Now I know how a reactor works. Seriously, you managed to explain this complex subject very understandingly.

“the core is gone” *crab dance* 😂😂

I'm surprised at the low views, this is a well informed and put together video.

You didn't see graphite because IT'S NOT THERE!

Excellent breakdown. I'd like to see more coverage of how the RBMK refueling system operates, and the specifics of how the control rods are physically actuated (what actually moves them, its not shown in most schematics).

RBMK-1000 and RBMK-1500 have equal cores, but -1500 has turbolizers inside fuel channels. Because of fuel assembly cracks, the power of -1500 had been reduced.

Its so specific and the humor is quite spectacular. Very nice video bro!!

Not boring at all. 🍻 Good explanation. I read "Midnight In Chernobyl". It gives a great explanation of the construction of the rbmk and how it functions. It also goes into great detail of the politics used to try and hide this disaster from the world. Anybody interested at all about this disaster should read it. If you are a nuke reactor nerd it is a real page turner.

This is a FANTASTIC overview! The HBO series left me wondering about core design of the RBMK-1000s. This video and the excellent reference links filled that gap. Thank you - a former US Navy nuclear sub officer. And I continue to wonder about the 2% U235 enrichment number. The point has not been emphasized about alpha-T - the temperature reactivity coefficient. Typically the lower the enrichment, the closer the alpha-T value comes to a positive number, or at least a lower magnitude negative number. One wonders if a higher enrichment could have lessened the ultimate power excursion with a more negative alpha-T.

Thank you for putting this together! I've been curious about exactly what was inside an RBMK for years, this was the clearest explanation I've yet seen.

Really nice presentation, technical yet concise. I’ll take this over an HBO drama any day. Well done 👍

I thoroughly enjoyed the ending, cheers for the informative video

Amazing explanation, it felt effortless to learn from you. Great way of presenting. All hail the core crab!

Superb breakdown of this monster sir. I was born and raised in Belarus in 1979. Felt the wrath of 1986 disaster. Multiple safety and operational guidelines were overlooked in favor of getting this thing online ahead of schedule. Kurchatov scientist refused to take the blame for their poor design and blamed the operators. RBMK 1000 was flawed from the beginning. Chief Nuclear Physicist and main designer of RBMK 1000 Anatoly Alexandrov refused to accept the fact that his reactors were flawed and basically were a ticking time bomb. The result of their arrogance is still being felt by the people in Ukraine, Belarus, Russia and Europe.

the job you've made is simply incredible, it's very detailed and comprehensible for the non initiated. Thank you, and best reguards for the future

Your video is probably the best on this topic, and I've seen a ton

The ending was 10/10

Very cool, great detailed description. Hope to see future work!

This is some quality content. Keep up the good work!

Very informative. The music at the end is ridiculous I love it.

Thank you very much for the video, its nice and very informative. The equipment shown at 5:01 is not a steam drum, but the steam generator of a VVER reactor (Soviet-type PWR).

Im so glad you have made this video

Excellent production mate. Now I know how a nuclear reactor works. I don’t have to throw you out of the helicopter

Excellent content and explanations. Keep up the good work

Very good explanation of a very complex structure! Thank you!

Such a well made video. Laughed at the end lmao

Best RBMK video on KZfaq......well done👌👌👌

Very good vid. Great info great ending. Deserves more views.

This video should have way more views. I just subscribe to your channel so continue this great work.

Excellent upload thanks for you time on this !

Wow it's almost like the Fast acting Scram Rods should have been mandated after the Leningrad incident. And thus avoided the explosion.

Excellent!! Thank you so much!

you explain very well, I think this is the first time I can say that I understand what really happened and why there was an explosion, thank you

Well done explanation and plenty of diagrams/figures. Congratulations.

Very good video and narrator!

I give it a 3.6. Not great, not terrible. :)

From start to finish this is great content my friend! This is a certain gem of a channel. I hope you soon have many people subscribe just like I just did. 👍🙋‍♂️😃

Very very good and broad explanation, especially for "beginners" in reactor technology. Very understandably visuals too with examples and explanations 👏👍

Love it, very good explanation.

Awesome content fella

Very informative explanation

What a fantastic overview! Very thorough

THANK YOU I've been playing with the HBM's Nuclear Tech Mod in Minecraft which just added RBMK Reactors to the game and have been wondering about the actual design of their IRL counterparts and every video I've found has focused on the Chernobyl Incident itself but never going into any actual detail about how the reactor works.

Love these videos :) I’m obsessed with reactors

Well spoken and informative many of these deliveries about the rbmk tend to waffle

Did you read the IGNASS reports? They´re linked even at WIkipedia, is the official accident report, very interesting, if véry heavy reading. There were numerous problems, 99% related to protocol. The official Soviet ´Vienna´ report was INGASS-1 but later it became INGASS-7, which is now the official version... Should look for a link, just remind me. It´s fascinating because the computers they used were too weak to effectively monitor such a physically large reactor (there´s 4000 sensors in those so-called ´technical channels´ at the edge/center of the core) and it had a *way* too low sampling rate. There was officially only 30MW left, but in reality the fission-rate at the bottom of the core was outside human control for hours probably. It takes a couple of microseconds for the amount of neutrons to double, and the energy released by fission builds up two-fold every few microseconds INSIDE the fuel itself in a (evidently) exponential curve. However, the heat transfer takes much longer, and hence the most important thing to measure is the amount of neutrons being generated at any one given moment. Reactors ´pulse´ continuously between super and subcritical, as you can imagine it´s impossible to keep it stable at say 2,184295 billion trillion neutrons :-) In fact, RBMKs had survived multiple power excursions, because they´re strongly build things and each fuel assembly sits in it´s own ´midget core´ so to speak (hence every channel can be isolated immediately in case of trouble) and this was another ´plus´ for the Soviets that came back to haunt them... All these channels are welded to the upper biological shield, and from 7 channels failing simultaneously at a specific pressure, the lid starts rising and has enough energy to pull open the whole channel-assembly. Since a disaster where 7 channels undergo catastrophic failure at any given time was considered unlikely, since this would be *really* a bad day at work, I suspect Soviet engineers just stock to this semi-modular approach, even if beyond a certain point ´doom accumulation scenarios´ may be looming. The computer is responsible for calculating the amount of ´effectively present control rods´ or ORC if I recall it correctly. The computer had switch out all neutron detectors, detecting only 30MW, suspected to be decay heat. So they always got a ´positive´ reading during the whole buildup to/into the accident. Even worse was the sampling time, which was into the minutes. So regardless of the situation, the situation reported to the operators trough SKALA-computer was outdated by the time it was printed/presented on the panels. Only the direct analog detectors remained,and since there was no direct neutron-counter readout in the control room they were literally operating this thing blindly in the nuclear sense. You gotta read this! Enjoyed this too however :-) www-pub.iaea.org/MTCD/publications/PDF/Pub913e_web.pdf PS. It remains a way too complex matter to effectively distill to the point everybody will understand... Even the operators didn´t understand, and even I broke my head for the last 20 years if if they HAD known what was going on (the operators) if there was a way out... There was not, as the report explains, since they didn´t learn from the operator-mistake made at TMI-2 in 1976.

Wonderful, understandable presentation....Thank you!

Thank you for this vid.

MOAR!!!! Thanks for this!!

Very informative video, thankyou.

the outro had to be the best part

Rbmk was comparatively easier to run and to train operators on. The earlier VVER reactors required intricate switching sequences to keep the water under constant pressure and to remove gases from the coolant. The VVER had a negative void coefficient compared to the positive void coefficient in RBMK, which made catastrophic risk much lower. VVER was basically a scaled up pressurized light water reactor and had inherent safety features but the horizontal arrangement of the steam generators and complex pump systems made getting operators trained to run them difficult.

A very good video!!! Thanks!!!

Good to know the reactors have been upgraded to addresses some of the issues.

Now please explain to me how an RBMK reactor core "explodes", comrade.

Great video - thanks very much.

Nice video my guy

Very well made an explained. Graphite displacers moved back into the reactor first, during normal operation this wouldn't really matter. But because when they hit A3-5 almost all the control rods moved back in at once, the heat and steam pressure caused a series of those channels to rupture as illustrated. Now you have graphite displacers next to graphite neutron moderators. Reactivity went haywire, running away like a runaway diesel until that heat and pressure couldn't be contained anymore. The results of which we're still grappling with today.

Great video.

An amazing video preety much spot on the rbmk. I ve spent countless hours studying the rbmk design and the official accident report. Generally it is a badly regarded reactor because of the accident. The issue is that with any design the moment you deviate from the officially stated operational parameters you risk causing harm. All of the operators knew what had happened...they just did not know it could happen.... And Dyatlov wasn't a mad man as depicted by the hbos miniseries.

The fuel assembly shown at 4:15 is for the CANDU reactor, not RBMK )

Realistically this would have never happened had they either broaught the reactor back up to a higher operating power when the test was delayed to prevent poisoning, or when the reactor fell to critically low power and stalled in a xenon pit, just shut it down and wait for the xenon to decay before restarting. They rushed the unstable reactor because they had no idea about the quirks caused by the positive void reactivity and the operation of the control rods. They also removed nearly all of the control rods, pumps were running a lower pressure , and steam voids were created. There were a lot of things done wrong to cause that accident. Worst yet, as they activated A3-5, there were already ruptured fule rod and control rod chanels, and the rods got jammed.

well done mister!

Some reason I find Chernobyl and SL-1 reactor accidents similar. In both cases the operators were performing assigned task or drills that they seemed to not fully understand the associated risk and dangers.

This was a great video for the knowledge and to top it off crab rave was used as the outro 10/10

Best in the WEST, there's no such type of reactor as "western reactor" RBMK is one of the design which is still being used in Russia alongside light water reactors of VVER series, which are considered "western" after chernobil explosion

So Akimov should've turned the БАЗ switch first, and only after insertion of those turn the АЗ-5? I remember reading about a somewhat similar incident at Leningrad NPP in 1975, where the operator did just that, ending up destroying a single channel and damaging a few others, instead of blowing up the whole reactor like at Chernobyl.

Nice one. Thank You!

Looking back now, many of the scientists and experts, both within and outside of the Soviet Union, all say that the initial design of the RBMK reactor should've _NEVER_ been approved for use in _ANY_ generating station, let alone built or put into service! I'm no expert, but I have to say after viewing all this, I would have to agree with the majority... There are far too many flaws in the design... Far too many parameters that must be monitored and adjusted on a never-ending basis throughout the entire process from reaction control to heated water through the turbine hall, condensers, and finally back to the reactor vessel itself! There's just far too much that could've gone wrong, and actually _DID_ go wrong, especially with that generator power wind down/coolant pump testing that led to the disater... Thank you for this very in-deprh presentation!

Very informative and easy to understand. Well done.

That was excellent. Now do more.👍

excellent video!!!!

Im glad they have imporved the CPS and the other safety features of the RMBK reactors but it should have been done before the disaster

10/10 outro

3:57 Canadians left the video edit: forgot to add: thank you for adding a picture of diablo canyon-the most idyllic plant in existence.

Nice!

Now I know how a reactor works I don’t need you On a serious note it is to my understanding that AZ-5 is the very last resort to emergency shutdown that should have only been used before 4 other actions need be taken

13:00 RIP headphone users.😎 If I understood things correctly the RBMK reactors are not using a heat exchanger to power the turbines instead they use circulated highly radioactive water from the core to power the turbines? Are there any major benefits compared to a pressurized water reactor except lower production cost?

Did every channel with water flowing on it have it's own feed and return pipe? And these must have their own cutoff valves to refuel on the go? What an amazing structure...

Nice vídeo

In RBMK-1500 insertion time of control rods was reduced to 12s due to higher MW(t)[4500-4800MW(t)] power of the reactor than RBMK-1000 [3000-3200 MW(t)]

I cant help but wonder if turning the feed water pumps back on after rather than hitting the shut down would have prevented this horrible disaster?

Great video. Nothing more to say. Just a really great video. :thumbsup:

I believe I have a correction here. Since water has the capacity to absorb and slow down neutrons, the presence of water shall increase the reactivity as the chances of a neutron colliding increases. at 6:16 you mentioned, reactivity increases as water leaves the system.

So was it the radiation that made the crabs dance like that? If so, it seems like that was one positive outcome of the explosion. Seriously, though... great job explaining the RBMK 1000/1500 reactors.

I relly like your video, and how detailed it is, you´ve clearly put a lot of work into this! However, I have a few pet peeves if you´d like - not major concerns, but something that boggles me a bit. For instance, 0.25m X 0.25m is defined as a square. Rectangular shapes does include the squares, but squares are not very often referred to as rectangular, so your reference is quite weird at this point. And I understand that you want to teach me something about a pretty advanced structure, namely a Soviet nuclear reactor. Also, constantly using the SI metre as your basis for all measurements makes me question your qualifications. Any engineer in "the west" would automatically use mm for this purpose in a high tech application as a nuclear reactor clearly is. About positive void coefficient - one western reactor actually operates under this condition - the CanDU - I suspect you also know this, but I think it could easily have been mentioned. However, they have really extensive measures in place to safeguard their operation as they are well aware of the problem. I think the main problem with the RBMK was that it also had a problem with the safety measures. If the RBMK could have been thoroughly scrutinised with the intent of mending all of its safety concerns, they would be perfectly safe to operate even today. Sure, it is a flawed design - but looking back through history, which design hasn´t been flawed? It´s all about how we address the problems and then deal with them, isn´t it? One single thing about your video really provokes me, though! When you imply that the "wrecklessness of the operators" was the main issue, as you continue to tell that other circumstances "also contributed" to the accident, my claim is that you´ve got it all a$$backwards. The operators could never have known about this danger, as every single bit about this construction error was kept from them. None of the operators should ever have been blamed, not even Dyatlov, as none of them could have known. They were all teached and told that these reactors could never fail, and they could always rely on the AZ-5 button to shut the reactor down if that insane case would ever occur. It compares somewhat to you driving your car around. One day, you wanted to stop for a child crossing at a ped-x. Everyone blames you for not engaging the brakes, even though you know you did. Except they didn´t work on that day. The manufacturer knew they wouldn´t work because it was the first tuesday after a full moon, but they didn´t tell anyone. However, they find it convenient to just blame it on you and shut the f up.

This video is perfect, i have been doing research on the chernobyl disaster and this video helped me out, and i'm quite surprised to such low views, Try to post it on r/Chernobyl and the views will go up dramatically

The RBMK (Russian: реа́ктор большо́й мо́щности кана́льный, РБМК; reaktor bolshoy moshchnosti kanalnyy, "high-power channel-type reactor") is a class of graphite-moderated nuclear power reactor designed and built by the Soviet Union. The name refers to its design where, instead of a large steel pressure vessel surrounding the entire core, the core is surrounded by a cylindrical annular steel tank inside a concrete vault and each fuel assembly is enclosed in an individual 8 cm (inner) diameter pipe (called a "technological channel"). The channels also contain the coolant, and are surrounded by graphite. The RBMK is an early Generation II reactor and the oldest commercial reactor design still in wide operation. Certain aspects of the original RBMK reactor design, such as the large positive void coefficient, the 'positive scram effect' of the control rods[3] and instability at low power levels, contributed to the 1986 Chernobyl disaster, in which an RBMK experienced an uncontrolled nuclear chain reaction, leading to a steam and hydrogen explosion, large fire, and subsequent core meltdown. Radioactive material was released over a large portion of Europe. The disaster prompted worldwide calls for the reactors to be completely decommissioned; however, there is still considerable reliance on RBMK facilities for power in Russia. Most of the flaws in the design of RBMK-1000 reactors were corrected after the Chernobyl accident and a dozen reactors have since been operating without any serious incidents for over thirty years.[4] Nine RBMK blocks under construction were cancelled after the Chernobyl disaster, and the last of three remaining RBMK blocks at the Chernobyl Nuclear Power Plant was shut down in 2000. As of February 2024 there are still 7 RBMK reactors and three small EGP-6 graphite moderated light-water reactors operating in Russia.[1][5] All have been retrofitted with a number of safety updates. Only two RBMK blocks were started after 1986: Ignalina-2 and Smolensk-3. History The RBMK was the culmination of the Soviet nuclear power program to produce a water-cooled power reactor with dual-use potential based on their graphite-moderated plutonium production military reactors. The first of these, Obninsk AM-1 ("Атом Мирный", Atom Mirny, Russian for "peaceful atom," analogous to the American Atoms for Peace) generated 5 MW of electricity from 30 MW thermal power, and supplied Obninsk from 1954 until 1959. Subsequent prototypes were the AMB-100 reactor and AMB-200 reactor both at Beloyarsk Nuclear Power Station. By using a minimalist design that used regular (light) water for cooling and graphite for moderation, it was possible to use fuel with a lower enrichment (1.8% enriched uranium instead of considerably more expensive 4% enrichment). This allowed for an extraordinarily large and powerful reactor that could be built rapidly, largely out of parts fabricated on-site instead of by specialized factories. The initial 1000 MWe design also left room for development into yet more powerful reactors. For example, the RBMK reactors at the Ignalina Nuclear Power Plant in Lithuania were rated at 1500 MWe each, a very large size for the time and even for the early 21st century. For comparison, the EPR has a net electric nameplate capacity of 1600 MW (4500 MWthermal) and is among the most powerful reactor types ever built. The RBMK-1000's design was finalized in 1968. At that time it was the world's largest nuclear reactor design, surpassing western designs and the VVER (an earlier Soviet PWR reactor design) in power output and physical size, being 20 times larger by volume than contemporary western reactors. Similarly to CANDU reactors it could be produced without the specialized industry required by the large and thick-walled reactor pressure vessels such as those used by VVER reactors, thus increasing the number of factories capable of manufacturing RBMK reactor components. No prototypes of the RBMK were built; it was put directly into mass production. The RBMK was proclaimed by some as the national reactor of the Soviet Union, probably due to nationalism because of its unique design, large size and power output and especially since the VVER was called the American reactor by its detractors in the Soviet Union, since its design is more similar to that of western PWR reactors. A top-secret invention patent for the RBMK design was filed by Anatoly Aleksandrov from the Kurchatov Institute of Atomic Energy, who personally took credit for the design of the reactor, with the Soviet patent office. Because a containment building would have needed to be very large and expensive, doubling the cost of each unit, due to the large size of the RBMK, it was originally omitted from the design. It was argued by its designers that the RBMK's strategy of having each fuel assembly in its own channel with flowing cooling water, was an acceptable alternative for containment. The RBMK was mainly designed at the Kurchatov Institute of Atomic Energy and NIKIET [ru], headed by Anatoly Aleksandrov and Nikolai Dollezhal respectively, from 1964 to 1966. The RBMK was favored over the VVER by the Soviet Union due to its ease of manufacture, due to a lack of a large and thick-walled reactor pressure vessel and relatively complex associated steam generators, and its large power output, which would allow the Soviet government to easily meet their central economic planning targets.[6] The flaws in the original RBMK design were recognized by others, including from within the Kurchatov Institute before the first units were built, but the orders for construction of the first RBMK units, which were at Leningrad, had already been issued in 1966 by the Soviet government by the time their concerns reached the Central Committee of the Communist Party of the Soviet Union and the Soviet Council of Ministers. This prompted a sudden overhaul of the RBMK. Plutonium production in an RBMK would have been achieved by operating the reactor under special thermal parameters, but this capability was abandoned early on.[7] This was the design that was finalized in 1968. The redesign did not solve further flaws that were not discovered until years later. Construction of the first RBMK, which was at Leningrad Nuclear Power Plant, began in 1970. Leningrad unit 1 opened in 1973. At Leningrad it was discovered that the RBMK, due to its high positive void coefficient, became harder to control as the uranium fuel was consumed or burned up, becoming unpredictable by the time it was shut down after three years for maintenance. This made controlling the RBMK a very laborious, mentally and physically demanding task requiring the timely adjustment of dozens of parameters every minute, around the clock, constantly wearing out switches such as those used for the control rods and causing operators to sweat. The enrichment percentage was increased to 2.0%, up from 1.8% to alleviate these issues. The RBMK was considered by some in the Soviet Union to be already obsolete shortly after the commissioning of Chernobyl unit 1. Aleksandrov and Dollezhal did not investigate further or even deeply understand the problems in the RBMK, and the void coefficient was not analyzed in the manuals for the reactor. Engineers at Chernobyl unit 1 had to create solutions to many of the RBMK's flaws such as a lack of protection against no feedwater supply. Leningrad and Chernobyl units 1 both had partial meltdowns that were treated, alongside other nuclear accidents at power plants, as state secrets and so were unknown even to other workers at those same plants. By 1980 NIKIET realized, after completing a confidential study, that accidents with the RBMK were likely even during normal operation, but no action was taken to correct the RBMK's flaws. Instead, manuals were revised, which was believed to be enough to ensure safe operation as long as they were followed closely. However, the manuals were vague and Soviet power plant staff already had a habit of bending the rules in order to meet economic targets, despite inadequate or malfunctioning equipment. Crucially, it was not made clear that a number of control rods had to stay in the reactor at all times in order to protect against an accident, as loosely articulated by the Operational Reactivity Margin (ORM) parameter.[8] An ORM chart recorder and display were added to RBMK control rooms after the Chernobyl disaster. A 45-year lifetime is envisaged for many of the units, after mid-life refurbishment

finally someone in youtube got it right

11:03 Look up Chernobyl Unit 2, there's images of Unit 2's Reactor Hall

nice

There are other two interesting things not mentioned in video. In rbmk-1000 core, there was an empty space at the bottom. This space was intended to be filled with graphite and control rods. But later it turned out graphite and rods need to be cut shorter, probably to equalize fuel burn. This led to a fact that there was a lot more water at the bottom. Additionally, bottom control rods WERE NOT CONNECTED to the AZ-5 button at the time of disaster (reactors were designed and build in rush because their designers over promised), they were meant to be connected later. This meant that upper rods had to go all the way to the bottom, creating spikes in reactivity, and it took a lot of time, allowing this water at the bottom to boil even more. If the bottom rods were operational, they would stop reactivity at the bottom of the core earlier. When you read about those flaws it's hard to blame mainly dyatlov. Designers such as Dollezhall and Alexandrov that was supervising him, should have gone to jail.

11:45 ..at the time the reactor is already at the critical state.. Actually "critical state" means a completely different thing in the nuclear reactor world: "A critical state reactor is a nuclear reactor that is operating at a steady state, where the number of neutrons being produced is equal to the number being absorbed. This means that the reactor is controlling a self-sustaining fission chain reaction, where each fission event releases enough neutrons to maintain a series of reactions. "

*Watches in PWR operator* Good information that gets glazed over/ignored/misunderstood.

Nice

Great video. But I suggest you to not crop old footage shot in 4:3 ratio to fit a 16:9 frame, leave black bars at the sides if you want, but don't crop the video.

The End Is Just Epic 😂😂😂

I came for the reactor physics, I ended up with a real good video and FUCKING LAUGHING LIKE A MADMAN AT THE END BRAVO.

Bravo for vact💪👌

First of all, nice video. I appreciate your work. Regarding the AZ-5 emergency shutdown button: isn't it the one on the left upper corner instead of the middle one you are showing here? In the various photo's I saw, including those from the control room of reactor 3, the infamous az-5 button is not in the middle. Thanks again!