Why Is It So Hard to Stop Meltdowns?

[@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?

[@MERCS-V8]

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 🤯

[@gownerjones]

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.

[@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"

[@TheMadScientistOfLuton]

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

[@REDACTED741]

I sense some concept errors. From someone who doesn't know what they are talking about.

[@evanflessner1529]

It’s hard to stop a meltdown, but it’s even harder to start one

[@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.

[@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.

[@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

[@鬼塚アレクセイ]

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?

[@lynxrbeam8732]

Problem is I’m pretty sure the stuff the military uses is bomb stuff. Dunno the exact composition as I hate chemistry, but I’m pretty sure they enrich it enough that it can be used for bombs, so they wouldn’t want to sell that to commercial companies to “make power plants” if you know what I mean.

[@mas7rreaper126]

@@lynxrbeam8732yea you just said one of the most Ignorant things I ever seen about nuclear energy and I seen alot

[@jpheitman1]

​@user-gi6db4bw2o The issue isn't the low enrichment, it's cutting corners to save money. In particular, RBMKs didn't have a negative temperature coefficient of reactivity - since it would yield a cheaper design - while all US civilian power plants must have a negative coefficient. The safety features, quality control and trained personnel are what make Navy reactors safe, not the percentage of Uranium in the core.

[@exiaR2x78]

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

[@siyabendyaslak8880]

😂😂😂

[@Borisi-jq3tb]

*unintentional fission surplus

[@raven4k998]

yeah normally meltdowns happen because they do not know that the reactor is melting down due to limitations in the tech for monitoring in the systems are not perfect and heat build up can happen outside normal operating situations you check into meltdowns the operators did not know the reactor was overheating to meltdown the monitoring tech has it's limitations

[@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.

[@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

[@zacharytaylor190]

What we learned from SL-1: Never have a single rod control the reactor Don't manually manipulate the control rods with fuel in the core Never attempt to pull on a stuck control rod Ensure no interpersonal grievances between operators during critical phases among others. What we learned from Three Mile Island: Sometimes less information is safer Layout procedures clearly Always have a peer checker during critical operations Ensure regular maintenance on valves and pumps Have a dedicated Press Representative to give accurate and reassuring information to the public among others. What we learned from Chernobyl: Don't design reactor control rods with graphite followers Never place the reactor in a configuration for an extended period that allows for xenon buildup In reactors with positive void coefficients, don't preform rapid reactivity manipulations Don't operate near All-Rods-Out Don't ever allow for field changes to established procedures Don't change shift during a reactivity manipulation Thoroughly brief the next shift Allow questioning of authority among many others. What we learned from Fukushima: Place onsite power generators above the flood plane Design the reactor to withstand the 1000-year event Have at least 2x redundancy for emergency power generators Fit sparklers to the reactor to safely burn off hydrogen Have the spent fuel pool at ground level Have redundant systems for core cooling Allow controlled venting to occur in the absence of power Better coordinate with emergency management agencies among others. I think that covers the most glaring points.

[@JoeMama1190yesyes]

Real

[@jairo8746]

"Design the reactor to withstand the 1000-year event" This is no joke, Fukushima's earthquake was the 4th most powerful ever recorded since 1900.

[@iexist_nt]

Also Chernobyl: Don't ignore safety protocols because the reactor is taking a lil too long to heat up DON'T TURN OFF THE COMPUTER TELLING YOU TO SHUTDOWN IMMEDIATELY

[@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.

[@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.

[@Alpacaluffy]

2:14 the diagram is of a PWR reactor, but you are describing a BWR reactor. In a Boiling Water Reactor, water directly passing through the core spins a turbine, but in a Pressurized Water Reactor, the water is kept under high pressure and does not boil, instead heating a separate loop that boils water and spins the generators.

[@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

[@Dr_Larken]

4:30 OK I can’t stop seeing it so, the light in the background looks like a demon core!

[@def_not_sans]

THATS WHAT I SAID

[@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.

[@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.

[@raven4k998]

yeah normally meltdowns happen because they do not know that the reactor is melting down due to limitations in the tech for monitoring in the systems are not perfect and heat build up can happen outside normal operating situations

[@Mars0984]

After watching this, I feel that nuclear energy is very safe. All 3 of those meltdowns could have been avoided. With knowledge and awareness, and heeding due warnings and red flags, this is the safest source of energy in my opinion

[@Leon玲央]

It will never be the the fastest source of energy, if solar energy aswell as water and wind energy exist.

[@iexist_nt]

​@@Leon玲央the first two are unreliable, however they're still very viable and not enough of it is used

[@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?

[@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.

[@znotch87]

6:52 Its crucial to have accurate information.... why does it feel like a plug is coming?

[@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.

[@NotAvailable-b6d]

Time 4:00 not correct .. The residual heat is from the daughter isotopes (the pieces the uranium was split into) .. As the daughter isotopes decay they give off heat and various types of radiation .. The decay rates range from minutes to thousands of years and it is this decay that makes the waste products radioactive .. Spent Fuel rods are so hot they need to be stored in a cooling pool of water for 5 years more or less depending on the type of fuel .. Technically there is some fission taking place in the fuel after the control rods have shut the continuing reaction, but the heat energy is negligible compared to the heat from daughter isotopes ..

[@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

[@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

[@mightymightyenapack2530]

3 mile island scared most Americans into using oil more.

[@QuintinCallender]

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.

[@vipersb1]

Nuclear power is by far the safest way to generate power. It's kind of like flying, people are scared of it when in reality, it's the safest option.

[@malachiwilt3891]

It's definitely not lmao

[@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

[@thoriummarcell403]

It is interesting to note that both Chernobyl and Fukushima were designed before the first major nuclear power plant accident (Three Mile Island 1979). All of the nuclear-power plant accidents combined killed 1000 times less people than flying, and 100 times less than any non-nuclear forms of generating same amount of electricity (including renewables, eg. hydro killed 240000 people in Banqiao, 11 million had to be deported). Any reactors designed after 1979, the first major accident (that, by the way, killed 0 person, and not even any significant contamination release) are immensely safe, with effectively 0 victims total. We can now design even safer molten salt based storage and passive heat removal systems with inherent passive safety and efficient heat-utilization, minimizing the nuclear island (and minimizing volume and construction costs making it extremely economical if regulation does not artificially make it prohibitively expensive, or politics simply ruin breeding reactors like it always happened in the West, SNR-300 in 1985 Germany and Integral Fast Reactor in 1994 USA - yes, demolished by criminal anti-human wealth-centralizing politics, look it up and wake up) and also helping intermittent weather-dependent renewables that otherwise threaten our civilization if deployed without calculating resource use and usefulness/limits.

[@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.

[@chrisdiehl8452]

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

[@lawrencemeldrum3375]

as a parent of two under 5 I thought the title of the video was referring to something else

[@osvaldomichel]

Just as dangerous

[@coolsnake1134]

Unfortunately there's a saying, modern safety practices are written in blood, for example in the automotive world cars used to be way more unsafe in the '50s and '60s versus nowadays, for example a common method of injury and an automobile collision was getting ejected from the car, that was solved via seat belts that keep the driver and passengers in the vehicle, however people were still getting injured by the dashboard even if they weren't getting ejected. That was dealt with by making dashboards out of softer materials, removing anything sharp and pointy from the dashboards like by changing the design of light switches and radio knobs as well as installing airbags to lessen the force when your head hits the dashboard or steering wheel. GeForcees were also a common factor in motor vehicle collision injuries, and those were reduced by adding things like crumple zones so that the body of the vehicle crumples in a specific way to reduce the felt impact by the occupants. Also things like break away motor and transmission mounts were used so that instead of the engine getting pushed into the cab, the motor mounts break and the engine drops free below the vehicle and stays away from the occupants

[@coolsnake1134]

And to reduce vehicle fires after collisions various safety features were added to the electrical and fuel systems, for example in a modern car any airbag activation will trip the fuel pump circuit and require a dealer or body shop to reset it, also the gas tank was repositioned so it's not susceptible to damage from minor rear end collisions and the filler neck was moved from behind the license plate to a more protected location usually on a rear quarter panel and it's now located higher up. Also they now contain a check valve so that fuel cannot spill during a rollover

[@coolsnake1134]

And on me regulatory side, you have organizations like the NTSB in the US that sets safety standards for new vehicles, and on the operator side you have updated driver training programs for new drivers as well as awareness campaigns for the dangers of intoxicated or distracted driving and also enforcement of traffic regulations like police pulling over distracted drivers or things like speed traps red light cameras etc

[@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_Snake99]

lmfao, run

[@VejmR]

Wdym?

[@TrevorSullivan]

This is a really well made video. Nice work bud. Nuclear power is the best form of energy production we have as a species.

[@MiltonGrimshaw]

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

[@HE-pu3nt]

The problem is that with all the talk of progress and learning, the nuclear industry is pushing hard to keep all the old clunker reactors going. If say American Airlines were running planes designed in the 50's & 60's, and built in 70's, there would be ALOT of accidents. There's one sure way of stopping meltdowns, don't build them bigger than 150-200Mw thermal output. There just isn't enough decay heat in a reactor of this size to meltdown through the reactor vessel.

[@HE-pu3nt]

I meant 150-200mw electrical output.

[@RGD2k]

Ugh. Decay heat: 6% of the heat is from the shit left over from atoms shattering. That takes about a month or so to mostly fade away. So even if you scram the reactor, and really, no-one designs reactor core which would have any difficulty doing this, and then some, so that part always works. Even so, say you *were* at 1 000 000 kW power. Now you're at 6% of that, which is still 60 MW. 60MW is a *lot* of heat generation, and getting that out of a solid-fueled core requires keeping the primary coolant moving. Now, water is used in pressurized water reactors as the primary coolant. It has already quite a high latent heat: That is, it takes a little over 4kJ to increase the temp of water by one degree celcius normally, but when it's kept under enough pressure to prevent boiling by forcing the boiling point up higher, then at around 360 degrees C, it takes about 15kJ per degree to heat it up, and that heat capacity has more than doubled from around 6.5 kJ per degree when it was around 340 degrees. That fact, that water does carry such a crazy amount of heat at those temperatures, and goes on to carry **even more as it gets hotter** tends to be **very good** for evening out temperatures inside the core. Because the last thing you want is one small part of the core running say +20 degrees hotter than the rest. If that were to happen, the water might boil just there, (because of hydraulics, the pressure is almost the same everywhere the same body of water touches, so too is the boiling point) creating a void that would suddenly insulate that hot spot, which would allow it to get suddenly *even hotter*. This would be bad, so using water, which is quite unique in both having such a high heat capacity, as well as doing this neat trick, helps keep the thing safer. Of course, there is still another problem. You see, there is a thing called radiolysis. This is where ionising radiation (whose defining feature is that individual quanta of radiation are strong enough to knock loose electrons from molecules, thus, 'ionising' them), well, breaks the water molecules up into separate atoms. Those atoms then get reverted to just a highly explosive perfect-ratio mix of O2 and H2, and bubble up out of the water and collect somewhere... just waiting to explode and *definitely* let all the pressure out. Oh, and the zirconia cladding used to keep the Uranium inside the fuel pellets and away from the water? That tends to also cataylze steam to turn into explosive hydrogen-oxygen binary explosive gas too. Especially when it's hot. So letting the primary cooling stop moving in a solid-fueled, water cooled, fission reactor is a recipe for Fukushima-style explosion. Very expensive, and you might accidentally panic and order a large-scale evacuation that will go on to result in many deaths. Which is what happened. What, you thought even *one* life was lost because of the nuclear accident at Fukushima? It was a Tsunami that did that. A couple of technicians wading through the spilt primary coolant basically had bad sun-burn on their legs, from the alpha-radiation from the water, but made a recovery. But yes, the *evactuation* destroyed enough peoples lives to the point they were then lost to mental illness, and who *wouldn't have died* if they *hadn't been evacuated*. Worst of all is, when the precisely made fuel elements melt, you can't pull the reactor core apart anymore for recycling. It all becomes one huge lump. Can this ever be fixed? Hell yes: Just use a Liquid-Fluride Fuel. It's a nuclear reaction, it doesn't care at all what state of matter the Uranium is in, only how it's configured (placed, whether surrounded by neutron reflectors and moderators, basically how the neutron-economy goes). State of matter (solid, liquid, gas) has to do with how the molecules are stuck together, and that's to do with the electrons on the outside: all of chemistry is, so chemical reactions *care* about state: But not nuclear reactivity. Have it dissolved in an ionic-bonded liquid. (a salt). That way it's already conveniently molten and can be easily removed to a container where it can't be critical and *can be passively cooled without needing a pump*. Using gravity and a thing called a freeze-plug valve. This is where you just run a small air-cooling pump against where you want the 'valve' to be closed, and the extra cooling allows the molten fuel to freeze there, as long as that fan keeps blowing. Stop the fan, and gravity safely and automatically pours out the fuel to the safe-storage. Where you can later warm it back up with electric heaters, and pump it back up into the core, when you want to restart. Why does this work? Well, such molten fuel has a liquid range such that even if cooling fails, you can't actually get the salt hot enough to 'boil' itself. Therefore no pressure to keep it liquid is needed. Do you know what we call an 'ionically bonded compound which is a gas'? Think about it, sometimes it's even called a 'fourth state of matter': Plasma. It's really just a salty gas. Turns out if you ionize a gas, and shatter it into separately-charged fragments (ions), the electric forces tend to make it want to keep together, just exactly the way ionic gasses are anyway, because those materials have atoms that trade electrons and will happily sit about as ions, and not neutralise. But what this means is, it generally takes ludicrously high temperatures to boil an ionic liquid. Some ionic liquids will just chemically disintegrate first. Rather than having to take the heat from where it's stuck in solid fuel rods in the core, away with a coolant, you can instead pump the fuel itself out of the core and take it to a heat exchanger. Better yet, if you don't take the heat away, the core itself can be designed such that the thermal expansion of the fuel itself automatically reduces the reactivity of the core, meaning the chain reaction automatically slows down as it gets hotter. So you don't even need to *try* to keep it running, it just runs itself. It's stable, rather than unstable. The lab reactor that proved all this actually had a 'mishap' where the control rods got stuck for unrelated reasons to do with being a prototype. The temp just went up a bit, there was a scary moment for the operator I'm sure, and then it just, stopped there. 'idling' at a new, slightly higher temperature. No melt-down even. Didn't even trip the freeze-plug thing, just, happily sat there waiting for someplace for the heat to go. Boring. Exactly as you *want* a nuclear reactor to be. Why the hell does anyone water-cool a reactor then? Well, there's no good technical or defendable rational reason, it's just the way it panned out. The people used to building the water cooled ones had sales teams, and there were no people building commercial molten-salt ones. And the sales people probably had no idea the collosal disservice they were doing the world by selling more. One of the inventors of the water-cooled reactor - name on the patent, even - went on to write a letter to congress to *plead* for a ban on them. Because they were never meant to be made so big that they were a danger, from being possibly unable to be cooled in an emergency. So often, technologies succeed catestrophically - they're popular and that becomes a terrible thing, the damage done by not fixing things so badly broken, because it's the status-quo. Many fantastic technologies fail to 'make it' in the market, not for any fair technical reason, but often just because they're 'not a done thing'. They're unfamiliar, or are 'too stale' an idea to be a novelty. Or even, they arn't done because they haven't been done, because they weren't done while they were patented, and now they can't be patented (because that's how patents work) so investment doesn't want to lose money by being the 'loss-leader' to push them to market without protection from market competition. Yeah, really. Rich people are most often just born that way. They're not automatically less idiotic than any other randomly chosen group of people. The rich generally get richer, without having to work at it. So there's no real evolutionary pressure to keep them 'lean and mean' so to speak. The disparity grows far faster than anyone can do anything about it, and the best we can hope for is for the ultra rich to take the opportunity to pay to make big things happen. But to know what to buy, they'd need to know how to do the work that they've avoided ever doing. The kind of work that is maths homework. That is frustratingly finding and facing your inability continuously, until it feels like you're getting no-where, and are just 'not cut out for' it. That takes a lot of self-discipline. And if someone is so ultra-rich that they grew up surrounded by so many yes men that they never grew out of thinking they can get away with just blaming others to avoid culpability - well, they're never going to be able to grasp the knowledge they'd need to be able to be wise with their obscene wealth, to actually be worthy of the power they wield. So, if those last couple of paragraphs struck a nerve, because you 'have better things to be doing' then learning STEM. Prove me wrong: join brilliant.org and learn what you need to in order to really understand. You'll need at minimum enough maths to appreciate how game theory and quantum theory and some simple Bayesian probabilty solved using statistical mechanics leads naturally to the empirical gas laws from first principles. And then you can understand what entropy is, and why the second law is why we can't have nice things, or , how the only thing that matters about the economy, is the cost of energy. You can discard all of the 'management theory' nonsense of economics. Then look at the steel, concrete, time and energy costs of energy sources, and finally be qualified to judge nuclear fairly.

[@crabohato4954]

Umm, I'm sorry or happy that happens to you?

[@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.

[@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!

[@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?

[@lunanyxia]

Dyatlov is currently watching this on the toilet.

[@grzyb11]

why is it so hard to admit that the graphite is there

[@lunanyxia]

@@grzyb11because he didn’t want to assume responsibility and the fact that he can indeed be wrong.. he had a superiority complex where he thought he knew better than anyone and for him the very thought that he might not have complete control over the situation made him become unreasonable in a desperate attempt to protect his own pride

[@JoeMama1190yesyes]

Nah the HBO miniseries depicted Dyatlov wrongly, irl, his different. That Chernobyl Guy made a video on him

[@MegaSunspark]

Thank you for this explanation of why reactor cooling is so important even after the reactor is shutdown. That the nuclear fuel continues to generate large amount of heat months and years after the "shutdown".

[@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.

[@HCheatNcool]

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

[@stevecurran5206]

it's actually not hard. thousands of nuclear power plants don't melt down every day. and the meltdown at TMI didn't harm anyone but the utility investors. more people have died working in the solar and wind industries than in the entire history of the nuclear power industry. oh, and the moderation was not technically correct in every case.

[@thepandasir5375]

.... but theres not even thousands of nuclear power plants.....

[@andycopeland7051]

And birds. Wind has killed a bunch of birds

[@seantaggart7382]

​@@thepandasir5375so? Its mostly due to scares

[@jd4200mhz]

still the most dangerous part of a nuclear plant is not the fuel, but human greed

[@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.

[@lynxrbeam8732]

@@TestyCoolboth are usefull. I actualy like the way he put to. “5 years” doesn’t tell me anything bc I don’t know how many plants there are. If one plant runs for 5 years and doesn’t have an accident, fantastic, if 200 plants run for 5 years, and none have an accident, that means something. So basically you just calculated “plant hours” by thinking of it that way. So just saying 1000s of yrs to start is just easier.

[@xxnoxx-xp5bl]

'Pollution from coal-fired power plants is responsible for more than 100,000 deaths per year, whereas the crisis at the Fukushima nuclear plant is unlikely to kill a single person.' I know which bothers me more...

[@Alpacaluffy]

Global warming

[@abhijitmohanty8541]

Atoms for peace⚛🕊

[@randallreed7415]

(Free floating neutrons necessary for fission chain reaction) pieces of atoms ⚛️ 🤔

[@AstroCreep77]

I prefer to call them an “unrequested fission surplus”.

[@docbrosstudio7680]

Meltdowns are hard to stop, but easy to prevent.

[@SunShine-xc6dh]

Yep just don't do nuclear its really that easy

[@JoeMama1190yesyes]

​​​​@@SunShine-xc6dh Nah bro, nuclear is good. Meltdowns are really rare and hard to create. Plus, it's really clean compared to non renewable energy sources and safe too. Plus nuclear waste is actually not that bad, it's stored safely in a dry casket while it decays slowly overtime, and renewable energy also creates waste too

[@jjlortez]

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

[@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

[@Liminal-Galaxy-System6819]

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.

[@michaelkaliski7651]

The problem with water cooled reactors is that the water itself is a neutron moderator. If you lose the liquid coolant then the reactor is going to continue to heat up. The actual explosion process in such accidents is either a steam or hydrogen explosion and not a nuclear detonation. The nuclear fuel can never form a mass capable of a nuclear explosion. For this to happen, a critical mass of Uranium needs to be forced together and held under extreme pressure for a certain amount of time to allow the chain reaction products to build up sufficiently to initiate a nuclear detonation. Even within a pressurised containment vessel this simply isn’t possible. The containment would rupture well before sufficient pressure had built up. Chernobyl and Fukushima were probably the worst case examples where the containment vessels ruptured and the nuclear fuel was blown out and dispersed by steam explosions. That absolutely removed any risk of a nuclear explosion but did cause radioactive contamination over wide areas.

[@anxiousearth680]

A moderator in nuclear terms is a bit counter intuitive. Moderators _speed up_ the reaction by slowing down neutrons so that they are more likely to react. A water moderated reactor would actually cool down as the water evaporates. Of which the infamous RBMK was not.

[@merlin7766]

Great post, I worked in the nuclear industry in a fuel fabrication facility. I have lost count of the times that I have had to explain to people that nuclear power plants cannot explode like a nuclear weapon.

[@morgan40654]

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.

[@morgan40654]

@@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.

[@TowelsKingdom]

Oh "meltdown". That's one of those annoying buzz words. We prefer to call it an un-requested fission surplus. Mr. Burns

[@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.

[@Lex-vf2fo]

So, isn’t this the same thing people have been saying “we’ve thought of everything, it’s super safe!” And then bam - “it was a 1 in a billion chance we didn’t account for”

[@Jupiter-rs4zl]

Modern reactors have so much safety systems shoved in them its basically impossible to have chernobyl 2.0

[@MakarovFox]

long live to nuclear power

[@BabyMakR]

I never understood why they made the bottom of the reactors concave. That design HELPS the fuel clump together and almost forces it to increase the reaction. Making it slightly convex would spread the fuel out and reduce the chances of neutrons from hitting fissionable atoms. Putting the concave structure outside the vessel means that the radioactive material is now uncontained. Keep it inside the reactor, and sure the reactor is scrap, but you can still contain it.

[@atomicblender]

The vessel is under extremely high pressure, so the natural shape is a sphere or a tube with concave ends. Similar to a pressurized tank. Otherwise, yeah, it would make sense to spread out any melted fuel if it was possible

[@Alpacaluffy]

@@atomicblender Interesting thought! How about BWR designs that are not pressurised? Might be something to do with internal recirculation?

[@Alpacaluffy]

So, I did some online research. Turns out, reactors are concave because it is the most efficient design. In nuclear reactors, there is something known as neutron leakage, when neutrons escape the reactor core. This lowers the neutron density, reducing the number of neutrons available to sustain the chain reaction. The lower we can make the core surface area to volume ratio, the lower the proportion of leaking neutrons we will get. Although the ideal shape would be a sphere, using a cylindrical shaped core is way more economic, practical and allows more stuff to be packed into a core.

[@BabyMakR]

@@atomicblender Sure, but there are ways to make structures at the bottom so that any debris do not pool into such an efficient mass.

[@robinhood5627]

When a reactor core melts the corium can and will form into fission conducive lumps where small re-criticalities occur, which in turn ramps up the heat of the molten fuel dramatically. So no, hitting the concrete foundation under the reactor is NOT enough to stop the meltdown, infact in experiments it was determined that corium can eat through about 1 meter of concrete per day if the fuel forms fissionable formations. You didn't mention the chemical reaction that forms hydrogen gas from the cooling water which can then ignite to blow the reactor and/or building apart, spreading parts of the core the close vicinity into the environment. And that almost every single reactor built is situated in LOW land value areas, because it was easier for permits and cheaper for construction. These areas are low value exactly because most of them are in areas of flooding, faultline, near active volcanoes or tsunami zones. Not great places to build these monstrosities. Regulatory capture is a big issue too, where the industry lobbies and pays off the regulators to keep old plants operating well beyond their planned lifespan in a very dangerous and irresponsible game of nuclear chicken. Remember a plant can operate flawlessly for 40 years, but it only needs one bad day... Spent fuel pools are super dangerous, most of them contain the full lifespan inventories of their reactors fuel changes, some containing 4000 spent assemblies still requiring cooling. If you think a "small" meltdown of a reactor core is bad, imagine this x20 in an unshielded spent fuel pool. It would make Chernobyl look like a campfire in comparison. And finally, neutron bombardment and metal fatigue of the core materials. Most of these plants are over 40 years old! they are super complex machines with hundreds of miles of pipeline, ductwork, cabling and so on, with many of these parts highly irradiated once first used. Eventually they become embrittled, lose their durability and cracks form, leaking radioactive water or gasses as the plant ages. Tritium is one big emission from most elderly plants. The recent tritium release from fukushima is nothing compared the standard everyday releases from most aged plants in the USA. But they don't tell you that bit. Ohhh and anyone saying nuclear is the "green" energy source of the future... I got some bad news for you. The mining, milling, processing, manufacturing and transportation of the fuel assemblies emits about as much CO2 as a gas power plant. So while the reactor itself is emission free, the fuel cycle most certainly is not.

[@nopenope7510]

nuclear has much more reliability and can fit in a much smaller space than a field of solar panels or wind turbines... sure they might be resource intensitive but they can last for almost 50 years producing up to 1500 MWe for the grid. i hope in the future the world isnt just filled 90% with solar panels 🤣

[@robinhood5627]

@@nopenope7510 Of course nuclear does have its place. But I just wish it wasn't so greenwashed and misrepresented as some kind of biblical saviour technology. As with ANYTHING man makes it is inherently flawed and potentially extremely dangerous technology. We cannot be flippant and careless with this. I put this argument to you though. Instead of looking for MORE energy and new sources of energy, why are we not instead looking for ways to cut down our consumption of energy? To need LESS of it. To become more efficient in our lives and work. And to promote more energy free forms of entertainment and living? Less is more.

[@brutonstreettailor4570]

Word for word everything you have said is true and i couldn’t of put it better myself, although reading your post i actually thought it was myself commenting !!

[@anxiousearth680]

1. Source 2. That's what the containment vessel is for 3. Source 4. Source 6. There's no special tritium, or super special tritium. Tritium is tritium. A weakly radioactive element that even occurs naturally and is ever present in our water. The Fukushima discharge is being monitored by the IAEA and three separate governments. The IAEA releases reports on the situation and live data. It seriously doesn't get any more transparent than that. 7. Incorrect. NREL has made a study on the impact of various energy sources from cradle to grave. Look up Lifecycle Assessment Harmonisation, NREL.

[@wjohnson100]

Reactor power is not generally controlled by the control rods but by steam demand. Control rods generally control steady state temperature. Raising rods increases steady state temperature. Over the long term, control rods accomodate fuel depletion. As fuel depletes, the rods are raised.

[@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

[@steppahouse]

What most post-apocalyptic fiction, from zombies to pandemic, whatever, almost always misses what happens to all the nuke plants. There are failsafes upon failsafes, but if there is a complete civilization/societal collapse, or anything that prevents these operators and systems from working, they will all fail. It's too depressing to work into your world-building so most authors just handwave it away.

[@jonathankydd1816]

most plants are dsigned to fail-safe. it's really only in the case of a disaster causing significant damage or opperator failure/ bypassing safety that causes meltdowns. While there may be a couple plants that end up melting down, i'm pretty sure most would end up failing safe.

[@steppahouse]

@@jonathankydd1816 Interesting. So then what does a fail safe status look like six months, a people years, ten years, etc with no one does anything?

[@IsntPhoenix]

2:15 how does the water vaper not become contaminated, or does steam not become radioactive from high levels of radiation exposure

[@swatboy763]

I am not 100% certan but it’s twofold reasoning, one is that the steam condenser im between the reactor and turbine helps to keep the coolants separate. Aswell as cladding put on the fuel like zirconium. I 100% am not an expert but this is what I understand

[@IsntPhoenix]

@swatboy763 u sound like an expert!

[@swatboy763]

@@IsntPhoenix I'm not but thanks

[@brucea9871]

Your explanation of why nuclear reactors continue to produce heat long after they are shut down is incorrect. The real reason is decay of the fission byproducts. When uranium (or other nuclear fuel) fissions it produces highly radioactive fission byproducts - much more radioactive than the original fuel. (I won't go into the reason they are so radioactive since it involves nuclear physics and would take a while to explain.) Even if fission of uranium is stopped the highly radioactive fission byproducts are very unstable and continue to decay, releasing large amounts of heat. One other thing: as some other commenters pointed out we have not had nuclear power for thousands of years.

[@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.

[@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.

[@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.

[@chazclark86]

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

[@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.

[@Lex-vf2fo]

What we consider safe isn’t always changing. Safe is safe. And when we find out something new that proves that what we considered safe wasn’t, it means it was NEVER safe.

[@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.

[@mykhailopak5269]

6:00 Please, don't say Chernobyl was caused by negligence, or carelessness, or turning off some magical safety systems. The plant was ran by competent engineers, luminaries of their field. What caused the catastrophe was the inherent design flaw and political corruption that prevented the party members, and their immediate subjects from fixing the design flaws, despite engineers' constant reporting on the potential issues (that were known and were pointed out well before the incident)

[@dumdumlegacy3251]

Understandable but it still happened

[@SanosukeTanaka]

the question I wish people would ask, "is nuclear power safer than what we have now?" and the answer is yes. coal has killed more in individual incedents, or in each year, than nuclear has in it's entire lifetime.

[@hugosalazar7617]

I’m a nuclear operator. Nuclear energy is the safest and cleanest form of energy we have. Looking back at any accident that occurred or major disaster was do to poor design, location, poor training, and of course lack of fucks given by those in charge in those time periods. In a way it’s a good thing. That way we learn and evolve nuclear facilities to be as safe as possible. For example back in the day the plant I work at they made chemicals on the side. They made phosphoric acid and a byproduct of acid is arsenic. Well they didn’t know what to do with all this arsenic back in the 70s so they just buried it in drums. So now we have the epa show up every week to do extra testing on the ground water to make sure none of that arsenic has leaked out.

[@ImpmanPDX]

The only way to stop a runaway reaction is to have an exponentially increasing countermeasure which is incredibly hard to design. Once the runaway starts it is extremely hard to stop. The best method in this case is a negative feedback system.

[@thedubwhisperer2157]

Given that we have built nearly 700 nuclear powerplants, the very few total meltdowns appears to show that it's not actually so difficult to stop...

[@glockmat]

Worthy reminder that one of the worst nuclear disasters of all time.... Was a dental clinic that closed in Goiânia, Goiás, Brasil, and the Xray machine was just left there, without any oversight with the radioactive charge of Cesium-137 still in there, today we use electron cannons, some scavengers found it, opened it and you know the rest

[@cflyin9]

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

[@Alpacaluffy]

I think what you are talking about is the RCIC, or Reactor Core Isolation Cooling. The RCIC is used in BWR-3 through BWR-6 boiling water reactor designs. The RCIC system is a single train standby system for safe shut down of the plant. The system is not considered part of the emergency core cooling system (ECCS), and does not have a loss of coolant accident (LOCA) function. The RCIC system is designed to ensure that sufficient reactor water inventory is maintained in the vessel to permit adequate core cooling. This prevents the reactor fuel from overheating in the event that the reactor is isolated from the secondary plant.

[@tommyschmid5831]

The weakness is always the necessary cooling of the fuel rods. When they were long enough in use they will generate so much afterheat that they need to be cooled for years.

[@magicofthestone]

A question should with an upward inflection.

[@tabcaps5819]

Good NPPs can stop a meltdown, great NPPs can stop one before it even happens

[@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.

[@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.

[@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.

[@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!

[@PlatzhalterCrew]

Why are the bottom parts of reactor vessels not shaped in a way that the corium already spreads out inside the reactor vessel instead of melting through?

[@Alpacaluffy]

So, I did some online research. Turns out, reactors are concave because it is the most efficient design. In nuclear reactors, there is something known as neutron leakage, when neutrons escape the reactor core. This lowers the neutron density, reducing the number of neutrons available to sustain the chain reaction. The lower we can make the core surface area to volume ratio, the lower the proportion of leaking neutrons we will get. Although the ideal shape would be a sphere, using a cylindrical shaped core is way more economic, practical and allows more stuff to be packed into a core.

[@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.

[@wirebeam]

I don't consider three mile island to be a major event. The containment dome did exactly what it was designed to do and the amount of radiation leaked into the environment was equivalent to a chest x ray

[@Bmywudt2]

Is it possible to replace reactors with Mega energy storage?

[@Alpacaluffy]

You still need something to create energy to store!

[@MrElifire84]

Realistic estimate of risk relative to other risks needs more attention. We keep shouting how bad a melt down is but honestly how bad is a Nuclear incident relative to other industrial incidents? How bad is radiation really? Answer? On a real physical level, Nuclear incidents have amounted to a whole lot of nothing. On a public perception level, they have been disastrous! So additional safety and engineering is fine but it won’t solve what ails us. Nuclear needs a rebranding. It needs to be shown compared to other risks that we accept out of hand and we need to stop focusing on the conventionally accepted public mentality that it is something unique and different. Its not. It’s just a thing like so many others. And compared to those other energy sources it is fantastically better, safer and way cooler.

[@syntaxusdogmata3333]

I think "nothing" is a strong word. The effects of the Chernobyl disaster, for example, are still being felt. I agree, however, that the public perception is far worse than the reality warrants. When asked what nuclear waste is, your average citizen describes decaying barrels of glowing green radioactive sludge that seeps uncontrollably into the ground water, as depicted in popular media. When asked how much radioactive waste has been produced historically by power plants, they either have no clue, or their estimates are grossly inflated. This is why I follow channels like this one. It brings much-needed doses of reality to absorb.

[@SocialDownclimber]

This is absolutely false, and misinformation like this is one of the reasons people don't trust nuclear power advocates. Nuclear accidents like Chernobyl and Fukushima have caused enormous damage to the communities and economies of the regions where they happened. I will grant you they caused very few deaths compared to the public perception. However the real damage was economic and social, having to evacuate and abandon large areas due to radiation and contamination risks. Nuclear is not really like anything else except perhaps an effusive volcanic eruption.

[@MrElifire84]

@@syntaxusdogmata3333 “Nothing” in comparison to most other “something’s”. Chernobyl is a great case in point. Actually reading the UN and Who reports on Chernobyl paint a far different picture than the perception. It’s terrible some deaths occurred but the number is relatively small. If memory serves, the last estimate was somewhere around 70 to date including induced cancers. In comparison to many other industrial accidents, it’s small fry. Nuclear on its worst day kills less people than some other energy industries do every day. This is why I indicated in my comment to think comparatively.

[@mhirasuna]

@@SocialDownclimber Chernobyl was a different kind of reactor, not allowed in the west. At Fukushima, more harm was done from the evacuation than from the radiation that was released.

[@SocialDownclimber]

@@mhirasuna That is because people evacuated from the area where the radiation was released. If you injure yourself during an evacuation from a burning building, you don't think "Oh I hurt myself, I should have stayed and burned to death".

[@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.