Chernobyl Explosion Theories: Sich's Theory - The Last Seconds of Reactor Four
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- Опубликовано: 1 окт 2024
- Almost everyone can agree on the events that unfolded at Chernobyl. It is established fact that 01:23:39, the AZ-5 button was pressed, and the control rods began to descend into the reactor. The graphite displacers attached to the bottom of the control rods displaced water in the lower 1.25 metres of the reactor, causing a sudden and dramatic increase in power at the bottom of the reactor. What nobody can agree on is what happened after 01:23:44 AM. Some form of explosion tore the building apart, but the nature of the explosion remains unknown. Countless theories have been suggested; these are just a few of them.
This video is a much more scientific approach to the accident, and one from a world-famous Chernobyl physicist. Alexander Sich was the first US nuclear engineer to have the opportunity to go to Chernobyl to examine the accident, spending more than 18 months in the Chernobyl Exclusion Zone, recreating the events that occurred in the reactor and the ten days following. These findings were published in his thesis, Chornobyl: Accident Revisited.
This theory of the explosion is generally regarded as one of the best, and so I thought that people might be interested in hearing how many scientists agree that the explosion occurred, and the buildup inside the reactor beforehand, and therefore we will be examining Sich’s theory of the accident today.
Very detailed video, I was expecting another proponent of a "nuclear explosion" and am happily surprised that it was not. Given that there was a fire after the explosion, my guess is that a great deal of the graphite burned which would explain the lack of graphite below the lower biological shield.
While graphite can withstand very high temperatures, combined with high pressures it seems reasonable to me (as a non-scientist) that it simply vaporized. Graphite does not melt, or rather, does not have a liquid state; it changes instantly from a solid to a gas around 2500C. I also wonder if it's possible that it's simply contained within the corium, but as I said, I'm not a scientist.
@@jasonhaynes2952 That's not 2500 °C, it's 3600°C. And that means if the graphite was vaporized from the heat so would have been the fuel.
Oh good god, those figures are terrifying. 1480 gigawatss Peak thermal power is obscene, 300+ tons of fuel in one unit is ridiculous.
@mattaddison1910 I'm don't know mate, but now that I think about it, the 300 ton figure The Chernobyl Guy said was probably the corium total, fuel and molten reactor components.
It's around 200 metric tons.
I’m pretty sure the soviets used their rbmk reactors as a way to produce nuclear weapons as well, may be why they held that many tons of fuel.
Imagine the DeLorean needed 1480 Gigawatts of electricity instead of 1.21 to travel in time..
@@jwalster9412 Doc would have pulled all of his hair out
For an a few instants, humanity has became the creator of heat and light more magnificent than that of the Sun, several times. None of those times has it ever been benevolent to humanity, even if the intent was originally supposed to be beneficial for humanity.
You should make a video about your theory
I plan on in the future. :)
I'm not sure about a lot concerning this incident but it seems to me that the graphite mystery might be solved if it were possible to recreate the conditions right before the explosion because I think the carbon had a thermite type reaction with uranium oxide adding to the power of the explosion by turning huge amounts of pure hard compact carbon into gas instantaneously but I don't have any uranium or graphite lying around to test and see
plenty of it buried in Ukraine lol
You've got the failed zirconium welds and water being explosive at those temps too?
There's plenty of uranium underground in Canada's Northwest Territory, as well. You just have to do a bit of mining in an environment comparable to northern Siberia, no problem!
Thats an absolutely insane amount of thermal energy holy hell dude
9.47 Konstantin Pavlovich Checherov in the frame?
Alexander Kupny has an interview with Checherov. Unfortunately, very low quality.
Checherov is the most authoritative scientist who studied the Chernobyl reactor. And he claims that only a very small part of the fuel is in the melts. You can trust only those researchers who personally took samples, including the "elephant's foot" and melts and personally were in an empty reactor shaft.
I know; Checherov's theory of the explosion is coming up soon. It's definitely unusual, and it goes against a large amount of the scientific consensus in the seconds before the explosion.
I dont agree with everythin Checherov said and I think calling him the most authoriative scientist isnt right.
However, some of his assumptions are proven now. Based on newer anlaysis on different samples they took in different places in europe after the accident, it`s pretty sure that there was a chain of nuclear explosions before the final explosion. It wasnt just steam and hydrogen explosions. In the way the reactor is constructed (simliar to a rocket silo), most of the fuel and graphite was catapulted in the atmosphere before the final steam explosion messed up the rest of the building.
And I share his opinion (shared by some more trustworthy german scientists) that the chernobyl ruin actually is no security risk of continental scale. The damage is done and there is barely anything left there. It`s a story kept up by corrupt ukrainian officials and western nuclear industry to get their fingers on the billions of dollars of public money that was spent there in the last 2 decades.
But he also said a lot of unreasonable stuff that lead to questions who he even is (there always was this "who is this guy, never heard of him at kurchatov institute" whispering around him!).
Many thanks for your latest installment! Enjoying all your videos since the beginning. You accurately state that the equilibrium neutron multiplier Beta value is 0.0 That is, number of excess neutrons equals none, and flux remains constant at the chosen power level. Regarding steam explosion, consider normal operating pressure of 70 Bar (1,000psi). Once the lid lifted, if pressure was thus reduced to ~1 Bar, water in the core would flash into steam all at once. Not to mention, the raising of the lid might very well have pulled all of the upper control rods up with it. Thanks for your excellent reporting.
Doesn't the fire that burned for like 10 days after the explosion explain where the graphite went? It just burned up.
This is an excellent video that's well researched. I'm saving another one of your videos. Thank you
Could the falling "black snow" reported by area residents have been pulverized graphite?
That and the remnants of the roof.
Graphite can burn, that could easily happei in a ruptured reactor core. The corium must have had temperature of several thousands of degree initially, so any carbon present in it's vicinity would turn into CO or CO2 gas very quickly. Additionally, such liquid can burn easily through almost anything, including concrete and steel. Ps. Nuclear reactor's normal state is critical or super critical In the operation of a nuclear reactor, criticality is the state in which a nuclear chain reaction is self-sustaining-that is, when reactivity is zero. In supercritical states, reactivity is greater than zero.
can you make a half life video on akimov
most likely Sasha Akimov at 3:20 . Rest in peace.
5:55 as physicist it feels inaccurate hearing something measured in Watts referred to as energy, but I'm not familiar with the exact terminology of nuclear engineering.
Regardless, thanks for making this video! I love this kinda 'the devil's in the details' (for lack of a better word) analysis. Very well presented and explained, imo!
For nuclear reacts their "power" is commonly expressed in Watt of Thermal Output (how much heat the reacot itself is producing) amd also in watts of electricity generated. If i recall correctly the RMBK was rated for skmething like 3000 MW of thermal, but only produced about 1000 MW electrical
Given everything we know about Chernobyl and the USSR nuclear energy program
It's probably a miracle that this was the only accident of this magnitude in Soviet history
In any moment now, a nuclear reactor in china might suffer a major accident. They have terrible safety culture, and is full of corruption.
Khyshtym (sp?) Was really bad too in the 50s, though not as extreme of course, but pretty extreme for how relatively unknown it is
Meanwhile america had 2 incidents in the same timeframe. 🤷🤣
Don't forget the British had the very first meltdown in Windscale back in 57'
@@tylerdurden4006 MINOR incidents. an explosion of this magnitude couldn't happen in BWR reactors for a number of "sciency" reasons, but basically, they didn't have a positive void coefficient that would allow a spiraling chain reaction of this magnitude to happen so quickly. I think the biggest problem with Chernobyl is that the power spiked so quickly there was no time to react and mitigate the damage.
What you've described here is less violent than what many nuclear engineers have described.
this theory does sound plausible, but it does the lack the part of the reaction that conserns quantum particle behavior, and it does seemingly ignore what happens when water flash heat´s
Just a bit of feedback: i can clearly hear your breathing in throughout the video. Its not so bad that I want to turn off the video. But depending on how easy it is to filter it out in post, it would make future videos more enjoyable to watch.
Contentwise and visual: amazing video. And interesting subject
Don't know if there would have been enough time for sufficient hydrogen to build up to create the largest explosion but steam... Water expands 1670x its size when flashing to steam. If you can't keep that pressure in then it's going places.
i think also if hydrogen was the reason for destruction it would be much worse, as combustion like that really has power to it compared to the steam
Also the oxygen from the corroding zirconium.
Also potentially explosive together with the water depending on how the welds went.
This makes me remember a number of railroad disaster photos I have seen. Low boiler water instantly flashed to steam, extreme instant pressure causes an explosion that kills the crew and throws the boiler down the track ahead of the train.
The graphite, and maybe even some fuel went into the atmosphere when it was pulverized by escaping steam.
Very detailed.
How much of that graphite burned and got released into the atmosphere?
@@gordonjenner2375 And if we subtract this from the total graphite that was in the reactor core, do we end up with more than is estimated to be in what remained of the reactor core?
2:30 The RBMK 1000 control rods had a known design flaw. Graphite is a moderator (it slows free neutrons increasing reactivity). The first one meter were coated in graphite, the very thing intended to reduce reactivity actually increased it while entering the core. When these control rod tips hit the bottom they moderated (slowed) all the free neutrons spiking reactivity, power and heat. This had happened before with less tragic results and was somewhat understood. This flaw was corrected in other reactors after the disaster. A U235 nucleus absorbs a neutron causing instability and to split. A chain reaction can only occur when a sufficient number of neutrons are slowed enough to create this effect.
A very small correction to your otherwise excellent comment. The graphite section was 4.5 meter in length, not 1 meter. And it wasn't strange it was there.
Water can both be a moderator, and a neutron poison. The RBMK is so over-moderated with graphite that for it, water solely acts as a neutron poison. The control rods are water cooled too. When pulling them up out of their channel, the water stays behind. Ergo, you replace one poison (boron) with another (water). This will create a drag on reactor power, and makes for uneven fuel burn-up. To combat this, they hung a graphite displacer from the boron section via a telescope. Theoretically, this made the control rods a much more powerful control. It is a very aggressive way of reactor control. The problems arose from that displacer not reaching all the way to the bottom. The 1.25 meter of water below it would be moved out of the way when the control rod was inserted back into the channel, giving that momentary spike in reactivity. Under normal operating conditions this wasn't much of an issue, but in emergency conditions, or when the reactor was operated outside its design envelope, this could, and did, become a major hazard.
What's worse, initially the displacers did reach all the way to the bottom, but in order to save some concrete, they secretly shortened them so they could make the under-reactor rooms smaller. This "improvement" was never communicated with the designers, nor was it looked into what this would mean for reactor characteristics.
@@swokatsamsiyu3590You explain the need for the 'followers' quite well. I'd just add that under 'normal' circumstance there were precise limitations as to how many rods could be removed and how far out they were allowed. This was to mitigate how many rod channels had water in the very bottom. With only a limited number, most of the graphite followers did not cause this power spike in the lowest areas of the core. But during this test, in order to raise up power and counter-act the xenon, this limit was violated and too many rods were pulled too high. This created the unusual situation of a large number of rod channels having water in their lowest reagion.
@@mikefochtman7164 I very much disagree with your wording. The limits on withdrawing rods were the precise opposite of "precise," and had apparently nothing to do with controlling the tip effect or limiting water columns at the bottom of the channels.
First of all, the limit was based on the reactivity worth of the inserted rods. In other words it would prohibit rod configurations (e.g., many rods partially inserted) where there was no tip effect whatsoever, and allow configurations (e.g., a few rods inserted fully, with the rest withdrawn) that did pose a safety risk. Positive scram effects were possible with an ORM value that was above the limit. The limit was primarily based on maneuverability and fuel efficiency concerns. The operators were unaware that it had anything to do with safety or preventing reactivity accidents.
Furthermore, the rod worth could only be calculated over the course of ~15 minutes by the Skala computer, and these tests were generally only run at 1 hour intervals. The regulations allowed the reactor to be operated for many hours even if the computer was malfunctioning. In other words, the operators would almost always have an outdated and/or inaccurate value of inserted rod worth. There was no way to control the parameter in real time, so operators would typically behave the way they did on April 26th. This so-called "precise limit" was totally worthless as a means of ensuring reactor safety. It was a fig leaf just used to put some engineers in jail and salvage the government's reputation.
@@gordonjenner2375 Yep! They did what should have been done on Day 1: put a compressing/telescoping fitting on the joint between the boron and the graphite. That way the graphite can cover the entire bottom of the channel, without making the actual channel longer.
Also they added the BSM fast shutdown system: control rod channels that only have a film of water on the edges, so they can insert in just 2 seconds without displacing water.
I read your guys discussion here. That was impressive!
Graphite dust explosion, perhaps? Dust can be surprisingly energetic.
Another great video, the graphite probably fueled the fire.
Graphite can't fuel a fire. It takes in far more heat than it releases.
And the Zirconium
I had exposure to the radiation from Chernobyl when the US wanted to make a show of force in Germany. We were out marching in the rain consisting of the fallout from Chernobyl on May 1st 1986. The result is that I have a nodule on my thyroid as well as lesions on my head, neck and shoulders. The biopsy revealed that it is consistent with exposure to radiation. This happened in Regan’s peacetime Army. I’m being treated for it now. There are probably more people suffering from this same exposure. I was literally singing, “I’m a Radioactive” at the time. ☢️
Man that background ambience just has a theme of doom that fits perfectly for this subject…
I had a reactor 4 nightmare scenario after eating Moe’s a couple days ago. I Had to put the dogs down.
Keep that Scottish (?) accent under control pls
I want Michael Bay to explain it
The Whole Reactor was just an accident waiting to happen.
Typical Russian/ Soviet design, make it cheap don’t worry about all the design flaws ( because Soviet RBMK reactors don’t Explode .
It was absolutely Crazy, And Criminal to make a reactor without a containment building . But this is the Soviets, make it cheap , don’t waste money on any systems that might not be required
what if I have 100 tons of plutonium-239 and 100 dollars of reactivity 💵 😳😶🌫️
"of all the major theories" - I'm gonna be *that guy*, but if there is more than one way to explain something and it isn't settled yet,, it's NOT a theory but a hypothesis, at least in scientific terms, and since you're discussing pretty scientific stuff I thought I'd point that out. Roughly speaking theory is explanation that has been tested repeteadly, is confirmed by all the evidence while being contradicted by none.
What could have been done if this button had not been pressed ? Is there any other action that could have been taken? Or was disaster enviable at this stage ?
There was an opportunity to prevent criticality by manually inserting the control rods that insert from the bottom of the reactor, which would counteract the positive reactivity of the descending graphite, however there would have been no reason to do this in the eyes of the operators. If they had just waited, a power surge would have begun that would automatically caused the reactor to shut down, causing the explosion anyway.
That's enough power for 1,224 DeLorean's.
FU google. Can't ee any more content because what i choose to run on my machine. (ad blocker). You're now doing evil. Good thing you took it out of your mission statement.
Chernobyl underwent a prompt critical nuclear excursion. The energy release at the power levels cited for 2 seconds would amount to a TNT equivalent release of 700 tons. As this is an exponential rise and the power level is only crudely estimable, the actual release may be substantially less or more than this. In either event, this was clearly a huge energy release measured in not less than tens of tons of TNT equivalent energy and more likely in hundreds of tons to a kiloton of TNT equivalent energy release. It was a low to very low yield nuclear detonation.
That nuclear physicists do not want that to be the answer is irrelevant. That there is a dominant myth that reactors cannot ever nuclearly “blow up” is just that - myth. It happened here. It happened at SL-1. It happened at KIWI-TNT.
The instant this energy was released other things happened as well. Nuclear fuel and cladding stores hydrogen gas as an inter-metallic hydride equivalent. In essence the naked protons fill the Fermi sea of electrons in the metal lattice. For transition metals like nickel, uranium and a few others this storage density can reach to greater than the equivalent storage density of cryogenic hydrogen in the same volume sans metals. This is what makes nickel-metal hydride batteries so useful for storing energy.
During those few seconds the intense fluence of neutrons, gamma and x-rays rapidly dissociated an immense amount of the water, and raised the temperature in all of the metals driving the hydrogen out of the fuel and cladding. The hydrogen gas mixed with oxygen from dissociation and the in rush of oxygen from the air as the lid was ejected then led to the spontaneous recombination of the hydrogen and oxygen in a massive restricted detonation wave.
Simultaneously, the sudden high pressure gas release from the dissociation and conversion of the water to steam drove the core apart radially and vertically. It became a giant mortar launching the lid into the roof, and detonating as it did so destroying all of the walls and roof. The reaction creating a temporary imbalance in forces that blew the bottom of the reactor down seven feet into the basement allowing the sand shield to flood in through the gap as the now molten fuel poured to the lowest point combining with the sand to create the corium that poured down through the five levels of the basement and sub-basements to become the elephant’s foot.
In no way was it a “steam explosion”. Steam cannot explode. Vessels under high pressure can fail releasing huge volumes of water that instantly flash to steam and as an expanding vapor cloud carry great force. But it is wrong to call this a “steam” explosion.
With the hydrogen gas release this was more analogous to a massive BLEVE.
Does the corroding Zirconium fit in anywhere for you?
@@bobdrooples Yes. Rapidly oxidizing in the high temperature environment, leaving the hydrogen from the water behind to mix with air.
Your arguments cogently explain the issues and fit the known facts better than the Sich approach. Most people do not understand the consequnces of prompt criticality and its associated very short doubling time. An analysis of what the doubling time may have been in the worst affected channels would be very interesting.
Could you explain or make a video on why if the core melted and reached the water underneath it would have caused a massive nuclear explosion.
Is it true that there was a video recorded in the reactor control room during the incident that has never been released? I also heard there was a voice recording of what was said but it has been released to some extent. It would be very interesting to actually see a video of who did what and when. If it’s truly there we will never see it in the open world, too much corruption and payoffs of those who did dumb things but want remain anonymous
Dyatlov asked for audio from the control room to be played at the trial. He was refused, probably because it didn't match the prosecutor's narrative.
Video of that era would have been on film. The film may not have survived both the massive explosion and high levels of radiation after.
I dont understand why removing the water increases the fission rate as water acts as the moderator.
In the RBMK, graphite is used as a moderator. So between the water and graphite it is what we call 'overmoderated'. Changing the amount of moderator a little bit by removing some of the water (or just boiling it to steam) has little effect on the moderation rate. But water is also a slight poison in that it absorbs some neutrons. So in the RBMK design, removing water has little effect on moderation, and a stronger effect as a poison. This gives it a positive void coefficient (boiling the water adds positive reactivity) Much different than the west's BWR technology where water is the principle moderator and has a negative void coefficient.
When or what was the point of no return? When was the moment the crew had no more means to prevent the explosion? Maybe you already have a video covering that topic?
I don't think I do, but the earliest time we can confirm it was unavoidable was about 01:22:30, when calculations based on control rod positions indicate any attempt to shut down the reactor would result in a runaway and subsequent explosion.
Thank you very much, for you answer.
I'm a noob here but could graphite just burn?
Thank you for this incredible video. And I don't mind it being very sciency and detailed. I love sciency and detailed, especially when it provides me another piece of my puzzle. I can't wait to see the next one. Well done!
Great videos. You should do a modern update. Russians invaded and took no precautions. There’s no numbers right now from how many people were sick from the site.
the number is the offical + two million
Unless you go into the sarcophagus you’ll be fine being near Chernobyl
@@curtisnoble. while that is generally true; the invading russians are making it *much* worse than it otherwise would be. They're digging trenches in overturned ground; causing environmental background levels to rise; i'm not sure if the IAEA has gotten a reading, but it is up.
@@curtisnoble.Russian dug in positions in the red forest and lived there for weeks.
@@StritarD unless you’re in the sarcophagus you’re fine. Sure there’s still come danger. But majority of the contamination in the area of the area is gone.
Where most of tons of graphite disappeared? Temperature of sublimation of graphite is 3642C and many blocks just sublimated. Some graphite blocks, 250x250 mm, became oval, outer part evaporated. Estimated temperature in the core of over-critical reaction , less than one meter in diameter, in 3-30 fuel rods, was put at 16,000C-160,000 C. At the same time paint outside of scheme " L " ( lateral biological protection, filled with water) wasn't even burnt out.
Could the graphite burned up? And I have no idea, as I do not know what’s all in the core now..but could of the fact they dropped tons of lead/sand/boron onto the core further damaged the lower biological shield more? Man… either way… when anything goes prompt critical, and it’s not a nuclear bomb…. It’s a BAD thing!
Great video, I look forward to more.
Is it possible that the missing graphite was consumed during the explosion and post-fire? With the water breaking down, it could have also formed CO/CO2 and be off gassed. How much was vaporized and sent into the atmosphere?
This entire story is the same Friggin 5 sentences repeated 15 different ways.
I always wondered if they had turned the water pumps back on at the original power surge if that would have been enough to get control rod's back in although the az button would probably still make it go pop
There wasn't any kind of abrupt surge until AZ-5 was pressed, and the pumps were still operating. They did need to add more water to keep reactivity steady, but it probably would have taken a minute or two to make a difference. Someone probably would have pressed AZ-5 before then regardless.
@@MinSredMash there was a very rapid increase in power before the az button was pushed the test to see if the spooling down turbine could power the pump's meant a reduced coolant meant a surge on power that made the bio shield blocks bounce up and down it's even in the vid the power surge before they were there knickers and pressed the az button
@@gingernutpreacher You should watch the other videos on this channel to be disabused of elementary misconceptions (like everything you just wrote).
The so-called "bio blocks bouncing" is a perfect acid test for people who confuse fan fiction with history.
@@MinSredMash so testimonials are to be dismissed?
@@MinSredMash so you're saying there wasn't a big rise in power from around 215mw when they turned the pumps off? What ever you're taking I don't want any because it makes you eat your arm off and speak in a pottery's acsent
Crazy how we're still in orbit with the sun huh...
Nobody disagrees on what happened
I never heard any mention of the fact, that the graphite would have that effect on the level of cooling water. That is a realy interesting detail. In the Video it was mentioned that this void effect would raise the output from 200 to 500. It is of course just my stupid comment but it is usually said within popular scientific information or publicly available information that the power output was drasticly lowered, due to xenon poisening of the reactor and that this was the cause for the reactor having less than a third of the output, due to causes unknown at that time, while working in a way that would generate much more energy.
The reactor layout was extremly complex and it was controlled analog with a huge amount of buttons. That would mean, as i imagine, that within all of the rods of reactive fuel power levels and even heat in the end result could fluctuate without the control havin any detailed insight. With less energetic output there was also a measurement flaw induced that woud reduce the detail in which core parameters were measured.
I however am not totaly convinced about one thing being mentioned, and that is one basicly trivial thing. I dont think it would be right to make a definite distinction between a catastrophic development and a basic reactor control error, that could happen all the time, with literally every possible consequence as a result. Its just a small criticism, but to me, it doesnt make to much sense to reduce it to the cause being the water within the fuel rods being raised and therefore air bubbles causing the criticality and the controls not knowing, because both factors, cooling water as well as the controls, are also part of the regular reactor function, without any type of error. It just sounds to simple of an explanation. But i too know that the explanation given is that the void coefficent of the bubles would lead to the cores melting due to an energy spike...
The main component is within the theory, that reactor components in addition to said misfunction are all the ingredients to build a type of nuclear bomb, or to have the inventory explode and release radiation... but that is just a limited timeframe being explained. What is happening with the timeframe before the reactor even existed. The Reactor was assembled and the inventory was put there, which of course is the reason for it being released the way it happened. If you look at it like this, it is obvious that the cause for a explosion would be a basicly >thermobaric< reaction. But that would be like saying, it is because friction leads to fire... I think a better explanation should take into consideration much more details, and possibilitys, but i guess the tragic thing is, that this doesnt work with nuclear reactors and that almost everyone of them has the potential to explode or release radiation due to a mishap.
Great video mate, very informative 👍
A video I'd like to see would be about the cranes. There were building cranes that were abandoned after the disaster. They stood abandoned for over thirty years. Are they still there? If not when did they vanish and what became of them?
Dismantles partially for the construction of the rolling roof prior to installation.
I'm sure the cranes you are talking about are at reactors #5 and #6 which are a short distance south of the main complex, the cranes were there for the construction of those units but all work at #5 and 6# was abandoned after the accident.
you are 10% accurate.
If i understand correctly, he's saying there were _three_ explosions, not two, with the third being the most powerful and being caused by.... water exploding? doesn't compute...
try welding shut a piece of pipe with water inside and throw it in a fire)) you will be amazed
Steam takes up almost 2,000 times as much room as water does, this is why you don't throw water on a burning fryer unless you want that water to flash boil setting fire to your entire kitchen. Now imagine something a dozen times hotter than scalding oil and you have the centre of an uncontrolled nuclear reactor and instead of turning on a tap you instead pump several tons of water directly into the centre of it.
You ever seen a steam locomotive that has blown its boiler?
6 times the pressure, 2 times the temperature, many times the volume here.
I dont see how the explosions could have been anything except water turning to steam and then splitting to hydrogoen and exploding
There was a theory put forward in a paper that proposed a prompt criticality explosion. I'm curious to know if this was every followed up on.
Honestly? I would imagine that there was a minor actual nuclear detonation mistaken for a steam blast.
no, if such a reaction is started, it will not end until there is no more fissionable material left. you would be looking at a big crater and not at an otherwise intact powerstation today if that was the case
@@supersst838lol no that's not how this works
The Uranium in a nuclear reactor will not detonate like in a nuclear weapon. It is not rich enough in U235, and there are too many factors impeding such an event. Which is good. Because the Hiroshima bomb contained 65 Kg of weapon grade Uranium but only about 1.2 Kg reacted before the weapon blew itself apart, so if a nuclear reactor with several hundred tons of Uranium could actually undergo a 100% efficient detonation then most of Eastern Europe and Western Russia would have been flattened. Luckily none of this is possible and I speak only hypothetically.
It’s insane how all this happens in seconds!
There's no theory - we know what happened. Chernobyl was a prompt critical event. This video would be better if you discussed the different between delayed neutrons and prompt neutrons. We normally control reactors on delayed neutrons. Thermal power is also not really the appropriate measurement when discussing neutron power.
The reactor could destroy itself without going prompt critical. It's enough to rupture three fuel channels and then simple depressurization of water will pop the lid off.
@@MinSredMash "The Chernobyl Unit 4 accident was a prompt critical reactivity excursion that occurred when the operators reduced power to well below the permissible safe operating level and, at the same time, neglected to follow low power operating procedures."
US NRC Staff Report NUREG-0933 Section 5, Chapter 2
@@MinSredMash "The Chernobyl reactor tragically demonstrated the behaviour of a
reactor following the sudden insertion of a large positive reactivity. In
that accident power increased from a low level to an estimated 10 000
per cent full power in less than 2 seconds. Why didn't the delayed
neutrons limit the rate of power increase? The remainder of this
section describes the effect (or non-effect) of delayed neutrons in more
detail, to be able to answer this question [...] A reactor in this state is said to be prompt critical, that is,
critical on prompt neutrons alone. This kind of rapid power increase
caused the Chernobyl core to explode."
Canada Deuterium Uranium Reactor Fundamentals introductory operations course, Ch 19 Sec 4.
I should add that there is plenty of information out there which says that we don't know whether that happened or not. Indeed, I found articles in the press that presented this as a "new theory", etc. But it is stated as an uncontroversial fact in primary source materials I found. The first source provides a detailed account of it with all of the math and graphs etc. Of course, I am not qualified to judge whether their conclusions are sound. But it mentions precisely the distinction that OP drew. And it is so rare that I find that in a RUclips comments section that I felt that I should say so. I comment on videos about stuff that I know pretty well, and usually no one ever cares, either, lol.
There are often alternative hypotheses accounting for any complex event. The best thing one can do is try to assign appropriate weight to various evidences. Granted, my ability to do so is limited by my lack of expertise, but these sources seem pretty authoritative...
@@bsadewitz First of all, no one can prove exactly what happened during the explosion because no data exists. Second of all, that sentence was written by buffoons repeating demonstrable falsehoods. A great example of why impression credentials don't mean you can't be full of shit.
The real reactor was the friends they made along the way
verry bad film 34 jears after the acudent end you see nobody know what have heppent?lol
It really doesn't matter how it happened, but it did. This should be a warning for the nuclear fission reactors, every possibility should be addressed.
I do think how it happened matters greatly. after all understanding exactly what happened can only contribute to making reactors safer and more reliable
FUSTERCLUCK
they literally covered this WHY DID IT HAPPEN? in the bloody Chernobyl mini series. seeing you are using imagery from it one must ask what is the status of the Elephant's Foot!
the status is sitting still irradiating the basement
as in the inert gas triggered the boom :)@@gordonjenner2375
Still a debate today: why was AZ-5 pressed? It's pressed because the experiment is over or because there was rise in reactivity?
It's not a debate; people who were in the Control Room have confirmed it was because they should have pressed it at the start of the test, and Toptunov had not done so because he was expecting a different order to press the button. He communicated with Akimov who gave the order to press the button. This is supported by the testimony of those who were put on trial.
Both options are totally plausible and even complementary. Observing a slight increase in reactivity could jar the SIUR's memory that the shutdown was overdue.
Dyatlov stated in his testimony and interview, the button was pressed as a matter of routine, and was done under calm emotional conditions. He also testified the designers had "played a dirty trick" on them, meaning (in my opinion) the operators simply wanted to scram the core and were not aware of the dire consequences to follow, which happened due to the already known design flaws. A scram button should decrease neutron flux, do it effectively, and do it quickly. For reference on the details of the very first scram system (controlled by an actual rope which could be cut with an axe), see Chicago Pile 1 (Wikipedia)
They failed to understand and obey the design limitations that only bank scrams be used, not full scrams. The designers knew that they built a bomb. And they included limits to never do a full core scram in such circumstances, knowing that to do so would cause first a massive power excursion. Doing bank scrams would create lesser power excursions.
But as in all human things, caveats like that get lost along the way, or are intentionally ignored by those not understanding the reasons they were there. They instead substitute simple thinking - like the need to urgently insert as much negative reactivity as possible, or that the job is done - now just turn it off. Either is grossly careless and stupid. And the consequences are as we saw.
The true fault goes back to the design. No reactor should ever have been built in this way. The fault goes further back though to the economic and political pressures combined. Maximizing efficiency was their god. That over-rode the technical issues allowing and necessitating the creation of a fatally bad design.
@@tunneloflight False. There was never even any hint of a suggestion or requirement to perform anything less than a 'full scram' in those conditions. I'm not sure what you're referring to by 'bank scram.' This is not a term that exists for the RBMK.
You do a decent job with these videos, but you really need to have another person check your scripts for logical fallacies. The accuracy of someone's analysis of the accident is not dependent upon the funding of 3rd party research that his analysis does not rely upon.
Nobody ever mentions that Chernobyl was the ONLY power source to a Soviet project that also was at the top of the CIAs most hated installation list, known as the Duga "woodpecker" for the noise it made on radios, Over The Horizon Radar. But I'm sure the CIA would never orchestrate such a thing.
Duga-1 is not the only installation USSR had. There was also one built near Mykolayiv and another near Komsomolsk-on-Amur.
@@YouShisha1393 The others weren't as powerful were they? Duga was supposed to have been able to tell them when a Cessna landed at Miami Dade.
@@bobjones8372 The Duga installation near Chernobyl didn't emit anything whatsoever. It was a receiver.
@@MinSredMash I believe there were two emitters, back and to the side of the giant receiver.
@@bobjones8372 The transmitter was located in a different region of Ukraine entirely. But in general you shouldn't pay attention to silly rumors about Duga. The Soviets were disappointed with its performance anyway. In the Russian-speaking world the most popular idiot conspiracy theory is that someone in the military blew up Chernobyl to conceal the embarrassment of the malfunctioning array.
The uranium that remained in the reactor vessel reverted back to its primordial state (Lava) and melted its way down and out through the bottom of the steel reactor vessel. Graphite is a soft and crumbly material, it’s possible that a large amount of it was turned into powder by the force of the secondary explosion.
The problem here is that there a large number of graphite blocks remaining in the reactor, and that the lava would still have to pool in a perfect third of the reactor despite containing almost the entire inventory of the fuel. It doesn't make sense.
That is not at all the “primordial state” of uranium lmao
That's not what "primordial" means oh Lord
@@thatchernobylguy2915 Fuel melts, graphite doesn't, didn't the fuel just dribble out of the graphite blocks and congeal into one big tentacled blob of corium? It makes sense seeing as the fuel channels (were initially) vertical and liquids drain downwards.
this has all been determined. get a job.
If it had been determined then there would be a definitive reason for the explosion, and yet there isn't. There are only theories.
Get some manners.
Sorry, but this video is terrible, it explains nothing. You can't describe in details real causeof disaster andwhat happened, without explaining nuclear physics.. Why you never talk about Xenon poisoning?
I think the accident was caused by the man who wrote up the test procedure. We never here about who he was or what happened to him.
Apparently in part that man was Anatoly Dyatlov, which tells you something.
@@markusw7833 no, it was written by the reactor designers, but not followed
@@supersst838 Do you know what INSAG-7 is?
Saladfingers...