. As best as an analogy can be regarding nuclear physics to career party men that have not a single idea about anything regarding nuclear physics.

When I saw the nurses hands, I saw that as plausible, the firefighters were fighting the fire for hours, they were climbing on rubble, if there is graphite all over the ground, the were probably kicking it, stepping on it and the pieces of the irradiated building materials, dust. They have never really said much about the heat of fighting a fire period, the weight of the suits in summer. I've seen modern fire fighters throwing up from pure exposure to the heat.. So yeah, I could see these people physically coming into contact with particles, for just the layman watching this, I think they were effective with getting the point across. So many who probably watched this were not even born yet. I learned about it on the 28th, my 17th Birthday, and as much as I prefer accuracy and am a total geek about it, I hope with the dramatization of this story, it shocked people, made new generations become interested. Growing up with the cold war, and in those years is such a foreign concept to the youth of today.

I think using boron-enriched sand, they were hoping it would melt and encase the debris in borosillicate glass, preventing dust and soot from escaping into the atmosphere...

Yeah, the 2-4 Mt explosion was probably the most outrageous thing they made up for the show. The initial Chernobyl explosion that started the accident and which includes the maximum amount of fission material in contact with water and at the highest temperature, is estimated at 10 tons of TNT (not KILOTONS, just TONS, and that might actually be for the stronger second hydrogen explosion). Some of the lava drip feed dropping into the water tanks below would be extremely unlikely to cause an explosion in the first place, not even talking yields. And even if some explosion did happen, it would be much smaller than the initial explosion because the strength of the explosion would be determined not by what the total amount of water in the tanks is, but how much of it can you instantly vaporize - ie. how much of the lava you can get in contact with the water at any point in time. If the whole melted core instantly dropped in the water tanks then perhaps you could get an explosion strong enough to destabilize the some part of the reactor complex and cause more trouble, but realistically you would just get a slow drip feed of lava coming through some pipe (what actually happened) which would just be dropping into the water, making nice lava rocks there and the water perhaps getting warm enough for a nice swim. Obviously, as discussed, the characters in the show could just be exaggerating the threat in order to get resources from the government, but the way it's portrayed is as if it that was the actual threat and no effort is made to show that it was just an exaggeration. I think there is an actual interview with some Soviet official who mentions this very thing - the possibility of a megaton explosion - but the idea is so preposterous on its head that you couldn't possibly take it at face value - which the creators either did, or they didn't but thought it would be a good idea to add it for dramatic effect anyway.

in his analogy he says " near the speed of light" objects with mass with enough energy can go " near" the speed of light.

Really glad you are continuing this series!

There is a really good book (The Legacy of Chernobyl by Zhores A. Medvedev) that goes into the fear about the lava (corium) reaching the bubbler pools. If i remember correctly, it was actually a fear that the entire reactor might collapse into the bubbler pools because of how much material had been dropped from helicopters. They worried that the foundation had been compromised by the impact of material from the helicopters.

So I heard something interesting from a Nuclear Physicist who was working in Russia at the time of Chernobyl. First, Sand and Boron was their second option, they initially tried and dump sand mixed with other metals like lead (which apparently would have made it worse). Not sure if they actually did that, or they were warned before they did it. And secondly, They should have used Cadmium instead of Boron because it's a much better neutron emission absorber, but it was too expensive for the Soviet Union to acquire (or they just didn't want to spend all the money)

I know it's late so your probably wont read but, it's massively refreshing for someone to correct themselves like you did at the start of the video. I always think it's a sign of someone who actually knows what they're talking about. Smartest people I know always doubt themselves and learn stuff even when they're teaching you. Good videos thank you.

All electromagnetic radiation induces current on wires, and this is observable even with radio waves. With gamma radiation it's much more severe, and you could foreseeably break any circuit elements like a resistor, diode, etc if they're not beefy enough to stand up to the extra flow of electrons. Especially if your filament is only rated to handle the internal battery, that could potentially burn right out.

I revised Chernobyl recently so I’ve been revisiting your channel, still enjoying your videos!

The main reason soviets were so concerned about underground smelting nuclear fuel, it could easily get into rivers water underground feeding branch (in theory) and could contaminate drinking water source for hundreds of million people.

The ending of this episode with the geiger clicks getting faster and more intense with the claustophobic sense of darkness, pipework, failing lights.... it was incredibly stress inducing to watch... i remember feeling so tight in my chest and my heart pounding. The cinematography and story telling (yes we know bits were over dramatised) but still -- for those 3 engineers who really did it are incredible

The bullet explanation he uses takes into account he is mostly talking to military staff. The bullet concept is easy to grasp for this audience. A sign of a great teacher is when they can rapidly size the type of audience they are in front of and adapt the dialogue so that it makes sense to them. I think, considering the audience, that it is an excellent analogy. If he had been in front of physicist, he would have used a different route ( we can assume)

25:00 Firstly no it's not cinematic liberty, I have heard of this entire conversation way before the TV series came out and it was a legit worry from what I understand. My guess is the fuel mix here wasn't simply normal reactor fuel but also being used for weapons production, ergo some of it could have been more enriched than officially acknowledged. I believe the worry wasn't particularly for a steam explosion but for the fuel to come into a configuration conducive to a prompt criticality or nuclear detonation. Remember this was the height of the cold war and these reactors were a source of bomb material and the KGB would have silenced anything that would expose there weapon secrets. I know a fair bit about nuclear weapons and I don't for a moment believe a 2 to 4 megaton nuclear explosion would have come from Chernobyl, but the people in that room did.

You should do a video on the "natural nuclear reactor" in Oklo, Gabon. Conditions were just right for a self-sustaining nuclear reaction in the uranium ore, with groundwater acting as the moderator. It was discovered because the amount of U-235 in the ore from the mine was significantly lower than normal.

In the first episode, it shows those on the bridge being covered in ash from the fire. They seem to be in those same clothes in the hospital? Maybe that's why the nurse instructed Lyudmilla not to touch the baby? Love these videos, by the way! Stellar commentary and insight!

The bullet analogy was specifically because he was talking to Soviet party members. They are all constantly at risk of a bullet because of how the USSR politics worked. It would hit it home to them the danger; that was the point, not accurately explaining it to them. If he did that, they wouldn't have listened. Not only did they not have radiation units/specialists at the hospital, the Soviet government also removed a lot of radiation medical journals and textbooks from the libraries after so the public couldn't look up if they were irradiated. A first-responder doctor interviewed said that she went to a library to look, and the shelves were just empty. The smoke was because the building was still on fire. The multi-megaton steam explosion was a real concern. It was based on an interview with a nuclear physicist (Vassili Nesterenko) who worked on Chernobyl during the aftermath. "Our experts studied the possibility and concluded that the explosion would have had a force of 3-5 megatonnes. Minsk, which is 320km from Chernobyl, would have been razed, and Europe rendered uninhabitable". He also said that "there were trains with a thousand cars in Misnk, Gomel(?) and Kiev, ready to evacuate the population."

Really enjoying this series... looking forward to the rest of your reactions. Really like how you led with the comments and corrections... and in general just really succinct and simple explanations. I think you'll gain a lot more subs based on how popular the HBO series has become, and how cult like of a following its gotten. But as an aside I would absolutely love to see a react video in the same vein as this for The China Syndrome... I love that movie, but I am hardly even a layman in my knowledge of nuclear science and as such I have little idea how accurate/inaccurate the things depicted in that movie were. Regardless, its just a fun, classic 70's disaster thriller; and well worth a dissection I think! Can't wait to see more content, awesome stuff!

I was in Pripyat in 2019, before Covid, the hospital is still there. The basement's been blocked up with sand so, it's not as easy to get to anymore but there's a few pieces of helmet you can see in the reception hall.

I find all this very interesting. My dad was stationed in Germany when Chernobyl blew. My poor mom had to keep 2 3yo toddlers inside for days, wile pregnant, because of the particle cloud. We all have "Chernobyl bumps", even my little sister who was in utero.

Keeping the healthy away from the radiated people made sense. Those people were on the bridge and the ash and dust fell on them like snow. Their clothes were likely very active, but they couldnt get them to strip them off like the firefighter gear in the chaos

You are mistaking his analogy of each atom of uranium, neutrons bullets. In fact it is a very good analogy. He isn't saying they are traveling the speed of light. He is saying that each atom of uranium was giving off those neutrons, which were like bullets. That is the main key of using fission to begin with

The man in the hospital with the baby was covered in radioactive ash at the end of ep1. As for the nurse using the word "sick" i think they were forbidden from using words that had to do with admitting there was a nuclear explosion. She can't say he was exposed to radiation.

The sand and boron mix was intended to stop the reactor from ejecting radioactive dust. They essentially were trying to cap it with glass and boron to stop it from ejecting anything else

The “no retained pressure thing” came up with a discussion of the powder in a typical rifle cartridge. If you ignite, it will go poof and the bullet will go basically nowhere because there’s no barrel to contain the pressure.

Loving your explanations so far. One thing I've wondered about this show is if any of the inaccuracies were actually because that's what people believed at the time? We know a lot more about radiation now because of Chernobyl.

Estimates for the thermal explosion place the magnitude in the low kiloton range which would probably disperse the balance of the core material in No.4 along with No.3, perhaps No.1 and 2 as well. Even compared to the original event, the potential for contamination would be immense. I suspect the writers may have taken the input from an expert advisor and conflated the potential for contamination with explosive power. Not really sure, though, as fallout predictions from a 3 megaton surface detonation are hard to come by.

As you correctly guessed, the two-to-four megaton is highly inflated. However, that's not even the half of it. Not only is that number inflated, it's completely fabricated, since the fuel is nowhere near enriched enough to even actually explode. Even the largest pure-fission bomb created (Ivy King) only had a yield of 500 kilotons, and that was using 60kg of highly-enriched uranium that was probably enriched to 80-85% U-235. In comparison, while most commercial reactors today use low-enriched uranium around 18-20% (apart from naval reactors which use in excess of 50% and scientific reactors that sometimes use even weapons-grade (85%+) enriched uranium), the fuel pellets in RBMK reactors were filled with uranium dioxide pellets, which typically only contain a 3-5% concentration of U-235. For reference, a fission bomb could feasibly be created with 20% enriched uranium, although it wouldn't be practical to design. That being said, nuclear explosions are very difficult to create. Not only do you have to have a supercritical mass of enriched U-235, but it also has to be arranged in such a geometric fashion that essentially the entire mass undergoes fission almost instantaneously. This happens because there are two types of neutron release that fuel the nuclear reaction: prompt critical and delayed critical. Prompt criticality is caused by the neutrons produced fission reaction itself, whereas delayed criticality is caused by the neutrons from the rapidly decaying fission products. The former is what happens in nuclear weapons, as the critical mass is geometrically shaped so that prompt criticality can be sustained by all of the U-235, leading to a massive release of energy. However, most nuclear reactors, (including the RBMK reactors at Chernobyl) use delayed criticality, as it's a much easier process to control via the heat of the core and control rods. When the Chernobyl meltdown occurred, water turned to steam within the coolant tubes, allowing the temperature of the reactor to skyrocket. This increased reactivity, which increased heat, which turned more water to steam, and so on and so forth, until the fuel rods themselves cracked. At that point, it's likely a small portion of the fuel underwent prompt criticality, but since it was not arranged in such a way as to facilitate a prompt chain reaction within all or even most of the fuel, what instead happened was that even more heat was released. This heat actually LIQUIFIED the metal rods surrounding the pellets. Upon contact, the liquid metal evaporated what was left of the water coolant in the reactor, prompting a steam explosion. I suppose that's a lot of words just to say: "Yeah lady, there ain't no way in hell that the radioactive slag melting through containment into a water chamber is even going to explode like an atomic bomb, much less actually explode with the force of 2-4 megatons, which even with weapons-grade uranium can only be achieved with thermonuclear (fusion) weapons." And now y'all know why nuclear reactor fuel itself can't go boom.

I thought I heard somewhere (although I can't remember where) the scene about the secondary thermal explosion was intended to demonstrate the scientists attempt to embellish the dangers so that they could receive more resources, and that it was a gamble for them since they naturally didn't want to lie but knew some bending-of-the-truth would be necessary for safety. Maybe it was in the commentary or something. Anyway if that's the case then they didn't explain it up until this point.... but the embellishment is a minor plot point further in the series so maybe it was shuffled around in editing.

22.57 yes, they actually believed that it might cause really bad reaction especially because it would take other reactors which were all working through all of this with them and cause them to explode too.

Thanks for the mention! Great narrative again. So good to have someone with knowledge and a level head give a response to this show. 👍 Btw, I think the 2-4 Mt line is as exaggerated as you think it is. Just doing a really quick back of an envelope calculation, let’s figure out the maximum energy that could possibly have been deposited, (and in reality I think the amount released in a steam explosion would have been way less than this). The core of an RBMK has a mass of around 200 tons, and for the sake of argument let’s say that, of the 5,000 tons of sand they dropped 300 on top, 300 tons made it to mix with the core, and let’s make the very generous assumption that all that combined core material and sand reaches the water at about the same time. Now I’m going to assume the “lava” (usually called corium) is about 20% ZrO2, 20% UO2 and 60 % sand) so the specific heat capacity will be approximately 760 J/kgK. That’s 500,000 kg x 760 = 3.8x10^8 J/K. Now assume that the temperature of the corium is about 2,800°C (I got this from a Wikipedia entry about corium), and let’s assume that hitting the water takes it down to nearly 0°C, so the release of energy is 1.06x10^12 J. This is a lot, but a megaton is 4.184x10^15 J, so this is actually 0.25 kilotons of energy: or between 8,000 and 16,000 times smaller than this claim. No scientist would have made this claim, only a script writer trying to add drama to the show [Edit: or a Soviet propagandist]. In doing so, drawing a parallel with the unit used to measure the yield of large nuclear weapons is, I’m sure, entirely deliberate.

The ending of the episode is haunting as darkness swallows them and the sound of their machines going crazy from radiation feels like in that moment all hope was lost.

13:20 interesting point, goes hand in hand with the final episode when they say "why worry about something that isn't going to happen" and how even after the disaster they still had this mentality

The sand was used to starve the fire of oxygen Your analogy of thermal power post scram might be incorrect. The Thermal power of a 1000 MWe plant is ±3000 MW. 5% of that is 150 MW which is what the thermal output is directly under scram conditions. So your basic values are still correct, just that the 33% efficiency of converting heat to electricity is included in the 15%

I haven't watched it myself, but I kind of want to see your take on "The China Syndrome." I think it's one of those films whose cultural impact far exceeded its own quality as a film. Much like how Rosemary's Baby and the Exorcist created and provided the basic script for our decades long Satanic Panic, I suspect the China Syndrome basically launched hysterical (as opposed to well informed) anti-nuclear panic in the US.

The radioactive water spout is one of my favorite details in this episode. It's such a simple thing but so scary, and you can see the gears turning in that dude's head when they get close to it. "Wtf am I doing???"

I love the footnotes that accompany charts, much appreciated!

Stellan Skarsgård... The moment you said his name, I realised that Baron Harkonnen was at Chernobyl! 😀

I'm very happy you took issues with the 2 to 4 megaton explosion. I highly doubt there is enough thermal energy in the whole core to reach even a kiloton. If you think about it at the peak of accident the top thermal output was 32.000 W. Some experts say that maybe he real peak was closer to 300.000 W but that lasted for a brief moment (I don't know for certain but I doubt that this energy surge could last for more then a few seconds but I could be wrong since I'm not a nuclear physicist). If we consider that a megaton is equivalent to 4×10¹⁵ J we would need an energy source as powerful as this reactor at peak power (3×10⁵ W) for 13 billion seconds (more then 400 years) and all that energy must be released instantaneously otherwise it wouldn't be much of an explosion.

The firefighters clothes are still in the basement of that hospital and still fatally radioactive to this day

Soap is not used to make things more slippery to make them slip off you. Soaps use polarity to clean. One side is polar and water soluble, the other side is nonpolar and binds to anything that is also nonpolar. Either the water dissolves what the soap can't bind to, or the soap binds to it and the water.

"We cracked 1000 subscribers, holy cow." This aged well. Now then: Boron and Sand. The silica in the sand keeps the boron separate. The boron can, potentially, begin to melt into a lump. Thus you dump sand, boron, and lead onto the core. The sand tries to keep the boron and lead from melting into one massive radioactive lump around the core, and ensures spacing remains between the particles of boron and lead. Back to a void concept. Others already covered the oxygen denial aspect, but they did not cover the question of "why sand" as opposed to other mediums we had at that time for the same job. Second - yes... Gorby was rather deadpan any time he was incredulous. He was all smiles when he was in control, but when surprised he fell back onto the old Stalin-esque stoicism. In fact this is where the idea of "Russians don't smile" comes from. During the Stalin era men showed... nothing. Any and all emotional reactions would be seen as weakness by Stalin and his circle, and this radiated down through society. Pun intended. Third - concerning the flashlights. The old Soviet flashlights these gentlemen used had silver lined wires in them to attempt to ensure that they'd function through all temperatures during emergencies. The silver wire sheaths kept conductivity very high for the circuit. Now then... the ionized particles can 'skip' across these silver sheaths and over charge them. This would burn out the bulbs. Think EMP on a localized scale. The same thing happened during Starfish Prime, but to a vastly higher degree. The same also happens during coronal mass elections. The silver made them vastly more susceptible to this phenomena.

The tanks were later revealed to be mostly empty after all, I've heard, but they were not aware of this at the time. I believe the 2-4 megatons was the thought at the time, but revealed to be false as you yourself stated.

The actor playing Gorbatjov is David Dencik, an absolute national treasure here in Sweden. He’s also awesome in Tinker, Taylor, Soldier, Spy. Highly recommend that movie.

"Why did I see graphite on the roof? Well you didn't because apparently it's not there

Concur on the 2-4 megaton explosion. Although the explosion could be bigger than I expected. If we for the sake of argument assume the reactor fuel could some how vaporize all 7000m^3 of water and then the hydrogen burned with O2 how much energy would that release? 7000m^3 of H2O is about 7x10^6 KG of water which has about 780,000kg of H2. That’s about 3.875*10^8moles of H2. 1 mole of H2 burned with O2 releases 286,000J. So our H2 would release about 26.5 kilotons of energy. That would be the absolute worst case. It would also mean our reactor fuel was outputting an equivalent amount of energy in order to vaporize the water which isn’t possible. (Chernobyl itself would have had to explode for almost an hour to equal that amount of energy).

Funny you should mention Jack Ryan and show the clip from The Hunt for Red October. Stellan Skarsgård played in that film :) Edit: They thought that the threat of an explosion of that magnitude was possible. The Battle for Chernobyl (2007) documentary shows that. They were genuinely concerned. That is also why they went through the trouble of trying to dig the tunnel and all that stuff.

Thank you for your wonderful breakdowns on the realism or use of dramatic effect in these disaster shows. It’s terrifying how their bureaucracy got in the way of people doing their job properly. What I learned of nuclear science I learned from my brother, who was a nuclear engineer, and it’s sobering learning that when things are done improperly, the shit hits the fan very quickly, and that is what happened at Chernobyl.

I watched a documentary about the "Liquidators", the guys who were dumping the sand into the reactor from the roof. The last one of them died in 2012.

There is footage of the event soon after the catastrophe in daylight showing a plume that was blue-white, certainly not black

Could the "do you want to get sick" bit be a reference to how little understanding of radiation some people had/have?

Yeah, those poor firefighters, standing amongst debris that came freshly ejected from the destroyed core. The fallout from the disaster was not just the graphite, but all the spent and unspent fuel particles scattered around, pieces of irradiated control rods, etc.... And then they carry some of it to hospital, they touch people, etc. and most of the hospital staff do not know anything about how it works, but some do.

I’m an electrical engineer, I have a Masters in Electrical Engineering from the _Massachusetts Institute of Technology._ Radiation isn’t causing the flashlights to fail…the flashlights are failing presumably due to the fact that the atoms of nearby air are still being ionized _(stripped of their electrons),_ so the rapidly varying electric & magnetic fields would *likely* produce damaging surges of both electrical current & voltage…so…it isn’t the radiation itself, it’s the Nuclear EMP (or Electro-Magnetic Pulse)