How Chernobyl Exploded - PART ONE: April 25th, 1986

The time is midnight, April 25th, 1986. A pleasant warm Friday in the northern region of the Kyiv oblast. And in a little over 25 hours, this scene will be changed forever. Tomorrow, the fourth reactor of the Chernobyl Nuclear Power Plant will explode, two dying due to the explosion, and another twenty-nine succumbing to radiation related illnesses. The total number of deaths can only be estimated in the thousands. But how did Chernobyl explode? Let us follow that story along.
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.

[@WhereIsTheCheese]

It’s a shame that the cgi didn’t capture the sheer awesomeness that is Akimov’s mustache.

[@thatchernobylguy2915]

Truly a shame for all the mustaches and beards in the Control Room

[@henriknilsson7851]

Yes, the youthful aggression of Toptunov’s nascent mustache is also a sight to behold!

[@chieftainmk_11]

@@thatchernobylguy2915Truly.

[@Ur4niumCran3ium]

@@thatchernobylguy2915it’s really a shame

[@hemfri07]

And there are no special CCCP cigarettes,and some new age guru to advise them what to do"just breathe,and feel calmness (+metalic taiste in mouth+ozone)Sandguru would say that is normal,and we neeed more beardes and silly mustaches,like adi hade :) :) :)☺☺☺ +voce over"RAISE the power-raise the power" - ,or from movie "EdWood" line Bella lagossi "Pull the strings,Pull the strings" ....KABOOOOOM!

[@AskMrScience]

Rock em Sock em robots in the control room. There's your problem!

[@thatchernobylguy2915]

Couldn't afford actors. D:

[@scottsparrow4982]

They'll knock your block off!

[@chrish2112]

Frankly, I'd be concerned if they didn't have Rock 'em Sock 'em Robots in the control room.

[@oscarr.g.509]

One does not simply delay a turbine rundown experiment in an RBMK nuclear reactor 👌 I'm currently reading Midnight at Chernobyl (following your references), and having these videos this week is like the icing on the cake. THANK YOU !!!

[@Winston-lf7sb]

exactly. design was ok. it was being operated improperly. trying to run diagnostics and shut down while being constantly asked to turn back on to produce power. they should have cancelled the diagbostic or pushed hard and run the diagnostics without delays. they kept turning it on and off. pulling these rods up and down out of the reactor without then properly, and slowly cooling. they warped the rods and jammed the entire mechanism.

[@TikhonT.]

1:56 I am summoned every time the red mercedes is mentioned

[@Frankthetank-zr5mc]

Thanks for posting. Don’t let one day mess it up.

[@ericluffy7970]

This is am awesome breakdown. I'll take as many spins as I can get on these subjects. Helps to get the best perspective generally to make us all most best to stop it from reoccurring

[@ericluffy7970]

Dude! I just got it! That was a Fallout joke wasn't it? You're a freaking genius! Don't let one day mess up 1,000 years 😂🎉😮😢

[@danielle3064]

Yoooo this is exactly the kind of timeline breakdown I've been wanting! Can't wait for part 2! This channel is so slept on you deserve all the views!

[@aluminium5738]

11:54 PLEASE have mercy on my guy's name lol, it'd be pronounced as "deek" be weary of lip-smacking too, stay hydrated

[@thatchernobylguy2915]

I'll try my best :)

[@bumblebeerror9019]

I stumbled upon your channel by accident - I’ve had a massive special interest in nuclear disasters for months now, Chernobyl in particular, and you’re the first person I’ve found who has a detailed rundown of the events and sources for them listed !! Excellent work, my guy.

[@MadScientist267]

Ah yes the "hey guys I found this wiki thing" version. Magnifique!

[@markusw7833]

As xenon is mostly a product of iodine-135 decaying which is a product of nuclear fission when power is lowered xenon's concentration increases while the higher power iodine-135 is decaying and the lower power xenon let's call it utilization is less. Then, after about 4-6 hours, xenon concentration begins to be steeply reduced as its iodine-135 precursor is reduced and excess xenon is decaying. Ultimately with a power reduction the concentration of xenon is reduced as well, which is why the Kiev delay actually resulted in a depoisoning of the reactor. I think it's really important to know what the plan was for finishing the turbine vibration measurements. If the idea was to complete them at alternating loads between the two turbines then this is the virtually unknown event that got the ball rolling toward disaster. The Kiev delay depoisoned the reactor so the xenon narrative in the HBO mini-series is complete nonsense, but it's extremely likely the power level was intentionally reduced under 700 MW so that the remaining turbine could be disconnected with less steam in the system to complete these measurements as well the rundown test without shutting the reactor down. In addition to there being a video on this (in the Unanswered Questions series) we have recently found what appears to be an operating log confirming an intentional decision accompanying a KOM switch from Chernobyl. This separate program being left over is what caused a deviation from the power figure in the rundown testing program. The confusing thing is with turbogenerator no. 7 being disconnected at 13:05 their intentions for whether they originally intended to complete these measurements with both turbines available at 1500-1600 MW or if they intended to complete them at a lower power with one turbogenerator already being disconnected is unclear.

[@mattipaajanen4109]

Just to add, the Xe-135 is not present uniformly in the reactor, but its local concentration depends on the local power density. Thus, reducing power by inserting control rods, reduces power at top of the reactor, and leads the top to poison further by Xe-135, whereas the bottom half can actually de-poison at the same time. But, I have no insight to power distributions and how it varied during power changes, this is mere speculation.

[@markusw7833]

The reactor was poisoned mostly in the center. The neutron flux distribution at low power was double humped with the peak at the top, meaning the top may have been the least poisoned. The graphite displacers did not cover the full height of the core based on this logic, that not much was going on at the top and bottom peripheries.

[@shawn8464]

Huh

[@Dream25_]

Another great video. I was thinking a month or so back how I would like to put together as detailed a timeline as possible for at least the week building up to the 26th, either to catalog in social media posts or just for my own personal reference, and I have a feeling that's pretty much what you've got planned for this week, so I'm really excited.

[@ExploreGamesAndMore]

Nice video. Looking forward to the rest of the parts, but please take your time. I really appreciate all the detail you put in.

[@ellenbryn]

Hearing about it in so much detail so many years later is surreal. I appreciate it very much. I just wonder if the current generation can imagine what it was like pre-internet and, mostly, pre cable TV, when we might get as much news in a week as most of us can view now in half an hour by following links and watching full color videos, sometimes live, from all over the world. back then we just had a few news shows a day on TV; more in-depth info of what happened yesterday was in the morning paper. or we could listen to news radio which often had more current breaking news, but ssldom reported anything outside one's local area.

[@thing_under_the_stairs]

So true. Back when it happened, I got the majority of my information about Chernobyl from National Geographic, since they went into far more detail than the average paper or newscast did!

[@willyengland]

Very detailed and clear! 👍👍 Thank you!

[@thatchernobylguy2915]

You're welcome! Glad you enjoyed it!

[@kevinh.6587]

I always like checking out the videos on chernobyl. (I don't know why) anyway, thjs was an excellent video and excellent informative video and the best series on chernobyl i've seen. Thank you for sharing.

[@michaelmoser4537]

you didn't mention a known design issue: the RBMK had an unusually large positive void coefficient. RBMK doesn't keep water inside the reactor under pressure, now you end up with fewer water within the reactor, as the water evaporates. This creates temporary voids. Now water is also a neutron absorber, so that these voids are resulting in a stronger chain reaction and increasing the thermal output. This means you have a positive feedback loop built-in, by design. Eventually the whole thing exploded... The book "Midnight in Chernobyl" by Adam Higginbotham mentions an accident at the first installation of the RBMK reactor in Leningrad (a partial meltdown, like at Three Misle Island!) "On the night of November 30, 1975, just over a year after it had first reached full operating capacity, Unit One of the Leningrad nuclear power plant was being brought back online after scheduled maintenance when it began to run out of control. The AZ-5 emergency protection system was tripped, but before the chain reaction could be stopped, a partial meltdown occurred, destroying or damaging thirty-two fuel assemblies and releasing radiation into the atmosphere over the Gulf of Finland. It was the first major accident involving an RBMK reactor, and the Ministry of Medium Machine Building set up a commission to investigate what had gone wrong. Afterward, the official line was that a manufacturing defect had led to the destruction of a single fuel channel. But the commission knew otherwise: the accident was the result of the design faults inherent in the reactor and caused by an uncontrollable increase in the steam void coefficient. Sredmash suppressed the commission’s findings and covered up the accident. The operators of other RBMK plants were never informed of its true causes. Nevertheless, the commission made several important recommendations, to be applied to all RBMK-1000 reactors: develop new safety regulations to protect them in the event of coolant loss; analyze what would happen in the event of a sharp rise in steam in the core; and devise a faster-acting emergency protection system. Despite their apparent urgency, the reactor designers failed to act on a single one of these directives, and Moscow promptly ordered more of the reactors to be built. The day after the Leningrad meltdown, the Soviet Union’s Council of Ministers gave its final approval to construct a second pair of RBMK-1000 units in Chernobyl, expanding the station’s projected output to an impressive 4,000 megawatts"

[@boloto98]

holy shit that's a great video! quality stuff! i'm exited to see the next part

[@Just.A.T-Rex]

Almost as good as the Stanford lecture series on nuclear physics and power and the classes specifically on Chernobyl. Great rehash of everything that professor went over with some more info on the background of the choices made.

[@swokatsamsiyu3590]

Too bad I can only give one "like" because this is just awesome. What a well-done video with these animations laying it out in such detail. There is one little oopsy pertaining to the Xenon poisoning. When you lower reactor power, initially Xenon levels will actually go UP because it will be produced as if you still were at full power, and the now lower neutron flux thus less burn-out. There's another thing. Every time you lower reactor power, you start that whole Xenon song-and-dance all over again. But apart from that, the video is great. Can't wait to see the next video in this series!

[@thatchernobylguy2915]

Both of these are mentioned in the video. At 3:30, for example. The second part is in the next video. :)

[@swokatsamsiyu3590]

@@thatchernobylguy2915 Got it. And now you're making us wait for the next part🙃

[@veteransniper6955]

4:35 I think there too much shift of the blame to operators According to reactors design regulation all reactor safety critical parameters must be constantly monitored; continuous indication must be provided to operators; there must be thresholds determined and automatically checked and automatic shutdown initiated if safe range is violated. This was done for parameters like reactor's power, or power's increase rate. On the other hand, operative reactivity margin wasn't in the list of safety critical parameters, no of the above requirements was met, reactor's manual allowed to operate reactor up to several hours with program that calculates operative reactivity margin not working. While operative reactivity margin printout at that time indeed was lower than prescribed in reactor's manual, the flaw in program that calculated it was identified, and operator used graphical method to determine required parameter, which was within range, and it was later confirmed by processing recorded data. So there was no neglect to operative reactivity margin from operators, but it was neglect to that parameter by reactor designers

[@cascadianrangers728]

Jesus I never knew they turned off the emergency cooling system through physically closing the goddamn valves. The thought of that much uranium sitting there and heating up with no way to stop it aside from control rods is blood chilling

[@spitfire0005]

Why am i so hooked on everything surrounding old reactors and especially the history and happenings of old Russian reactors?

[@adamf663]

One thing you needed to emphasize is that xenon-135 is generated with a 4 hour delay through iodine-135 decay. That's why the spike appears. When the power output crashed, the xenon was still being generated at the rate from when the reactor was running at 1600mw. Once XE135 absorbs a neutron, it becomes XE136 which isn't a neutron poison. With most of the control rods out, and only xenon and water holding back the reactor, it was like a stretched slingshot. When the reactor was scramed, the graphite portions caused a runaway positive void feedback loop at the bottom of the reactor. XE135 vanished, water flashed to steam, and the static graphite moderator caused power levels to reach 200x maximum in a fraction of a second.

[@markusw7833]

The number of control rods may have been within regulation or close to it. Also, INSAG-7 mentions the presence of xenon rather than its disappearance as a factor.

[@MinSredMash]

Xe-235 doesn't "vanish" just because of a modest increase in reactivity over the course of 10-20 seconds. Basically no one in the Soviet Union has ever raised the subject of xenon burnoff as an initiator for the power surge. It is basically fan fiction for Western physicists who didn't do the math. If you like I can link a Spanish study that found the influence of xenon burnoff to be a quite trivial contributor to the power excursion.

[@adamf663]

@@markusw7833 a runaway reaction's neutrons will change the xe135 into xe136 which isn't a neutron poison. Listen to physicists to understand the physics. Scott Manley has an excellent discussion on the topic.

[@markusw7833]

@@adamf663 What you're repeating is what you saw in the HBO mini-series. Trust me, Scott Manley and Craig Mazin could not research this topic properly and they are no physicists. Scott Manley's video is riddled with errors. People much smarter and more qualified than Scott Manley make demonstrable errors on Chernobyl because their skill sets have not been honed for the deception confounding this topic, and I'm being gracious in phrasing it this way.

[@adamf663]

@@markusw7833I have fact checked that and educated myself by watching physics lectures. A huge thing HBO got wrong is that xe135 production is delayed due to it being created through a radioactive decay chain. It is created based on reactor activity of 4+ hours prior. The reactor a crash was due to xe135 being created at a 1600mw rate while being burned at a 700mw->500->30>300mw rate. However, it can be burnt in a flash given enough excess neutrons, like would happen in a positive void feedback loop. kzbin.info/www/bejne/p2THZKWwe7mlgsksi=GZEye1hGzn97YtF6

[@dianaholwerda8850]

wow, what a video this is amazing.

[@Timinator257]

Watching this on April 25th, 2024

[@milkshake1993]

Same 😂😂

[@cmillerg6306]

Watching this on 26 April 2024

[@louisburland5346]

Considering it’s just been uploaded that’s not saying much

[@Hugh-Janus69420]

Hey i really liked the video buddy.

[@thatchernobylguy2915]

Thank you! :)

[@Frankthetank-zr5mc]

Me too!

[@chieftainmk_11]

How did you find that image of Boris Stolyarchuk during the time of Chernobyl? Every google result is him nowadays or from HBO Chernobyl

[@thatchernobylguy2915]

It's in a TV report from 1985 :)

[@chieftainmk_11]

@@thatchernobylguy2915 Got any links or anything of the sort?

[@NemoAviation2507]

i love your videos :)

[@thatchernobylguy2915]

Thank you!

[@MrLego_Gaming]

Lets Go he made this video

[@fixedguitar47]

Going to have to go do the VR Chernobyl tour again

[@thatchernobylguy2915]

Never played it, need to try it out...

[@fixedguitar47]

@@thatchernobylguy2915 One of the first things I did when I got my headset was the VR guided tour of Chernobyl. I knew I’d never get to go and honestly I’m glad I just did the VR tour. Same with the pyramids. You get about 90% of the experience without any of the headache.

[@nomercyinc6783]

this reactor was always going to fail regardless of user inputs. this design was faulty from the drawing board

[@primerye]

Always wondered why they all wear little caps making them look like they are working in a food preparation facility. Is the equipment so fragile that shed scalp hair would damage the mighty nuclear friggin' reactor machinery?

[@thatchernobylguy2915]

The caps are to prevent any radioactive particles from getting in their hair and contaminating them. The caps are washed at the end of every shift- the NPP had its own specialised washing department as part of the decontamination workshop. :)

[@primerye]

@thatchernobylguy2915 oh wow, thanks for the clarification.

[@HuNgerforrock]

@@thatchernobylguy2915 They had more mustache than hair, they've should protect that with something

[@richardgadberry8398]

I'm giving this a score of 3.6 roentgen.

[@MS831985]

3.6... Not great, not terrible.

[@AdamMGTF]

Is that swan lake in the background?

[@thatchernobylguy2915]

Yes :)

[@sirnamenloss4791]

Thank yoiu!!

[@ilovecaracals]

I waited until today (April 26th 2024) to watch this or else I will have to search for a documentary that I havent watched yet

[@TestSubjectQWTD]

Is it just me, or when the Chernobyl control room is in CGI it kinda looks like a TARDIS?

[@daedalus6433]

Well, to be fair, both have lots of buttons and levers that do a lot of things xd

[@hemfri07]

Great facts thou

[@Sam-and-colby-edits992]

Why did it say the 25 instead of the 26

[@markusw7833]

The incident occurred after 1 am on the 26th. On the 25th much of the power reduction and some related events occurred. It provides context.

[@Dayznology]

Will you ever make a server?

[@bagofholding]

Remember names? Oh no...is there going to be a test?

[@amydamjanovic9183]

But wait, a reactor can’t explode!

[@GeneralGayJay]

Stuff usually goes to shit if you have the wrong people.

[@dougyoung349]

That Chernobyl Guy: Where do you get your information ? Every other film on this event details that they were testing the use of a turbine's output while it is slowing down. They needed to know if they would have enough power to keep the reactor instruments going until the generators come on line. The test had nothing to do with vibration.

[@danielle3064]

There are credits at the end of the video. They were performing multiple tests in addition to the generator rundown test

[@thatchernobylguy2915]

As Danielle said, there were multiple tests being performed. In my previous video (The Truth About the Rundown) this is touched upon.

[@markusw7833]

Every other film on this event misses critical details.

[@dennisford2000]

Dyatlov where have I heard that before….😂

[@hansgustavsson7838]

Good video but you really need a new mic... damn

[@SonOfAB_tch2ndClass]

3.6 not great not terrible!

[@elenapic6859]

so I won't be having friends that are named Dyatlov, or specially leaving them in charge, sorry, too much coincidence

[@JJsOriginals]

Done documentaries, done YT documentaries, done HBO, done shiey... Fuck it, let's find out one more time. 😀

[@Arbitrageur_]

Fuck yeah

[@dusktilldawny666]

Could you actually explain what happens in an atom? You know, the usual stuff like P shells and D shells? Or even have the slightest comprehension of physics. A big ask, I realise. But hey, if it makes you some revenue, who am I to complain. .

[@thatchernobylguy2915]

As in, what happens in an atom during fission? Or just what is an atom?

[@dusktilldawny666]

I was thinking more about the weak nuclear force involved, but that's cool, we can discuss fission...

[@markusw7833]

You know that not explaining what happens to an atom doesn't invalidate content, right? That, in fact, you don't need to have a clue about P shells or D shells to know much more significant things about the topic you have no clue of?

[@petergibbons607]

how many videos of this do we need? why don't you come up with something unique instead of copying other people's videos?

[@challengerpat9810]

11:54 that guy's name 😂😂😂😂

[@PoisonOn30Fps]

Early

[@coltonmills5996]

It took me seven months in a Roblox game to learn how to blow up a Rbmk 1000 a Lena long time but I was The first one

[@hemfri07]

Let's be serious now,the Reactor Boljsoy Moznosti Kanalni-RBMK,"High powe Channel type Reactor",could operate fine,without aparatchic from polibyro and communist party+wish to be promoted and finaly have toilet paper every friday at home ;) - since i am from eastern europe i know how soviets looked at us from Yugoslavia-we exported goods,to them,and they were happy to get things from Yugoslavia,they were soooooo poor,no meat,no food,no candy,empy store shelfs,but ICBM rockets and military hade to be strong (even they used antique technology from 50's)-tryeing to compete with USA,that was allready in 22 century..hahahaha ☺☺☺

[@SombraCheeks]

I did it im sorry

[@archivis]

:)

[@DrEvil814]

What is the point of the added noise? Lower you noise floor, this video is unwatchable

[@ProgNoizesB]

blablabla.. as if we did not already knew..... DISLIKED... you brought nothing new. BYE

[@cmillerg6306]

Please please please delete the highly distracting music. Its a problem with many of your vids

[@misterjustice995]

😖😖😖

[@moskitt9324]

Chernobyl Guy you will not believe ! I wrote to Oleksandr Kupny a day ago, does he have a photo of Yuriy Trygub? because he played a significant role and there is no photo anywhere. he didn't have a photo and here I see a recent video with a photo of Trigub!!!!!!!! thank you friend !!!

[@thatchernobylguy2915]

You're welcome. :)