You say that somewhat in jest, but there are serious engineering applications where "What if someone intentionally tries to make it do the thing we really don't want it to do?" ..is a significant consideration.
@@jermainerace4156 Agreed. Just that the implication is the designers were completely irresponsible and the operators weren't at fault. Interesting idea that a nuclear worker could become suicidal -- maybe with a big enough dose. And the HBO series (the final arbiter of historical disputes) implies that because accident details were made secret, they were not known to those who would have had the need to know them.
@@zackthompson2505 Many people do that inadvertently by not fixing slow leaks. Eventually enough leaks out that the car overheats or the oil pressure warning comes on and they are like "ZOMG what happened?"
@@bethlarson7144 You're not getting the meme, are you? Also, quite a few logical simplifications AND omitting very important data, so not really "excellent". I must say though it is explained in a user friendly way. Overall, not great, not terrible (in both literal and meme meaning).
You missed the important point of why the power level spiked. Once the reaction starts, the xenon gets burned off. The Chernobyl core was so huge that it wasn't uniformly controlled by the control rods, and the reaction took off again in the bottom part of it. This started burning off the xenon in a hurry. Now you have a situation where prompt neutrons are causing fission (carbon moderator still there), and all of the control rods are out of the reactor, and the xenon that was keeping fission from happening was getting burned off like dry grass in a self-feeding cycle. In the world of high energy physics, this is what is known as an "Oh [expletive] moment". There was a perfect moment, when ALL of the xenon was gone, and ALL of the control rods were out, and ALL of the fuel - some 200 tons of it - was free to react, completely uncontrolled. And it did. There is at least one paper out today that even claims a nuclear yield. Small, but larger than the chemical explosion could ever have been. The reactor hall was cast concrete, Soviet construction, and could probably have actually withstood a substantial chemical explosion, but was kicked aside like cardboard in the face of this blast. Radiation-resistant windows a meter thick were blown to bits like plain window glass. That is what happened at Chernobyl. A worst-case scenario, with 200 tons of uranium reactor fuel, totally uncontrolled. The United States already knew about xenon poisoning, having experienced it first hand with the startup of the Hanford B reactor, where we too yanked out all the control rods in a futile attempt to jump start a reactor that for some reason unknown at the time just would not react. We were very fortunate that we did not create the same accident here. The only reason we didn't was because Hanford B had been built too small, and could never start properly, given the effects of xenon. Beginners luck
@Tom R yeah, the spike was going, but the control rods prob gave an extra kick that didnt help anyone. Ignalina and a few other stations had already modified the rods to be less reactive, but thanks to KGB and the "saying there are problems creates problems so just say its fine" mentality, the information never went to Chernobyl
I lived in Satu Mare, Romania in 1986, Kiev is about 830 km away, town on Pripyat about 900 km. We actually learned very quickly, and not from the West, back then we were under Iron Curtain, but from our own government who was monitoring things (work started on our own first nuclear power plant at Cernavoda). I remember being a distinct fear of the fallout cloud drifting down to Transylvania since there aren't many high mountains in the way, except the Carpathians. It didn't, and we were relieved.
i hate how hbo took the soviet party line and simply blamed the guy who followed orders and then went further to lie about his conduct during the explosion etc
@@gallyturndrop5320 blame the overly sized reactor that required seasoned staff to make sure it didnt fubar itself (not the college grads that manned the station) not lie about Dyatlov when it came to his reaction to the meltdown (he knew that the core exploded and never blamed any of his subordinates) not make up some strong female radiation scientist that never existed forgetting the attempts to stop the fires ended up creating the whole radioactive lava problem etc in short they put too much blame on the people involved and not enough on the system itself (they did place some of the blame but the lions share should go to the soviet system itself) the system that put men trained or untrained in charge of what amounted to a gigantic radioactive pressure cooker bomb that would inevitably go boom
Man...this dude is gifted. To be able to explain such difficult stuff, making it easy to understand. And above all, making it interesting and entertaining. Wow.
The expression, "buy cheap, buy twice" comes to mind when thinking about Chernobyl. Skimping on safety measures to save money, ended up costing them a lot more in the long run. It always does.
And in any future events feed in the human element. One day someone in rush to get home for one reason or another will do something wrong and... Bang????
It's a communism pure nature. They even speeded up the construction to get bonuses from the government and that speeding was due to hull skin installation skip.
True about nuclear energy generation in general. Nuclear in itself is the epitome of that “buy cheap” concept, since the idea of fractional long term fuel costs makes bean counters cream their breaches. They damn sure aren’t lowering power bills because nuclear fuel is cheaper.
Sorry, no 10:50 an operator didn't hit the wrong button. It had been run at half power and there was a xenon build up along with a lack of coolant void and graphite cooldown. This made any power change difficult. This is known and is in the WNA page about the accident. From there you are correct.
Agreed, the problem was the electrical grid needed power and those operators didn't allow the power to be reduced, so it stayed around 50% for 19 hours, which contributed to the Xenon poisoning.
That's not strictly speaking true. One of the operators switch the reactor from local automated operation to global automated operation. Sort of a nuclear autopilot. However, he failed to set the power level that he wished the reactor to stabilize at. Because of this, the reactor went to the power level that had been specified last - near zero. And, of course, and we know from experience now that RBMK reactors are notoriously unstable at low power levels. PARTICULARLY when the fuel rods are older and due for replacement.
@@VComps Not according to the The International Nuclear Safety Advisory Group (INSAG): The drop in power occurred at 00:28 on 26 April during transfer from local to global power control. The INSAG-7 report states: "The INSAG-1 report describes the precipitous fall in power to 30 MW(th) as being due to an operator error. Recent reports suggest that there was no operator error as such; the SCSSINP Commission report (Annex I, Sections 1-4.6, 1-4.7) refers to an unknown cause and inability to control the power, and A.S. Dyatlov, former Deputy Chief Engineer for Operations at the Chernobyl plant, in a private communication refers to the system not working properly." The timeline from the World Nuclear Association words it differently: With the power level at about 500 MWt, control was transferred from the local to the automatic regulating system. The operator might have failed to give the 'hold power at required level' signal or the regulating system failed to respond to this signal. This led to an unexpected fall in power, which rapidly dropped to 30 MWt. So it isn't quite clear what happened, but still, the Iodine pit - Xenon poisoning sequence described by the professor was happening anyway and they should have shut it down, but instead they tried to increase reactivity ultimately ignoring safety standards. Then we have the positive void coefficient making things even worse - the poor souls were doomed. One of the things may not be instantly obvious for someone not living under such a regime is why they ignored so many regulations. It wasn't simply negligence, people in the Eastern bloc, especially in the Soviet Union still remembered the days when a failure to get results was considered sabotage (as the system of scientific socialism was supposed to work flawlessly) and punished severely.
@@PJL7095If he draws the graphs like hundreds of time he's gonna have a whole image of them in his head which is amazing. I got this kind of feeling when I study basic physic during my highschool years.
Instead of the nucular stuff I started thinking about that! At speed of a neutron my brain realized the image has been flipped around. Sort of semi made more likely by the fact that he appears to be writing with his left hand. Now I'm back to thinking about the nucular stuff.
I barely passed pre calc in high school yet now I am able to explain how a RBMK reactor works and exactly how the Chernobyl disaster occurred. Not exactly the most casual conversation starter lol...
Just please mind, that his explaination of what the reactor operators did is very simplified to the point of being wrong. For all its factual faults, the HBO series does show this pretty well. They sceduled the test to a certain time and lowered the power level to half, but then they left it there for hours because Kiev told them they need the power for longer and that they should do the test later in the night. After that period the reactor was already poisioned, and that is why the power level dropped so hard.
@ I fully agree with you, and I was not really tryibg to say this video is bad for it, I just wanted to get accross, that there is a little more to the accident than what was said here, but that does not make this explaination a bad one. For people who just want to know what gernerally happened this is probably one of the best and most accurate descriptions for such a small timeframe.
Secondly, the shut down button did the opposite of what the operators hoped and the fatal flaw was noted years prior. The graphite tips were meters long and lowering them all at once was like a nuclear bomb detonator.
Professor Ruzic, thank you for your amazing work. You are a great communicator, explaining such complex subjects in a very accessible manner is a valuable skill. My 7yo boy loves your content. Very funny to watch Mr7 explain to his grandfather, a retired professor of finance, how the Chernobyl incident unfolded. “Grandpa, they used the wrong moderator and didn’t know about xenon poisoning”.
@@fallsdp they knew about the instability of the RMBK reactors, but it was covered up because it was too embarrassing. The tip of the rods being made of graphite is actually a safe design for smaller reactors, it is also very efficient. But bigger reactors can do unexpected things when you use such rods. (They have naively scaled up the design, without considering safety.) The only way for the graphite ended rod to cause fatal problems was in case of a massive Xenon poisoning, and removal of almost all rods, boiling off all the water (see void coefficient). Everything which can go wrong went wrong at the same time. The Three Mile Island reactor was designed for exactly that, what if _everything_ goes wrong at the same, including an aircraft suicide bombing the reactor. So when thing went wrong (without the bombing), it failed relatively safe (with only a minor leak).
i have enjoyed many videos from this channel but was expecting this one to be a little more detailed around the neutron flux and the reason why the control rods had graphite 'tips' (the reality is the rods were about half graphite) scott manly has a better explanation with much more detail. I also have my doubts that the containment buildings really could perfectly contain a steam explosion of the scale of chernobyls.
A containment building would not have contained what happened in Chernobyl. Containment buildings are designed to hold up 80psi of pressure. The explosion at Chernobyl is estimated to have reached over 1500psi. Just before the reactor blew, energy output reach 30,000MW thermal, 10x higher than the reactor was designed. There is a hypothesis that Chernobyl was a fizzled nuclear explosion. There were two explosions.
In a nuclear explosion, over pressures of 12 psi or greater kill virtually everyone and destroys all but specially built facilities above ground in the blast zone, such as a nuclear missile silo.
TheRealUnconnected Three Mile Island in Pennsylvania is a good example of out containment buildings. The reactor partially melted down yet no huge release into the air of radiation. Well...not that we were told.
@@Iwillnotbepushed 'no huge release into the air of radiation' Radioactive elements in the form of volatile gases, like Iodine, were released. However, unlike Chernobyl, solid matter was not released.
@ TheRealUnconnected The main reason for this design of the rods was an attempt to place the reactor in a room of LOWER HEIGHT AND DEPTH. Typical Soviet style of "economy". Also, the designers chose a dangerously low speed of movement of the rods, citing an allegedly sufficient change in the coefficient of reactivity per second. Link to the site created by the engineers of the Chernobyl nuclear power plant (in Russian): accidont.ru/sitemap.html. This site is unmanaged since 2013. No feedback. All tables, graphs and printouts you are interested in are there. As well as different opinions of experts about the causes of the accident. design flaws of the reactor and personnel errors. And descriptions of other emergencies at RBMK reactors.
"what is eight feet wide, four feet tall, weighs two tons, and slices apples into three pieces?" answer: "a SOVIET designed and built machine to cut apples into four slices!"
@peterbradshaw8018 - I think you missed his point. It's not just self-motivation that makes a difference in college and in life, but having good, engaging teachers that help each student learn & explaining complex ideas, situations, etc that make the most difference.
I love it. How else do you suddenly get millions of people even casually studying nuclear energy. Imagine how many minds have been peaked to go back to school and study nuclear energy? So crazy.
I've visited actual Chernobyl several times in the past 20 years, and I have very good understanding of how it works and why it is a flawed design. When it is safe to go to Ukraine again, I plan on going again, because I want to see how much Pripyat has changed and I want to see the new shelter project. :)
Thank you so much! Seriously…thank you. I have viewed so many explanations of this event, and now I can say that I fully understand it now. This is the single best presentation that I have come across. Thanks again.
0:30 RBMK, not RMBK. Also, this explanation is not very accurate. They got the reactor to operate at half power in the afternoon of the 25th of April as they were preparing for the safety test they were supposed to have completed in 1983. Then they got a phone call from the higher ups to not do it during the afternoon cuz it was the end of the month and electricity consumption was at its peak. They were tasked to postpone the test to the night. They left the reactor at half power and because of that a lot of xenon was created but not burned. That's how the xenon poisoning happened. That's why the reactor's power dropped to 30 instead of staying steadily at 700, not because an operator pressed the wrong button.
As a matter of fact, it may be exactly "because an operator pressed the wrong button". It's impossible to know because it did not took long to Akimov and Toptunov to die after the accident, and we don't even know for how long they held consciousness. You should not take what the series tell you at face value. 50% is approximation and romanticization, we will never know what really happened there for several reasons, some of them may be, 1- they died soon after the accident and maybe didn't have time to tell very well what happened and how it all happened, they might even have been shell-shocked, under severe PTSD, delusional or in and out of a comatose state before they died, unable to put it all to words, or make any sense. 2- they may have told everything from their perspective, however.... USSR, KGB, FSB, and the truth may be buried somewhere rotting in some top secret archive file, never to see the light of the day. 3- they were very green, especially Toptunov, and he was the one responsible to get to the power levels required(I believe Dyatlov stated that during his official debriefing), and maybe he never knew what he did wrong. 4- the cause of the sudden power death in the reactor may be just another design flaw or equipment malfunction, triggered by Toptunov. The series itself does not make clear what really happened when the power fell suddenly to near shutdown levels. We just see the surprise on the face of Akimov and Toptunov, and after that, Dyatlov's rage. I read one of the INSAG's(INSAG-7/1992 official report) reports into the accident and even they are not sure. They oscillate between equipment failure/fault and an operator error on Toptunov's part. Some argue that the action Toptunov took to switch the reactor from local to global power control, IS the operator error itself("....pressed the wrong button."), others argue that the global power control system may have had a FLAW that caused the severe drop in power. Maybe Professor Ruzic knows more than I do, coz he simply studied/investigated more into the matter. I do not have time to read all of the reports nor his credentials to understand it all.
@@jefersonnl In "Midnight at Chernobyl" Higgonbotham states that Toptunov, when moving from local to global automatic control, did not reset the reactor power level desired leaving it at near zero. He then failed to act to correct it. Higginbotham also states that Deputy Chief Engineer Dyatlov demanded that the test be done at 200 MW which Akimov initially strongly protested. Under badgering Akimov finally conceded to Dyatlov even though he outranked him in terms of running the reactor. Higginbotham also states that Toptunov knew the reactor was unstable at low power and when Dyatlov demanded that he pull more control rods, he initially refused. But just like Akimov, he conceded to Dyatlov's threats and demands and violated safety protocols by pulling almost all the control rods. Tregub (prior shift Senior Reactor Engineer) had remainded at the reactor control station after his shift and advised Toptunov on which rods to pull - fully complicit in Dyatlov's disasterous intervention to get reactor power going again. Dyatlov, during the investigation and trial, denied that he was even in the room. If Higginbothom's account is correct, then Dyatlov bears most of the responsiblity for violating the published procedure by insisting it be done at 200 MW in an unstable reactor and bullying the reactor engineers (and Akimov) into violating critical safety measures. Poor Toptunov had only been a senior reactor engineer for 2 months when he activated the AZ5 system that was supposed to shut down the reactor but in sad fact became the final insult that initiated the destruction of Chernobyl Reactor #4.
@@richardvaughn168 I want to read this book! it has been on my list of books to read even before the series premiere. I believe the book is basically in agreement with some sources I came across, like the INSAG and the IAEA.
@@jefersonnl there are many things the HBO series either modified or got wrong, but there are plenty of other facts they got right. We know based off records that the test and shutdown was going to happen during the day shift, but they were requested (demanded) to not take the reactor lower so factories could meet their obligations for the month. the reactor then remained at that 50% power level (rather than proceed with the next drop to 700 MW for the test) where simulations have shown xenon to build up to significant levels over the course of the following hours. this combined with the lack of proper training for the test by the operators likely led to the reactor going from almost desired power to almost nothing as the reactor stalled. At that point, the operators started fighting to get the reactors power up to 200 (a power level that would still have failed the test) and took it off automatic control. the politics behind dyatlov being promoted upon a success that night I had not heard (but not unthinkable) but he did push the operators to do things that they were never trained for and violate every rule in the book to get his test, at which point the reactor sprung to life uncontrollably due to the voids and damage caused by smaller scale uncontrolled reactions nobody had any ability to know were occurring. (the RBMK-1000 was fuckoff huge in all dimensions, leading to varying reactions that were unmonitored across the whole thing.
@@trinalgalaxy5943 Ohhh really!?? Noooo wayyy!!.... seriously, I don't even know what to answer. As a matter of fact, I'm beginning to question the wisdom of coming here and writing this in the first place.
*looks at reactor design notes* "Under no circumstances should less than 30 control rods be in place to ensure safe operation" Blyat! *Continues to remove all of them*
The engineer overseeing the experiment, Dyatlov, had another similar accident earlier in his career. It didn't have the dramatic results as Chernobyl but his son died as a result. The man was dangerous.
At the time Dyatlov was quite defiant and refused to accept responsibility, claiming that he had been lied to and that vital information about the graphite tipped control rods (and the danger they represented) was kept from him. In the years after his death when more secrets about the Soviet nuclear industry were exposed it turned out he was right. Vital information HAD been kept from him, and all the other RBMK reactor operators working at the time. It has since been learned that an incident like Chernobyl had almost happened before (at the Leningrad plant in 1975), and although the cause was known the authorities chose to keep it a secret lest it expose a failing in Soviet reactor design. In fact the commission who investigated that incident made several recommendations to improve safety but they were ignored and the whole incident was covered up. Was Dyatlov merely a hapless pawn in a deeply flawed system? Many would say yes, now that we know the full extent of how far the obsession with secrets went. Myself I don't think he was totally blameless, but had the authorities chosen to pass on the safety recommendations rather than keep their silence the entire incident would not have happened.
@@woopimagpie the fault was in the blue prints from the off Dyatlov got the blame.this is why people should not act the cunt in the work place .with nuclear fission.
@@woopimagpie Glad to see you've done your research unlike the HBO Chernobyl series minions who think they know everything. From my reading, the reactor was designed by the "Ministry of Medium Machines" which was a USSR top secret government ministry. All secrets were kept away from nuclear engineers.
@@woopimagpie I grew up about 400km from the Chernobyl site. I was only 4 at the time. The soviet mentality you touched on still exists to this day. It's part of the culture at this point. Project power, downplay weakness. It's not until something catastrophic happens that the rest of the world gets a good look at the dysfunctionality that is the Russian system.
10:50 no one hit a wrong button!! Where do you get that miss information from? They where shutting down the plant to round about half power preparing for the test. But then the grid needed more power. So they stayed on this low power for some time. Meanwhile the core got xenon poisoned due to low power operation. Then they started the test by lowering the power to ~2/3 power. Because of the poisoned core the power continued to drop in power. Then they tried to bring the core back up to a power level suitable to perform the test. They did this by removing all but 1 control rod (against all regulations). Then the power skyrocket because the xenon was burning away. In an attempt to shut down the reaktor they pressed az5 causing all control rods to go back into the core. But because the tips of the rods where made from graphite they first caused another spike in power. Which resulted in the explosion of the core.
This is a great presentation. I had never considered the role of Xe before, but of course -- the rapid burn off of the accumulated Xe with the control rods removed left little course. I am curious however why the other safety defect of the RBMK, the positive void coefficient was not mentioned. My understanding was that at low power the RBMK had a positive void coefficient so, e.g., a steam bubble is a 'void', which causes power to increase, which makes more steam, more voids, etc. leading to an uncontrolled positive feedback. The control rods as i understood had two design flaws. The graphite follower which would moderate neutrons and the metallic bottom of the rod which would displace water -- and introduce a void.
He does mention it when he mentions that when water boils in an rbmk, the moderator (graphite) is still present and allowed to operate even more efficiently bc water isn't absorbing neutrons (water self-dampens it's modeerating ability by absorbing many neutrons). He just doesn't use the technical term.
@@WINuFAIL Not entirely. A positive void coefficient is an increase in reactivity due to a void that creates a positive feedback loop. That is what creates the super critical event. Void --> increase in reactivity --> increased power --> increased temperature --> increased void --> and so forth.
@@stephenfriedenthal8312 Yes I understand. What he and I are saying is that the reason the opposite happens in other reactor types is because water is the coolant AND moderator, with no graphite present. A void means no coolant but also no mod, so reactivity and power decrease. He describes this mechanism without mentioning that this creates a feedback loop. So basically he described the first half of it.
@@stephenfriedenthal8312 I agree - there is too much talk about the role of xenon. Xenon doesn't explain the pos.void coefficient as you rightfully explained. The RBMK was unstable at low power and the voids were't pushed out by the flow of water and remained in the bottom of the core resulting in potentially dangerous power anomalies.
@@WINuFAIL In the RBMK, a void means the water is less dense which means less hydrogen which leads to a decrease in neutron absorption by the hydrogen and an increase in neutrons so power increases' not decreases.
That’s the single best explanation of physics of the Chernobyl disaster. There are a couple of the things that professor might have not been aware of. 1. The whole idea of that *experiment* grew from the successful attack on the Soviet built Ozark reactor in Iraq conducted by the Israel Defense Force. The experiment was to prove that the power plant can withstand power cut off due to the attack and to sustain itself just by the power of mechanical inertia of the turbine-generator. 2. They hurried this up because in the Socialist system it was very important to report the success to their Communist Party bosses in the eve of the 1st of May, the major Soviet Holiday. Should the experiment be a success, all the participants would be rewarded by bonuses and promotions to the top managers of the plant.
From what I understand, the Experiment was actually to see if the freewheeling turbine can generate enough power to keep the safeties and cooling pumps running during the 1min gap between a power loss event and the backup generators spooling up to make enough power to then support the aforementioned safety systems.
14:04 So that says 2014" on it. Looks glowing red hot, but those lamp shade things were lowered after the accident. So what is glowing that hot? The carbon fire was not that big from videos from after the accident. So what is that? And how if it was that hot could you or your camera not get blasted with a lethal dose of gammas?
Thank you sir. This was an absolutely enthralling lecture. I watched the 2019 Chernobyl miniseries and while I do understand there may be factual inaccuracies in the HBO series your lecture helps me to comprehend just how dangerous the Chernobyl disaster was in 1986. Thank you once again sir.
This poisoning was known before this event. The Chernobyl operators just weren't qualified or slaves to a Communist system where all that mattered was results.
"The Dyatlov Effect" has a nice ringing to it, however, it should be not about nuclear reactors, but about the culture of pushing people and things beyond a limit you shouldn't, all in the name of results. Once I was a spectator to something like that, when I saw a rocky project manager push people to the brink for a couple of days in order to meet a deadline, and it ended up with an assistant DBA overwriting a live production database with a test copy in the middle of the working day. Of course people were nervous and exhausted in the first place, but he put some security issues and good practices aside like allowing trainees root access to production servers, coz the real DBA had to have a break after working for several hours straight. I remember I was part of the 'liquidation effort', we had to put that guy aside, let him have his nervous breakdown, relieve the rest of the guys, and manage the damage. Lessons were learned that day. Never again something like that happened in our department. Of course, one of the most important things we learned is, do not put unstable, authoritarian nor arrogant people in charge of things like management. Sometimes leaders have to act as a buffer protecting his/her team from outside pressure while they do their work to the best of their abilities, and not actually transfer the pressure on to the team. That's part of good leadership, take a few blows in the name of your guys. Of course, Dyatlov was a product of the system that raised and taught him(so was the reactor and its flaws), and that can't be overlooked.
I would rather call a different thing Diatlov Effect: When you press the SCRAM button and your reactor explodes afterwards... because of reasons. (The SCRAM pushed all control rods inside at the same time, which caused the final fatal runaway)
I'm an industrial pipefitter and although this may seem like overkill to learn this kind of stuff, it is incredibly useful to understand the intricacies of the process and history. Thank you very much for posting all your videos. The history and future of power generation is so important to understand, even if people aren't an installer and welder of the process piping like I am.
Given that it was badly fitted pipes what sunk the USS Thresher, knowing how to pipe fit it no small matter. My dad had used to work for a company which build compensators for pipe systems and at one point they did them for nuclear power plants. The amount of courses and lectures he had to take in order to do his work was beyond belief.
I cam here after watching your Fukashima video, and am a little confused about one thing. In this video, you mention that all reactors other than RBMK have their reactions slow down when they lose water, however in the Fukashima video you mentioned the main problem was losing the supply of cooled water to the reactor and spent fuel. Shouldn't Fukashima have been OK without water then?
Yes, the morning shift had contaminated shoes which set off the alarms. Needless to say that led to a few very tense hours as everyone first assumed it was a malfunction with our power plant.
Glad somebody else noticed this. Sure it isn't water cooled but we most certainly are still using graphite moderated reactors, admittedly not building any more new AGRs though.
I worked at a UK AGR, they were inherently safe IMHO. Main protection was automatic trip of control rods, they relied on gravity, followed by numerous secondary and tertiery shutdown systems. . Water filled reactors have accounted for quite a few of the accidents in the past. .
There was 2 explosions if i recall, one where the steam blew the biological shield, as in the lid of the reactor and the caps, off and the other came few seconds after where oxygen combined with the red hot graphite + hydrogren to cause the big boom!
Well made video! Just one thing: Even if the RBMK had a containment building many professionals think it would not have survived that explosion. The HEAVY lid of the reactor flew about 30 meters high.
Reinforced concrete is believed to have far more strength when dynamically loaded during an explosion or an impact. A real life example of this the Longarone dam in Italy which survived loads estimated 100 times what it was designed for when a mountainside slid into the reservoir. Unfortunately very little research is done in this area because of the huge costs of blowing up life sized structures.
Even if it did crack it, the hole would've been quite small, and less material outside, meaning less people have to clean it while being in place with 20 thousands Roentgen/hour
Man If I'd had you as a professor in high school my life would be so different because I'd actually pay attention to you because I can understand what you're saying. Can't say the same for the professors I had. So depressing.
UK Magnox and AGRs also use graphite moderators, but they differ from the RBMK reactors in that they use a gas coolant (carbon dioxide) in the primary circuit and boil water via a heat exchanger (which does not come into contact with the actual reactor). Also, the gas will naturally circulate via convection to take away decay heat, but do require control rods to drop in to shut the reactor down in the event of a fault. It also doesn't have the positive void coefficient issue that the RBMK reactor does. The AGRs also don't have a separate containment building, but have a 5-7 metre thick reinforced concrete pressure vessel. In any event, that seems to be a bit of an omission. The last AGRs are due to close down in the next decade or so. Their biggest problem appears to be the expense of decommissioning, as there is a large amount of irradiated graphite to deal with, and the reactor core is a lot larger than in a PWR. It's also that very large core which means it's not prone to runaway decay heat issues as there's a lot of thermal mass involved which slows down events. It means that the sort of thing that happened at Fukushima ought to be impossible as it doesn't rely on powered cooling systems after an emergency shut-down. nb. there was never an issue of Kiev losing all its power during the planned exercise. There were four RBMK reactors at Chernobyl, and only one (reactor #4) of them was to be shut down for refueling.
Fakse - 2019 there were still 10 RBMK reactors (graphite-moderated) and three small EGP-6 (also graphite moderated) light-water reactors operating in Russia,[1][5] though all have been retrofitted with a number of safety updates.
Always be on alert if someone tells you "everything you needed to know about a specific topic". Nuclear power plants are complex machines although the physics behind it may seem simple. Complex machines are prone to failure, human error, negligence and profit-maximizing cost savings in maintenance due to greed or incompetence. It's easy to say that an event, exactly like Tchernobyl, might probably never occur again. But there are myriads of things that can and will go wrong with probably devastating consequences. And that doesn't even take into account the consequences of the still non-existant long-term storage option. Or the nuclear waste that had been dropped to the sea-floor for decades. Just think about Fukushima. Surely not identical to Chernobyl. But still a catastrophe. And a perfect example for human ignorance.
Moral of the story: - Never build positive Void coefficient reactor - Build a good containmentbuilding - Moderator and Coolant must be same water - Every worker needs knowledge of Xenon 135
This is one of the best, clear, logical presentations I have seen, on what happened, many thanks for doing this. Hopefully this knowledge and wisdom gained can prevent future disasters. For any young viewer, Chernobyl accident was a big deal at the time, it was terrifying at the time knowing that radiation was falling out of the sky and nothing you could do about it.
Extremely scary time to live through. The consequences of this accident will last forever. Generations and generations will be dealing with the mess. We were always told - 'A meltdown can't happen'. Nuclear power is dangerous, very dangerous.
What bothered me at the time, even though I was and still am deeply into physics, the information given out on the media was "maddeningly unhelpful". Lots of units like Bq, Gy, rem and Sv but no one seemed to have any hard facts.
The Chernobyl guy was a self-taught expert on the RBMK reactor. His previous background was submarine reactors. He was noted for his ability to cite technical manuals. The weakness in RBMK reactors had been identified about a decade earlier and it was published. But someone redacted the part of the report that talked about preventing an explosion. Whether the lead guy had clearance for the redacted portion (probably) and whether he could have accessed it (pre-web) is undetermined (or at least unpublished itself).
I can't life like a submarine Reactor because of this Life I am D O I N G like the Prof. In the Video Demonstration is writing behind All and All behinder and behind it... that's not possible... i can't understand it... it's nonsense for us all... Super... Dummel Will Not Life... Amen...Ciao Wiktor Witas Kuhn from Bremerhaven and Amen You All, I try everything to escape this 20000000 ttilliard Super Nintendo... that's impossible... I Love You Math ... ❤❤❤
I doubt it would have mattered much. The same political pressures and the same lack of care for safety to satisfy those pressures would exist. The problem was not one flaw with one reactor, or one bad decision by an operator without all the information. It was a failure at nearly every level.
Well, it could happen to western reactors too. And it has happened. Fukishima Daichi runs on General Electric reactors. The containment vessel failed, because of poor design. Still leaks radiation in the sea. Most of the reactors running today are designed in 60s and 70s. To say, that it is impossible to happen, because it hasn't napened yet, is not very smart. The scenario will be different, for sure, but the result will be the same - contamination.
To be fair, what happened at Fukushima was VERY different than what happened at Chernobyl: in particularly, highly different explosion locations and causes (and that's saying nothing of the earthquake/tsunami impetus).
@@DanielFolsom , you are right. But, isn't true, that every nuclear accident happened because of different reasons? If some nuclear accident happens in the future, do you think that somebody in the neighborhood will care if it is the same or different compared to Chernobyl or Fukushima? Western reactors have their own problems, that also can cause similar or worse contamination. The biggest problem of them all - neglegence. It is common everywhere. So we can't sit back and relax, because Chernobyl can't happen in the Western world. It will be TMI, Fukushima or god knows what else...
@@velinr There is no industry in world, literaly NONE that work in safety lewels of Nuclear power plants. and results are here,... Nuclear power is Cleanest and safest of them all. period. Like it or not. amout of peaple dying per Watt of nuclear power is waaaay below any other energy source, including renewables. Sadest thing about Fukushima that trouble over power plant overshadowed 15000 causalities of earthquake and tsunami.
@@marianmarkovic5881 , I'm not against nuclear energy. I believe that the future of the energy is nuclear. But the efficiency, at current level of applied technology, is very bad. And there is lot of waste. And there are lot of problems. And we should not be nearsighted nor one-sided about. Appearantly, the safety is not high enough, after such incidents happens.
10:00 That was better explained in the Chernobyl series, they actually ran it at half power for the whole day because the power was needed, then they didn't hit the wrong button, they put it into automatic mode and it almost stalled because it wasn't calculating for the Xenon.
Sir I respect you IMMENSELY but may I query...my understand was it was *due* to the Xenon content that the engineer stationed at the time stalled the reactor as it had been running at half power building up Xe 131 for about 11 hours before the accident as Kiev stated the test had to postpone the test till the night.
Thank you for this video. Indeed you need physics to protect. RBMK's didn't rely on people, but automation and people in extreme circumstances. A few more important factors and a slight correction. There is a lot to criticise the crew over, but it's important to note the explosion was in fact caused by the crew sensing a problem, panicking and hitting the emergency SCRAM button. RBMK's computer control was relatively advanced for the time. The thinking was that in most situations this reduced the risk of crew error. As we now understand, yes that's true, but it can also reduce the experience of crews to handle unexpected events outside of usual operational bounds. The reactor was in fact at 50% power throughout the day before the test at 1am, so for many hours. The reduction in power to a target 22% was supposed to be very brief. There was an unexpected delay to the experiment, which caused Xenon to build up. RBMK's don't shut down to refuel, they're so big you refuel in sections whilst the reactor is running. That's got serious implications for the accident because it took the crew outside of usual operating bounds, exactly the type crews who rely heavily on automation struggle with. With RBMKs there is less contingency in the grid because the reactors never shut down. That created huge pressure to get the test done then, as it might be years before there was another chance. Secondly, crews always relied on automation to run these big beasts, but below 50% RBMK's are manual. That's like going from an automatic hatchback to a 16 speed Mack truck. Thirdly, because the reactors virtually never went below 50% power, the night crew had never run it manually before, nor had they powered down a reactor., because RBMK's are always on. No one hit the wrong button, they were targeting 22% and didn't account for Xenon. They hit the right button, the SCRAM, when it was clear this reactor wasn't behaving as predicted. But the rod design with moderator tips caused that spike and the rest is history.
It's so low-tech for such a high-tech subject. But I must admit, that backward writing looks really cool. I think maybe this professor made a deal with the Devil.
This description is not totally accurate, the description of why the power dropped "wrong button press" is wrong, and the reason it spiked is inaccurate. This needs updating.
Don't bother wasting your time Nic, any attempts to correct all the inaccuracies in this video will be deleted. It's rather sad that this 'professor' would rather educate people with garbage misinformation about Chernobyl.
@@professorrinse8028 - That's not strictly true. If you watch the next vid in this series called "Xenon can be a problem", it goes on to explain in detail about xenon poisoning. More interestingly, there are several posts from a licenced nuclear operator who has posted a staggering number of pages detailing his criticisms to the vid and countering with his actual experience. th-cam.com/video/RZQwL-2WTgA/w-d-xo.html
The 'Professor' says it's an RMBK reactor in the description, and states the Chernobyl technicians simply pushed the wrong button which caused reactor 4 to explode. This whole video is laughably inaccurate, but hey, this is TH-cam, all one needs to do is dress like a professor, say a few technical words and everyone thinks your spiel is true.
@@professorrinse8028 - It's not that inaccurate if the button he was referring to was the "AZ" button which inserted all the control rods. He very briefly mentions that the operators were not aware that the Boron Steel rods were poorly designed and that a surge of power could be observed when the rods were inserted.
I think it’s implied the RBMK should have a containment vessel, analogous to the Western LWR containment configuration - not that the RBMK reactor should use containment as designed for the LWR. Most certainly, the containment for the RBMK would have to be specifically designed for it, one of the specifications being able to contain a hydrogen explosion. Obviously, using a Western design intended for use by an LWR would not suffice for an RBMK. I have read Russian designers discarded the idea of a containment structure because a:) they believed with certainty the reactor characteristics were such that a Western style containment was unnecessary, and b:) the reactor was intended to be refueled while in operation via a large crane above the reactor vessel; hydrogen explosion-proof containment would have impeded this feature, or made it impractical if not impossible. Regarding an operator hitting the wrong button, this is the second video where I’ve heard this, the first being n MIT lecture on nuclear engineering. I believe the source material came from an official report by a nuclear regulatory agency; I’ll post a link to the report and updathe post w the agency. The two presentations are very similar with respect to the technical details and the timeline, causing me to infer they’ve both used the same source material. After reading the NRC’s report and rewatching Professor Ruzic’s essay, I’m unable to substantiate any of the comments who declare this video is full of misinformation and mistakes. Professor Ruzic does interject his dry sense of humor when he’s critical of operator performance, and clearly interprets the actual events and human factors elements with an engineering and professorial point of view with full benefit of hindsight, but that’s how root cause analyses go. I suggest instead that the people who commented that Ruzic made errors have trouble with his perspectives, points of view, opinions and style. That’s too bad, because looking at issues from multiple angles and personalities is a critical benefit of TH-cam. Being able to watch many different videos on a singular subject is such an advantage, especially when the videos ultimately prove out a consistent sequence of events and series of facts, along with weeding out the content creators that are less than rigorous in their factual reporting.
You're referencing SL-1 as if it were an industry standard and not an experiment. Not to mention it was 25 years before Chernobyl. Nice try to draw false comparisons though. The same incident wouldn't happen here. Just look at France.
@@clint6716 Ah, yes, comparing a steam explosion caused by improper control rod operation to a steam explosion caused by improper control rod operation is totally a "False Comparison"...
@@Kohdok you missed the more important parts of my response. This was in 61, before most of the safety precautions that were ignored in Chernobyl even existed. There 'containment' structure was 1/6th the size it needed to be and not made of the right material. Comparing these two incidents disingenuously ignores all the research that took place between the two events, and more so discounts the even more modern advancements since. The answer is still no, it wouldn't happen here.
@@Kohdok yeah because one happened 20 years before the other, before we even knew how to deal with all of the bullshit that comes along with the shit. Long island was an unfortunate reality, but he's right. A chernobyl could never have happened after long island, cause we wisened up, while the Russians didn't know.
The first to notice was engineers at the Swedish Forsmark Nuclear power plant. Alarms starting to go off about external contamination and after doing checks and coming to the conclusion that "It ain't us" they alerted the IAEA that "Something has happened, somewhere, and we think we know where".
"Water drains away, the reaction stops" works until you realize there's decay heat and that too can cause catastrophic problems. Fukushima Daiichi was caused by the decay heat cooling systems' power sources being washed away, and replacements not making it there in time.
that caught my ears as well. In this lecture the prof suggests that LWR is bulletproof because when water vapourises then fission stops end of story. Then in his next video about Fukushima he explains how the fuel overheated when the water vapourized, ending up in fuel meltdown in 3 LWR reactors.. Nevertheless a great presentation, but the Japanese and the nuclear scientists after 10 years still do not have a clue what to do with the melted fuel in the Fukushima reactors. And they were kept under water for 10 yrs and still needs to be permanently cooled, so taking away the moderator does not seem to stop fission completely... I assume you still need the control material(rods) to absorb neutrons to be able to drive fission further down, but that does not work with melted fuel anymore, right? Or if you have an LWR reactor with fully inserted control rods, when the water is taken away, it would still melt? Which basically means you need both water and control rods...
@@sspringbok modern reactors will maintain stable enough temps without coolant just through the convection of air. Intrinsically safe by design. Older ones however would still need water coverage. Spent fuel in the pools are typically now arranged in a way that supports convection cooling to sufficiently cool them ans thus need water coverage.
I think it’s about the water acting as both coolant and an enabler of the fission itself. With no water, the fission and the heat generated from fission are minimized, so there is nothing to cool.
Would have a containment structure have been able to withstand that steam and thermal explosion? After all, it lifted “Elena”, the 2000 ton lid clear off the structure and turned it on its side.
Notice the buttonhole on his jacket's lapel appears to be on the wrong side: its actually the video that's backwards he's writing normally from his point of view, then the entire video is mirrored horizontally before upload
And a month down the line, I guess that free moment never came, did it? His explanation had a couple of small inconsistencies based on what we know, but he stuck the landing on how it happened. I’ve watched quite a few of his lectures; doesn’t seem like your typical “know it all” professor to me - just a guy who loves what he does.
Admittedly I did come here after watching Chernobyl because I wanted a focused breakdown, but before here I probably watched 30 other videos. This was so well explained and I enjoyed every second of it - I wish I had you as a professor back in the day. Thank you very much.
Great explanation. Obviously simplified to make a point. However, be careful saying that something can't happen. Seems like overconfidence breeds complacency, and complacency leads to accidents. When people say something can't happen - this ship cant sink, this reactor can't explode, this dam can't break - the world likes to prove us wrong.
An excellent presentation. Enrico Fermi built the very first carbon moderated reactor with no containment in a squash court at University of Chicago. Werner Heisenberg's first reactor was moderated with heavy water and had no containment building and that blew up and destroyed his lab. We Brits used air cooled carbon moderated reactors with no containment in Windscale to create Plutonium for our bombs, and one of the reactors (Piles) caught fire in 1957. Then of course there's Three Mile Island, and Fukashima, both of which were "safe", then we have the THIRTEEN Ukrainian Nuclear Power Plants in the centre of a bloody war zone in the 21st century. Human ignorance, complacency, stupidity, and greed cause these disasters, and always will!
@@pavel9652 don't get me wrong, I love these videos. I have watched a lot of them and learned a lot. It was just that I didn't know where the squeaking was coming from XD
@@carrito1981 Haha, I mistakenly responded to your comment, while responding to the other one. Nice catch, you are fast ;) I already deleted it, sorry for the confusion. I think the squeaky marker is a staple here ;) Stay curious!
No containment would have prevented Chernobyl from exploding. The reactor got into an unstable region producing a phenomenal amount of power. It's simply bad reactor design. "Doctor, it hurts when I do this." "Don't do that!"
Excellent explanation of the differences between the reactors in the "west" and in the Soviet Union. Lies were the downfall of the Soviet Union. So many lives lost due to lack of information. It's sad. God bless those that gave their lives unknowingly.
I was wondering how he was able to write backwards so effortlessly. Then i looked closer, either he is wearing a women's jacket, or the buttons are on the wrong side. The video is flipped.
@Illinois EnergyProf The elephant's foot beneath reactor 4 is made of uranium that got through the bottom of the reactor vessel (melting the bottom of the reactor vessel). Are the bottoms of the new reactor vessels fitted with the same materials that the control rods are made of, so in the case of an uranium fuel meltdown the fision reaction will be stopped by that material on the bottom of the reactor vessel, the fuel will solidify and there will be no danger that the uranium lava will leak into the ground contaminating the water?
Nuclear fuel by itself, while radioactive and not safe to be around, is not something that fissions normally or requires a neutron absorber like a control rod. New reactors, old ones even that where not soviet built, have thick concrete surrounding them which is more than enough to stop the nuclear material from eating through.
@@JPminer814 Then why did the elephant's foot sunk beneath the reactor's core. Why was everybody fearing that radioactive material will get into the groundwater?
The reactor was poisoned because the power level was accidentally allowed to drop to a very low level, not because the reactor was running at half-power.
If you know a lot about nuclear reactors you probably know a lot about half life’s. Iodine has a half life of 6 hours and after that 6 hours half of that turns into xenon. If that nuclear reactor just dropped to a low level exponentially that wouldn’t cause a xenon poisoning. What does how ever cause a xenon choke is a reactor running around half power for too long
If there was a containment building, would this not act as another level of bomb by having it fill with gas until it also blew? What protections are there for this in containment buildings?
A bomb losses energy breaching a containment. So there may not be enough energy to breach a second container. Built properly then anything sans the most negligent act(s) or sabotage and any explosion will be contained.
Thank you for a very easy to understand film. I've been to Chernobyl hundreds of times. This topic interests me both as a job and as a hobby. I would be happy to discuss this topic with those interested and even organize a trip there.
Did you get a professor on HBO's Chernobyl series? RBMK exploded due to design features and coincidence of circumstances. The operator pressed the correct button, but it worked unexpectedly badly. And this happened as a result of the poisoning of the reactor and a small number of absorber rods in the core.
I believe you’re misunderstanding comrade. RBMK reactors do not explode.
Disgraceful. Spreading misinformation at a time like this
They don't explode, they _detonate._
Take him to the infirmary comrade. He’s delusional.
It was all an imperial ruse, the CIA dropped a dirty bomb on Chernobyl.
...except when they do...
I want this guy to read me bed time stories about science disasters.
Read
@@susbox5554 ugh, thanks
Satan will do that for you in your sleep.
@@nathanlaframboise8074 your welcome
I want Angela Lansbury to read me bedtime stories about science disasters
The Soviet report concluded that the reactor didn't have a workable fail-safe for when the operators disable all the fail-safes.
You say that somewhat in jest, but there are serious engineering applications where "What if someone intentionally tries to make it do the thing we really don't want it to do?" ..is a significant consideration.
@@jermainerace4156 Agreed. Just that the implication is the designers were completely irresponsible and the operators weren't at fault. Interesting idea that a nuclear worker could become suicidal -- maybe with a big enough dose. And the HBO series (the final arbiter of historical disputes) implies that because accident details were made secret, they were not known to those who would have had the need to know them.
@@jermainerace4156 You're embarking on a discussion of quality control philosophy, which is good.
@@jermainerace4156 Agreed. I too remove all the oil and coolant out of my car then drive cross country. You know, for quality of craftmanship checks.
@@zackthompson2505 Many people do that inadvertently by not fixing slow leaks. Eventually enough leaks out that the car overheats or the oil pressure warning comes on and they are like "ZOMG what happened?"
Goodbye normal comments section, hello HBO's Chernobyl references
Hello.
There’s graphite in the comments...
BasedGod Strugglin' you didn’t see graphite in the comments. You DIDN’T! because it’s NOT! THERE!
3.6 normal comment not great not terrible
You didn't read HBO Chernobyl references. YOU DIDN'T!!!
So now I know how an RBMK reactor works. Now I don't need you.
You're Delusional. Get him to the infirmary.
Now, you can throw him out of the helicopter.
*Throws him out of the helicopter into the reactor core*
Shut up asshole the Professor did an excellent job,.
@@bethlarson7144 You're not getting the meme, are you? Also, quite a few logical simplifications AND omitting very important data, so not really "excellent". I must say though it is explained in a user friendly way. Overall, not great, not terrible (in both literal and meme meaning).
"Hes delusional, take him to the infirmary"
3.2 rontgens....not great, not terrible.
@@michaelbell8834 3.6 roentgen not great not terrible
Not only informative, but how does that guy write everything backward?
flip the vid horizontal
He got so much wrong.
@@markhowes6575 what?
PentaxSource so his actually right handed 🤔
its a mirrored image, he writes normally and the way it is filmed produces the effect.
You missed the important point of why the power level spiked. Once the reaction starts, the xenon gets burned off. The Chernobyl core was so huge that it wasn't uniformly controlled by the control rods, and the reaction took off again in the bottom part of it. This started burning off the xenon in a hurry. Now you have a situation where prompt neutrons are causing fission (carbon moderator still there), and all of the control rods are out of the reactor, and the xenon that was keeping fission from happening was getting burned off like dry grass in a self-feeding cycle.
In the world of high energy physics, this is what is known as an "Oh [expletive] moment".
There was a perfect moment, when ALL of the xenon was gone, and ALL of the control rods were out, and ALL of the fuel - some 200 tons of it - was free to react, completely uncontrolled. And it did. There is at least one paper out today that even claims a nuclear yield. Small, but larger than the chemical explosion could ever have been. The reactor hall was cast concrete, Soviet construction, and could probably have actually withstood a substantial chemical explosion, but was kicked aside like cardboard in the face of this blast. Radiation-resistant windows a meter thick were blown to bits like plain window glass.
That is what happened at Chernobyl. A worst-case scenario, with 200 tons of uranium reactor fuel, totally uncontrolled.
The United States already knew about xenon poisoning, having experienced it first hand with the startup of the Hanford B reactor, where we too yanked out all the control rods in a futile attempt to jump start a reactor that for some reason unknown at the time just would not react. We were very fortunate that we did not create the same accident here. The only reason we didn't was because Hanford B had been built too small, and could never start properly, given the effects of xenon. Beginners luck
thanks for the info especially about Hanford B
@@sygos Extra channels had been built into Hanford B as a contingency, and it was a relatively simple matter to load these and create a bigger core.
I've been waiting for this comment all year long. Apparently, many still don't get it
But no one is going to mention that the graphite tipped boron control rods caused the power level spike?
@Tom R yeah, the spike was going, but the control rods prob gave an extra kick that didnt help anyone. Ignalina and a few other stations had already modified the rods to be less reactive, but thanks to KGB and the "saying there are problems creates problems so just say its fine" mentality, the information never went to Chernobyl
his voice: calm and soothing.
his marker: 2:55 screams of the damned, but pitched up
I lived in Satu Mare, Romania in 1986, Kiev is about 830 km away, town on Pripyat about 900 km. We actually learned very quickly, and not from the West, back then we were under Iron Curtain, but from our own government who was monitoring things (work started on our own first nuclear power plant at Cernavoda). I remember being a distinct fear of the fallout cloud drifting down to Transylvania since there aren't many high mountains in the way, except the Carpathians.
It didn't, and we were relieved.
Where did you hear it didn't? There are weather maps of the time showing the worst radiation reached Romania and all the way to Spain
@@octavianr526 absolutely! It was one of the red areas if I can remember
You need to watch the map of the cloud cause it did in fact hit Romania
"An operator hit the wrong button in the control room..."
*Looks at Dyatlov*
I wasn't in the room
I was in the Toilet.
Akimow DID THAT!
i hate how hbo took the soviet party line and simply blamed the guy who followed orders and then went further to lie about his conduct during the explosion etc
ϟhitlord what did you want them to do
@@gallyturndrop5320 blame the overly sized reactor that required seasoned staff to make sure it didnt fubar itself (not the college grads that manned the station) not lie about Dyatlov when it came to his reaction to the meltdown (he knew that the core exploded and never blamed any of his subordinates) not make up some strong female radiation scientist that never existed forgetting the attempts to stop the fires ended up creating the whole radioactive lava problem etc
in short they put too much blame on the people involved and not enough on the system itself (they did place some of the blame but the lions share should go to the soviet system itself)
the system that put men trained or untrained in charge of what amounted to a gigantic radioactive pressure cooker bomb that would inevitably go boom
Man...this dude is gifted. To be able to explain such difficult stuff, making it easy to understand.
And above all, making it interesting and entertaining.
Wow.
Did you see the series? That was very good.
I totally agree with you.
You forgot to mentioned his ability to write the opposite direction while explaining stuff
@@1414AdetySomeone in the comments suggested that he flips the video in post-production, which I think makes sense.
@@1414Adety That's the actually impressive thing.
The expression, "buy cheap, buy twice" comes to mind when thinking about Chernobyl.
Skimping on safety measures to save money, ended up costing them a lot more in the long run. It always does.
And in any future events feed in the human element. One day someone in rush to get home for one reason or another will do something wrong and... Bang????
It's a communism pure nature. They even speeded up the construction to get bonuses from the government and that speeding was due to hull skin installation skip.
True about nuclear energy generation in general. Nuclear in itself is the epitome of that “buy cheap” concept, since the idea of fractional long term fuel costs makes bean counters cream their breaches. They damn sure aren’t lowering power bills because nuclear fuel is cheaper.
It’s like when I do any form of carpentry “measure once, cut 3 times, realize I bought shitty materials, quit”
Sounds like Soviet logic to me.
Sorry, no 10:50 an operator didn't hit the wrong button. It had been run at half power and there was a xenon build up along with a lack of coolant void and graphite cooldown. This made any power change difficult. This is known and is in the WNA page about the accident. From there you are correct.
Agreed, the problem was the electrical grid needed power and those operators didn't allow the power to be reduced, so it stayed around 50% for 19 hours, which contributed to the Xenon poisoning.
That's not strictly speaking true. One of the operators switch the reactor from local automated operation to global automated operation. Sort of a nuclear autopilot. However, he failed to set the power level that he wished the reactor to stabilize at. Because of this, the reactor went to the power level that had been specified last - near zero. And, of course, and we know from experience now that RBMK reactors are notoriously unstable at low power levels. PARTICULARLY when the fuel rods are older and due for replacement.
@@VComps Not according to the The International Nuclear Safety Advisory Group (INSAG):
The drop in power occurred at 00:28 on 26 April during transfer from local to global power control. The INSAG-7 report states: "The INSAG-1 report describes the precipitous fall in power to 30 MW(th) as being due to an operator error. Recent reports suggest that there was no operator error as such; the SCSSINP Commission report (Annex I, Sections 1-4.6, 1-4.7) refers to an unknown cause and inability to control the power, and A.S. Dyatlov, former Deputy Chief Engineer for Operations at the Chernobyl plant, in a private communication refers to the system not working properly."
The timeline from the World Nuclear Association words it differently:
With the power level at about 500 MWt, control was transferred from the local to the automatic regulating system. The operator might have failed to give the 'hold power at required level' signal or the regulating system failed to respond to this signal. This led to an unexpected fall in power, which rapidly dropped to 30 MWt.
So it isn't quite clear what happened, but still, the Iodine pit - Xenon poisoning sequence described by the professor was happening anyway and they should have shut it down, but instead they tried to increase reactivity ultimately ignoring safety standards. Then we have the positive void coefficient making things even worse - the poor souls were doomed.
One of the things may not be instantly obvious for someone not living under such a regime is why they ignored so many regulations. It wasn't simply negligence, people in the Eastern bloc, especially in the Soviet Union still remembered the days when a failure to get results was considered sabotage (as the system of scientific socialism was supposed to work flawlessly) and punished severely.
The squeeking of the pen gives me more chills than he actual Chernobyl accident
How does he write backwards so fast
Constant 7th octave.
I want to smack the pen out of his hand and tell him to
"Raise The Power"
Comrade Chief Deputy Engineer, I shall need that order in writing.
"He's procrastinating"
Just do what I tell you. Even as stupid as you are, you ought to be able to accomplish that...
“I apologize...”
GIMME A PING VASILY!!!!!!!
Oops.... wrong movie...
@@hawkeye0927
Kohai... if you must resort to ballsing up movie references, you've already lost.
....oh sh×t... even wronger movie.
😁
I'm very impressed with how well this guy explains the process, step by step.
I’m impressed by how he can write backwards
@@PJL7095If he draws the graphs like hundreds of time he's gonna have a whole image of them in his head which is amazing. I got this kind of feeling when I study basic physic during my highschool years.
AM I ONLY ONE WHO IS MORE IMPRESSED BY HIS REVERSE WRITING THAN HIS EXPLANATION!!!!!
Unless they just invert the video in post...
yes
You didn't see his reverse writing... YOU DIDN'T BECAUSE IT'S NOT THERE!
Instead of the nucular stuff I started thinking about that! At speed of a neutron my brain realized the image has been flipped around. Sort of semi made more likely by the fact that he appears to be writing with his left hand. Now I'm back to thinking about the nucular stuff.
@@HappyDuude No.
I barely passed pre calc in high school yet now I am able to explain how a RBMK reactor works and exactly how the Chernobyl disaster occurred. Not exactly the most casual conversation starter lol...
Just please mind, that his explaination of what the reactor operators did is very simplified to the point of being wrong. For all its factual faults, the HBO series does show this pretty well. They sceduled the test to a certain time and lowered the power level to half, but then they left it there for hours because Kiev told them they need the power for longer and that they should do the test later in the night. After that period the reactor was already poisioned, and that is why the power level dropped so hard.
@@0nkelD0kt0r i completely agree with you. Ive read some articles about it too
You're comparing math to theoretical physics. That's your first mistake.
@ I fully agree with you, and I was not really tryibg to say this video is bad for it, I just wanted to get accross, that there is a little more to the accident than what was said here, but that does not make this explaination a bad one. For people who just want to know what gernerally happened this is probably one of the best and most accurate descriptions for such a small timeframe.
Secondly, the shut down button did the opposite of what the operators hoped and the fatal flaw was noted years prior. The graphite tips were meters long and lowering them all at once was like a nuclear bomb detonator.
Professor Ruzic, thank you for your amazing work. You are a great communicator, explaining such complex subjects in a very accessible manner is a valuable skill. My 7yo boy loves your content. Very funny to watch Mr7 explain to his grandfather, a retired professor of finance, how the Chernobyl incident unfolded. “Grandpa, they used the wrong moderator and didn’t know about xenon poisoning”.
First mistake was to do the test overnight. Sleepy tired third shift performing a simple 1000 step procedure.
Not only that,... peaple trained for it (who also stoped it like 3 times midway trouth b4 was not there either.)
It was the nightshift doing it overnight. They could not do it during the day because Kiev needed the electricity.
First mistake was in approving the production of the RMBK.
Probably government getting bribes from the Energy companies as usual.
@@fallsdp they knew about the instability of the RMBK reactors, but it was covered up because it was too embarrassing.
The tip of the rods being made of graphite is actually a safe design for smaller reactors, it is also very efficient. But bigger reactors can do unexpected things when you use such rods. (They have naively scaled up the design, without considering safety.)
The only way for the graphite ended rod to cause fatal problems was in case of a massive Xenon poisoning, and removal of almost all rods, boiling off all the water (see void coefficient). Everything which can go wrong went wrong at the same time.
The Three Mile Island reactor was designed for exactly that, what if _everything_ goes wrong at the same, including an aircraft suicide bombing the reactor. So when thing went wrong (without the bombing), it failed relatively safe (with only a minor leak).
i have enjoyed many videos from this channel but was expecting this one to be a little more detailed around the neutron flux and the reason why the control rods had graphite 'tips' (the reality is the rods were about half graphite) scott manly has a better explanation with much more detail. I also have my doubts that the containment buildings really could perfectly contain a steam explosion of the scale of chernobyls.
A containment building would not have contained what happened in Chernobyl. Containment buildings are designed to hold up 80psi of pressure. The explosion at Chernobyl is estimated to have reached over 1500psi. Just before the reactor blew, energy output reach 30,000MW thermal, 10x higher than the reactor was designed. There is a hypothesis that Chernobyl was a fizzled nuclear explosion. There were two explosions.
In a nuclear explosion, over pressures of 12 psi or greater kill virtually everyone and destroys all but specially built facilities above ground in the blast zone, such as a nuclear missile silo.
TheRealUnconnected Three Mile Island in Pennsylvania is a good example of out containment buildings. The reactor partially melted down yet no huge release into the air of radiation. Well...not that we were told.
@@Iwillnotbepushed 'no huge release into the air of radiation'
Radioactive elements in the form of volatile gases, like Iodine, were released. However, unlike Chernobyl, solid matter was not released.
@
TheRealUnconnected
The main reason for this design of the rods was an attempt to place the reactor in a room of LOWER HEIGHT AND DEPTH. Typical Soviet style of "economy".
Also, the designers chose a dangerously low speed of movement of the rods, citing an allegedly sufficient change in the coefficient of reactivity per second.
Link to the site created by the engineers of the Chernobyl nuclear power plant (in Russian):
accidont.ru/sitemap.html. This site is unmanaged since 2013. No feedback.
All tables, graphs and printouts you are interested in are there. As well as different opinions of experts about the causes of the accident. design flaws of the reactor and personnel errors. And descriptions of other emergencies at RBMK reactors.
"what is eight feet wide, four feet tall, weighs two tons, and slices apples into three pieces?"
answer: "a SOVIET designed and built machine to cut apples into four slices!"
You can remove the quotation marks, that's not even close to what was said in the HBO Chernobyl series.
With professors like that, I'd be a lot more motivated in my degree...
Exactly!
If you have to get motivated by someone other than yourself you are not ready for university life.
@peterbradshaw8018 - I think you missed his point. It's not just self-motivation that makes a difference in college and in life, but having good, engaging teachers that help each student learn & explaining complex ideas, situations, etc that make the most difference.
I love how everyone watches a TV show and suddenly everyone is now an expert in nuclear fission
I love it. How else do you suddenly get millions of people even casually studying nuclear energy. Imagine how many minds have been peaked to go back to school and study nuclear energy? So crazy.
I've visited actual Chernobyl several times in the past 20 years, and I have very good understanding of how it works and why it is a flawed design. When it is safe to go to Ukraine again, I plan on going again, because I want to see how much Pripyat has changed and I want to see the new shelter project. :)
TH-cam commenters aside, I'm willing to bet that most people will want to look for knowledge outside of the HBO series and come away smarter.
@@Saavik256 go to fukushima and report back
It’s the bullet!
Thank you so much! Seriously…thank you. I have viewed so many explanations of this event, and now I can say that I fully understand it now. This is the single best presentation that I have come across.
Thanks again.
0:30 RBMK, not RMBK. Also, this explanation is not very accurate. They got the reactor to operate at half power in the afternoon of the 25th of April as they were preparing for the safety test they were supposed to have completed in 1983. Then they got a phone call from the higher ups to not do it during the afternoon cuz it was the end of the month and electricity consumption was at its peak. They were tasked to postpone the test to the night. They left the reactor at half power and because of that a lot of xenon was created but not burned. That's how the xenon poisoning happened. That's why the reactor's power dropped to 30 instead of staying steadily at 700, not because an operator pressed the wrong button.
As a matter of fact, it may be exactly "because an operator pressed the wrong button". It's impossible to know because it did not took long to Akimov and Toptunov to die after the accident, and we don't even know for how long they held consciousness. You should not take what the series tell you at face value. 50% is approximation and romanticization, we will never know what really happened there for several reasons, some of them may be, 1- they died soon after the accident and maybe didn't have time to tell very well what happened and how it all happened, they might even have been shell-shocked, under severe PTSD, delusional or in and out of a comatose state before they died, unable to put it all to words, or make any sense. 2- they may have told everything from their perspective, however.... USSR, KGB, FSB, and the truth may be buried somewhere rotting in some top secret archive file, never to see the light of the day. 3- they were very green, especially Toptunov, and he was the one responsible to get to the power levels required(I believe Dyatlov stated that during his official debriefing), and maybe he never knew what he did wrong. 4- the cause of the sudden power death in the reactor may be just another design flaw or equipment malfunction, triggered by Toptunov. The series itself does not make clear what really happened when the power fell suddenly to near shutdown levels. We just see the surprise on the face of Akimov and Toptunov, and after that, Dyatlov's rage. I read one of the INSAG's(INSAG-7/1992 official report) reports into the accident and even they are not sure. They oscillate between equipment failure/fault and an operator error on Toptunov's part. Some argue that the action Toptunov took to switch the reactor from local to global power control, IS the operator error itself("....pressed the wrong button."), others argue that the global power control system may have had a FLAW that caused the severe drop in power. Maybe Professor Ruzic knows more than I do, coz he simply studied/investigated more into the matter. I do not have time to read all of the reports nor his credentials to understand it all.
@@jefersonnl In "Midnight at Chernobyl" Higgonbotham states that Toptunov, when moving from local to global automatic control, did not reset the reactor power level desired leaving it at near zero. He then failed to act to correct it. Higginbotham also states that Deputy Chief Engineer Dyatlov demanded that the test be done at 200 MW which Akimov initially strongly protested. Under badgering Akimov finally conceded to Dyatlov even though he outranked him in terms of running the reactor. Higginbotham also states that Toptunov knew the reactor was unstable at low power and when Dyatlov demanded that he pull more control rods, he initially refused. But just like Akimov, he conceded to Dyatlov's threats and demands and violated safety protocols by pulling almost all the control rods. Tregub (prior shift Senior Reactor Engineer) had remainded at the reactor control station after his shift and advised Toptunov on which rods to pull - fully complicit in Dyatlov's disasterous intervention to get reactor power going again. Dyatlov, during the investigation and trial, denied that he was even in the room. If Higginbothom's account is correct, then Dyatlov bears most of the responsiblity for violating the published procedure by insisting it be done at 200 MW in an unstable reactor and bullying the reactor engineers (and Akimov) into violating critical safety measures. Poor Toptunov had only been a senior reactor engineer for 2 months when he activated the AZ5 system that was supposed to shut down the reactor but in sad fact became the final insult that initiated the destruction of Chernobyl Reactor #4.
@@richardvaughn168 I want to read this book! it has been on my list of books to read even before the series premiere. I believe the book is basically in agreement with some sources I came across, like the INSAG and the IAEA.
@@jefersonnl there are many things the HBO series either modified or got wrong, but there are plenty of other facts they got right. We know based off records that the test and shutdown was going to happen during the day shift, but they were requested (demanded) to not take the reactor lower so factories could meet their obligations for the month. the reactor then remained at that 50% power level (rather than proceed with the next drop to 700 MW for the test) where simulations have shown xenon to build up to significant levels over the course of the following hours. this combined with the lack of proper training for the test by the operators likely led to the reactor going from almost desired power to almost nothing as the reactor stalled. At that point, the operators started fighting to get the reactors power up to 200 (a power level that would still have failed the test) and took it off automatic control. the politics behind dyatlov being promoted upon a success that night I had not heard (but not unthinkable) but he did push the operators to do things that they were never trained for and violate every rule in the book to get his test, at which point the reactor sprung to life uncontrollably due to the voids and damage caused by smaller scale uncontrolled reactions nobody had any ability to know were occurring. (the RBMK-1000 was fuckoff huge in all dimensions, leading to varying reactions that were unmonitored across the whole thing.
@@trinalgalaxy5943 Ohhh really!?? Noooo wayyy!!.... seriously, I don't even know what to answer. As a matter of fact, I'm beginning to question the wisdom of coming here and writing this in the first place.
This prof. should be awarded a prize! I really enjoyed your video and did not even notice how it was over! Thank you very much.
Considering he got information wrong, I don't thing awarding him would be the best idea.
@@WolfHeathen lmao
Never thought i would like nuclear disaster so much
12:54 the "squeak squawk squeak" puts so much more emphasis on the drama
It had my dogs looking for mice 😅
*looks at reactor design notes* "Under no circumstances should less than 30 control rods be in place to ensure safe operation" Blyat! *Continues to remove all of them*
You should look at those again.
The engineer overseeing the experiment, Dyatlov, had another similar accident earlier in his career. It didn't have the dramatic results as Chernobyl but his son died as a result. The man was dangerous.
At the time Dyatlov was quite defiant and refused to accept responsibility, claiming that he had been lied to and that vital information about the graphite tipped control rods (and the danger they represented) was kept from him.
In the years after his death when more secrets about the Soviet nuclear industry were exposed it turned out he was right. Vital information HAD been kept from him, and all the other RBMK reactor operators working at the time. It has since been learned that an incident like Chernobyl had almost happened before (at the Leningrad plant in 1975), and although the cause was known the authorities chose to keep it a secret lest it expose a failing in Soviet reactor design. In fact the commission who investigated that incident made several recommendations to improve safety but they were ignored and the whole incident was covered up.
Was Dyatlov merely a hapless pawn in a deeply flawed system? Many would say yes, now that we know the full extent of how far the obsession with secrets went. Myself I don't think he was totally blameless, but had the authorities chosen to pass on the safety recommendations rather than keep their silence the entire incident would not have happened.
@@woopimagpie the fault was in the blue prints from the off Dyatlov got the blame.this is why people should not act the cunt in the work place .with nuclear fission.
@@woopimagpie Glad to see you've done your research unlike the HBO Chernobyl series minions who think they know everything. From my reading, the reactor was designed by the "Ministry of Medium Machines" which was a USSR top secret government ministry. All secrets were kept away from nuclear engineers.
@@woopimagpie I grew up about 400km from the Chernobyl site. I was only 4 at the time. The soviet mentality you touched on still exists to this day. It's part of the culture at this point. Project power, downplay weakness. It's not until something catastrophic happens that the rest of the world gets a good look at the dysfunctionality that is the Russian system.
Tbh Dyatlov was more or less directed from the politburo to run this test.
The whole test was stupid.
10:50 no one hit a wrong button!! Where do you get that miss information from?
They where shutting down the plant to round about half power preparing for the test. But then the grid needed more power. So they stayed on this low power for some time. Meanwhile the core got xenon poisoned due to low power operation. Then they started the test by lowering the power to ~2/3 power. Because of the poisoned core the power continued to drop in power. Then they tried to bring the core back up to a power level suitable to perform the test. They did this by removing all but 1 control rod (against all regulations). Then the power skyrocket because the xenon was burning away. In an attempt to shut down the reaktor they pressed az5 causing all control rods to go back into the core. But because the tips of the rods where made from graphite they first caused another spike in power. Which resulted in the explosion of the core.
This is a great presentation. I had never considered the role of Xe before, but of course -- the rapid burn off of the accumulated Xe with the control rods removed left little course. I am curious however why the other safety defect of the RBMK, the positive void coefficient was not mentioned. My understanding was that at low power the RBMK had a positive void coefficient so, e.g., a steam bubble is a 'void', which causes power to increase, which makes more steam, more voids, etc. leading to an uncontrolled positive feedback.
The control rods as i understood had two design flaws. The graphite follower which would moderate neutrons and the metallic bottom of the rod which would displace water -- and introduce a void.
He does mention it when he mentions that when water boils in an rbmk, the moderator (graphite) is still present and allowed to operate even more efficiently bc water isn't absorbing neutrons (water self-dampens it's modeerating ability by absorbing many neutrons). He just doesn't use the technical term.
@@WINuFAIL Not entirely. A positive void coefficient is an increase in reactivity due to a void that creates a positive feedback loop. That is what creates the super critical event. Void --> increase in reactivity --> increased power --> increased temperature --> increased void --> and so forth.
@@stephenfriedenthal8312 Yes I understand. What he and I are saying is that the reason the opposite happens in other reactor types is because water is the coolant AND moderator, with no graphite present. A void means no coolant but also no mod, so reactivity and power decrease. He describes this mechanism without mentioning that this creates a feedback loop. So basically he described the first half of it.
@@stephenfriedenthal8312 I agree - there is too much talk about the role of xenon. Xenon doesn't explain the pos.void coefficient as you rightfully explained. The RBMK was unstable at low power and the voids were't pushed out by the flow of water and remained in the bottom of the core resulting in potentially dangerous power anomalies.
@@WINuFAIL In the RBMK, a void means the water is less dense which means less hydrogen which leads to a decrease in neutron absorption by the hydrogen and an increase in neutrons so power increases' not decreases.
That’s the single best explanation of physics of the Chernobyl disaster. There are a couple of the things that professor might have not been aware of.
1. The whole idea of that *experiment* grew from the successful attack on the Soviet built Ozark reactor in Iraq conducted by the Israel Defense Force.
The experiment was to prove that the power plant can withstand power cut off due to the attack and to sustain itself just by the power of mechanical inertia of the turbine-generator.
2. They hurried this up because in the Socialist system it was very important to report the success to their Communist Party bosses in the eve of the 1st of May, the major Soviet Holiday.
Should the experiment be a success, all the participants would be rewarded by bonuses and promotions to the top managers of the plant.
From what I understand, the Experiment was actually to see if the freewheeling turbine can generate enough power to keep the safeties and cooling pumps running during the 1min gap between a power loss event and the backup generators spooling up to make enough power to then support the aforementioned safety systems.
14:04 So that says 2014" on it. Looks glowing red hot, but those lamp shade things were lowered after the accident. So what is glowing that hot? The carbon fire was not that big from videos from after the accident. So what is that? And how if it was that hot could you or your camera not get blasted with a lethal dose of gammas?
You didn't see comments from before the HBO miniseries because they're not there.
"Why worry about something that isn't going to happen"?
"Ohh, that's perfect. They should print that on our money"!
*folds US currency to display the events sequence of 9/11*
Thank you sir. This was an absolutely enthralling lecture. I watched the 2019 Chernobyl miniseries and while I do understand there may be factual inaccuracies in the HBO series your lecture helps me to comprehend just how dangerous the Chernobyl disaster was in 1986. Thank you once again sir.
I'm most impressed by his ability to write from behind the text he is writing.
Flipped the video horizontally
You record the video writing normally, then mirror it after recording
@@Chiberia - You could have the camera looking at him in a mirror to do it oldschool.
@@Thunshot Makes sense.
@@Chiberiayep. He’s probably right handed and married. You can see the ring on his finger. Flipping the video makes sense
Should call this poisoning of the reactor, The Diatlov Effect."
This poisoning was known before this event. The Chernobyl operators just weren't qualified or slaves to a Communist system where all that mattered was results.
@@TheJMBon
Still, the Dyatlov Effect is a really cool name. 😆
@@HT-ww3zg agreed
"The Dyatlov Effect" has a nice ringing to it, however, it should be not about nuclear reactors, but about the culture of pushing people and things beyond a limit you shouldn't, all in the name of results. Once I was a spectator to something like that, when I saw a rocky project manager push people to the brink for a couple of days in order to meet a deadline, and it ended up with an assistant DBA overwriting a live production database with a test copy in the middle of the working day. Of course people were nervous and exhausted in the first place, but he put some security issues and good practices aside like allowing trainees root access to production servers, coz the real DBA had to have a break after working for several hours straight. I remember I was part of the 'liquidation effort', we had to put that guy aside, let him have his nervous breakdown, relieve the rest of the guys, and manage the damage. Lessons were learned that day. Never again something like that happened in our department. Of course, one of the most important things we learned is, do not put unstable, authoritarian nor arrogant people in charge of things like management. Sometimes leaders have to act as a buffer protecting his/her team from outside pressure while they do their work to the best of their abilities, and not actually transfer the pressure on to the team. That's part of good leadership, take a few blows in the name of your guys. Of course, Dyatlov was a product of the system that raised and taught him(so was the reactor and its flaws), and that can't be overlooked.
I would rather call a different thing Diatlov Effect:
When you press the SCRAM button and your reactor explodes afterwards... because of reasons.
(The SCRAM pushed all control rods inside at the same time, which caused the final fatal runaway)
I'm an industrial pipefitter and although this may seem like overkill to learn this kind of stuff, it is incredibly useful to understand the intricacies of the process and history. Thank you very much for posting all your videos. The history and future of power generation is so important to understand, even if people aren't an installer and welder of the process piping like I am.
80s 888888888888888888888
Given that it was badly fitted pipes what sunk the USS Thresher, knowing how to pipe fit it no small matter. My dad had used to work for a company which build compensators for pipe systems and at one point they did them for nuclear power plants. The amount of courses and lectures he had to take in order to do his work was beyond belief.
I love watching this once a month or so. When can we see some new videos Prof? They are so informative yet relaxing.
AAAHHH! SQUEAKY MARKER! MY FLESH IS MELTING!
Yea he needs some WD-40.
jesus christ i was tearing my room apart thinking a mouse was here. EXACT sound when they get caught on a glue trap.
Same! yikes.
Yeah man....This horrible nerve ripping sound....Unbearable...
I'm watching this with my dog and he is NOT enjoying that sound
He wanted to make sure he wore a period correct Soviet suit for this presentation.
Ha ha ha true. Soviet suits are almost as vulgar as their wall tile patters.
This is just how lecturers dress.
And they thought Obama's tan suit was bad.
Yeah, that tie....!
Herb Tarlac suit.
I cam here after watching your Fukashima video, and am a little confused about one thing. In this video, you mention that all reactors other than RBMK have their reactions slow down when they lose water, however in the Fukashima video you mentioned the main problem was losing the supply of cooled water to the reactor and spent fuel. Shouldn't Fukashima have been OK without water then?
Fukushima's problem was decay heat, there was no active nuclear reaction at the time of the accident. But that's only my guess, I'm not an engineer
The first ones who noticed an anomaly were people at a nuclear power plant in southern Sweden.
Yes, the morning shift had contaminated shoes which set off the alarms. Needless to say that led to a few very tense hours as everyone first assumed it was a malfunction with our power plant.
The night shift went, “No it’s not us, reactors fine.”
“Ok the wind was coming from the direction of Cherno... uh oh.”
@@davyt0247 Cher-oh-no-byl?
sweden is already so degenerate, they don't need to fear defects caused by radiation
Surely the AGR power stations in the UK also use a carbon moderator?
Glad somebody else noticed this. Sure it isn't water cooled but we most certainly are still using graphite moderated reactors, admittedly not building any more new AGRs though.
I worked at a UK AGR, they were inherently safe IMHO. Main protection was automatic trip of control rods, they relied on gravity, followed by numerous secondary and tertiery shutdown systems. . Water filled reactors have accounted for quite a few of the accidents in the past. .
ieer.org/resource/factsheets/table-nuclear-reactor-accidents/
There was 2 explosions if i recall, one where the steam blew the biological shield, as in the lid of the reactor and the caps, off and the other came few seconds after where oxygen combined with the red hot graphite + hydrogren to cause the big boom!
Well made video! Just one thing: Even if the RBMK had a containment building many professionals think it would not have survived that explosion. The HEAVY lid of the reactor flew about 30 meters high.
Reinforced concrete is believed to have far more strength when dynamically loaded during an explosion or an impact. A real life example of this the Longarone dam in Italy which survived loads estimated 100 times what it was designed for when a mountainside slid into the reservoir.
Unfortunately very little research is done in this area because of the huge costs of blowing up life sized structures.
It couldn't have hurt.
Even if it did crack it, the hole would've been quite small, and less material outside, meaning less people have to clean it while being in place with 20 thousands Roentgen/hour
@George Thomas It's estimated that the lid has a weight of at least 1000 (metric) tons.
Man If I'd had you as a professor in high school my life would be so different because I'd actually pay attention to you because I can understand what you're saying. Can't say the same for the professors I had. So depressing.
right?
UK Magnox and AGRs also use graphite moderators, but they differ from the RBMK reactors in that they use a gas coolant (carbon dioxide) in the primary circuit and boil water via a heat exchanger (which does not come into contact with the actual reactor). Also, the gas will naturally circulate via convection to take away decay heat, but do require control rods to drop in to shut the reactor down in the event of a fault. It also doesn't have the positive void coefficient issue that the RBMK reactor does.
The AGRs also don't have a separate containment building, but have a 5-7 metre thick reinforced concrete pressure vessel.
In any event, that seems to be a bit of an omission. The last AGRs are due to close down in the next decade or so. Their biggest problem appears to be the expense of decommissioning, as there is a large amount of irradiated graphite to deal with, and the reactor core is a lot larger than in a PWR. It's also that very large core which means it's not prone to runaway decay heat issues as there's a lot of thermal mass involved which slows down events. It means that the sort of thing that happened at Fukushima ought to be impossible as it doesn't rely on powered cooling systems after an emergency shut-down.
nb. there was never an issue of Kiev losing all its power during the planned exercise. There were four RBMK reactors at Chernobyl, and only one (reactor #4) of them was to be shut down for refueling.
Unless you hit 88 MPH, the flux capacitor is useless.
Not if you've got some 200 tons Uranium fuel at hand.
Hahaha... LMAO !!! Great Scott , you are correct.
@@kalleklp7291 wasn’t it plutonium the car ran of?
@@quantumpilot6843 Yes, you're right...but with the "Mr. Fusion generator," it can even run on garbage. :)
The most fictional thing in that movie wasn't the time travel or the flux capacitor, it was a Delorean doing 88 miles an hour.
Fakse - 2019 there were still 10 RBMK reactors (graphite-moderated) and three small EGP-6 (also graphite moderated) light-water reactors operating in Russia,[1][5] though all have been retrofitted with a number of safety updates.
Timm Bacher 'we - meaning the rest of the world' lol
Always be on alert if someone tells you "everything you needed to know about a specific topic". Nuclear power plants are complex machines although the physics behind it may seem simple. Complex machines are prone to failure, human error, negligence and profit-maximizing cost savings in maintenance due to greed or incompetence.
It's easy to say that an event, exactly like Tchernobyl, might probably never occur again. But there are myriads of things that can and will go wrong with probably devastating consequences. And that doesn't even take into account the consequences of the still non-existant long-term storage option. Or the nuclear waste that had been dropped to the sea-floor for decades. Just think about Fukushima. Surely not identical to Chernobyl. But still a catastrophe. And a perfect example for human ignorance.
It was a RBMK reactor. Not a RMBK Reactor.
Moral of the story, don’t test your safety systems.
Test it, but without 200 tons of enriched uranium inside, heated to water vaporizing temperatures.
Test it, but make sure for every safety system you have, 2 more should be in standby. One that works with no humans or machines needed, just physics.
Lol
Moral of the story: don’t be a commie
Moral of the story:
- Never build positive Void coefficient reactor
- Build a good containmentbuilding
- Moderator and Coolant must be same water
- Every worker needs knowledge of Xenon 135
The jet doesn't "disappear into vapor". It may disintegrate into smaller pieces, but it doesn't "vaporize".
This is one of the best, clear, logical presentations I have seen, on what happened, many thanks for doing this.
Hopefully this knowledge and wisdom gained can prevent future disasters.
For any young viewer, Chernobyl accident was a big deal at the time, it was terrifying at the time knowing that radiation was falling out of the sky and nothing you could do about it.
Extremely scary time to live through. The consequences of this accident will last forever. Generations and generations will be dealing with the mess. We were always told - 'A meltdown can't happen'. Nuclear power is dangerous, very dangerous.
What bothered me at the time, even though I was and still am deeply into physics, the information given out on the media was "maddeningly unhelpful". Lots of units like Bq, Gy, rem and Sv but no one seemed to have any hard facts.
The Chernobyl guy was a self-taught expert on the RBMK reactor. His previous background was submarine reactors. He was noted for his ability to cite technical manuals. The weakness in RBMK reactors had been identified about a decade earlier and it was published. But someone redacted the part of the report that talked about preventing an explosion. Whether the lead guy had clearance for the redacted portion (probably) and whether he could have accessed it (pre-web) is undetermined (or at least unpublished itself).
I can't life like a submarine Reactor because of this Life I am D O I N G like the Prof. In the Video Demonstration is writing behind All and All behinder and behind it... that's not possible... i can't understand it... it's nonsense for us all... Super... Dummel Will Not Life... Amen...Ciao Wiktor Witas Kuhn from Bremerhaven and Amen You All, I try everything to escape this 20000000 ttilliard Super Nintendo... that's impossible... I Love You Math ... ❤❤❤
This is what happens when you choose key people on key departments based on politics
@@diggydumbo9294 "Exactamundo."
He could've been self-taught to eyeballs, that woudn't change anything. Simply because submarine reactors are PWR which have nothing to do with BWR.
I doubt it would have mattered much. The same political pressures and the same lack of care for safety to satisfy those pressures would exist. The problem was not one flaw with one reactor, or one bad decision by an operator without all the information. It was a failure at nearly every level.
"Safety first." "I've been saying that for years." "Now raise the f***ing power."
Well, it could happen to western reactors too. And it has happened. Fukishima Daichi runs on General Electric reactors. The containment vessel failed, because of poor design. Still leaks radiation in the sea. Most of the reactors running today are designed in 60s and 70s. To say, that it is impossible to happen, because it hasn't napened yet, is not very smart. The scenario will be different, for sure, but the result will be the same - contamination.
To be fair, what happened at Fukushima was VERY different than what happened at Chernobyl: in particularly, highly different explosion locations and causes (and that's saying nothing of the earthquake/tsunami impetus).
@@DanielFolsom , you are right. But, isn't true, that every nuclear accident happened because of different reasons? If some nuclear accident happens in the future, do you think that somebody in the neighborhood will care if it is the same or different compared to Chernobyl or Fukushima? Western reactors have their own problems, that also can cause similar or worse contamination. The biggest problem of them all - neglegence. It is common everywhere. So we can't sit back and relax, because Chernobyl can't happen in the Western world. It will be TMI, Fukushima or god knows what else...
Remember, a meltdown hadn’t happened yet in Chernobyl, but did that mean it couldn’t, no!
@@velinr There is no industry in world, literaly NONE that work in safety lewels of Nuclear power plants. and results are here,... Nuclear power is Cleanest and safest of them all. period. Like it or not. amout of peaple dying per Watt of nuclear power is waaaay below any other energy source, including renewables.
Sadest thing about Fukushima that trouble over power plant overshadowed 15000 causalities of earthquake and tsunami.
@@marianmarkovic5881 , I'm not against nuclear energy. I believe that the future of the energy is nuclear. But the efficiency, at current level of applied technology, is very bad. And there is lot of waste. And there are lot of problems. And we should not be nearsighted nor one-sided about. Appearantly, the safety is not high enough, after such incidents happens.
YOU DIDN’T SEE ANY GRAPHITE BECAUSE IT’S **NOT THERE** !!!
10:00 That was better explained in the Chernobyl series, they actually ran it at half power for the whole day because the power was needed, then they didn't hit the wrong button, they put it into automatic mode and it almost stalled because it wasn't calculating for the Xenon.
and it used graphite as a moderator not carbon
@@boonamai8926 maybe teaching not to trust this guy because there is quite a bit of mistakes
Sir I respect you IMMENSELY but may I query...my understand was it was *due* to the Xenon content that the engineer stationed at the time stalled the reactor as it had been running at half power building up Xe 131 for about 11 hours before the accident as Kiev stated the test had to postpone the test till the night.
He is trying toconvince people "it is safe here nothing to wory about" that is why his explanation of the Chernobyl accident is so sketchy.
@@Bialy_1 I mean it is safe when operated correctly...Chernobyl was far from that to begin with
It's a RBMK reactor and fuel rods can be replaced during operation. The reactor doesn't need to be shutdown.
So many experts on here and half couldn’t find their own ass with both hands and an Admiral Byrd expedition.
Thank you for this video. Indeed you need physics to protect. RBMK's didn't rely on people, but automation and people in extreme circumstances. A few more important factors and a slight correction. There is a lot to criticise the crew over, but it's important to note the explosion was in fact caused by the crew sensing a problem, panicking and hitting the emergency SCRAM button.
RBMK's computer control was relatively advanced for the time. The thinking was that in most situations this reduced the risk of crew error. As we now understand, yes that's true, but it can also reduce the experience of crews to handle unexpected events outside of usual operational bounds.
The reactor was in fact at 50% power throughout the day before the test at 1am, so for many hours. The reduction in power to a target 22% was supposed to be very brief. There was an unexpected delay to the experiment, which caused Xenon to build up. RBMK's don't shut down to refuel, they're so big you refuel in sections whilst the reactor is running. That's got serious implications for the accident because it took the crew outside of usual operating bounds, exactly the type crews who rely heavily on automation struggle with.
With RBMKs there is less contingency in the grid because the reactors never shut down. That created huge pressure to get the test done then, as it might be years before there was another chance. Secondly, crews always relied on automation to run these big beasts, but below 50% RBMK's are manual. That's like going from an automatic hatchback to a 16 speed Mack truck. Thirdly, because the reactors virtually never went below 50% power, the night crew had never run it manually before, nor had they powered down a reactor., because RBMK's are always on.
No one hit the wrong button, they were targeting 22% and didn't account for Xenon. They hit the right button, the SCRAM, when it was clear this reactor wasn't behaving as predicted. But the rod design with moderator tips caused that spike and the rest is history.
Fabulous explanation
world’s loudest pen
Its not a pen its a marker
And thats completely normal marker
@@av28379 it's a fucking pen
@@CuoreSportivo It's a marker. Comrade Sportivo is delusional, take him to the infirmary!
It's so low-tech for such a high-tech subject. But I must admit, that backward writing looks really cool. I think maybe this professor made a deal with the Devil.
This description is not totally accurate, the description of why the power dropped "wrong button press" is wrong, and the reason it spiked is inaccurate. This needs updating.
Don't bother wasting your time Nic, any attempts to correct all the inaccuracies in this video will be deleted. It's rather sad that this 'professor' would rather educate people with garbage misinformation about Chernobyl.
@@professorrinse8028 - That's not strictly true. If you watch the next vid in this series called "Xenon can be a problem", it goes on to explain in detail about xenon poisoning.
More interestingly, there are several posts from a licenced nuclear operator who has posted a staggering number of pages detailing his criticisms to the vid and countering with his actual experience. th-cam.com/video/RZQwL-2WTgA/w-d-xo.html
Nic Wilson - Please watch the next vid in this series called "Xenon can be a problem" th-cam.com/video/RZQwL-2WTgA/w-d-xo.html
The 'Professor' says it's an RMBK reactor in the description, and states the Chernobyl technicians simply pushed the wrong button which caused reactor 4 to explode. This whole video is laughably inaccurate, but hey, this is TH-cam, all one needs to do is dress like a professor, say a few technical words and everyone thinks your spiel is true.
@@professorrinse8028 - It's not that inaccurate if the button he was referring to was the "AZ" button which inserted all the control rods. He very briefly mentions that the operators were not aware that the Boron Steel rods were poorly designed and that a surge of power could be observed when the rods were inserted.
I think it’s implied the RBMK should have a containment vessel, analogous to the Western LWR containment configuration - not that the RBMK reactor should use containment as designed for the LWR. Most certainly, the containment for the RBMK would have to be specifically designed for it, one of the specifications being able to contain a hydrogen explosion. Obviously, using a Western design intended for use by an LWR would not suffice for an RBMK.
I have read Russian designers discarded the idea of a containment structure because a:) they believed with certainty the reactor characteristics were such that a Western style containment was unnecessary, and b:) the reactor was intended to be refueled while in operation via a large crane above the reactor vessel; hydrogen explosion-proof containment would have impeded this feature, or made it impractical if not impossible.
Regarding an operator hitting the wrong button, this is the second video where I’ve heard this, the first being n MIT lecture on nuclear engineering. I believe the source material came from an official report by a nuclear regulatory agency; I’ll post a link to the report and updathe post w the agency. The two presentations are very similar with respect to the technical details and the timeline, causing me to infer they’ve both used the same source material.
After reading the NRC’s report and rewatching Professor Ruzic’s essay, I’m unable to substantiate any of the comments who declare this video is full of misinformation and mistakes. Professor Ruzic does interject his dry sense of humor when he’s critical of operator performance, and clearly interprets the actual events and human factors elements with an engineering and professorial point of view with full benefit of hindsight, but that’s how root cause analyses go. I suggest instead that the people who commented that Ruzic made errors have trouble with his perspectives, points of view, opinions and style. That’s too bad, because looking at issues from multiple angles and personalities is a critical benefit of TH-cam. Being able to watch many different videos on a singular subject is such an advantage, especially when the videos ultimately prove out a consistent sequence of events and series of facts, along with weeding out the content creators that are less than rigorous in their factual reporting.
When you realize they mirrored this video...
...you realize that you're dealing with clever folks.
Mind - blown!
Is that what they did?
I was wondering why he could write backwards so well
Duuude... You just made me feel so dumb xp.
It should have been so obvious!
Wow, yeah hadn't thought of that, LoL
9:53 "Now the reactor is humming along"
reactor: beeep
I found that very funny
😆 I missed that.
like your vital signals are dead... beeeeeep
Fantastic job explaining it simply. I feel like I finally understand how it works.
"Can a Chernobyl happen here? Absolutely not!"
>SL-1 has entered the chat...
Yeah but usa good, russia bad
You're referencing SL-1 as if it were an industry standard and not an experiment. Not to mention it was 25 years before Chernobyl. Nice try to draw false comparisons though.
The same incident wouldn't happen here. Just look at France.
@@clint6716 Ah, yes, comparing a steam explosion caused by improper control rod operation to a steam explosion caused by improper control rod operation is totally a "False Comparison"...
@@Kohdok you missed the more important parts of my response. This was in 61, before most of the safety precautions that were ignored in Chernobyl even existed. There 'containment' structure was 1/6th the size it needed to be and not made of the right material. Comparing these two incidents disingenuously ignores all the research that took place between the two events, and more so discounts the even more modern advancements since.
The answer is still no, it wouldn't happen here.
@@Kohdok yeah because one happened 20 years before the other, before we even knew how to deal with all of the bullshit that comes along with the shit.
Long island was an unfortunate reality, but he's right. A chernobyl could never have happened after long island, cause we wisened up, while the Russians didn't know.
Great lecture, along with seeing Chernobyl on HBO. Now I have a much better understanding of what happened in 86. Shocking and Horrifying..
Not good, not terrible.
The first to notice was engineers at the Swedish Forsmark Nuclear power plant. Alarms starting to go off about external contamination and after doing checks and coming to the conclusion that "It ain't us" they alerted the IAEA that "Something has happened, somewhere, and we think we know where".
"Water drains away, the reaction stops" works until you realize there's decay heat and that too can cause catastrophic problems. Fukushima Daiichi was caused by the decay heat cooling systems' power sources being washed away, and replacements not making it there in time.
that caught my ears as well. In this lecture the prof suggests that LWR is bulletproof because when water vapourises then fission stops end of story. Then in his next video about Fukushima he explains how the fuel overheated when the water vapourized, ending up in fuel meltdown in 3 LWR reactors..
Nevertheless a great presentation, but the Japanese and the nuclear scientists after 10 years still do not have a clue what to do with the melted fuel in the Fukushima reactors.
And they were kept under water for 10 yrs and still needs to be permanently cooled, so taking away the moderator does not seem to stop fission completely...
I assume you still need the control material(rods) to absorb neutrons to be able to drive fission further down, but that does not work with melted fuel anymore, right?
Or if you have an LWR reactor with fully inserted control rods, when the water is taken away, it would still melt? Which basically means you need both water and control rods...
@@sspringbok modern reactors will maintain stable enough temps without coolant just through the convection of air. Intrinsically safe by design. Older ones however would still need water coverage. Spent fuel in the pools are typically now arranged in a way that supports convection cooling to sufficiently cool them ans thus need water coverage.
@@lynel1985 only gen 3 can passively cool with convection I believe, all reactors in the US are gen 2
If the water-moderator system breaks, you lose the water, won't it cause the reactor to heat up/meltdown since it loses its coolant?
I think it’s about the water acting as both coolant and an enabler of the fission itself.
With no water, the fission and the heat generated from fission are minimized, so there is nothing to cool.
@@mattm3901 The fuel is still hot for years due to beta decay.
@@JC-lu4seyeah but not hot enough to go into thermal meltdown
@@Lanse1984Fukushima blew up after a successful shutdown!
Would have a containment structure have been able to withstand that steam and thermal explosion? After all, it lifted “Elena”, the 2000 ton lid clear off the structure and turned it on its side.
Has anyone noticed that every word he's writing on his clear board is backwards to his point of view?
Notice the buttonhole on his jacket's lapel appears to be on the wrong side: its actually the video that's backwards
he's writing normally from his point of view, then the entire video is mirrored horizontally before upload
Yeah I noticed and it blew my mind.
hmm... pretty sure they're called RBMK reactors not RMBK?
Correct.
@@jeffreykreft5442 can you please list them? im interested
And a month down the line, I guess that free moment never came, did it? His explanation had a couple of small inconsistencies based on what we know, but he stuck the landing on how it happened. I’ve watched quite a few of his lectures; doesn’t seem like your typical “know it all” professor to me - just a guy who loves what he does.
@@kippis05 He blows it at the explanation of the power spike. Just completely glosses over it.
wrong he's explaining how an RMBK reactor explodes, there wouldnt be a video on how an RBMK reactor explodes because thats impossible
I've been watching a bunch of your videos just for fun and knowledge, and I love them! Thank you. You are an amazing teacher.
whenever you conduct a test, you better be prepared to handle a test failure.
"We, And by 'we' I mean the entire world..." hahahahahahahh LOL
Admittedly I did come here after watching Chernobyl because I wanted a focused breakdown, but before here I probably watched 30 other videos. This was so well explained and I enjoyed every second of it - I wish I had you as a professor back in the day. Thank you very much.
Isn't it RBMK instead of RMBK ?
Noticed that too... Once might be a typo, but five or six times? Really??
One of many inaccuracies
@@TheNheg66 im interested, what are the other inaccuracies?
Writing backwards level: "3.6 Roegents, not great, not terrible."
Well that's not great but its certainly not horrifying
Not at all
Well this comment’s not original, but not funny
Michael Solis it not 3 roegent its 15000
The footage is mirrored.
This shit comment doesnt even make sense. Wtf
Great explanation. Obviously simplified to make a point. However, be careful saying that something can't happen. Seems like overconfidence breeds complacency, and complacency leads to accidents. When people say something can't happen - this ship cant sink, this reactor can't explode, this dam can't break - the world likes to prove us wrong.
An excellent presentation. Enrico Fermi built the very first carbon moderated reactor with no containment in a squash court at University of Chicago. Werner Heisenberg's first reactor was moderated with heavy water and had no containment building and that blew up and destroyed his lab. We Brits used air cooled carbon moderated reactors with no containment in Windscale to create Plutonium for our bombs, and one of the reactors (Piles) caught fire in 1957. Then of course there's Three Mile Island, and Fukashima, both of which were "safe", then we have the THIRTEEN Ukrainian Nuclear Power Plants in the centre of a bloody war zone in the 21st century. Human ignorance, complacency, stupidity, and greed cause these disasters, and always will!
Don't compare Three Mile Island to Fukushima. Three Mile Island is re-starting soon.
@@MrSummitville Fair point as far as the release of radioactivity is concerned, but both sites still suffered core meltdowns.
When he started with the markers I thought there was a mouse in my room.
@@pavel9652 don't get me wrong, I love these videos. I have watched a lot of them and learned a lot. It was just that I didn't know where the squeaking was coming from XD
@@carrito1981 Haha, I mistakenly responded to your comment, while responding to the other one. Nice catch, you are fast ;) I already deleted it, sorry for the confusion. I think the squeaky marker is a staple here ;) Stay curious!
@@pavel9652 all good my friend!! :)
No containment would have prevented Chernobyl from exploding. The reactor got into an unstable region producing a phenomenal amount of power. It's simply bad reactor design. "Doctor, it hurts when I do this." "Don't do that!"
Excellent explanation of the differences between the reactors in the "west" and in the Soviet Union. Lies were the downfall of the Soviet Union. So many lives lost due to lack of information. It's sad. God bless those that gave their lives unknowingly.
I can’t write backwards nevermind words like neutrons & moderator.
I was wondering how he was able to write backwards so effortlessly. Then i looked closer, either he is wearing a women's jacket, or the buttons are on the wrong side. The video is flipped.
@Illinois EnergyProf The elephant's foot beneath reactor 4 is made of uranium that got through the bottom of the reactor vessel (melting the bottom of the reactor vessel). Are the bottoms of the new reactor vessels fitted with the same materials that the control rods are made of, so in the case of an uranium fuel meltdown the fision reaction will be stopped by that material on the bottom of the reactor vessel, the fuel will solidify and there will be no danger that the uranium lava will leak into the ground contaminating the water?
Nuclear fuel by itself, while radioactive and not safe to be around, is not something that fissions normally or requires a neutron absorber like a control rod. New reactors, old ones even that where not soviet built, have thick concrete surrounding them which is more than enough to stop the nuclear material from eating through.
@@JPminer814 Then why did the elephant's foot sunk beneath the reactor's core. Why was everybody fearing that radioactive material will get into the groundwater?
I believe this man consumes large quantities of whiskey.
Wasn’t the xenon already poisoning the reactor because they were running the reactor at half power for 10 hours.
The reactor was poisoned because the power level was accidentally allowed to drop to a very low level, not because the reactor was running at half-power.
If you know a lot about nuclear reactors you probably know a lot about half life’s. Iodine has a half life of 6 hours and after that 6 hours half of that turns into xenon. If that nuclear reactor just dropped to a low level exponentially that wouldn’t cause a xenon poisoning. What does how ever cause a xenon choke is a reactor running around half power for too long
If there was a containment building, would this not act as another level of bomb by having it fill with gas until it also blew? What protections are there for this in containment buildings?
A bomb losses energy breaching a containment. So there may not be enough energy to breach a second container. Built properly then anything sans the most negligent act(s) or sabotage and any explosion will be contained.
Thank you for a very easy to understand film. I've been to Chernobyl hundreds of times. This topic interests me both as a job and as a hobby. I would be happy to discuss this topic with those interested and even organize a trip there.
I only wish I could present such organized, thoughtful material in my own job.
Did you get a professor on HBO's Chernobyl series? RBMK exploded due to design features and coincidence of circumstances. The operator pressed the correct button, but it worked unexpectedly badly. And this happened as a result of the poisoning of the reactor and a small number of absorber rods in the core.
I can't stop watching this channel, everything's so interesting and well explained.