I watched half this video and feel about ready to fall asleep your visuals are dull and your delivery is plain, incredibly monotone and boring. I will be thumbs down and never wasting my time on any of your work again
Up to 16:00 proper analysis. Then totally bonkers. The radiation caused a particular deformation in children´s hearts dubed the "Chernobyl Heart". Nobody wants to count the real deaths like the suicide squats cleaning the roof therefore they´re excluded and nobody has ever run a real medical evaluation due to tight censorship around the dangers of radioactivity.
As a matter of a fact, the big failure here has been to deactivate half the recirculating pumps, decreasing water to allow the xenon buildup to make the reactor crazy.. This is horrifying.
I have just started watching the video, but if that's what is actually being said, he fell for the Soviet propaganda and gaslighting by Legasov. It has been well established that in order for the printout from the SKALA computer to reach the control room on time it would require the workers to run with literally supersonic speed
This has to be the most comprehensive, laymen explained video of Chernobyl I have ever seen. Well done and I finally understand fully (for the most part) how this accident happened.
@@dachhhit’s abstracted to be able to be simulated in this case. He clearly defines how he added each feature and what caveats it comes with. Halfway through and nothing has been made up Edit: yup, finished the video and this tracks with the events from the reactors perspective albeit again a very simplified model. It’s a python visualization not a fluid sim
@@JeronimoStilton14 no, it doesn't "track". It ignores the most important factor for the majority of the video, and fails to show the actual problem. You're right that its not a sim, its a cartoon.
@@dachhh the most important factor was xenon poisoning, if you’re talking about the geometry of the control rods it really wasn’t relevant to the beginning. If it makes it into the sim then it’s introduction point is really irrelevant lol
Being someone who has studied and has great interest in nuclear physics, as well as working in the nuclear and particle accelerator industry, your reactor simulation is very well made and accurate, whilst being very easy to understand. Great job!
@@peterectasy2957 As far as I understood, water has the ability to moderate the reaction by absorbing or slowing neutrons (not clear which one, but the idea still stands). When the pumps are 50%, water takes more time to cool down, and therefore evaporates faster -> leaving voids. Voids do not have the same moderation properties and thus the positive feedback. I don't know anything about nuclear reactions, it's just what I've figured from the video.
@@peterectasy2957Xenon is a neutron poison because of its large neutron cross section area. Basically, a neutron atom has a huge chance of absorbing stray neutrons which in turn causes the reactivity to go down.
I would totally play a game with these graphics. But perhaps in dark mode instead. This is a fantastic simulation that should be shown to all chemistry and physics students.
It's funny you mention it, I totally regret I made this in Python and not the game engine GODOT. Would have been really fun if it was an interactive game
Oakflat is a great nuke sim I know of. Its not as pretty as this graphic is, but it clues you how to run a reactor after taking time to balance it and work with it.
Or maybe they don't empower your teachers because they don't need 10billion nuclear physicists. As always rulers don't have your best interests at heart.
it probably isnt because he is better at teaching. it probably is because you actually clicked on the video and actually wanna learn this subject. in school you are forcefed knowledge which isnt really that fun or productive or efficient but when you wanna learn something that interests you then you are much more likely to learn and retain the information.
Also don't think this is complex physics either. This is a toy model. That's not to say that models aren't extremely useful and used all the time in the real world. But "complex" goes much much deeper than anyone in youtube can communicate to a general audience.
Please note, I've found sources in the literature saying reactor was going supercritical before pushing the SCRAM button, while other sources claim after SCRAM button was pushed it caused the reactor going supercritical. In my video, Ive assumed the first is true. It's a historical detail (or advanced Nuclear reactor detail) I'm not sure which is correct.
The correct answer is it went supercritical AFTER the button was pushed, the discrepancy is entirely fabricated to downplay just how bad the old reactor was designed and how risky the experiment was that was being performed. While both Western and soviet historians and scientists long accepted it was possible it could have gone supercritical before SCRAM, lately, experiments and a better understanding of physics have shown the SCRAM procedure is needed to push the situation over the edge into supercriticality.
@@BartJBols Exactly, overall, it was a quite good video, but I believe he fell (like many others did) for some Soviet propaganda. Besides this channel I can also recommend another one, called "That Chernobyl Guy", he has been studying the accident for years, debunking Soviet lies and read literally thousands of books by former employees and reactor operators, statements made by nuclear physicists and engineers, blueprints for the Chernobyl plant, and much more. It is a good channel if you want to go down the rabbit hole.
Just a quick note, at 3:23 you wrote control rods submerged out of reactor, and pulled inside reactor. My understanding is you submerge the rod inside of the reactor, and then to heat up, you'd pull the rods out of the reactor. Just making sure I'm reading it correctly
The following day Pravda published an article boasting that one soviet nuclear reactor has managed 2 achieve it monthly power production quota in a few seconds 😉
I also want to point out that given the information the control room staff had, dyatlov included, they did the best they could and their decisions are decisions that, given the same information, I, and I've talked to several plant process engineers who say they, would have made. Additionally the assumption about the control tank was entirely valid as well given the limited information dyatlov had to work with. The criticality happened after the scram. Here was the reasoning. They held the reactor at half power due to grid controller restrictions. So when dyatlov comes in they try to lower power to the testing threshold. However, the power keeps decreasing. So they stabilize it at 200 and start the test. In order to run the test the reactor must be shutdown anyways. This is why it was no deal that they had poison, it would be shutdown regardless, so they continue the test because the outcome is the same. Once the reactor is scrammed the test officially starts. The reasoning behind going ahead at 200 instead of 600 was because if it passed at 200 it would automatically pass at 600, so they might as well try the test anyways. Once they scram the reactor to start the test, THEN it goes supercritical. The super criticality before the scram is a complete fabrication by the Soviets to try to place more blame on the operators and the staff, to make it seem like they made bad decisions. When in actuality they did what any other staff would have done given the same circumstances.
The xenon aspect of reactors is just fundamentally fascinating. The idea that you're generating Xe at the previous rate, and burning it off at the "power now" rate makes it an interesting twist to reactions.
The half-life of Xenon 135 is approximately 9 hours. It was decaying and being burnt off at a faster rate than it could be produced. That is why the reactor should have been switched off and not re-started for at least 3 days.
@@playgroundchooser If you have the time, there is a series of videos covering this very well in the MIT OpenCourseWare channel. Its just a taping of a lecture, but its very good and goes a little more in-depth. This was an excellent visualization and would complement the MIT videos well.
Xenon comes from two sources. Directly from fission, but also from the decay of radioactive iodine. And radioactive iodine comes from fission but decays with a half-life. So when you reduce power, there is still a lot of iodine in the reactor from operating at the high power level. Over a few hours, this iodine continues to decay into xenon. So... even though you've reduced power, xenon is still produced in the reactor at the higher rate for a while. Eventually the iodine concentration drops as it decays, but this can take many hours.
This has to be one of the best explanations and visual effects I’ve seen for explaining how the reactor works and how it failed.
หลายเดือนก่อน +942
Remember, this entire thing happened because they couldn't see what was going on, wanted it to do something, it wasn't working, and their decision was to force it.
@@thegrandpowerchannel314 It was a common issue in the Soviet Union. The Chernobyl Disaster wasn't even the first accident with the RBMK. A similar (complete loss of coolant flow in one part of the reactor due to pump failure) accident caused a partial meldown in a plant near Leningrad all the way back in 1975, but the control rods were inserted early enough that a Chernobyl-level disaster was avoided. In the end, the construction crew was blamed for negligence during construction. Anything suggesting design flaws with the RBMK was covered up. The release of fallout was never reported on, and there wasn't enough for alarming radiation levels to be detected in the West to force the Soviets to admit anything. We only know because of historians taking advantage of public access to Soviet archives while that was possible between the collapse of the USSR and the rise of Putin. Basically, there were very strong incentives for everyone, at every level, to handle everything on their own and report to the bosses that everything is fine. Because if everything turned out fine, and the boss could report to his superiors that everything was fine, they wouldn't care to check anything. While making the government lose face when reality disproves their claims like "Soviet designs are the safest in the world" was an instant, permanent career ender.
"Ridiculously Badly Made Kettle" that should be on a T-shirt, it is brilliant! Fantastic video, I recall trying to model chain reactions for my video critical mass but gave up. Your is just great. And the runaway reaction was the cherry on top. Great video!
I think you made the smart choice not to code this! For me it took waaay too much time. But glad you liked it! thanks a ton :D
หลายเดือนก่อน +4
@@Higgsinophysics I was going to ask you about exactly this. It's hard to make things like this stable - _a lot_ of fiddling with the coefficients like how quickly the water heats and cools, how readily the xenon burns away, and things like that.
yeah that is 100% true. Not only do I have to make the logic and graphics but there is a lot of fiddling as you mention. Actually, I did cheat a bit to get my simulation to match the Chernobyl accident. For example, you can see sometimes the rods move slower. Sometimes the xenon chance is higher. I had to cheat so the simulation didn't have to run for hours
This is the best visualization I’ve seen of this incident. I finally feel like I have a better understanding of what actually happened in the reactor itself. Thanks for this!
Try watching the MIT OpenCourseWare series on Chernobyl. Its a little dry compared to this excellent visualization (its just a series of college lectures), but it goes further in depth and explains it VERY well.
The best made simulation video on the reactor physics of the Chernobyl accident! Subbed. If I may offer a suggestion, I think like the neutron count, a live reading of the Xenon, water and steam values alongside it would help visualizing it even better.
I've read about this accident numerous times for work and grappled with understanding each component of this event. You brought it all together into a simple visualisation. As they say, telling a story simply demonstrates true understanding. Brilliant work.
This is the clearest explanation I've ever seen on Chernobyl. It's really interesting to see all the factors that came into play. Thank you so much for posting this amazing video!
It was very simplified, (and I dont pretend to have a better understanding than our host by a long shot) but the visualization was excellent. MIT put out some fantastic taped lectures on the subject that would be even better if this visualization were incorporated. We live in a wonderful age for information.
This is probably one of the best youtube videos i have seen in my life. And i use youtube for a while now. Seriously the quality is amazing and i've learned quite a lot. Its also a really cool model that lets you get a grasp of the actions happening in each moment. The model was slowly introduced so that every little element was understood before the big model came into place. The graphs where very useful and gave a good overview. I cannot press this enough but i really thank you for this contribution. I loved it
I found this an outstanding portrayal of reactor science. I previously knew enough - Xenon’s effect, control rods tipped with moderator - to put it all together as you progressed. Just exceptional!! Thank you.
Thank you for this. Very fascinating. Pro tip: if you use cards at the end of your video to link to some of your other videos, be sure the last 20 seconds doesn't have any visual content so the cards don't cover it up. I can't see the top half of the Y axis on your death rates chart.
So, the visual simulation is interesting, but it runs the risk of having wildly different time-constants compared to the real-world system. In particular, Xenon burn-off has a time constant several orders-of-magnitude too slow to explain the rapid acceleration in Chernobyl-4's reaction rate. Xenon build-up played a key role in setting up the accident, by getting the operators to remove all but a handful of control rods, and by unbalancing the reaction so that it was proceeding entirely at the top and bottom of the reactor, and was almost totally stalled in the center of the reactor. But Xenon burn-off was NOT an important feedback factor in the reactor's rapid power rise. In addition to the slow time constants included in several simulation papers as well as the INSAG accident reports, it's relatively straight-forward to prove this from first-principles by observing that Xenon's absorption cross-section, of 2 million barns, or 2e-18 cm^2, times the neutron flux of an RBMK-1000, which was, IIRC, on the order of 10^14 /s/cm^2 at full power. So that tells us that at full power, your average Xenon-135 atom is going to take on the order of 500 seconds to absorb a neutron. Even during the transient, at 10X or 100X the normal reactor power, the transient was so rapid that only a small fraction of the Xenon atoms could be expected to burn off. It's a relatively slow feedback factor. Also, the accident can't be properly understood without understanding the role of the asymmetric power distribution prior to the accident. With the middle of the reactor was in the depths of a Xenon pit shut-down, there were really two separate, entirely decoupled reactions, one at the top of the reactor, and the other at the bottom. Thus pushing the control rods further into the middle of the reactor had little effect because the middle of the reactor was already dead, but pushing the graphite segments further down had a very significant effect. The SCRAM effectively shifted reactivity from the dead middle of the reactor to the over-active bottom of the reactor, further accelerating the reaction. Void reactivity was a known consideration to the reactor designers, and RBMK-1000 doesn't have a universally positive void coefficient in all scenarios. In particular the void coefficient is negative early in the fueling cycle and becomes positive later as more fuel is burned up and more control rods have to be removed to maintain reactivity. Chernobyl-4 was late in the fueling cycle, and the Xenon pit caused the operators to pull out even more control rods until the void coefficient became terrifyingly positive. That was a transient property of Chernobyl-4, not a universal condition of the RBMK-1000 in all conditions. One of the mitigations for void reactivity and other positive feedback factors is the even faster negative feedback from doppler broadening as the fuel temperature rises. That's one of the fastest feedback mechanisms and is supposed to help in stabilizing the reactor, but between putting the reactor into a configuration where it had a huge void coefficient, much larger than even a late-cycle RBMK-1000 normally would, and generating an asymmetric reaction that would be pushed over the cliff by the SCRAM event's modest reactivity spatial shift from the dead middle to the overheating bottom, the operators managed to thoroughly overwhelm doppler broadening's ability to limit a rapid transient. Regarding it "going supercritical", what you really mean is prompt thermal supercritical, as being delayed supercritical isn't all that exciting and merely implies that the reactor's power level is increasing, possibly very slowly. When the reaction needs to wait for the slower decay groups to achieve supercriticality, power rises very slowly, with time constants in the tens of seconds. When exceeding a dollar of supercriticality, reaction growth only needs to wait for the next neutron generation, and thing get out of hand very quickly, on the order of 10^-4 seconds, which is still wildly slower than prompt fast supercriticality in a bomb, 10^-8 seconds per generation; even in an out of control Chernobyl-4, the reaction still has to wait for graphite moderation between neutron generations, preventing it from significantly exceeding the level of energy release required to disassemble the reactor. For most of Chernobyl's power transient, it probably wasn't prompt thermal supercritical, and was probably growing at a rate throttled by of one of the fastest two delay groups, but when all the water flashed to steam, things got pretty crazy and none of the papers I've read can agree on the exact course of events. I'm still trying to understand the simulations myself and when exactly they may have reached prompt thermal supercriticality.
The thing also overlooked here (in the simulation) are the graphite followers of the control and protective rods. If they'd been extended all the way to the bottom of the active core, then triggering EPS (aka SCRAM), would have simply let graphite go off from bottom as absorbing elements were inserted. This wasn't the case though, due to building size restrictions (remember the core height of ~7m). Thus, initially water was displaced by graphite at the bottom of the core by falling control rods, leading to pisitive scram effect, I cannot say if this started the power excursion, but at least accelerated. Then further down the few seconds, the positive void coefficient kicks in, coolant tubes rupture and mechanically jam control rods...
It's not a "visual simulation", it's a visual representation of ∑ solutions that stem from physical syntactic observations. Pardon the semantics, because I like the rest of your response.
@@defeatSpace Well, your model is not a solution of the true physically representative partial differential equations. Visually pleasing, yes, nowhere close to even rudimentary understanding of the physical phenomena in play. And if you'd like to split hair, you wouldn't refer to total power or flux as 'reactivity'. Reactivity is a unitless measure that is involved e.g. in the term void coefficient you refer to.
I think once the water flash-boiled, the xenon "burped" out of solution and escaped as gas (under high pressures), by simply venting to atmosphere. The graphite-tips accelerated the rates of thermal neutron production so fast, and the positive void coefficient meant once the steam bubble fraction was high enough, it just over pressurized the vessel and went boom. Then the xenon escaped and it really went boom and melted down. Just a pure, shit design with dumb operators and cockiness about safety.
@@nicklockard the Xenon and other fission gasses didn't mostly escape. Because they were within the fuel-matrix. During power excursion some did escape first to gas gap of the fuel rods, later as the fuel cladding shattered to coolant and out to atmosphere. However, this was insignificant on how the power excursion went. Things had unfolded by that time
Superbly clear, layered explanation. I especially liked the visual presentation of your simulation. Extraordinarily dramatic visualization at the end. Well done, many thanks.
Excellent explanation. I hope many people will appreciate the step by step format you've used here. I hope in another video you will further explain the different types of moderators used in the production of nuclear power, both safe and unsafe. Perhaps also a video on why U235 is only used at a specific percentage for the safety of the reactor. All around great visualization of a horrible tragedy.
My brain doesn't work with numbers at the level that physics needs, so I became an artist. That's part of the reason that seeing this explained in this graphical way actually made it easier for me to fully understand what went wrong. Thanks so much for this! I do want to keep my understanding of the sciences up to a minimal level of competency, and your efforts are greatly appreciated regarding that goal.
This is an absolutely incredible description and demonstration of the errors made! Fantastic video and simulation. Is there a way we can use the simulation ourselves to experiment with?
YES! This is the video I've been searching for! Please do make a video about how negative void coefficient rectors work. For a long time I have been confused on how both types of reactors work and how the Chernobyl accident occurred. Your simulation and explanation finally made it make sense. Thanks!
One small caveat is around 15:40. There was so much heat that the water actually didn’t just evaporate it. Chemically separated the hydrogen and oxygen apart from each other. Then there was so much heat in the reactor that it had a hydrogen explosion.
That is... horrifying, it's like a lithium battery failure on steroids. Thankfully bad designs like this have long since taught us how to build far safer reactors
There were two explosions, first a steam explosion and then a more powerful hydrogen explosion. Heat alone doesn't separate water into hydrogen and oxygen. Even if that were the case, the splitting of the water would require as much energy as the later recombination during the explosion would produce: 2 · H2O -> 2 · H2 + O2 requires as much energy as 2 · H2 + O2 -> 2 · H2O produces. There is thus no amplification of energy and no explosion. What actually happened was the reaction of steam with graphite or zirconium fuel cladding: C + 2 · H2O -> CO2 + 2 · H2 Zr + 2 · H2O -> ZrO2 + 2 · H2 Now this produces only hydrogen and no oxygen, pure hydrogen is not explosive. Thus it can only explode AFTER the pressure channels have already ruptured and it mixes with air. Or in the case of Fukushima: The steam reacted with the zirconium for a longer time at much lower temperatures and pressures. Because hydrogen is hard to contain it escaped the pressure vessel and accumulated slowly in the primary containment, mixing with air. Then it exploded.
I could be alone on this, but I kinda wanna play this simulation as some form of a puzzle game -- different reactor designs and you have to not go into a meltdown while trying to match power demand and fix issues that pop up.
To my understanding, it wasn't the chain reaction that caused the explosion, but the buildup in steam pressure that caused the lid to blow, then when oxygen(from the air) entered the reactor, it caused a secondary explosion. The Illinois Energy Professor has a great video on how the steam pressure built up when the Scram button was pressed. He explained that the chain reaction from the spike in power superheated the graphite tips and they were then being lowered for the boron control rods to lower back into the reactor the superheated graphite came into contact with the water supply instantly vaporizing all the water, causing the pressure to build, leading to the subsequent explosions.
Yes, all explosions in nuclear reactors are either pressure or chemical related, reactor it self cant really explode like nuclear bomb which is big missconception people have as they are not made for rapid energy relese as bomb is, it can only out of control and melt (thats why its called meltdown) creating hazard that melts to ground and any extra explosions cause exposure of radioactive material to atmosphere.
If someone dies in a house fire because of smoke inhalation, would you say that the fire was not the cause of their death? It may not have been the direct cause but the connection between the fire and the smoke is so tight most wouldn't state the difference. When people say that it wasn't a nuclear explosion they mean something different. An explosion is a shock wave. In a steam explosion the shock wave is caused by the pressure vessel bursting. In a true nuclear explosion the reaction rate goes up so fast that there is an intrinsic shock wave as the neutrons propagate trough the material.
The thing with the superheated graphite sounds like you don't quite recall it correctly. The usage of the term superheated is wrong (it refers to liquids or vapors but not to solids). Also whenever water "instantly vaporizes" it must have been above the boiling point and suddenly lost pressure. There is no way to heat something above its boiling point anywhere close to instantly by touching it with something hot. What actually happened after AZ5 was pressed: 1) Chain reaction runaway causes rapid rise in temperature 2) Rise in temperature causes rise in pressure, bursting the vessel 3) Burst vessel causes rapid loss in pressure and causes water to flash into superheated steam (steam explosion) 4) Superheated steam comes in contact with graphite (or zirconium) and produces hydrogen 5) Hydrogen mixes with ambient air and ignites (hydrogen explosion)
@@entcraft44 i never claimed the steam went above the boiling point just that the tips of the control rods weren't boron and the water supply entered from the bottom so when the heated graphite rods "tips" came into contact with the actual water supply, that caused significant amounts to vaporize and cause the steam explosion. Like I mentioned, go check out the Illinois energy professors videos on chernobyl. Extremely informative and well done.
@@walterp1028 And I never claimed you claimed... No need to get defensive. I did watch his video now and unless he has a second video about Chernobyl that I can't find: you misremember what he said. And again: It is impossible for significant amounts of water to vaporize because they are being suddenly touched by a hot object. I am no professor but in this I am certain.
Thank you for making the huge effort of explaining this to a person who doesn’t know anything about nuclear reactions, but loves to dive into the unknown to try to understand how disasters happened 😊
Human error, the fact that this rundown test must be done is the main factor for this disaster. It was the Russian culture at that time, the inability to be able to question authority is and will be the making of a disaster again.
It was certainly human error, but that's also in part due to them not fully knowing how the reactor worked. IIRC the regulations stated they were to never fully raise the control rods, but a reason was never given. It's easy to imagine that they thought AZ-5 could get them out of virtually any situation, which makes it easier to understand some of the decisions they made.
@@xIcarus227 I think the reason for raising all the control rods was because the reactor had stalled. Who did it, who forced them to do or threatened them is kinda my point, human error. I honestly think they understood what could happen but they did not foresee everything. The Rundown Test must be Done!.. it is all very sad when you think of a working culture like that. I worked through the 70’s and 80’s with bosses from the European block. They did think differently than people from the West.
@@repozitory look it up, both have a containment aspect, part of the RBMK was the actual lid as it was extremely heavy, in Japan the earthquake and subsequent tsunami far exceeded the design parameters of the plant, I also cannot figure out why their backup generators were below sea level. Both are great studies for nuclear plant engineering. Keep in mind, one was caused by a natural disaster, the other was a human disaster in the making.
I would really enjoy seeing a simulation of a different design, like what you mentioned at the end, a design with a negative void coefficient. Very interesting video!
Your simulation is spot on. Having been quite interested in the Chernobyl incident for a long time and having watched both documentaries and the series on Chernobyl, I must say this video explained the accident way better than them all. Also being a Physics Major myself, I must say we need more simulations like this that are precise and explain the point way batter than any book or image. This is a really well done video and I'm happy it came in my feed.
Thank you! I used Manim with a Verlet integration for the physics solver. It's stitched together by me and sadly not available. Mostly because right now the code is confusing and poorly structured. It could be really fun to release of others found it useful though.
@@Higgsinophysics would be interesting to see someone recreate the mechanics involved here in Godot or similar, let people mess around with various reactor designs and get a feel for how they've changed over tge years
Hello. A little audio advice: apply an audio compressor plugin to your speech track, it'll make your voice sound more evenly and professionally. Also move away a bit from mic, you have a condenser mic I suppose, they are very sensitive and sound best on some range.
You know audio? I have a question. I have a Blue Yeti microphone. It sounds the best with the "heart-shaped" setting. 1) do you even know what my shitty explanation is referring to? 🤨 2) what's happening on that setting? 🤔
Beautifully made, very clear. I seem to recall the TV miniseries also explained it in the final episode, though without the graphics and simulation you use to really drive the point home.
Completely underrated question, as Dyatlov himself considered it one of the main issues of the RBMK in his book. The positive void coefficient is (obviously) very dangerous, as it allows the positive feedback cycle to keep going. Answering your question, the design of the reactive zone itself (e.g. the distance between rods) defines, whether the reactor will have positive or negative void coefficient, and it cannot be changed since it's built. Also I'd like to mention that Dyatlov personality is now considered diabolical in western countries due to lack of translated information and influence of the HBO series, which is sad.
Water acts as a neutron moderator, which increases reactivity. Thus steam bubbles decrease it (negative void coefficient) Water also acts as a neutron absorber, which decreases reactivity. Thus steam bubbles increase reactivity (positive void coefficient) As AN1Kl said, which effect is dominant depends on the design of the reactor, namely which other materials are also present and where. Compared to water graphite is a slightly worse moderator and a much worse absorber. Thus in the presence of a lot of graphite the neutrons are already well moderated and the positive contribution to the void coefficient is dominant. Also, it is not quite true that the void coefficient can not be changed after building the reactor, at least for the RBMK which is a pretty flexible design. In the aftermath to the accident, fuel enrichment was increased and additional absorbers installed. (This of course increased the fuel costs, which is why they haven't done it before.) These changes do change the material in the core and therefore the void coefficient.
Great explanation. The Chernobyl series was very hard to watch not for lack of having to sit on the edge of my seat the entire time but because of the sheer devastation that took place.
Today all this is taught in school, but back then: a) they didn't know about positive reactivity b) they were a research team c) it was 1986, nuclear reactors were a cutting edge of science d) they had a plan, but no idea what they were doing, control equipment didn't give them full picture, because it just didn't exist at the time -- and actually this exact catastrophe gave an idea what controlling equipment is required, so even a failed experiment was an experience and led to increase of reactor safety worldwide e) "computer" mentioned in the video was a calculator in modern terms, it was giving print outs twice per hour at best So no need to be emotional here, they simply did a test and failed. The rest of the drama and "conclusions" is seemingly based on tv show, not reality. Luckily in the real accident not many people have died, unlike the tv show. Many RBMK1000 reactors worked for decades after Chernobyl without issues.
a) Wrong. The designers absolutely did know about the positive void coefficient of reactivity. They (as in the designers, NOT the operators) also knew that the reactor could be unstable because of this. In fact they increased enrichment from 1.8% to 2.0% to battle this instability BEFORE Chernobyl happened. They increased it again after the accident to 2.4% because 2.0% still wasn't enough. The reason for using low enrichment is that it is cheaper. b) True. (Who is they? I assume those who designed the test) c) True. d) True, but... While they had little idea what *was* happening because of the limited instrumentation; the reason they had little idea of what *could* happen is that the design was a secret and concerns, prior accidents and the like were suppressed by the soviet union's system. e) Exaggerated. The computer calculated the ORM every 15 minutes. It also ran another program which recorded hundreds of data points every second.
So my question is was the efforts and deaths of the “containment” crews worth the effort? In other words, how would the outcome have been different if everyone just ran for the hills instead of intervening?
1:00 Chernobyl and RBMK reactors used actually very low enriched uranium, which explains their size, unenriched uranium has very little of uranium-235 so we need alot of unenriched uranium in one place to fission
Came across this today. Thanks for all the time you took to create this video and explaining it to everyone. As long as it was physics and simulation it looks beautiful, but its association to reality is what makes it scary and horrifying at the same time…
WOW, fantastic work with the simulation! I admit I'm a bit slow with the pickup on chemistry and physics sometimes, but this was wonderfully clear and I understood everything perfectly. Held my 2am adhd attention the whole time too. Totally fascinating
Hi! This was such a fascinating video to watch! I randomly saw this in my feed, and now I'm going to learn more about nuclear physics and the history of Chernobyl, thanks! Just one small thing, the graph at the end ( 16:28 ) is partially covered by the next watch recommendation. Looking forward to seeing more of your videos, subscribed!
Love the visualization, so well implemented and explained! If each of them had watched this 15-minute video before the day of test and had this picture in front of their eyes, I think they would not have made those mistakes.
Really excellent job! It's truly incredible that you built a model on such a small, visual scale that can still effectively convey the concepts happening. I'm sure you had to do a ton of tweaking on the parameters. Truly remarkable, and your visualization and communication is equally impressive. Excellent work.
I don't use commercial sponsors. Let's keep it that way. Support here:
Per video: www.patreon.com/Higgsino
One time: ko-fi.com/higgsino
I watched half this video and feel about ready to fall asleep your visuals are dull and your delivery is plain, incredibly monotone and boring. I will be thumbs down and never wasting my time on any of your work again
100,000% ???
well that is a new one. source?
Up to 16:00 proper analysis. Then totally bonkers. The radiation caused a particular deformation in children´s hearts dubed the "Chernobyl Heart". Nobody wants to count the real deaths like the suicide squats cleaning the roof therefore they´re excluded and nobody has ever run a real medical evaluation due to tight censorship around the dangers of radioactivity.
what program/tool did you use for the visualization?
@@LordKossity this app is really cool , I will build one my self , a simple priority queue and a memory pool writen in c++ will do
"The computer told them to turn off the reactor. They turned off the computer instead." Those words are equally funny as they are horrifying.
As a matter of a fact, the big failure here has been to deactivate half the recirculating pumps, decreasing water to allow the xenon buildup to make the reactor crazy..
This is horrifying.
Sounds pretty much like safety culture in my country.
@@manabellumrip
Nice way to put it (I'm an Indian)@@manabellum
I have just started watching the video, but if that's what is actually being said, he fell for the Soviet propaganda and gaslighting by Legasov. It has been well established that in order for the printout from the SKALA computer to reach the control room on time it would require the workers to run with literally supersonic speed
The particle climax is like something out of an indie horror game.
Satisfyingly terrifying. Or terrifyingly satisfying.
I guess it kinda is, technically lol.
Nah bro thats literally the most horrifying part of a real life documentary right there.
@@alexanderlevy158 No shit?
higgs spotted 🫵
This has to be the most comprehensive, laymen explained video of Chernobyl I have ever seen. Well done and I finally understand fully (for the most part) how this accident happened.
That chernobyl guy has a 2 or 3 part Series about how it happened that's really good to
Its also wrong, and mostly just made up.
@@dachhhit’s abstracted to be able to be simulated in this case. He clearly defines how he added each feature and what caveats it comes with. Halfway through and nothing has been made up
Edit: yup, finished the video and this tracks with the events from the reactors perspective albeit again a very simplified model. It’s a python visualization not a fluid sim
@@JeronimoStilton14 no, it doesn't "track". It ignores the most important factor for the majority of the video, and fails to show the actual problem. You're right that its not a sim, its a cartoon.
@@dachhh the most important factor was xenon poisoning, if you’re talking about the geometry of the control rods it really wasn’t relevant to the beginning. If it makes it into the sim then it’s introduction point is really irrelevant lol
The amalgamation of a laundry list of mistakes all climaxing by 15:08 is absolutely chilling.
😮
I felt chills at the climax. The video itself was that good!
This is a W for TH-cam recommendations. I criticize TH-cam recommendations a lot, but I have to give it credit when it recommends something like this.
All DEI hires!
The runaway reaction at 15:09 was very very satisfying after all that buildup.
Glad you liked it Bjartur! Thank you :D
Satisfying? I found it terrifying!
Lol i gotta agree, as amazing as this video is, that chain reaction gets my hairs up lol that was HORRIfying
Satisfyingly scary!!!!
It sounds like all my skin get covered by angry ants running around, its a HORROR sound!
Being someone who has studied and has great interest in nuclear physics, as well as working in the nuclear and particle accelerator industry, your reactor simulation is very well made and accurate, whilst being very easy to understand. Great job!
they should explain why more xenon is burn when water si small
@@peterectasy2957 As far as I understood, water has the ability to moderate the reaction by absorbing or slowing neutrons (not clear which one, but the idea still stands). When the pumps are 50%, water takes more time to cool down, and therefore evaporates faster -> leaving voids. Voids do not have the same moderation properties and thus the positive feedback.
I don't know anything about nuclear reactions, it's just what I've figured from the video.
@@peterectasy2957Xenon is a neutron poison because of its large neutron cross section area.
Basically, a neutron atom has a huge chance of absorbing stray neutrons which in turn causes the reactivity to go down.
@@peterectasy2957 When there is less water the neutrons don't get stopped as often by the water and thus can impact the Xenon even more.
@@peterectasy2957more water means less xenon burned, less water means more xenon burned. If both are burned, there's no stopping the reactor.
I would totally play a game with these graphics. But perhaps in dark mode instead. This is a fantastic simulation that should be shown to all chemistry and physics students.
It's funny you mention it, I totally regret I made this in Python and not the game engine GODOT. Would have been really fun if it was an interactive game
I really like the selected font, I'm like reading science publication but its animated.
Oakflat is a great nuke sim I know of. Its not as pretty as this graphic is, but it clues you how to run a reactor after taking time to balance it and work with it.
>GODOT comment aged somewhat poorly relatively quickly lol. @@Higgsinophysics
@@AWaifuInVR what did I miss?
watching as the neutrons went from 50 to 2500 in such a quick manner even though this was suposed to be slowed down by alot sent chills down my spine.
This is slowed down SO much. Actual prompt criticality is more like microseconds I believe.
And it's reached 30,000 only a couple seconds later😬
Moral of the story.... Don't get your rod stuck in the wrong place.
Nice 👌🏻 😂
You win
* Cylinder.
No Diddy
The physics side of me is mad but the immature teenage boy is laughing with a half life of 705 million years
Weird, how a guy on TH-cam with 20000 followers is better at teaching high complex physics, than almost every teacher I had ....
Or maybe they don't empower your teachers because they don't need 10billion nuclear physicists. As always rulers don't have your best interests at heart.
This guy is harnessing the power of Python!
it probably isnt because he is better at teaching. it probably is because you actually clicked on the video and actually wanna learn this subject. in school you are forcefed knowledge which isnt really that fun or productive or efficient but when you wanna learn something that interests you then you are much more likely to learn and retain the information.
Teachers want their salary. You forced to learn.
Guy on TH-cam with 20000 followers want to explain some thing. You want to learn some thing.
Also don't think this is complex physics either. This is a toy model. That's not to say that models aren't extremely useful and used all the time in the real world. But "complex" goes much much deeper than anyone in youtube can communicate to a general audience.
Please note, I've found sources in the literature saying reactor was going supercritical before pushing the SCRAM button, while other sources claim after SCRAM button was pushed it caused the reactor going supercritical. In my video, Ive assumed the first is true. It's a historical detail (or advanced Nuclear reactor detail) I'm not sure which is correct.
The correct answer is it went supercritical AFTER the button was pushed, the discrepancy is entirely fabricated to downplay just how bad the old reactor was designed and how risky the experiment was that was being performed. While both Western and soviet historians and scientists long accepted it was possible it could have gone supercritical before SCRAM, lately, experiments and a better understanding of physics have shown the SCRAM procedure is needed to push the situation over the edge into supercriticality.
@@BartJBols Exactly, overall, it was a quite good video, but I believe he fell (like many others did) for some Soviet propaganda. Besides this channel I can also recommend another one, called "That Chernobyl Guy", he has been studying the accident for years, debunking Soviet lies and read literally thousands of books by former employees and reactor operators, statements made by nuclear physicists and engineers, blueprints for the Chernobyl plant, and much more.
It is a good channel if you want to go down the rabbit hole.
Just a quick note, at 3:23 you wrote control rods submerged out of reactor, and pulled inside reactor.
My understanding is you submerge the rod inside of the reactor, and then to heat up, you'd pull the rods out of the reactor. Just making sure I'm reading it correctly
The following day Pravda published an article boasting that one soviet nuclear reactor has managed 2 achieve it monthly power production quota in a few seconds 😉
I also want to point out that given the information the control room staff had, dyatlov included, they did the best they could and their decisions are decisions that, given the same information, I, and I've talked to several plant process engineers who say they, would have made. Additionally the assumption about the control tank was entirely valid as well given the limited information dyatlov had to work with.
The criticality happened after the scram. Here was the reasoning. They held the reactor at half power due to grid controller restrictions. So when dyatlov comes in they try to lower power to the testing threshold. However, the power keeps decreasing. So they stabilize it at 200 and start the test. In order to run the test the reactor must be shutdown anyways. This is why it was no deal that they had poison, it would be shutdown regardless, so they continue the test because the outcome is the same. Once the reactor is scrammed the test officially starts. The reasoning behind going ahead at 200 instead of 600 was because if it passed at 200 it would automatically pass at 600, so they might as well try the test anyways. Once they scram the reactor to start the test, THEN it goes supercritical. The super criticality before the scram is a complete fabrication by the Soviets to try to place more blame on the operators and the staff, to make it seem like they made bad decisions. When in actuality they did what any other staff would have done given the same circumstances.
I appreciate you changing the inaccurate thumbnail.
Yo Kyle I binged your HLH series and came here to watch this fantastic presentation!
@@HominisLupis1day on 2week comment
@@RADICALFLOAT_951 day on 1 day on 2 week comment
What was the thumbnail?
@@danielle3064 barrels of green goo
The xenon aspect of reactors is just fundamentally fascinating. The idea that you're generating Xe at the previous rate, and burning it off at the "power now" rate makes it an interesting twist to reactions.
The half-life of Xenon 135 is approximately 9 hours. It was decaying and being burnt off at a faster rate than it could be produced. That is why the reactor should have been switched off and not re-started for at least 3 days.
I never understood why that was a problem until this video. It seems so obvious now!
@@playgroundchooser If you have the time, there is a series of videos covering this very well in the MIT OpenCourseWare channel. Its just a taping of a lecture, but its very good and goes a little more in-depth. This was an excellent visualization and would complement the MIT videos well.
its called Xenon poisoning.
Xenon comes from two sources. Directly from fission, but also from the decay of radioactive iodine. And radioactive iodine comes from fission but decays with a half-life. So when you reduce power, there is still a lot of iodine in the reactor from operating at the high power level. Over a few hours, this iodine continues to decay into xenon. So... even though you've reduced power, xenon is still produced in the reactor at the higher rate for a while. Eventually the iodine concentration drops as it decays, but this can take many hours.
This has to be one of the best explanations and visual effects I’ve seen for explaining how the reactor works and how it failed.
Remember, this entire thing happened because they couldn't see what was going on, wanted it to do something, it wasn't working, and their decision was to force it.
I think it was mostly caused by a lag in the xenon burn off, they just waited too long to put the rods back in
@@Lagger_94They disregard safety to rush the test. Not because safety tests are important - the paper saying "the safety test was sucessful" is
@@Carlos-ux7gvHmmm, disregarding safety protocols? Pushing the test? Man, this is some Black Mesa type of shit
@@thegrandpowerchannel314 It was a common issue in the Soviet Union. The Chernobyl Disaster wasn't even the first accident with the RBMK. A similar (complete loss of coolant flow in one part of the reactor due to pump failure) accident caused a partial meldown in a plant near Leningrad all the way back in 1975, but the control rods were inserted early enough that a Chernobyl-level disaster was avoided. In the end, the construction crew was blamed for negligence during construction. Anything suggesting design flaws with the RBMK was covered up. The release of fallout was never reported on, and there wasn't enough for alarming radiation levels to be detected in the West to force the Soviets to admit anything. We only know because of historians taking advantage of public access to Soviet archives while that was possible between the collapse of the USSR and the rise of Putin.
Basically, there were very strong incentives for everyone, at every level, to handle everything on their own and report to the bosses that everything is fine. Because if everything turned out fine, and the boss could report to his superiors that everything was fine, they wouldn't care to check anything. While making the government lose face when reality disproves their claims like "Soviet designs are the safest in the world" was an instant, permanent career ender.
Sounds like typical socialist behavior
the sound when big numbers go up is haunting with the right context
Man the last simulation when the Graphite moderation rods were stuck was an ABSOLUTE SCENE OF TERROR
Anyone that gets me to watch 15+ minutes while holding my interest earns my sub. Looking forward to learning more.
Spot on - I've also subbed!
Spot on - I've also subbed (after reading and realising this lmao)!
Yikes. Pretty low bar! 😕
Tell me what subjects you like, and I'll help you find some attention-holding channels. :)
Pretty sad that it takes so much effort to hold your short attention span
@@B3Band not sad imo
"Ridiculously Badly Made Kettle" that should be on a T-shirt, it is brilliant!
Fantastic video, I recall trying to model chain reactions for my video critical mass but gave up. Your is just great. And the runaway reaction was the cherry on top. Great video!
I think you made the smart choice not to code this! For me it took waaay too much time. But glad you liked it! thanks a ton :D
@@Higgsinophysics I was going to ask you about exactly this. It's hard to make things like this stable - _a lot_ of fiddling with the coefficients like how quickly the water heats and cools, how readily the xenon burns away, and things like that.
yeah that is 100% true. Not only do I have to make the logic and graphics but there is a lot of fiddling as you mention.
Actually, I did cheat a bit to get my simulation to match the Chernobyl accident. For example, you can see sometimes the rods move slower. Sometimes the xenon chance is higher. I had to cheat so the simulation didn't have to run for hours
0:51 "I'll assume you are lazy" you are correct sir
16:20 "please tell me how an RBMK reactor core explodes." to "please tell me how a reactor core with a negative void coefficient explodes."
someone already figured out how it could explode but it wasn’t published because of the Soviets. With free information it will be fine.
This is the best visualization I’ve seen of this incident. I finally feel like I have a better understanding of what actually happened in the reactor itself. Thanks for this!
Try watching the MIT OpenCourseWare series on Chernobyl. Its a little dry compared to this excellent visualization (its just a series of college lectures), but it goes further in depth and explains it VERY well.
Really great video! Loved all the animations and the build up with each one. The final runaway reaction was well worth the wait.
Glad you liked it! My bad code was running at around 1/5 seconds per frame with 40 neutrons, and around 2 minutes per frame at 20.000 neutrons :D
The pacing was perfect and I feel like I learned so much in such little time, amazing work
You explained positive void coefficient and moderation in a way I never understood before. Thank you! Keep making videos please.
The best made simulation video on the reactor physics of the Chernobyl accident! Subbed. If I may offer a suggestion, I think like the neutron count, a live reading of the Xenon, water and steam values alongside it would help visualizing it even better.
That's a great suggestion actually. I wish I had implemented that. Glad you liked the video.
So at how many other simulations did you look and how was this one better?
I've read about this accident numerous times for work and grappled with understanding each component of this event. You brought it all together into a simple visualisation. As they say, telling a story simply demonstrates true understanding. Brilliant work.
This is the clearest explanation I've ever seen on Chernobyl. It's really interesting to see all the factors that came into play. Thank you so much for posting this amazing video!
It was very simplified, (and I dont pretend to have a better understanding than our host by a long shot) but the visualization was excellent. MIT put out some fantastic taped lectures on the subject that would be even better if this visualization were incorporated.
We live in a wonderful age for information.
This is hands down one of the best science videos I have seen on TH-cam. Great job!
This is probably one of the best youtube videos i have seen in my life. And i use youtube for a while now. Seriously the quality is amazing and i've learned quite a lot. Its also a really cool model that lets you get a grasp of the actions happening in each moment. The model was slowly introduced so that every little element was understood before the big model came into place. The graphs where very useful and gave a good overview. I cannot press this enough but i really thank you for this contribution. I loved it
I found this an outstanding portrayal of reactor science. I previously knew enough - Xenon’s effect, control rods tipped with moderator - to put it all together as you progressed. Just exceptional!! Thank you.
Dude the simulation video concept is dope. Looking forward to more please
After watching all Chernobyl explanied videos, I'm happy to report that "Now I'm a NewClear Scientist"
For me, after watching, I still know more about concrete.
In Omer Simpson's voice : It's pronounced "nucular"
@@JoffreyTyrion 😮😮😮😮
after watching 2 videos and one short about RBMK reactors, i can confirm i have the same operating capacity as the operators who handled reactor 4
@@atmosphereventbutton please stay away from me!!! Oooohhh nooo my life is in danger 😂😂😂
Thank you for this. Very fascinating.
Pro tip: if you use cards at the end of your video to link to some of your other videos, be sure the last 20 seconds doesn't have any visual content so the cards don't cover it up. I can't see the top half of the Y axis on your death rates chart.
So, the visual simulation is interesting, but it runs the risk of having wildly different time-constants compared to the real-world system. In particular, Xenon burn-off has a time constant several orders-of-magnitude too slow to explain the rapid acceleration in Chernobyl-4's reaction rate. Xenon build-up played a key role in setting up the accident, by getting the operators to remove all but a handful of control rods, and by unbalancing the reaction so that it was proceeding entirely at the top and bottom of the reactor, and was almost totally stalled in the center of the reactor. But Xenon burn-off was NOT an important feedback factor in the reactor's rapid power rise. In addition to the slow time constants included in several simulation papers as well as the INSAG accident reports, it's relatively straight-forward to prove this from first-principles by observing that Xenon's absorption cross-section, of 2 million barns, or 2e-18 cm^2, times the neutron flux of an RBMK-1000, which was, IIRC, on the order of 10^14 /s/cm^2 at full power. So that tells us that at full power, your average Xenon-135 atom is going to take on the order of 500 seconds to absorb a neutron. Even during the transient, at 10X or 100X the normal reactor power, the transient was so rapid that only a small fraction of the Xenon atoms could be expected to burn off. It's a relatively slow feedback factor.
Also, the accident can't be properly understood without understanding the role of the asymmetric power distribution prior to the accident. With the middle of the reactor was in the depths of a Xenon pit shut-down, there were really two separate, entirely decoupled reactions, one at the top of the reactor, and the other at the bottom. Thus pushing the control rods further into the middle of the reactor had little effect because the middle of the reactor was already dead, but pushing the graphite segments further down had a very significant effect. The SCRAM effectively shifted reactivity from the dead middle of the reactor to the over-active bottom of the reactor, further accelerating the reaction.
Void reactivity was a known consideration to the reactor designers, and RBMK-1000 doesn't have a universally positive void coefficient in all scenarios. In particular the void coefficient is negative early in the fueling cycle and becomes positive later as more fuel is burned up and more control rods have to be removed to maintain reactivity. Chernobyl-4 was late in the fueling cycle, and the Xenon pit caused the operators to pull out even more control rods until the void coefficient became terrifyingly positive. That was a transient property of Chernobyl-4, not a universal condition of the RBMK-1000 in all conditions.
One of the mitigations for void reactivity and other positive feedback factors is the even faster negative feedback from doppler broadening as the fuel temperature rises. That's one of the fastest feedback mechanisms and is supposed to help in stabilizing the reactor, but between putting the reactor into a configuration where it had a huge void coefficient, much larger than even a late-cycle RBMK-1000 normally would, and generating an asymmetric reaction that would be pushed over the cliff by the SCRAM event's modest reactivity spatial shift from the dead middle to the overheating bottom, the operators managed to thoroughly overwhelm doppler broadening's ability to limit a rapid transient.
Regarding it "going supercritical", what you really mean is prompt thermal supercritical, as being delayed supercritical isn't all that exciting and merely implies that the reactor's power level is increasing, possibly very slowly. When the reaction needs to wait for the slower decay groups to achieve supercriticality, power rises very slowly, with time constants in the tens of seconds. When exceeding a dollar of supercriticality, reaction growth only needs to wait for the next neutron generation, and thing get out of hand very quickly, on the order of 10^-4 seconds, which is still wildly slower than prompt fast supercriticality in a bomb, 10^-8 seconds per generation; even in an out of control Chernobyl-4, the reaction still has to wait for graphite moderation between neutron generations, preventing it from significantly exceeding the level of energy release required to disassemble the reactor. For most of Chernobyl's power transient, it probably wasn't prompt thermal supercritical, and was probably growing at a rate throttled by of one of the fastest two delay groups, but when all the water flashed to steam, things got pretty crazy and none of the papers I've read can agree on the exact course of events. I'm still trying to understand the simulations myself and when exactly they may have reached prompt thermal supercriticality.
The thing also overlooked here (in the simulation) are the graphite followers of the control and protective rods. If they'd been extended all the way to the bottom of the active core, then triggering EPS (aka SCRAM), would have simply let graphite go off from bottom as absorbing elements were inserted. This wasn't the case though, due to building size restrictions (remember the core height of ~7m). Thus, initially water was displaced by graphite at the bottom of the core by falling control rods, leading to pisitive scram effect,
I cannot say if this started the power excursion, but at least accelerated. Then further down the few seconds, the positive void coefficient kicks in, coolant tubes rupture and mechanically jam control rods...
It's not a "visual simulation", it's a visual representation of ∑ solutions that stem from physical syntactic observations. Pardon the semantics, because I like the rest of your response.
@@defeatSpace Well, your model is not a solution of the true physically representative partial differential equations. Visually pleasing, yes, nowhere close to even rudimentary understanding of the physical phenomena in play.
And if you'd like to split hair, you wouldn't refer to total power or flux as 'reactivity'. Reactivity is a unitless measure that is involved e.g. in the term void coefficient you refer to.
I think once the water flash-boiled, the xenon "burped" out of solution and escaped as gas (under high pressures), by simply venting to atmosphere. The graphite-tips accelerated the rates of thermal neutron production so fast, and the positive void coefficient meant once the steam bubble fraction was high enough, it just over pressurized the vessel and went boom. Then the xenon escaped and it really went boom and melted down. Just a pure, shit design with dumb operators and cockiness about safety.
@@nicklockard the Xenon and other fission gasses didn't mostly escape. Because they were within the fuel-matrix. During power excursion some did escape first to gas gap of the fuel rods, later as the fuel cladding shattered to coolant and out to atmosphere. However, this was insignificant on how the power excursion went. Things had unfolded by that time
Superbly clear, layered explanation. I especially liked the visual presentation of your simulation. Extraordinarily dramatic visualization at the end. Well done, many thanks.
man, this is so beautifully explained! your channel deserves an order of magnitude more subs
Excellent explanation. I hope many people will appreciate the step by step format you've used here.
I hope in another video you will further explain the different types of moderators used in the production of nuclear power, both safe and unsafe. Perhaps also a video on why U235 is only used at a specific percentage for the safety of the reactor.
All around great visualization of a horrible tragedy.
2:16 I’m already confused because I’m not smart but I’m gonna keep watching, I’m interested.
Very underrated channel. Great video!
thanks a lot :D
Dude. This is awesome. Never seen a simulation on nuclear physics that's as easy to understand as this is. Great idea for a video and well done, sir.
I could fall asleep to those crackling and tinking noises. Awesome video.
'till the whole thing explodes...
My brain doesn't work with numbers at the level that physics needs, so I became an artist. That's part of the reason that seeing this explained in this graphical way actually made it easier for me to fully understand what went wrong. Thanks so much for this! I do want to keep my understanding of the sciences up to a minimal level of competency, and your efforts are greatly appreciated regarding that goal.
This is an absolutely incredible description and demonstration of the errors made! Fantastic video and simulation. Is there a way we can use the simulation ourselves to experiment with?
YES! This is the video I've been searching for! Please do make a video about how negative void coefficient rectors work. For a long time I have been confused on how both types of reactors work and how the Chernobyl accident occurred. Your simulation and explanation finally made it make sense. Thanks!
One small caveat is around 15:40. There was so much heat that the water actually didn’t just evaporate it. Chemically separated the hydrogen and oxygen apart from each other. Then there was so much heat in the reactor that it had a hydrogen explosion.
Hydro-zirconium reaction, I believe
That is... horrifying, it's like a lithium battery failure on steroids.
Thankfully bad designs like this have long since taught us how to build far safer reactors
There were two explosions, first a steam explosion and then a more powerful hydrogen explosion. Heat alone doesn't separate water into hydrogen and oxygen. Even if that were the case, the splitting of the water would require as much energy as the later recombination during the explosion would produce:
2 · H2O -> 2 · H2 + O2 requires as much energy as
2 · H2 + O2 -> 2 · H2O produces.
There is thus no amplification of energy and no explosion.
What actually happened was the reaction of steam with graphite or zirconium fuel cladding:
C + 2 · H2O -> CO2 + 2 · H2
Zr + 2 · H2O -> ZrO2 + 2 · H2
Now this produces only hydrogen and no oxygen, pure hydrogen is not explosive. Thus it can only explode AFTER the pressure channels have already ruptured and it mixes with air.
Or in the case of Fukushima: The steam reacted with the zirconium for a longer time at much lower temperatures and pressures. Because hydrogen is hard to contain it escaped the pressure vessel and accumulated slowly in the primary containment, mixing with air. Then it exploded.
One of the best, most informative, brief and pure content I've seen. Please keep up.
I could be alone on this, but I kinda wanna play this simulation as some form of a puzzle game -- different reactor designs and you have to not go into a meltdown while trying to match power demand and fix issues that pop up.
This was the BEST video explaining a nuclear reactor I have ever seen. The fact that they even used the Latex font was *chefs kiss* beautiful.
To my understanding, it wasn't the chain reaction that caused the explosion, but the buildup in steam pressure that caused the lid to blow, then when oxygen(from the air) entered the reactor, it caused a secondary explosion. The Illinois Energy Professor has a great video on how the steam pressure built up when the Scram button was pressed. He explained that the chain reaction from the spike in power superheated the graphite tips and they were then being lowered for the boron control rods to lower back into the reactor the superheated graphite came into contact with the water supply instantly vaporizing all the water, causing the pressure to build, leading to the subsequent explosions.
Yes, all explosions in nuclear reactors are either pressure or chemical related, reactor it self cant really explode like nuclear bomb which is big missconception people have as they are not made for rapid energy relese as bomb is, it can only out of control and melt (thats why its called meltdown) creating hazard that melts to ground and any extra explosions cause exposure of radioactive material to atmosphere.
If someone dies in a house fire because of smoke inhalation, would you say that the fire was not the cause of their death? It may not have been the direct cause but the connection between the fire and the smoke is so tight most wouldn't state the difference.
When people say that it wasn't a nuclear explosion they mean something different. An explosion is a shock wave. In a steam explosion the shock wave is caused by the pressure vessel bursting. In a true nuclear explosion the reaction rate goes up so fast that there is an intrinsic shock wave as the neutrons propagate trough the material.
The thing with the superheated graphite sounds like you don't quite recall it correctly. The usage of the term superheated is wrong (it refers to liquids or vapors but not to solids). Also whenever water "instantly vaporizes" it must have been above the boiling point and suddenly lost pressure. There is no way to heat something above its boiling point anywhere close to instantly by touching it with something hot.
What actually happened after AZ5 was pressed:
1) Chain reaction runaway causes rapid rise in temperature
2) Rise in temperature causes rise in pressure, bursting the vessel
3) Burst vessel causes rapid loss in pressure and causes water to flash into superheated steam (steam explosion)
4) Superheated steam comes in contact with graphite (or zirconium) and produces hydrogen
5) Hydrogen mixes with ambient air and ignites (hydrogen explosion)
@@entcraft44 i never claimed the steam went above the boiling point just that the tips of the control rods weren't boron and the water supply entered from the bottom so when the heated graphite rods "tips" came into contact with the actual water supply, that caused significant amounts to vaporize and cause the steam explosion. Like I mentioned, go check out the Illinois energy professors videos on chernobyl. Extremely informative and well done.
@@walterp1028 And I never claimed you claimed... No need to get defensive. I did watch his video now and unless he has a second video about Chernobyl that I can't find: you misremember what he said.
And again: It is impossible for significant amounts of water to vaporize because they are being suddenly touched by a hot object. I am no professor but in this I am certain.
Thank you for making the huge effort of explaining this to a person who doesn’t know anything about nuclear reactions, but loves to dive into the unknown to try to understand how disasters happened 😊
Amazing work here! Can you simulate the safe reactor design you mentioned?
Agreed, that would really help illistrate how much has been learned, and improved, since these early and dangerous designs
Never have I considered that it is quite difficult to keep the reaction going. Your visualizations were spot on. Thanks for sharing.
Human error, the fact that this rundown test must be done is the main factor for this disaster. It was the Russian culture at that time, the inability to be able to question authority is and will be the making of a disaster again.
It was certainly human error, but that's also in part due to them not fully knowing how the reactor worked. IIRC the regulations stated they were to never fully raise the control rods, but a reason was never given.
It's easy to imagine that they thought AZ-5 could get them out of virtually any situation, which makes it easier to understand some of the decisions they made.
@@xIcarus227 I think the reason for raising all the control rods was because the reactor had stalled. Who did it, who forced them to do or threatened them is kinda my point, human error. I honestly think they understood what could happen but they did not foresee everything. The Rundown Test must be Done!.. it is all very sad when you think of a working culture like that. I worked through the 70’s and 80’s with bosses from the European block. They did think differently than people from the West.
Russian reactors are the most advanced and reliable in the world today. Or are they the same for Fukushima?
@@repozitory look it up, both have a containment aspect, part of the RBMK was the actual lid as it was extremely heavy, in Japan the earthquake and subsequent tsunami far exceeded the design parameters of the plant, I also cannot figure out why their backup generators were below sea level. Both are great studies for nuclear plant engineering. Keep in mind, one was caused by a natural disaster, the other was a human disaster in the making.
@@derekparent752 A funny excuse for a project that was bound to fail and a critique of experimental work that got out of control
I ended up here randomly and was stuck here. that was super interesting. thank you.
This is one of the most underrated videos I’ve watched. Fantastic work!
This video right here caused a chain reaction of me checking out your other videos and subscribing. Great work!
please do the simulation on a reactor with a negative void coefficient, incredibly interesting !!!!!
I would really enjoy seeing a simulation of a different design, like what you mentioned at the end, a design with a negative void coefficient. Very interesting video!
@Higgsinophysics Amazing video, highly underrated channel. What software do you use for the Simulations??
Also interested to know what software used!
Your simulation is spot on. Having been quite interested in the Chernobyl incident for a long time and having watched both documentaries and the series on Chernobyl, I must say this video explained the accident way better than them all. Also being a Physics Major myself, I must say we need more simulations like this that are precise and explain the point way batter than any book or image. This is a really well done video and I'm happy it came in my feed.
Well done!
This is the best explanation Ive seen so far - I saw a lot already ☺️
that was really kind of you to write.. Thank you!
Beautiful video. You made an extremely complex dynamic understandable. Keep going.
0:25 - otherwise known as "xQc"
Fr💀💀
King
Excellent design, animation, explanation, data breakdown, everything 👍
Nice Video. What tools did you use to perform the simulation? Are these available by any chance?
Thank you! I used Manim with a Verlet integration for the physics solver. It's stitched together by me and sadly not available. Mostly because right now the code is confusing and poorly structured. It could be really fun to release of others found it useful though.
@@Higgsinophysics would be interesting to see someone recreate the mechanics involved here in Godot or similar, let people mess around with various reactor designs and get a feel for how they've changed over tge years
Fantastic video. I can tell you poured a lot of energy into the production. Thank you for sharing.
Hello. A little audio advice: apply an audio compressor plugin to your speech track, it'll make your voice sound more evenly and professionally. Also move away a bit from mic, you have a condenser mic I suppose, they are very sensitive and sound best on some range.
You know audio? I have a question.
I have a Blue Yeti microphone. It sounds the best with the "heart-shaped" setting.
1) do you even know what my shitty explanation is referring to? 🤨
2) what's happening on that setting? 🤔
Can't see last graph due to suggestion overlapping.
Great video ! Thanks for the nice explanations !
Underrated Channel. Good animation
Thanks a lot, appreciate the kind words
Beautifully made, very clear. I seem to recall the TV miniseries also explained it in the final episode, though without the graphics and simulation you use to really drive the point home.
So they basically started a car in cold weather, and then put it to maximum RPM without any oil in the engine
Not the best analogy but yes
Sheesh bro, I hae absolutely no idea about nuclear physics but your graphics and explanation made everything so easy to understand. Awesome video!
5:20 how does the design of the reactor determine positive/negative void coefficient?
Completely underrated question, as Dyatlov himself considered it one of the main issues of the RBMK in his book. The positive void coefficient is (obviously) very dangerous, as it allows the positive feedback cycle to keep going. Answering your question, the design of the reactive zone itself (e.g. the distance between rods) defines, whether the reactor will have positive or negative void coefficient, and it cannot be changed since it's built. Also I'd like to mention that Dyatlov personality is now considered diabolical in western countries due to lack of translated information and influence of the HBO series, which is sad.
Water acts as a neutron moderator, which increases reactivity. Thus steam bubbles decrease it (negative void coefficient)
Water also acts as a neutron absorber, which decreases reactivity. Thus steam bubbles increase reactivity (positive void coefficient)
As AN1Kl said, which effect is dominant depends on the design of the reactor, namely which other materials are also present and where.
Compared to water graphite is a slightly worse moderator and a much worse absorber. Thus in the presence of a lot of graphite the neutrons are already well moderated and the positive contribution to the void coefficient is dominant.
Also, it is not quite true that the void coefficient can not be changed after building the reactor, at least for the RBMK which is a pretty flexible design. In the aftermath to the accident, fuel enrichment was increased and additional absorbers installed. (This of course increased the fuel costs, which is why they haven't done it before.)
These changes do change the material in the core and therefore the void coefficient.
3:00 Okay, but "Ridiculously Badly Made Kettle" is now stuck in my brain.
Dude dropped the best video explaining what actually happened at Chernobyl and thought we won't notice.
Very rare to find good physics channels who know their stuff, immediately subscribed!
Assume we are lazy is good assumption 👍
This channel is incredibly underrated. I don’t even understand physics but I’m here for it.
15:15 Oh fuck
Wonderful explanation and visualisation. The only thing missing was mentioning Boron but perhaps that wasn't that important. Great work.
0:53 Im not lazy im dumb xD i need a explain with pears and apples
Great explanation. The Chernobyl series was very hard to watch not for lack of having to sit on the edge of my seat the entire time but because of the sheer devastation that took place.
Today all this is taught in school, but back then:
a) they didn't know about positive reactivity
b) they were a research team
c) it was 1986, nuclear reactors were a cutting edge of science
d) they had a plan, but no idea what they were doing, control equipment didn't give them full picture, because it just didn't exist at the time -- and actually this exact catastrophe gave an idea what controlling equipment is required, so even a failed experiment was an experience and led to increase of reactor safety worldwide
e) "computer" mentioned in the video was a calculator in modern terms, it was giving print outs twice per hour at best
So no need to be emotional here, they simply did a test and failed. The rest of the drama and "conclusions" is seemingly based on tv show, not reality. Luckily in the real accident not many people have died, unlike the tv show. Many RBMK1000 reactors worked for decades after Chernobyl without issues.
The SKALA computer has 7 minutes lag between measurement and printing the result))
"in the real accident not many people have died" oh man you are quite in over your head
a) Wrong. The designers absolutely did know about the positive void coefficient of reactivity. They (as in the designers, NOT the operators) also knew that the reactor could be unstable because of this. In fact they increased enrichment from 1.8% to 2.0% to battle this instability BEFORE Chernobyl happened. They increased it again after the accident to 2.4% because 2.0% still wasn't enough. The reason for using low enrichment is that it is cheaper.
b) True. (Who is they? I assume those who designed the test)
c) True.
d) True, but... While they had little idea what *was* happening because of the limited instrumentation; the reason they had little idea of what *could* happen is that the design was a secret and concerns, prior accidents and the like were suppressed by the soviet union's system.
e) Exaggerated. The computer calculated the ORM every 15 minutes. It also ran another program which recorded hundreds of data points every second.
Really incredible explanation! You made it very clear and I appreciate the time you took to publish this!
So my question is was the efforts and deaths of the “containment” crews worth the effort? In other words, how would the outcome have been different if everyone just ran for the hills instead of intervening?
About half of Europe uninhabitable for the next few hundred years is a conservative guess.
Literally millions upon millions of people would be dead
the threat of a steam explosion is a myth
@@andrewwalker9607 false
@@starwinter6845 false
Fantastic video and best simulation/explanation of the chernobyl accident I've seen. Thank you for this!
1:00 Chernobyl and RBMK reactors used actually very low enriched uranium, which explains their size, unenriched uranium has very little of uranium-235 so we need alot of unenriched uranium in one place to fission
Came across this today. Thanks for all the time you took to create this video and explaining it to everyone.
As long as it was physics and simulation it looks beautiful, but its association to reality is what makes it scary and horrifying at the same time…
I love how informative this is, yet still is funny
This is amazing. You made an extremely complex interaction understandable. Thank you.
excellent attempt at modeling the events out. thanks for the video !
Thank you for a wonderful video. Seeing the reaction finally skyrocket was horrifying yet fascinating. Great work.
WOW, fantastic work with the simulation! I admit I'm a bit slow with the pickup on chemistry and physics sometimes, but this was wonderfully clear and I understood everything perfectly. Held my 2am adhd attention the whole time too. Totally fascinating
Hi! This was such a fascinating video to watch! I randomly saw this in my feed, and now I'm going to learn more about nuclear physics and the history of Chernobyl, thanks!
Just one small thing, the graph at the end ( 16:28 ) is partially covered by the next watch recommendation.
Looking forward to seeing more of your videos, subscribed!
the particle uptick at the moment of reaction made my skin crawl homie well done
Love the visualization, so well implemented and explained!
If each of them had watched this 15-minute video before the day of test and had this picture in front of their eyes, I think they would not have made those mistakes.
Really excellent job! It's truly incredible that you built a model on such a small, visual scale that can still effectively convey the concepts happening. I'm sure you had to do a ton of tweaking on the parameters. Truly remarkable, and your visualization and communication is equally impressive. Excellent work.
Really great video, don't think I've ever learnt something so complex in such a short amount of time.