How Chernobyl Exploded - PART THREE: The Final Minutes
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- čas přidán 24. 04. 2024
- It is now 1AM, April 26th, 1986. Unbeknownst to the operators, they are now rocketing down the path to destruction. These next few minutes are critical for the survival or demise of the reactor, and they are equally misunderstood by the general public. So, let’s explore them.
With thanks to the following for creating the locations seen in this video:
Control Room 4 - Hydroproject.
/ discord
Control Room 3 - Unit Three
/ discord
Exterior - Gherkinbeans
/ discord
With thanks to Bobby and Sredmash for reviewing the scripts.
Akhimov deserves a CGI mustache. That thing was glorious.
True.
Please do not rule out Toptunov's mustache as well. It sure had the possibility of becoming equally epic.
@@swokatsamsiyu3590Akimov Too! And Stolyarchuk!
They all need cgi mustaches
metlenkos beard :)
"The pressure inside the core has been released" yeah that's one way to put it
"A rapid unintentional disassembly"
The best series about the event. No artificial drama, no BS. Top tier quality content on CZcams.
Only second to stanfords nuclear physics course here on CZcams:)
I think this is one story that requires no additional drama
laughable@@Just.A.T-Rex
I did not expect a part three this soon, a pleasant surprise.
It's Chernobyl Week, 7 videos over 7 days :)
Same
Well also it is the 26th of April currently in Ukraine. 12:30 AM at the time of writing this so the 38th anniversary of the explosion is very soon.
Imagine flying an airliner where the feedback from changes in the flight controls took two minutes to reach the pilots...
What a phenomenal conclusion of this 3 part series. Very, very well done. And you even included the exercise bike in the CGI representation of the control room, impressive attention to detail! The thing that still has my brains doing triple backflips is "had to wait 5 minutes before the system would spit out the results..." Good grief, when you're dealing with a reactor capable of doing a full about-face in literal nanoseconds, at least give it a computer system that isn't walking at a snail's pace.
The in-control-room display is a point of controversy among us. If you look at page 38 of INSAG-7 and in some other sources the suggestion is there was no such thing. The 01:22:30 printout is such a big deal presumably because of this. Yet I think in Shcherbak's book (possibly Karpan's) operators are being quoted as apparently referring to some display. Sredmash and That Chernobyl Guy are comfortable tying this display directly to the PRIZMA program that produced printout calculations whereas I'm not. So it's a surprisingly important detail that, as usual, is flying under the radar, and I find it particularly controversial.
@@markusw7833
I was more talking about the SKALA system in general, not necessarily a specific display. As ingenious as it was, it was also woefully underpowered for its intended task.
@@swokatsamsiyu3590 Right, there was a systemic limitation. Five minutes was actually the minimum time. Five to about fifteen minutes is the window. In general the ORM was simply treated as not that important.
@@markusw7833 Had the employee that was not present due to being told the reactor was shut down been there. Do you know if the computer they had for guiding ORM more advanced/faster?
@@Melanie16040 I don't know about this employee. Unless he factored the actual values of the coefficients of reactivity into his program or whatever rather than the misleading ones the operators had available I'm a little skeptical as to his value. This is another detail found I believe in Karpan's book that seems at odds with what I've been reading.
"He's in shock. Get him out of here."
I have seen dozens and dozens of doumentaries and books about this event, and people involved. This 3 episodes are absolutely best. IDK how did you manage that, but keep doing it!
This is by far the most nuanced and comprehensive explanation of what was going on inside Unit 4. Bravo! 👏🏻
I love the music because it matches the mood with the video and I’m just imagining the chaos that’s going on in the control room.
Agreed! The choreographic synchronicity of the opening with the cement mixer is perfect. It would be interesting to experience how Shostakovich would feel in this context, do you think?! The list of Ukrainian modern composers is vast, so can't single one out, but undoubtedly would resonate. Guonadottir's score for HBO is stunning and if U enjoy that check out Hildur's score for Sicario:Day of the Soldado. Anyway, cough better be quiet while we wait for live event. Though in Eastern Australia I see a pink Brown dawn appearing so may be snoring by then so give me a kick if disturbing the audience.....
What a really good 3 part series
Thank you so much, I'm glad you enjoyed it :)
"Because it's cheaper" sums up the MO of the Soviet era.
"positive SCRAM effect" is a term coined by reactor's designers in attempt to cover their backs and shift the blame to operators. It is like positive results for cancer or Alzheimer's test, you can have plus sign, but there is little positive about it. Purpose of SCRAM system according to USSR reactor designer's regulation is to "rapidly and sufficiently insert amount of negative reactivity needed to shut the reactor down and keep it in that state". It is used in cases of emergency, as a response to violation of safety critical parameters, and also to shut reactor down as last step of routine shutdown procedure. "Positive SCRAM effect" means SCRAM system doesn't meet basic requirement for that system. Moreover, "positive SCRAM effect" implies SCRAM system in some situations does exactly the opposite - it inserts positive reactivity, increasing reactor's power. This also makes various protections of the reactor to behave weird. E.g. during the event, reactor's protection detected abnormally high reactor's power level and abnormally high rate of power increase, and initiated SCRAM. Logically, it should lead to rapid insertion of amount of negative reactivity, enough to shut down the reactor and reliably keep it in shutdown state. With "positive SCRAM effect" the effect is opposite.
In combination with slow rate of insertion of control rods that power peak may be rather long and devastating, it took 4 seconds for the reactor to explode with power rise from several percent to 100x of nominal, while insertion time of control rods was about 26 seconds, few time slower than on reactors of similar size, but without such large positive coefficient. That was determined be totally inadequate, while reactor designer's regulatory documents require speed of operation of control mechanisms must be enough to provide robust and efficient control of reaction and reliable shutdown, including cases of emergencies and accident.
And of course positive reactivity coefficient not only opened and shortened path to unintended prompt criticality, but it also highlights control system's inadequacy. Positive reactivity coefficient not only makes the reactor unstable and hard to control, producing tendency to power swings, but also, with increase of positive reactivity coefficient, makes swings larger and faster, and this requires much faster control system to fight with than it would be needed without positive coefficient. While negative coefficient does the opposite, making the reactor more stable, self-regulating and able to counteract disturbances. That's why reactor designer's regulation state "the reactor should have negative power coefficient in general; in case the reactor would have positive power coefficient, special attention should be paid to investigate and ensure safety of the reactor in stationary, transient and accident scenarios"
I never took "positive" to mean anything else except a mathematical '+', and I'm unsure that the original Russian term even has such a dual meaning. It simply refers to the paradoxical, momentary increase in reactivity lower in the core following the insertion of the control rods (?)
I strongly suspect you're reading into it a connotation that simply isn't there.
Incidentally, IIRC, the operators were not aware of this.
I mean, based on the rest of your post, you probably have more of a grasp on the actual relevant concepts than I do, so I'm puzzled by your initial statement. It's just like "positive void coefficient" versus "negative void coefficient", or "it is negative 31 degrees outside".
Quick Note, Beta effective is the effective delayed neutron fraction. Different reactors will have different Beff values, which you are correct in saying define the boundary between a normal operating state and prompt critical. However, an addition of reactivity equal to Beff when the reactor is critical (ie keff=1 or p=0) is what defines the prompt critical boundary, not just the value of Beff. For example, if a reactor's beff value is 0.005 delta k/k, a keff of 1.005 would be prompt critical (the reactor is sustaining criticality on prompt neutrons alone). The value of Beff changes over core life, but remains constant from day to day operations.
I work in the nuke industry and have been to senior reactor operations class. It worries me that the ops folks had such a poor understanding of neutronics that they didn't recognize the impacts of the graphite tipped rods.
I'm not blaming them since they weren't trained, but the concept about reactivity margin and the neutron life cycle is covered very thoroughly these days, and rightfully so. An operator should know every potential impact on reactivity that can occur, no matter how slight.
It was nuclear experts who lacked an accurate understanding. That's how an RBMK reactor explodes. I don't know if that worries you or what.
@@markusw7833 the experts knew. This channel does a great job of covering that kn earlier episodes. But the design bases were a closely guarded state secret.
@@mikeall7012 No, the experts did not know. I have written scripts for this channel about the experts not knowing, albeit there were some warnings. In two and a half weeks you will see a roughly one-hour video that will rehash the key factors the experts did not accurately understand. Stick around.
It's incredible to me that they had to wait 5 minutes for readings to be returned to them, and that the read outs on the wall were limited to just one parameter at a time. Computing speed aside, it's insane that you couldn't just stick a few more panels there and display those things all the time.
Your finest masterpiece! So well done. Superb computer graphics in stunning detail, no other Chernobyl series comes close to this wealth of information. And yet, I feel a bit sad, what a terrible and needless tragedy it was. Sincere thank you for this great work and all you've done behind the scenes. These will be seen and enjoyed by many.
Excellent as usual. There is nothing on this planet that ignites my hunger for knowledge like the bits and pieces of details we still don't know about what was taking place in the core and how the ingredients came together in such a near perfect way to achieve the result we're all aware of. Hopefully one day I'll have something to contribute to those mysteries. 😅
Hey, I was looking forward to this, the series has been spectacular.
Thanks!
A brilliant recreation of events. Just the thing I was seeking. I must now re-watch these videos.
Thank you!
38th year of the tragedy tonight
This guy is the most unbiased presenter of evidence about this event. Thanks for your research and clear understandable presentations.
It's odd how wrong and even misleading HBOs Chernobyl seems to be, especially tragic for a series whose entire leitmotif is "Lies incur a debt to the truth".
There is much you haven't seen. The irony couldn't be greater.
Just curious, what exactly did the series get wrong and right? I was under the impression it was fairly well-researched.
@@legogenius1667 What exactly the series gets wrong is way too long to comment on here. Most notably the series gets high-level things not only wrong but diametrically wrong. It's a staggering failure of research. The ironic failure of it will be used as a point of departure for a couple of videos in June that will look into the seminal Soviet expert lies shaping the narrative from early on.
@@legogenius1667 Apparently the staff did nothing outside regulation, all the steps they did were not prohibited. They did not follow research protocol, but there were no rules against having the reactor at very low power, or bringing the power back up from a very low power state. The situation up UNTIL the disaster was, in the eyes of the staff, completely normal. There was no power-surge that Akimov or Toptunov were trying to stop with the AZ-5, Toptunov just pressed the AZ-5 because the test was over and the reactor was to be shut down. Dyatlov was not screaming, yelling and threatning the plant crew, and Bryukhanov did not have to do the Turbine run-down as only 4 other tests of this kind were performed on 16 reactors, none of the successful - and on the other hand experience showing that the cooling was adequate in the 1 minute period between loss of power and the generators starting.
This is exactly what I needed. Thank you! Looking forward to the real time video. : )
Really detailed and interesting. Thank you so much
Fantastic video and you deserve way more views it is criminal
Excellent series, top notch, thank you!
released on the 26th impressive
Yeah, the days of the week fell perfectly for this series :)
i just finsihed Chernobyl series an hour ago and had to get the real story and glad i stumbled on this channel because it is explained so well.
I am very excited because, this is my first year to celebrate the anniversary of the Chernobyl tragedy. It wasn't until a year ago that I researched everything about the tragedy (I had been putting it off for years) and it caught me, now I am interested in everything related to the subject. I am very happy to celebrate with you. Thank you for this video and all information 😃. From El Salvador 🇸🇻👋🏻
Shit, fell asleep listening to one, woke up to the other. Love the upload schedule.
lets go part 3 keep up the good work
Thank you!
So they were running a test on a xenon-poisoned reactor they did not really understand and which was inherently unstable and whose emergency brake acted like an accelerator in the early stage of its employment . Does that sum it up ?
i think you are delusional, i have to send you to the infirmary
The reactor's designers also did not really understand its behavior at low power. The test wasn't really problematic, it just coincidentally put the reactor in its most unstable operating regime. But yes, pretty much sums it up.
Excellent video!
I watched all of your videos, and they are really great and extremely insightful. To the matter itself: I strongly believe that if one chose to become a reactor operator then you will to accept from day one that you will have zero room for creativity in this profession. Here, it’s all about following regulations to the word without any fail ever. If you can’t live with that then please go for literally anything else.
Great series, and explains very well how the operators ended up in the situation that they did and felt pretty confident they could just hit the SCRAM button and go home without blowing anything up. There was one detail I'm sure I remember hearing on some documentary about the incident years ago, but have never heard mentioned since. Apparently it was necessary to type the required generator output into the control system, i.e. 500MW and this was quite easy to forget/not register properly, and when the shift changed it's possible Toptunov forgot to do this and that's why there was a sudden power decrease which resulted in the mass control rod withdrawal to get back up to 200MW.
For me this is the nub of the whole accident, without the sudden power decrease and subsequent actions to correct the low power level there would have been no accident (well at least not on this day, although the inherent problem of the graphite displacers was an accident waiting to happen)
I do feel Dyatlov has been given a pretty rough deal from the new series, which more or less pins the blame on him to a large extent, which just seems unfair. Legasov gets a positive representation in the series , biut it could easily be argued he was much more culpable than Dyatlove, he knew about the problems with the graphite tips and was part of the establishment that approved and built RBMK reactors, knowing full well they didn't have the technology to really make them safe (5-15 mins for a computer to tell you if your reactor configuration is safe, lol! that's just bonkers)
The "setting the output into the Control" thing is from Midnight in Chernobyl. I'm guessing this is Higginbotham misunderstanding it as that is actually more advanced than the real system LMAO.
In real life, there were three wires corresponding to the three groups of automatic control rods, which you would manually adjust the current flowing through where the voltage corresponds to the percentage output.
Given the behaviour of the system, with AR-1 withdrawing and AR-2 not moving, he just set it slightly too high, which is easy when you're dealing with a current on a wire.
It feels really counter-intuitive that too much coolant can be bad for a nuclear reactor. Yet we see a problem with flow rates here, and in Three Mile Island, where the operators became convinced that there was too much water in the system.
There was a rule against excessive flows for the main circulation pumps so they wouldn't cavitate or apparently destroy themselves, which was a consequence that did not occur at Chernobyl. However, there wasn't one for the reactor core. Soviet experts got quite clever in how they presented this. The consequence tied to Chernobyl is about the temperature of the coolant rising close to the boiling point, which INSAG-7 seems to attribute to lack of condensate feedwater flow as the reactor wouldn't be producing much steam which was supposed to subcool the coolant yet you see the operators being able to call extra feedwater flow from somewhere. Furthermore, apparently there was neither a prohibition on connecting all main circulation pumps or on operating with lack of subcooling, and a high coolant temperature occurred naturally in RBMK reactors. This will be discussed in a later video.
If you met any of these engineers in the pub the night before and told them 'Hey, don't run that test tomorrow, the reactor will explode' what could you tell them to convince them, rather than write you off a a drunk idiot?
Tell them the power coefficient is positive, the void coefficient is plus five beta and the steam coefficient never stops rising for the whole x axis. Would scare the living shit out of them.
Another year passed since it happened. It totally shaped the way we handle nuclear safety today.
I believe I also read somewhere that those bottom-inserted control rods were not attached to AZ-5 scram mechanism at the time. They already started changing this in RBMKs in 1986, but unfortunately it still hadn't been done in Chernobyl unit 4 by then. If it had been, then that alone might have been enough to prevent the explosion.
I don't get it... Why is was so hard for reactor designers to add a simple gauge (digital all analog) that will show (in real time mode) the exact number of control rods inserted? Why it needs to be calculated via SCALA with 5min lag every now and then? I get that neutron flow, or core temperature gradient in such enormous stucture like RBMK is rather comlicated and somewhat abstract matter that cannot be measured on the demand. But controls rods have very simple parameters: overall number of rods currently inserted in the core and depth (in meters) on witch those rods are actually inserted
The designers wouldn't bother to do that because the number of inserted rods was not regarded as critical to safety by them either.
"These next few minutes are critical for the survival or demise of the reactor."
How critical? Prompt Critical?
Da bum tisss
Honorary best joke in the comments award :)
The real reason for the Chernobyl incident? Reality could barely contain the power of Akimov's mustache, and Toptunov was also becoming a threat.
A KX-class incident was inevitable, and so the SCP Foundation had to terminate both mustaches under the guise of a "catastrophic reactor failure."
Wow I'm actually first, "No views".
I'm sorry, is there an exercise bike in the background of the animation of Dyatlov?
The Chernobyl Unit Four Control Room had an exercise bike in real life. The operators needed the opportunity to stretch their legs without leaving the room, so they had installed exercise equipment. Ignalina, for example had a full weightlifting set with a bench.
You can see the exercise bike in the background of a video in the Control Room before the explosion. Its current fate is unknown.
And in the '90s the operators started playing Pong on one of the new control room computers. Until the deputy chief engineer caught them in the act and cut the power cable with an axe.
I had a REACTION (sry) to the background music, can you tell which pieces you used?
Music is listed at the end of the video in order :)
It is! I turned the vid off after the last narration, My bad. Anyway, great video!
No joke, since you started posting videos, I've noticed a lot more people defend Dyatlov.
Three years ago, I legit got banned from an engineering discord server for getting into an argument about his role in the disaster.
I am really happy that my videos in some way have an impact.
My thoughts have always first and foremost been about the legacies of all those involved, and how I can change it for the better.
@@thatchernobylguy2915 Trust me, whenever the topic comes up, I find it way easier to just share your videos than attempt to explain something that I don't actively keep sources for. The guys in that control room deserved so much better, the least we can do as people interested in the disaster is clear their names and highlight the discrepancies with the official story.
Brilliant!
Its 38 years since the disaster tomorrow too
Happy Chernobyl Eve Everyone!!!!!
Of course, it seems now easy to blame the young Tuptonov, who retracted the control rods, as part of the chain that led to the accident. But as usual, it would be REALLY interesting to know what motivated him to his choices. Could he have retracted other rods? Or was he already in the Catch-22 situation with or without knowing it?
i just saw this video and i clicked instantly on it. I'M CURIOUS!
what chernobyl video game did you use for thumbnail?
This video posting lines up with the incident time in my local time
so how could this be avoidable? what should have happened in which situation to avoid the explosion? because i think the design alone is not the only reason for the catastrophe
15:14 "Combined, we now have approximately 6 times the reactivity threshold..."
I do not understand where you're coming from with this number. There is a beta eff of about 4.5 from the positive void coefficient, and 1.1 from the positive scram effect. Combined, that gives 4.5*1.1=4.95, or about 5. Where does the extra reactivity come from to bring this to about 6?
Not 4.5, 4 or 5.
@@thatchernobylguy2915 Okay, so the combined beta eff is either 4.4 or 5.5. Where does the "approximately 6" come from?
Petition to change the channel name to That Chernobyl Daddy..
All kidding aside, keep up the great work!
This is not what I expected my first super thanks to be.
I mean, sure. 100K subs and I'll change it to that for a day.
I was going for a little bit of humor instead of the usual, "great video, keep up the good work"
You do you, my friend. Im just along for the ride. Seriously though, keep grinding man. You have a lot of talent for this.@thatchernobylguy2915
@@Hugh-Janus69420 Seriously, thank you so so much for the super thanks though. It really means a lot :)
I just finished the second part. Lucky me
Another video 😭 you spoil us
Why was there a bike in the control room?
The Chernobyl Unit Four Control Room had an exercise bike in real life. The operators needed the opportunity to stretch their legs without leaving the room, so they had installed exercise equipment. Ignalina, for example had a full weightlifting set with a bench.
You can see the exercise bike in the background of a video in the Control Room before the explosion. Its current fate is unknown.
Chernobyl Guy, why are you so awesome?
I try my best :)
@thatchernobylguy2915 And your best is very good! I wanted to send a super thanks but i dont have the option.. :(
@@Hugh-Janus69420 The super thanks is there.
Wow views and likes are skyrocketing
LETS GOOOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!
Could they have just shut down the reactor during this whole ordeal or no?
After the second spike in feedwater flow, calculations have shown that pressing AZ-5 would 100% result in an explosion, no matter what. There are other ways of shutting down the reactor, but they had no reason to do them. :)
Actually Prompt critical is the wrong term - this is used when the Neutron rate is neither increasing or decreasing but is sustained only by Neutrons emitted immediately following a fission rather than those released from the resulting fission products seconds to minutes later. The term you're looking for is "Supercritical"
Supercritical would be a βeff between 0 and 1. As βeff reaches 5-6, this is far beyond the value regarded for prompt criticality.
A similar method of measuring criticality is the dollar system, where 0 dollars = critical, and 1 dollar = prompt critical.
The values for βeff are given in INSAG-7, the IAEA's 1993 official report on the Chernobyl Disaster.
I hope this helps. :)
That Chernobyl Guy is actually correct in his terminology. When neutrons aren't going up/down, is called a reactor being critical. It means nothing more than that reactor power is stable at some level, and the neutron generation being used/ being produced is in balance. 1 neutron produced -> 1 neutron being used. That's not prompt criticality, far from it.
Supercritical is when reactor power is going up. More neutrons are being produced/ used. This in itself isn't necessarily dangerous. You need a very small bit of supercriticality, or else you would never be able to get your reactor back up to power after a maintenance shutdown. And you can be supercritical on delayed neutrons. This is totally normal. Like I said, you'll need some of it to get your reactor back up to power.
Prompt criticality is something else entirely. It means the reactor is sustaining the fission reaction on prompt neutrons alone, which is very, very bad. At that point you will put your reactor in orbit because there is not a computer system or human in the world that is fast enough to prevent things from spiralling wildly out of control. See Chernobyl Unit 4 for the results of prompt criticality in a power reactor.
Prompt neutrons -> being born at the moment of a fission event.
Delayed neutrons -> they appear millisecond to sometimes even minutes from the fission products after a fission event. These are the neutrons we use to be able to control a reactor. Without these, that would be impossible.
@@swokatsamsiyu3590 Supercritical = "Oh shit, we've got to do something!"
Prompt Critical = Ka-BOOOOOM!!!!"
nice
Firt youtube video on actual facks is born
Call me crazy, but i still think the RBMK is an elegant design. It is a big advantage to be able to use low enriched uranium as fuel.
The management is solely to blame here as they are the ones who should have been more cautious assessing the risks involved of operating such a power plant. Also the supporting technology simply wasn't good enough at the time to provide necessary feedback to the operators. Nuclear reactors are simply too complex to be operated by hand, Three mile island is another great example of this.
Just like with an F16, without the computer, you would crash.
First
Safety culture of the USSR was the main issue. Don't say anything that may embarrass the party. Don't call politically advantageous things unsafe. Classify faults so the world and your citezens don't see the problem. So many defective products made in the mismanagement of the planned economy that many things had to be "rigged".
This accident was easily avoided.
As American college professors would put it nowadays, The explosion took place cause of lack of diversity in the control room. Why was there no black women, or trans black women?
you don't have technical knowledge to talk about tea kettle let alone nuclear reactors
Shoot, homey. Writing one sentence without capitalizing the first letter or ending with a punctuation mark doesn't speak highly of how well you understand tea kettles.
Feel free to enlighten us unwashed peasants, then. I'm sure we're all waiting with bated breath to hear your detailed explanations for both.
Ya know how many video's of this are around already? And every video have different versions of what exactly happens. So, DISLIKED. No use to post this after many has done already.
And do you know how many of those existing videos are shamefully and demonstrably inaccurate? All of them.
2N degrees centigrade is not "double" N degrees centigrade. Since the scale does not start at absolute zero.
7:00 You see here in the background, the Russian backup power source in case the diesel generators fail. Simply pedal!