Why Is It So Hard to Stop Meltdowns?

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📕📗Atomic Accidents - Meltdowns and Disasters by James Mahaffey amzn.to/3EAH9W8
☢️ Why do meltdowns happen and can we stop them?
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Chapters
00:00 Let’s Talk About Meltdowns
00:59 How Nuclear Energy Works
02:30 How a Meltdown Progresses
05:10 Why Meltdowns Happen
06:27 How Scary Is It?
07:57 Our Amazing Sponsor - Brilliant
09:06 How Do We Prevent Meltdowns
11:18 Meltdown-Proof Reactors

[@atomicblender]

To try everything Brilliant has to offer-free-for a full 30 days, visit brilliant.org/AtomicBlender The first 200 of you will get 20% off Brilliant’s annual premium subscription!

[@michealedwards2450]

why don't we just use a boraxs reator?

[@michealedwards2450]

a boraxs reator is a reator that is from 1800's it's was not high tech but it did not end with uraum or torum in stead it was boron yes boron it dose not make radashion in stead it make heat very fast mix boron with water and siver then you have heat the reachon can last for 3years...

[@Ilikefire2792]

That moment, you rediscover the CANDU reactor design lol

[@paulmobleyscience]

@atomicblender So why did you stop at the concrete floor in Fukushima? The corium is not on the concrete pad in the containment vessel...it has melted through to the wells below the containment vessel and is no longer contained. 400 tons of water per day leak into the basements where the corium is located, 130 tons per day is captured, leaving nearly 300 tons per day of untouched radioactive water streams into the Pacific Ocean every single day.

[@dynamogaming4953]

You are the most sensible youtuber in atomic energy hope ypur channel grows

[@ProlificInvention]

As Albert Einstein said: "It's a hell of a way to boil water"

[@tonamg53]

It’s also not that complicated. You just basically put some naturally find mineral that doesn’t like each other and tends to heat things up when they’re too close together… really close together! The boiling part is not hard… the hard part is how to stop it from boiling water and not given people free chest X-ray every minute….

[@atomgutan8064]

The best quote ever.

[@ProlificInvention]

@tonamg53 To be fair the uranium mining and refining process is extremely complicated as well as resource intensive resulting in 50,000 tons a year of refined U238 (depleted uranium metal) as a byproct that requires high level storage eternally, and untold tons of tailings and other mining related pollution. Then come the reactors: the most complicated engineered devices created by man some would argue, not up for argument is that fact that PWR and BWR reactors cost billions and take over a decade to make, and the fact that all generated long term high level radioactive waste will be stored onsite in giant cooling pools (and some are dry casked) permanently. Not to mention that radiation degrades metal over time so theres all the associated problems with that. Other than all that its a modern scientific marvel that our descendendts will pay for all their lives as it directly is used to create nuclear weapons and Depleted Uranium Munitions and thats why superior technologies have not replaced standard fission reactors.

[@tonamg53]

@@ProlificInvention Deaths from Fukushima accident: 1 ( due to evacuation and not related to radiation) Death from Chernobyl accident: UN estimate direct death at 50 and from radiation exposure over the years at around 4,000 people Death from coal power plant; premature death is estimated to be around 8,000,000 per year So in the past 37 years since Chernobyl accident, nuclear power is estimated to have killed 4,100 people… while Coal power and other fossil fuel burning is estimated to have killed around 300,000,000 people… And you have problem and safety concern with Nuclear? Seriously?

[@CARVIDS99]

As i said its a hell of a way to make electrons excited

[@BritishBeachcomber]

At 16 years old, my physics teacher took us on a day trip to the Aldermaston nuclear research site. I stood on the reactor core and the thought of all that energy, just inches below, blew my mind.

[@jamesthornton9399]

My Dad worked there instead of going to Korea.

[@cbskwkdnslwhanznamdm2849]

E=Mc2, we are surrounded at all times by a gobsmacking amount of energy 🤯

[@gownerjones1450]

You had a 16 year old physics teacher?

[@2Fat2Furi0us]

If you check his profile picture, do keep in mind said event he describes happened 1 month ago. Or one week before he posted this reply and updated his profile picture. 👀

[@2Fat2Furi0us]

That doesn't make sense. There is a coma there and he uses possessive for his teacher.

[@ThatJay283]

thankfully modern reactors (generation 3 and up) have passive safefy mechanisms to prevent meltdowns from happening at all. these safety mechanisms are designed on top of the laws of physics themselves, so they can't just be disabled.

[@Chris-uu2td]

Yes they have passive mechanisms that don't rely on external power or activation. However, disposing of the decay heat is still an issue, even with Gen3 reactors. Gen3 reactors emergency coolant water is dimensioned for 72h, during which the reactor core can be cooled passively. If after 72h neither water can be supplied in sufficient quantities nor the cooling loops can be restored, even a Gen3 reactor core will inevitably melt down due to decay heat.

[@seantaggart7382]

​@@Chris-uu2tdindeed But 72 hours? Thats plenty of time and honesty it Is really secure

[@Oureon]

@@seantaggart7382 Never asume something is fine or "plenty of time" when talking about nuclear reactors, i believe that is the ideal rule of thumb for nuclear power moving formard

[@seantaggart7382]

@@Oureon true but honestly They PLAN SO THAT ITS LIKE 2+2=100!

[@Chris-uu2td]

@@seantaggart7382 One might think so under normal circumstances. But it's basically what happened to 2 blocks in Fukushima: Power lines and water lines were down due to the earthquake. Streets were mostly destroyed and the emergency generators were flooded. To exhaust the decay heat of one block, they needed about 60kg (128lbs) of water per second (5184t per day). They simply couldn't replenish the emergency cooling water before it ran out and the reactor cores ultimately melted down. Or think about the zaporizhzhia nuclear power plant: We are lucky that Russian soldiers are either too dumb or not determined enough. It's rather easy to siege a nuclear power plant, render it's emergency generators inoperable and cut it from mains power and water supplies for more than 3 days.

[@TheSwissGabber]

decay heat after shutdown is mainly from the decay of fission fragments not from delayed fission. Not in the first 30s but after 5 minutes the decay heat is ~100x greater then delayed fission.

[@ddopson]

Is delayed fission even a thing? I know that "delayed neutrons" are a core aspect of stabilizing nuclear reactor power levels, but delayed neutrons come from fission product decays, not from U235 atoms that waited before fissioning. Once struck by a neutron, the fission event occurs faster than 10^-15 seconds. Or maybe you are using that term to refer to fission events triggered by the delayed neutrons, which I'd just think of as the reactor's shutdown transient curve. I've long been under the impression that the reactor would shutdown very quickly, possibly less than a second, but after doing some math and first-principles analysis, it seems that your intuition on timing is the more accurate description ... OK, I went way deeper on this than I had planned. The delayed neutron fraction is about 0.65%, and it's tempting (but wrong) to think that with the control rods in, all but 0.65% of the power evaporates almost immediately. Typical shutdown margin is only about 1%, which ensures the reaction rate will decrease to zero, but the delayed neutrons still have a very significant chance of triggering fissions, roughly 99% as high as their chance in a steady-state reaction (which was about 40% based on each fission generating 2.5 neutrons). So then I simplified what's known as the "point kinematics (differential) equation" by assuming that decay neutron production is non-varying and then solving for the steady-state power level when rho=-0.01 (ie, 1% shutdown margin). This yields about 40% of full reactor power, meaning that reactor power almost instantly drops to 40% on a curve determined by the 10^-5 second neutron generation time (aka, "lambda") -- ie, within a few milliseconds, hundreds of neutron generations have elapsed and you are already at or below 40% power. Then the rate of dropping all the way to zero, or to the 7% level of decay heat is going to be determined by the various delayed neutron group timings. I can get an intuition for that by pretending the faster groups are now prompt neutrons and solving the same math as before, and this is pretty crude, but best I can tell, yeah, it's going to take 10's of seconds to get below 7%, deep into the decay of group #2 w/ a 22-second half-life; if only group #1 and #2 remain and all other groups are treated as prompt neutrons, my simplified power level stabilizes at 14%, so yeah, it's going to take at least one 22-second half-life, plus a little to account for the rate at which those isotopes are produced being more than zero (somewhere between 13% to 40%). So yeah, seems like your intuition is backed up by the mathematics. And I got a bit nerd sniped. And understand the math a bit better than I did before. So, thanks.

[@0donger]

Glad someone corrected him. Decay heat is an issue for months after shutdown.

[@spvillano]

@@kevinmeganck1302 passive cooling is part and parcel of a gen 4 design. But, name even one meltdown that wasn't human induced. Yes, a malfunction of some sort occurred, but had a human action been correct, the meltdown would've been avoided. A good example, Chernobyl and TMI-2, both exclusively human errors that triggered the hot mess. Chernobyl, not recognizing xenon poisoning in the core until it "burned through" and the core experienced a rapid power excursion, TMI-2, misreading the signs and a lousy human factors design leaving a telltale lamp obscured from vision by being on the wrong side of a 7 foot tall console. And I know TMI quite well, it's around 3 miles from me and the remaining unit shut down in 2019. Kind of miss the cooling tower plume, was a convenient landmark that was visible for many miles around. Fukushima, again, human factors at a management level. Ignored warnings of an inadequate seawall and no venting outside the building through scrubbers for any hydrogen gas - something specified by the manufacturer as a safety improvement. A few meters taller and the site likely wouldn't have flooded and only the Japanese would even know that Fukushima even had nuclear plants. Getting emergency generators in place in time wasn't in the cards after a tsunami, so prevention was critical and ignored. Venting the hydrogen outside would've prevented what started as a TMI meltdown turning into Fukushima. And all had one other failure, which made things much worse - no communication with the local government about an emergency and precisely what was going on, even if it's uncertain.

[@kasel1979krettnach]

"Boran"

[@harrywhittaker7563]

Just what I was gonna say. Reactors normally operate on delayed fission, not prompt criticality or higher

[@dallebull]

Feels like we can do this 1000x safer nowdays, than in the 60-70's, when the plants that actually have meltdown was built. But for some reason we expect nuclear to be just as unsafe, it's like comparing an car from 1970 with one form the 2020s, there has been huge leaps in design and meterial science since then but apparantly not when it comes to Nuclear Plants?

[@gbulifant222]

The biggest thing in these reactor accidents (other than fukushima) was that these operators didn’t have the proper level of knowledge to understand what they were doing to their reactor plant and what was actually occurring. I agree with you that safety measures have improved, but at the end of the day a reactor will respond in a very similar way to changes in plant parameters and without proper training and full understanding of what the operators are doing, then no reactor is truly “safe”. Think about it, the US Navy had had nuclear reactors since the 60s and never had a reactor accident. Not even in the slightest. Thats due to full understanding of the reactor plants

[@NeovanGoth]

Yeah, arguing against new reactors because the ones from the 60s were unsafe feels a bit like refusing to fly with an A380 because the De Havilland Comet tended to crash so often back in the 1950s. It's just not a very good argument and makes it look as if there were no better ones.

[@philipschmid9352]

​@@gbulifant222Fokushima has disregarded multiple best practices and safety regulations in the construction of the reactor.....

[@arthurdefreitaseprecht2648]

Something that is important to note is that the old reactors are nowhere close to "unsafe", they normally have multiple safety features. The thing is, modern reactors would be even safer.

[@OzixiThrill]

@@philipschmid9352 They didn't disregard safety practices during construction, they refused to redesign the plant after construction. That's nowhere near the same thing.

[@sixft7in]

Commercial plants can learn a lot from US Navy ship-based reactor plants. Lots of safety built in. Very few accidents even though the fuel is HIGHLY enriched. --US Navy veteran nuclear reactor operator

[@user-gi6db4bw2o]

Yeah, but main problems are occuring when fuel is low enriched, like in RBMK series

[@rdspam]

About 1/6 the MW(th) output of a commercial reactor, correct?

[@Phil-D83]

Depends on the type of reactor, fuel type, coolant used,etc. Gen 1 and 2 reactors were very dangerous. The new gen 3+ are usually bullet proof. Molten salt one are excellent

[@sigurdkaputnik7022]

"usually bullet proof" - in this context, the word "usually" is, what worries me the most. Didn't they say, RBMK-reactors cannot explode? Usually?

[@Phil-D83]

@@sigurdkaputnik7022 nothing is perfect, but the newer reactors (especially the molten salt ones, look up the "integral fast reactor" ) are far less prone to it

[@excalibro8365]

@@sigurdkaputnik7022 USSR was hell bent on proving the world that communism the way. They are more interested in appearing more advanced than they were. Hence the cutting corners and overpromises.

[@SnailSnail-lo4pm]

​@sigurdkaputnik7022 anything is usually bulletproof up to a certain caliber.

[@yogoo0]

@@sigurdkaputnik7022They say the RBMK reactor cannot explode because they thought that there would be no one stupid enough to prime the reactor to explode. it may not be obvious to the common person, but to anyone even slightly knowledgeable in nuclear would know the only outcome of these actions. What they did is analogous to cutting your break lines because you were going too slow. In short the scenario is, this very dangerous reactor is not acting in the way that I am expecting, and I have decided to removed the control rods to raise the power even more to conduct a safety test. Do you see the irony of what was just said. Park rangers say it the best. There is a significant overlap between the smartest bear and stupidest human.

[@exiaR2x78]

Meltdown is one of those buzz words. We like to think of it as an unintentional energy surplus - Mr Burns

[@brutonstreettailor4570]

Quite a big omission in this presentation is that Fukushima didn’t suffer meltdowns, they suffered Melt-throughs which is different in that the cores ( which they still aren’t sure where they are) , melted through the concrete.

[@marckhachfe1238]

For me, the most mind blowing thing about this subject is the speed at which these things happen . These are not chemical reactions, these are atomic reactions that happen almost at the speed of light. Amazing. I always found it astounding how the entire pit in an abomb is consumed so quickly

[@DrDeuteron]

Not atomic, but nuclear. And faster than light. Electromagnetism is around 1e-15 s, while nuclear reactions are around 1e-20 s, or less, or more.

[@LukeA_55]

The fact that we were able to take multiple pictures within the first 10 milliseconds after a nuclear explosion is almost unbelievable

[@marckhachfe1238]

Agreed. In fact, i find those Rappatronic images to be INCREDIBLY mesmerizing an absolutely terrifying. When you look at them and realise that, that i that is the power of the atom in its purest form. Beautiful but very scary images. I have stared at them for a very long time in the past, contemplating what i was looking at. @@LukeA_55

[@marckhachfe1238]

@@DrDeuteron Yes, nuclear. My mistake. Gonna have to disagree with you on being faster than light. There is no way for the neutrons in the the chain reaction to move faster than light. Ive read extensively on this on the nuclear archive web page and i don't recall ever reading anything about faster than light. Not calling you a liar, im interested in what you mean. Can you help me out? I will never get bored of this subject. The conditions at the pit during supercritical reactions are just astounding. They make our sun look like a wet fart. Albeit, only for a fraction of a second (thank god)

[@rdspam]

Prompt critical reactions in a weapon are completely different than what happens in a nuclear reactor. Moderated delayed neutron chains are much, much slower.

[@Evil_EmperorOfficial]

Thank you for going into this. I am very interested in Nuclear Power and it is great to see someone cover it! Keep up the great work!

[@BakuganBrawler211]

With the advancement of SMRs hopefully in the near future factories could be powered by those allowing for far less strain on the power grid while also allowing them to act as power stations. I’d love if Conesville got a SMR for its business park.

[@RiDankulous]

I want my very own SMR in my back yard so I can can be 'off grid' 😆

[@bodabodaguy3193]

12:48 excuse me? Thousands of years? Ima need that source sir. Na like actually though, thousands as in plural? Bro wtf 😂

[@nukesrus2663]

Same idea as when someone says "thousands of man hours", not literally thousands of years.

[@TestyCool]

@@nukesrus2663 Ye I still find that misleading AF though. A jobs site doesn't say 1,562,358 man hours since last accident. It give days since for a reason.

[@rdspam]

Statistics in total operating units is extremely common. Aircraft accidents per flight hour, car accidents per mile driven, etc. A duration actually tells you little. A GM car plant with 10,000 employees operating for 300 days with no accidents and Steve’s bike shop, one guy, operating for 300 days with no accidents are not the same. Duration is a very dumb metric. 176 aircraft fatalities worldwide last year. Only 1 in 1908. Flying has gotten tremendously more dangerous?

[@rdspam]

“As of May 2023, there were 436 nuclear reactors in operation in 32 countries around the world.” “The average age of these nuclear reactors is about 42 years old.” That’s 18,312 years of operation, not including plants that have been retired. “Thousands” (2200+) in the US alone.

[@codaalive5076]

Thanks for another video. I would add Chernobyl was dual use reactor (military/civilian) from very different time and culture... After Fukushima they made stress tests at our local reactor, it was found a few ordinary fire engines can be used as a back up for existing 2 or 3 backups.

[@spvillano]

Chernobyl was a debacle when it was constructed. The roof was supposed to be reinforced and fireproof, instead a plain tar roof was installed. Which was flammable, exasperating the problem after the power excursion dismantled the reactor explosively. Had TEPCO not ignored the designer's production change of venting the reactor through scrubbers to the outdoors, Fukushima would've just been a TMI type of meltdown, with a few leaks from earthquake damage and far more manageable. Had they raised the seawall, as warned to do, the site never would've flooded. Both show risk acceptance beyond what should be considered acceptable - at a level not witnessed since the last two space shuttle explosions. Better to face a faded giant report than a pinnacle faded giant, with accompanying big black eye for regulators and operators alike. Or for example, TMI vs Fukushima/Chernobyl. Middletown, PA is still inhabited, no cancers since that meltdown and the second unit was only shut down for financial reasons in 2019. Chernobyl's remaining unit remains online (save when shut down due to some hostilities and foreign troops digging in and stomping around the grounds), but the entire region remains an exclusion zone for good reason. As thousands of Russian soldiers will learn as they contract various cancers fairly soon.

[@seantaggart7382]

Indeed And Really? You're unlikely to find a RBMK reactor nowadays

[@spvillano]

@@seantaggart7382 true, it's hard to find the 2 in Leningrad, 3 in Smolensk and 3 in Kursk. It's not like the cooling system leaves any sign that it exists. The last RBMK is schedule by Russia to shut down in 2034. Then, they'll be as common as the Dodo bird. If it wasn't for an unauthorized experiment, performed by workers that never should have performed it in the first place (the day shift was conversant with the test and all permutations of things that could've gone sideways), nobody would know the name Chernobyl. And in Soviet Russia, nobody talked about nuclear meltdowns, the nuclear meltdowns talked about you.

[@seantaggart7382]

@@spvillano yeah And bwrs are just better

[@codaalive5076]

@@seantaggart7382 BWRs are better than what? RBMK, PWR?

[@robertschemonia5617]

At 11:08. That is a BIG generator engine over that guys right shoulder. It looks like an EMD 2 stroke diesel, much like what EMD used in diesel electric locomotives for a LOOOONG time. They are still very common, super reliable, and very easy to repair and get parts for. That was an excellent choice for the power unit for a standby generator. Those engines are known for dependability and ruggedness. Fun fact! Just above the red writing on the side of tge engine is a valve. There is one of every cylinder. Those are blow down valves. They go directly into the combustion chamber, and are used to vent any possible moisture or oil buildup on the top of each piston from them not having been run for periods of time. If there was water or oil on the top of the piston, at best it could hydrolock the engine, at worst, it would bend or break that cylinders connecting rod and or piston. Fun fact 2: the older Detroit Diesel engines that were also used as generators, truck engines, and various other industrial applications worked almost identically to this monster EMD engine. From the individual self contained injectors with individual fuel racks to meter the fuel amd therefore engine speed, to having to have forced induction to even run, they are the same. Locomotives generally had a superturbocharger that acted as a supercharger at idle being driven by the crankshaft via an overrunning clutch, and at higher loads and RPMs they acted as a turbocharger, being driven bu the exhaust gasses.

[@rdallas81]

Yes

[@milosphotos]

The book he mentions at the end really is incredible. It was a pleasant surprise to see it in here! Great video otherwise, very informative and it captured my attention rather well :)

[@MiltonGrimshawMoote]

Of the nuclear accident we generally know about there has been 4 not 3 major accident, you missed out Windscale (now Sellafield) in 1957 in the UK. But beyond these there are many in the US and USSR that we only have the briefest of knowledge about because they were military accidents, Oakridge in the US springs to mind.

[@j_andrzejewskigaming6491]

Not to mention SL1

[@shaggyd485]

Can't forget about the SRE (Sodium Reactor Experiment) meltdown that occurred at Santa Susana Field Lab in 1959.

[@Mathignihilcehk]

@@shaggyd485 You can't really call an experimental meltdown an accident similar to Chernobyl. When you have an experimental research facility, a meltdown is expected as a possible outcome from the outset. Unless the experiment lost containment, that's just a data point. I guess you could call Chernobyl an experiment. But the experiment was supposed to be a functional test of the turbines, not a test of what happens when you remove all the control rods, poison the reactor for several hours, and then suddenly insert the control rods back. We already knew what would happen if you did that, even back then. Well... some scientists knew. The ones working the night shift evidentially did not.

[@cashewnuttel9054]

According to an angry Russian, the Americans caused Chernobyl because they kept taking away Russia's smartest people.

[@chuckdenure5780]

Good point. Did you know that they blew up a reactor on purpose in the open desert in Idaho only 1/4 mile from SL1, called the PBF (Power Burst Facility)? Boom. The camera film was grainy from the gamma flux.@@Mathignihilcehk

[@its-sneaky-b7295]

yo this video essay is really really good because i want to be a nuclear physicist in the future or just work somewhere that has to do with the nuclear reactor so thank you for spreading this information and awareness

[@runedahl1477]

The dangerous thing with these water cooled power plants is not the nuclear material but the water that is supposed to cool it. If the circulation of water stops the temperature of the water will increase tremendously. At 700 degrees centigrade large amounts of hydrogen is created and eventually this hydrogen will explode. The result is that nuclear material is blown up in the air and spread over a large area. In Fukushima all procedures for handling the reactor worked but since the tsunami had knock out all the backup diesel generators the circulating pumps had no power and did not work. What you see on the footage from the accident is not a nuclear explosion but one that is caused by the hydrogen. Similar things happen at Chernobyl and Three Mile Island. If you have one reactor that is not cooled by water under high pressure this would not happen. That is one of the benefits with molten salt reactors.

[@syntaxusdogmata3333]

Thanks for this comment. I didn't know that about water at 700°C. Something new to study! 👍

[@runedahl1477]

@@syntaxusdogmata3333 The pressure in their steam turbines are between 75 to 150 bar and you get what is called superheated steam. I am not a nuclear engineer but I know that superheated steam for ship turbines holds a working temperature of around 450 degrees centigrade. This is of course done with large boilers fired by gas or oil unless it is on a nuclear powered vessel. Unlike nuclear power plants ships have the possibility to dump steam to control the temperature or just simply shut down the boilers. Besides there are large safety valves that will open if the pressure gets too high. On a nuclear pressurized reactor you can not do that without also releasing radioactive material so you need very efficient cooling capacity. For both water and gasses there is a connection between temperature and pressure. If you take a well known gas like propane it has ambient pressure to the atmosphere at -42 degrees centigrade and will be in liquid form. If you have it in a tank at a temperature of 30 degrees centigrade the pressure inside that tank will be around 12 bar but the propane will still be liquid. Drop the pressure and the temperature will fall too. That is the basic principle of refrigeration.

[@gbulifant222]

@@runedahl1477Pressurized water reactors do not release radioactive material by dumping steam. The steam generators are located in a secondary loop to the primary. No radioactive material is in this loop => no radioactive steam dumps. If you lifted a primary relief, then yes potentially radioactive steam would be released but the radiation levels would be low and if you lifted a primary relief you have a lot to worry about because you’ve fucked up something severely at that point

[@runedahl1477]

@@gbulifant222 what spreads The radioactive material is not the steam but the hydrogen explosion that is caused by the enormous amount of hydrogen that is generated when the temperature of the steam goes above 700 degrees centigrade.This is what happened on all the three most known accidents. When it comes to gas explosion you have something that is called BLEVE (Boiling liquid evaporation vapor explosion). What is happening is that gas is spread over an area and self ignite. The explosion is huge and can resemble a nuclear bomb since you will also see a mushroom formed smoke cloud. There are probably some clips on KZbin if you want to see what it looks like. I have seen some footage that is not intended for public view but is shown to firefighters and people working with gas. The reason why it is not intended for public viewing is that it also shows people being killed in the explosion.

[@gbulifant222]

@@runedahl1477 I’m well aware of the mechanism by which a hydrogen explosion occurs in a reactor. However your statement about liquid sodium reactors isnt really a solution to the problem of being over 700° C. Pressurized water reactors aren’t designed to run that hot. No reactor is. If you’re above 700° C in any kind of reactor, you’re likely going to have a reactor accident. Even with liquid sodium, at that temperature you’re going to lift a relief and you know what happens when hundreds of gallons of liquid sodium starts reacting to exposed air? Also a very big boom

[@Steven_Edwards]

Funny enough, the guys at Oak Ridge that worked on PWR reactors for the Navy said: 'yeah they work great. Right up to about 60mw' after that you are ****ing insane'

[@Steven_Edwards]

I think around that was the point that they figured that if you had a meltdown, any steam that was created before it coiled that split the hydrogen and O2 to make a big boom any possible explosion would be extremely small. I guess they figured being in the ocean, even in the worst case they could flood it with seawater and still swim away rather than having some sort of meltdown that would go boom or kill everyone onboard.

[@sskuk1095]

Hey, I have a question: Could a meltdown be stopped / slowed by a design change, where at the bottom of the reactor vessel there is a sealed off chamber containing boron or other neutron absorbers and if a meltdown would take place, the melted core would come into contact with that material, absorb it and hopefuly lose so much of the radioactivity that it would not melt through the rest of the vessel? Thank you in advance for any answeres.

[@redbird8888]

No. The isotopes that are created are unstable and must decay, and that causes the heat buildup. A neutron absorber won't stop this, because it is inherent in the material, it is not a chain reaction anymore.

[@E85_STI]

I watched the three mile island documentary and it peaked my interest into watching these nuclear videos. I like the Thorium cup it’s proper for the video.

[@420sakura1]

Fit that change your mind about fmr president Jimmy Carter?

[@michaelbauer4065]

Canadian CANDU reactors which have been in operation since the 1950's are meltdown proof. The worst that can theoretically happen is a cracked fuel-rod which would force a shut down for a few weeks to remove the rod and clean the core. Also light water (regular water) poisons the reaction so during a disaster using water will cool the reactor and not accelerate the reaction. Since CANDU reactors use heavy-water as a moderator they use non-enriched uranium as fuel, light water isn't effective enough of a moderator to sustain a reaction with non-enriched uranium. So by displacing the heavy-water with light-water during a crisis the reaction becomes poisoned and stops. They also use control rods suspended in the air by electro-magnets so if power is cut the control rods immediately fall into the reactor and shut it down, they're propelled by gravity so it's reliable. They also have a special neutron absorbing liquid that's injected if conditions get much worse which completely kills the reaction and forces a full flush of the coolant loops before a reaction can happen again. Meltdowns are an issue that was solved before they were even a problem, by Canada. Canada sells the reactors for quite cheap as well, reactors have already been constructed in: Romania, China, and India. The only reason they're not used everywhere is because Canada is strict about countries weaponizing plutonium, which is why India can no longer buy them.

[@RiDankulous]

That is very interesting! I saw recent news that Canada is enabling some of their reactors to continue operation beyond their initial lifespan figure since they need a lot more energy.

[@michaelbauer4065]

@@RiDankulous Pickering, Canada's longest operating power-plant started in I believe it was 1971, it had been extended I think 3 times and is only 2 years younger than Switzerland's nuclear reactor which is the longest operating reactor in the world. Canada keeps renewing the contracts because the reactors are good. Plus we're not building a bunch of SMRs to keep the grid going. Ontario, the part of Canada with the most reactors, is one of the cleanest grids in the world and actually has the occasional day about once a year where the grid runs 100% green.

[@RiDankulous]

@@michaelbauer4065 That's great!

[@markhowell2606]

I have heard that one of the nuclear byproducts xenon can also somehow hamper nuclear reactions, can that gas be collected and used to shut a reactor down in an emergency situation? Why don’t we use primary coolants that have far less expansion ability than water? Maybe a salt of some kind.

[@spartan117ak]

well considering the two big melts have been an outdated reactor based on poorly translated stolen plans and a reactor placed in a dangerous tsunami zone(they were warned against building there) I'm pretty chill with reactors, just distrusting of the people who cut corners to build them

[@yanderevenom9793]

100%. There’s no way corners wont be cut for the big wigs ti make a buck. This is nothing but propaganda because wind and solar energy can’t be capitalized on. And yeah, they’re may have been only 3 major nuclear plan accidents but the effects of those are STILL being felt to this day.

[@Jtretta]

The power output of a pressurized light water reactor, the type sane countries use, is not controlled by the control rods when steady state in the power range. Yes, they will have an immediate effect on power, however the core is designed to automatically match the thermal power of the boilers without any control rod movement. RBMK cores have an active, automatic control rod system because they do the opposite, any power imbalance between the core and boilers amplifies itself causing either a shutdown or power spike if not corrected.

[@stevecummins324]

steam ejector pumps would appear to be by far the most obvious devices to use for emergency pumping of coolant. powered by steam, that would be turned on/off by a mechanically actuated valve. and other than the valve, and steam.water no moving parts to go wrong. they convert the heat from steam into some suction of water, and can then pump that water to a higher pressure than the motive steam.

[@seantaggart7382]

Indeed I think this one game had a good title for it RCIC Aka When power is gone steam powers it

[@Mathignihilcehk]

I mean, we were trying to use the heat from the reactor to power the pumps to keep the reactor cool way back during Chernobyl. The problem with Chernobyl being that they blew up the reactor in the middle of the test. They weren't even testing for that.

[@KC-rd3gw]

There's also boron injection which is like a liquid control rod. In the case of an emergency you can poison the core even without the help of the control rods. Also, control rods are fail safe and drop by gravity. The fission products continue to decay though so you still need coolant moving over the core till they decay away.

[@chazclark86]

Yo for once my recommended was decent. Loved this, happily explained. Big up. Everybody should know this.

[@dclem005]

In a nutshell why it was so difficult to be able to completely eliminate the possibility of ANY nuclear reactor from ever having a melt down is that the process of getting useable energy is a incredibly complicated process (ie one of the most complicated technologies ever used by man) and in the first few decades in which nuclear power was being used there was a bit of a learning curve the industry went through in order to understand it better and create more and better safety measures in using such technology.

[@MrChainsawAardvark]

Has any work been done recently with fluid core reactors - where the core doesn't melt because it wasn't solid in the first place? As I understand it, the nuclear fuel is made into salts, dissolved into a fluid, and then you control the control the output via neutron reflectors and stirring action. (I've heard both spin the stuff, so it concentrates at the edges like a centrifuge, or mixers that bring the fuel to the middle.) Speaking of melting down - why don't more reactors use horizontal fuel channels, rather than vertical ones?

[@u1zha]

I think many of the thorium power companies are fluid core? CopenhagenAtomics reactor for example. Liquid core, liquid moderator, liquid fuel blanket (breeding something something? I haven't yet grasped their exact plans). Re: horizontal fuel channels, I don't think it changes much in meltdown equation? The active zone is anyway close to spherical, right? And the amount of material that could melt down is thus the same. Control rods can drop inside the channels by gravity, if they're vertical. And I guess fewer structural supporting elements needed in vertical configuration.

[@torinireland6526]

CANDU reactors do use horizontal fuel channels.

[@richardshawver7264]

The delayed heat of a shutdown reactor is not from continued fissions as you said. The fission products in some cases also breakdown into simpler atoms. These by products while they release it ia not as great as a true fission. This rate is called half life of these by products. It is described as heat of decay. This produces approximately 7% of the average power level of the reactor. This is simple nuclear physic. I know I taught it for two years.

[@drumerjake23]

Awsome video!! Would you do one like this one for a RBMK reactor?

[@4everlearnin]

I’m reading the book mentioned in the video “Atomic Accidents: A History of Nuclear Meltdowns and Disasters: From the Ozark Mountains to Fukushima” I highly recommend this book it is well written and has research quality information. If you want to learn about something nuclear related this is the right book.

[@zolikoff]

"Stopping" a meltdown once it's already underway is rather pointless no matter how you want to define it, because at that point you've already lost the reactor. If you can't save the reactor...

[@jonathankydd1816]

well, a partial meltdown is better than a full meltdown. better to lose a single reactor than to lose the whole plant or possibly irradiate the surrounding areas in the case of a catastrophic meltdown.

[@stanleytolle416]

Best to develop molten salt reactor that can not melt down or explode.

[@b43xoit]

That's right -- if the fuel is normally molten, by design, a meltdown is no concern.

[@shoeskode136]

Meltdowns can still happen- Its not like the uranium can mix in with the salt

[@b43xoit]

@@shoeskode136 > Yes, it can. UF6 and I think there is another valence as well.

[@stanleytolle416]

@@shoeskode136 in Molten salt reactors the fuel is dissolved in molten salt which has a boiling point of around 1500⁰C (2700⁰F). The fuel can be uranium plutonium or thurium. These reactors can not reach these temperatures as the expansion of the fuel as it overheats will move the fuel atoms to far apart for the nuclear reaction to happen. Molten salt reactors also have a drain pipe that is plugged by chilled plug of salt. If power is lost or the reactor gets to hot this salt plug melts and the molten reactor fuel / salt drains into a lower drain tank that is designed not to support the nuclear reaction and shed off decay heat through non-powered air convection. So no, a molten salt reactor can not melt down or explode because the fuel is already melted.

[@shoeskode136]

@@stanleytolle416 wow. Thats. Impresive wowie

[@Thugshaker_thequaker]

My grandfather is a retired engineer who used to work on some nuclear related stuff. He is unable to talk about some of his past work. I haven’t seen him in years but I hope he’s doing well, he had some issues. Hope to talk to him about it sometime

[@LukeA_55]

I bet there's some awesome things he could tell you about. Don't wait till it's too late, there's so many things I wish I had talked to my grandparents about

[@brianmichelewallin]

You missed on. The 1959 partial meltdown is the Rocketdyne test site at the Santa Susana Field Laboratory (SSFL) in the mountains above Simi Valley, CA…

[@michaelWNY]

A risk assessment does only consider likelihood but also severity. Too many people just say "it's not likely" and consider nothing else. Good safety requires properly designed and maintained systems to deal with unlikely situations too. It's not what you know that is dangerous. It's what you don't know or don't consider.

[@michaelmappin4425]

Most of my Navy career was aboard nuclear aircraft carriers. There are drills in the reactor compartments every day. I have frequently heard the word SCRAM on the shipboard announcing system, but never an accident.

[@watchthe1369]

Chernobyl in Russia was a poorly designed reactor that never had a containment dome. Fukushima had containment and had the main failure caused by a steam explosion caused by over pressurization in the cooling pipe. Three mile Island was a reactor of the same type as Fukushima. Both of them had proper cantainment of the nuclear material, but the high pressure water/ steam cooling were the failure point on both.

[@chrisdiehl8452]

You forgot one thing. During the reaction, the elements are actually changing in to different elements, and those might react with other chemicals.

[@Amplifyrapzz]

The plant I work in still has all of the switches buttons and flashing lights but after 7 years of working there I got somewhat used to it

[@Tarimoth]

9:15 defence in depth relates to giving terrain IOT wear down an opponent, what you described with the fortifications of a castle relates to a final defensive line, meant for bringing the opponent to a stop IOT facilitate a counter attack and take back initiative or force a political resolution. Defence in depth does not mean layers of defence, it means lines of defence, to be occupied one after the other. It means trading an area for a favorable situation

[@sanketvaria9734]

back in 50s people used to think that in future we will drive cars that run on nuclear, it was called Nuclearpunk genre.

[@darrelstickler]

Pretty good. 95% correct. Informative and fair.

[@manloloyojosh1458]

So that classic episode of BEN 10 where he stopped the core meltdown of a nuclear reactor via a very cold and sick Heatblast was a lie? My childhood is ruined.

[@michaeljeferson9118]

There’s something that wasn’t touched on and I think was important to bring up when discussing meltdowns. Almost every major nuclear accident was caused by either workers or governments ignoring safety warnings. Fukushima’s sea wall was warned to not be tall enough and was ignored because they thought anything over a 10m wave was impossible / not likely. Chernobyl was a series of bad decisions combined with the Soviet government not telling their reactor workers about the flaw in the reactor it’s self. Three mile island is actually an example of how safe nuclear reactors can be because even though things went wrong and operators made mistakes the meltdown was contained due to proper safety measures.

[@LoveShaysloco]

Thats why i like the movie atomic twister for i dont remember which if the tornado damaged the diesel generator or just neglect. But thats why its good if they have a back up to the back up and you turn them on / maintain them

[@ernestestrada2461]

When a reactor is designed correctly, proper safeguards and training. You can drop the control rods and stop the nuclear reaction. What happened at Fukushima is poor training by management. There was a sister reactor that had no problem shutting down because they had practiced how to do it.

[@u1zha]

The sister reactor probably had pumps that functioned, unlike Fukushima that had pumps knocked out by tsunami? Can you provide a link? The video was pretty clear (if superficial) about the fact that dropping control rods does *not* stop the nuclear reaction. Back to 0:00 you go.

[@excalibro8365]

What happened in Fukushima was once in a millennia natural disaster. Japan is prone to earthquakes, but they are mostly tolerable thanks their earthquake-proof construction. There have only been a few instances of 9 magnitude earthquakes in recorded history and none of them were in Japan. No amount of training in any country can prevent that disaster.

[@Ultrony]

In Chernobyl actually they turned on the pump but one of the pump was built outdated cause of corruption, and the pressure in the core was already so high that when the 350kg control rod were going down the they started literally levitating and going up down , and graphite tips of rods caught on fire then the pressure goes on increasing and increasing and once it is out of control booommmmm and then Oxygen rushed in burning the available Hydrogen which was seperated from water steam because of high temperature. (This is what i remember from the miniseries Chernobyl) Hats off to the heroes who saved the Chernobyl accident risking there lives 🙏🏻🙏🏻

[@brennantyska5101]

That's wrong

[@sskuk1095]

I love that Thorium mug!

[@watchthe1369]

I like the Molten Salt varieties of reactors. When the reactor starts to overheat, the expansion of the salt throttles the reactor automatically. The working temperature of salt is wider span of temperature than water and it is not pressurized.

[@Martyz-TV]

The odds of a nuclear meltdown might be 200,000,000 to 1, but so too is winning Lotto which has one winner per week.

[@RiDankulous]

To me, the passive cooling (without need for generators to run water pumps) is the best bet for safety in the future.

[@Dylan-_-01]

3:50 Uranium does not hold heat after fission. However after insertion of the control rods, heat can still be produced. Uranium 235, when struck by a neutron, splits into krypton 92 and barium 144 releasing 3 neutrons. These isotopes then decay. It is this that continues to expel heat after shutdown.

[@theinspiringengineer-scien6393]

Best thing for stoppingg meltdows - renewable energy! ;) :D

[@LordRazer3]

Going to have to remember this video when I tell someone I know how a nuclear reactor works on the fundamental level and how easy it is to stop a meltdown. I couldn't build one but I could figure out how any of them works

[@Sk3tchPad]

There’s usually a third or fourth failsafe these days. Last resort is usually a Xenon or a gadolinium poison, although they’re so effective that the reactor has to be “rebuilt” afterwards.

[@19JMT96]

Awesome video, well written. Side note, idk if its just me but the plosives in the audio were getting to be a bit much at around halfway through. Dont know if you have a pop filter or account for this in post but figured id mention it.

[@VegarotFusion]

The SL-1 Nuclear Accident was an example of how not to design a nuclear reactor. It may be a small experimental design. But manually adjusting the control rods precisely by hand with the minimum number of rods is a recipe for disaster.

[@huntercovington9421]

I don’t think you properly convey how incredibly extraordinarily rare nuclear meltdowns are

[@thewiseperson8748]

Renewables and energy storage are much more promising than nukiller. Nukiller reactors are just too dangerous.

[@benhynes2592]

Great work!

[@infinite_ender638]

He kinda paraphrased the whole "the operators at chernobyl disabled the safety systems" thing. Yes, they did turn off the safety systems, but it was for the sake of conducting a test, where the real error came in when they were interrupted, and postponed the test for the night staff, which was much fewer and less informed of the details of what they were to be doing. also the three mile island control room disaster was mostly caused by the relief valve of the reactor being stuck open, letting water spill out of the cooling loop causing the reactor to overheat. the control room also lacked the critical information needed to keep them informed of the exact situation. where was an indicator to inform the operators of the intended stat of the valve (being if it was set to be opened or if it was supposed to be closed) but not the actual state of the valve, meaning the operators could see that they were losing pressure, but not that it was spilling out of the valve. Then there was the PR meltdown, which had much worse effects than the actual reactor meltdown.

[@jonathankydd1816]

True, but some of those were critical safety systems that were never supposed to be bypassed. for example, there was a hard limit on the number of control rods that they were allowed to remove. during the test IIRC, they removed beyond that limit because the reactor wasn't producing enough power to sustain it's own systems yet.

[@mack.attack]

Yeahhhhhh. If everything goes the way it's supposed to. But yet they found a football size hole in the reactor lid of Davis-Besse. Very comforting to know that was there in reactor that back in the day almost got hit by a tornado.

[@kizunadragon9]

TLDR because a runaway reaction creates it's own energy. heat is a byproduct of work, so all we are doing is really harnessing the reactions sloppy seconds to create electricity.

[@user-xq2of4fj6e]

We need to find a good way to deal with Radio Active Cesium before we allow more reactors to be built. Or we require the drilling of a deep well below each reactor. Deeper than a Nuclear test well. And it must be able to accommodate the Core nuclear fuel being allowed to drain to the bottom.

[@joewiehr1931]

The containment vessels do not work, they just build up presser then explode.

[@jjlortez]

If anyone has had to deal with a toddlers meltdown, you know just how hard nuclear meltdowns are to handle

[@cflyin9]

There something called Rici it uses left over steam to turn a turbo pump to feed water

[@jeffreyyoung4104]

When I was a kid in the 60s, the atomic energy commission and many of the builders of atomic reactors claimed electricity would be free when their grand plan to build all of these reactors, but we know what happened to that idea! In many cases of meltdowns, it is due to the reactor being used for a breeder reactor. That is the type that makes atomic weapons grade materials, and it is very dangerous for reactors to be used for such activity. When it isn't a breeder reactor, it is usually a new design of reactor that has no history of reliability. Take France for example, they only have one major design, when new ideas for upgrades are made, the upgrades will apply to all of their reactors, which makes it much safer than a hodge-podge of many different untested designs.

[@ArsenicShooter]

Why not grabbing a hole for the reactor itself under the structure during construction with a big trap door that could be manually opened to drop all the crap hundreds of meters underground, followed by a filling of some material to clog up that hole and keep it far away from the surface?

[@darylcheshire1618]

I think, in one incident the control rods either got bent or the tubes they went into were bent.

[@KING-zi6rx]

The incident at 3 mile island wouldve been a really good example of a partial meltdown I recommend Kyle hills vid if anyone interested wouldve loved to see it talked about in this vid tho also Chernobyl and the elephant foot wouldve been a good example for a full meltdown Edit: lol I made this comment before he brought them both up

[@ThomasAT86]

It's incredible, I mean this could literally help the world so much. I think the biggest hurdle, yet again, like with medicine, is politics, money, power, people not trusting the government and authorities due to issues in the past. Very sad!

[@rhystapscott]

Getting used to something being “as safe as it can be” causes complacency, which in turn causes problems.

[@Bmywudt2]

Is it possible to replace reactors with Mega energy storage?

[@mickgatz214]

How much of this water is radioactive? and the steam emitted from those tower things?

[@tuureluotonen1631]

Not much more radioactive than tap water, as it hasn't been in contact with radioactive material. Same with the steam.

[@Christian-oq3md]

the equiavalent of this video would be something like; "why are computers so big?" then proceed with 80ies footage of a computer :D

[@robertgutheridge9672]

Plus the fact that most reactors used in the united states are based on the Westinghouse design from the 1950's modern modular reactors are a 1000 times saftet

[@majorcornflakes4194]

This might be a dumb question but I’ve always wanted and explanation of how the cooling water avoids being contaminated with radiation but is still able transfer heat, in a manner that it can be released into the world. I’ve always wondered and it seems like too simple of an answer in my head to be right

[@LogicalHindu24x7]

The thick concrete dome is of no use when the reactor explodes like in Fukushima or Chernobyl and contaminates surrounding towns and villages. Most people only imagine this scenario when they think nuclear accident and hence oppose it.

[@coollittlebinch4689]

Thanks I love this video!!

[@magicofthestone]

A question should with an upward inflection.

[@thetowndrunk988]

It’s important to note- per Petawatt hour, nuclear is among the safest form of energy production out there. It has far less deaths per Petawatt hour than most anything else. Even wind has more deaths per Petawatt hour.

[@turboprint3d]

One of the issues is the designs of the reactors that failed , there was a particular ge branded prototype that ended up being sold to many power plants . This is a poor design , compared to reactors that shut down automatically due to physics when things go sideways . There were better designs available at the time but those prototypes were the ones chosen for a reason unknown to me . There are definately much better designs available currently.

[@tompepper4789]

I like your Thorium coffee mug.

[@DotAHeaD-JamieJupiter-Xander]

@9:30 Eyy! That's Pickering, Ontario's Nuclear Generating Station! How 'bout that OPG footage inside the Reactor Auxiliary Buildings showing the nuclear energy workers in plastic suits going into the Unit 8 airlock, eh? ^_^ Cool beans!

[@NorfarPS3]

"1000s of years rector operating worldwide" We haven't been operating rectors even close to that long.

[@user-gi6db4bw2o]

probably it was like global NPP years of operation

[@420sakura1]

I think they meant thousands of plants over the years. Which is still confusing. I domt.think we have had that many reactors.

[@carlosenriquez2092]

You'd have to ask my wife why it's impossible to stop her meltdowns. Usually I grab the kids and hide two counties over till she offers up cash or expensive electronics in exchange for our return. I'm pretty sure at least one of her therapists has attempted suicide, I blame my wife but yeah once a meltdown starts you just gotta let it burn out.

[@beeftec5862]

comedy fail

[@michaelzborovan4362]

I thought it was amusing... certainly not a fail to the empathetic of us...

[@robertschemonia5617]

Ha. That's funny. Got a good chuckle out of me.

[@Solid_Snake88]

lmfao, run

[@VejmR]

Wdym?

[@mightymightyenapack2530]

3 mile island scared most Americans into using oil more.

[@user-tu5nw7vo2q]

We are 3 miles from three miled islands

[@SYNtemp]

3:50 No, "delayed neutrons" exist but they are NOT the cause why fuel assemblies heat up even after the fission reaction has been stopped - the reason are the fission products (the atoms of elements that form as products after Uranium atoms splitting), they are quite different in their activity/half lives, some of them have short half-lives so they burn hot but disappear soon, some of them can stay for weeks or even years... so the heat caused by this fission products decaying is initially something like 10% of the "full power" but during about 1 hour, it decays towards some 3% and continues decaying... After few days, the assemblies would still be red hot but they would no more melt.

[@6NBERLS]

Most excellent.

[@crime_wavcorp]

thousands of years of reactor history? dang

[@anticat900]

It is the future, but we do use a poor design of reactor just because we always have and invested in it so heavily. We use reactors that are basically very large nuclear submarine reactors these work well in a sub where at idle it needs only a moderate amount of cooling. But when scaled up 100x for a commercial reactor the idle reaction is also scaled up and is now a not insignificant many megawatts of energy. This puts pressure on the safety systems to be large and complicated systems in themselves. It has been in the testing of these systems things have gone wrong at two disasters and the other when these systems were damaged beyond any easy repair. The answer is to keep these designs small and manageable like Rolls Royce are doing or to use completely different designs and accept investment will be required.

[@candlestyx8517]

You cant see, feel, smell or hear radiation, but it does make your mouth taste metallic. If this ever happens to you for no apparent reasom, then it means it is a very good idea to evacuate the area immediately.

[@billychi6961]

its hard to stop a meltdown but easy to prevent. All you need to do is drop all of the control rods. Every nuclear reactor incident could have been prevented by doing this. I realize it causes issues and downtime getting the reactor to start back up but it really is so pathetic that people could not foresee the issue and prevent it

[@vadimkorob2689]

A very interesting topic, but the change of pictures is so rapid that it borders on physical pain when viewing IMO