haha yes, al dente fissile material

@@TheAtomicAgeCM I tried to cook some, but for unexplainable reasons, I think my guests and I all got food poisoning from it. We've been vomiting for three days now, and it created strange rashes on the skin. Do you think I should see a doctor? (this was a joke, and a pretty bad one at that)

@@IIIAnchani I'm honestly surprised no one replied as if you were being serious lol, usually there's always that one r/whoosh person.

How did Wells even know about the bombs that early?

@@theschmedaparadox1018 Like Jules Verne, like Arthur C. Clarke, he knew his science, saw the future and was a visionary sci-fi author whose novels helped inspire the very advances he predicted.

@@videowilliams Fascinating stuff, I think I'll read some of his books.

It's not sad. It's just simply put stupid as hell. If I would've been in his staff I would've bitch slapped Slotin. Let him know and gladly be fired.

Same core also claimed Harry Daghlian's life a year or two before. He dropped a tamper brick on the core and it went into excursion. He was alone when working on the core (something he too had been warned against.)

You're welcome! Glad you enjoy it

MadSammi: If you have not read “ Racing For The Bomb “ by Robert S. Norris check it out. The responsibility and immense pressure on Gen. L. Groves was staggering. The book chronicles Groves early years, his training, work habits, intelligence, driving personality and monumental self confidence when making crucial decisions.

Perhaps you heard accounts of astronauts seeing flashes of light when exposed to gamma radiation.

I thought it was radiation ionizing the air the way they depicted it in the Chernobyl mini-series. It never occurred to me that it wasn't actually there, and just an effect from radiation in our eyes.

I thought it was Cherenkov radiation as they passed through the fluid in the eyeballs, but I am just repeating something i heard at one point, I’m no where near anything more than just an amateur interest level.

Thanks so much! Many more videos to come!

hello! thank you. get some sleep and check it out later, it'll be waiting for you :)

Shouldn't a been Slotin that screwdriver in there.

Thank you! Yes, I had no idea it used that much power beforehand. Oak Ridge was placed where it was to use the power capacity of the Tennessee Valley Authority

thank you!

thank you!

Thank you! More to come

Thank you! It is quite crazy how many resources were dedicated to it. I can't wait to see the movie! I have some plans for that one :)

Thank you! How long it took them to die definitely helps, but there's a lot of variation from person to person when it comes to dose. So, for example, they could have both gotten the same dose but still died at those different times.

Highest individual dose ever recorded if I'm not mistaken. (officially, anyways)

thank you! Pu-239 is on my list

it should really be just a huge area called "criticality" with a very small area inside that's the subset of nuclear explosions. nuclear explosion like in a nuclear bomb cannot happen by accident - they must be purposefully designed

@@TheAtomicAgeCM What is the reason why in the gun design bomb two halves of uranium are smashed together with a lot of energy? Why is it not enough to just put them together?

@@OpenGL4ever you have to smash them together very quickly before the energy of the chain reaction pushes them apart. if you do it too slowly, it'll blow itself apart before it can be stuck together long enough to make the full bomb yield - this is called a "fizzle"

@@TheAtomicAgeCM I understand. Thank you for your answer.

Very interesting, I'd like to learn more about that

I read that it was recycled for the Crossroads tests.

Thank you, and that's awesome! do you know what she works on?

i'll put it on the list, thanks!

Correct.

that's awesome! i've been there a few times, beautiful area

never learned that concept, but may not be a bad idea

a quick google search says Plutonium-gallium alloy en.wikipedia.org/wiki/Plutonium%E2%80%93gallium_alloy but I don't have first-hand knowledge of this

@@TheAtomicAgeCM sweet so it was casted not machined , i feel so stupid ! anyway thanks awesome video , tickling the dragons tail still give me goosebumps -yikes !!!

​@@daskarman you're welcome! i don't know for certain, but i feel like they have to be machined after theyre cast. maybe they weren't back then, or it was otherwise different. but uranium turnings ("waste" from machining) are something that exist

Complacency

For those of you never involved in R&D, there is never ever time/funds to design/build the proper test equipment. The "cowboys" are always faster than you can build proper equipment. This is why it takes soo long to get anything done now. It would literally be impossible to do the Manhattan Project today.

They did have safer methods available. Slotin was supposed to use shims to hold the reflector halves apart at known distances. By graphing the reciprocal of neutron count rate versus the reflector distance, then extrapolating the graph to zero (infinite count rate), it is possible to accurately predict a criticality without actually creating one. But this process was tedious. Insert shims, assemble reflector, take neutron measurement, disassemble reflector, remove shims, plot data point on graph, repeat many times... Slotin preferred to induce a delayed criticality, which was immediately recognizable from the exponential increase in neutron count rate. This got him the proof criticality was possible, after just one assembly of the core and without any quantitative measurements. After Slotin's accident - which was the second fatal accident during a criticality experiment - strict new rules were put into place. All critical or potentially critical assemblies were required to be performed with remote controlled machines.

:0 y e s

Tried hell, he did. A crude, but functional thorium breeder reactor.

the speed of light in air is only a minuscule amount slower than in vacuum, so the relatively slow beta particles from any unstable isotopes are insufficient at less than 20 MeV to induce Cherenkov glow in air. It has to happen in water or some other dense material where light is much slower.

@@Muonium1 I disagree, a criticality is more than enough to cause Cherenkov radiation in air.

@@terrydavis8451 well where are the >20MeV electrons going to come from then to exceed c in air??

The Little Boy bomb was horribly inefficient. The Fat Man bomb was better, but not that much better.

Hey thanks for bringing this up! I actually think i meant non-water reactors, but regardless. So you have fast reactors and thermal reactors, it has to do with if you split atoms with fast neutrons (the neutrons that come straight from an atom splitting, which go very fast) or thermal neutrons, which are fast neutrons that have been slowed down by a moderator. The reactor in The China Syndrome has water as a moderator - so it's a thermal reactor - you do this because it's easier to split atoms with thermal neutrons. A fast reactor would not have a moderator (in this case, no water), which means it's harder to split atoms and that means you need more highly concentrated fuel. BUT - you don't have to keep water at insanely high pressures and all the thick piping and structure that entails - just molten metal which doesn't boil at reactor temperatures so your piping and such can be much thinner. Now, as I mentioned earlier, it's really about moving away from water reactors because of what I just said about thick piping and high pressure water ($$$). You can have non-water reactors that are either thermal (using graphite as a moderator) or fast reactors.

@@TheAtomicAgeCM so the molten metal is in the primary cooling pipes but there's still water in the secondary that goes to the turbine? So they would use a metal that has a really low melting point I would assume? Lead?

@@C.Y.123 you got it! yeah lead is one, but its melting point is the highest of the metal coolant candidates. others like sodium or sodium-potassium have good bit lower melting points

@@TheAtomicAgeCM that's so cool. Thanks for the info. I've been teaching my daughters 9 and 12 about some of this stuff. Apparently they think meltdowns and disasters are really cool. Keep up the great work and thank you

@@C.Y.123 oh yes, it's great stuff, I love it :) you're quite welcome! glad to hear they like it, sounds like you got some future nuclear engineers on your hands haha. I will keep it up indeed, thank you. More coming soon!

Yes, not sure when though! I recorded a video for MELTDOWN: Three Mile Island from last year but I need to redo a lot of it--I've learned a lot about TMI since then. I want to do more research on Fukushima before I react to The Days, as well. So, expect my reaction to these two shows... eventually lol

@@TheAtomicAgeCM Keep it up anyway, fascinating stuff! Never knew I had such a thirst for nuclear knowledge.

The key differences are how far the reactivity exceeds criticality and how fast it gets there. If the reactivity is only slightly supercritical, then the criticality might self stabilize. For example, as the core heats up, its reactivity decreases. If the reactivity decreases to exactly 1, the chain reaction continues at a constant rate. This actually happened in an accident at Sarov in 1997 - similar to the Slotin accident a neutron reflector was dropped on a core, but the scientist ran away leaving the reflector in place. The stabilization temperature was below the melting point, so the chain reaction continued for days until the reflector could be removed with remote operated tools. A criticality with greater reactivity will not self stabilize. The most obvious result is melting the core, as you said. I suspect the core in the Slotin accident would have either self stabilized or melted. Criticalities with even greater reactivity can produce small explosions. But now we have to consider the speed of the reactivity increase, because an explosion requires temperatures much greater than the melting point. If the reactivity increases slowly, the core will heat up and melt before the reactivity reaches the level required for an explosion. The "real" nuclear explosion of a nuclear bomb requires a reactivity far above critical, and this must occur very rapidly. If either one fails - not enough reactivity or assembled too slowly - then the bomb will "fizzle" producing a relatively weak explosion (compared to the expected one).

Clarification - the core melting is only important because the molten core will spread out and/or melt into its surroundings (diluting itself with anything else that is meltable). In either case the reactivity decreases steadily as long as the core is molten. This stops the chain reaction. However, this process takes time. A molten core falling apart due to gravity requires tenths of a second. Meanwhile, nuclear reactions proceed in millionths of a second. If the reactivity is still substantially supercritical, the chain reaction will continue to intensify. So the core will not only continue to heat up, the heating rate gets faster. The core vaporizes and expands as a gas, in other words it explodes. Exploding the core always stops the chain reaction, because the core is now spread out into a large volume, so neutrons emitted from one atom are unlikely to strike another. The violence of the explosion depends on how many fissions occurred while the chain reaction was ongoing, which in turn depends on how high the reactivity was and how quickly it increased. This is why criticality accidents usually produce no explosion, and when there is an explosion it is a very small one (for example, scattering pieces of the critical assembly around the room but not damaging the walls). The reactivity during a criticality accident is not high enough to produce a powerful explosion.

yes it would still be fissioning sitting there. but the plan would be to come back and take it apart after they've thought about the best way to do it, they wouldn't just leave it there :)

thank you! "It's too much knowledge, sir!" "I can take more! I CAN TAKE MORE!!"

yes, indeed!

Correct. Hanford had access to electricity too, in large quantities.

It was also pretty damn desolate. I’ve visited when we spent a week at Dollywood. I can only imagine what it was like in the 30’s and 40’s.

Very good, I have Manhattan (2014) on the list to get to. I would like to revisit that book and/or find some more technical documentation about how they did criticality safety for uranium enrichment and plutonium reprocessing.

Nope, it isn't like a poison that spreads from the area of contact. His entire body took the dose, and with such short distance and the amount of radiation those blocks might as well have not been there at all.

Also if I'm not mistaken, they tried recreating two accidents in one here. I don't believe the blocks are lead. The incident with Harry Daghlian involved beryllium blocks as neutron reflectors in a very similar configuration as seen here, while the incident with Slotin involved the hemispherical reflectors. Ironically, the first incident prompted stricter safety protocols to prevent this very thing. Slotin's experiment called for wooden shims to be placed between the hemispheres to prevent them from closing like this, but Slotin was reckless and a bit of a show-off. He'd done this multiple times, enough that Enrico Fermi told him he'd be dead within a year performing the experiment with the screwdriver. He was correct.

@@logicplague Hmm, but his entire body only received the dose when the lead wall offered no protection. However, if the lead wall offers sufficient protection, only his upper body and right arm should have received the dose.

@@OpenGL4ever Even if the blocks are lead, lead doesn't protect against neutron radiation like you'd think it would. Because of their size and lack of charge, they pass through most matter quite easily. Shielding against neutron radiation is almost counter-intuitive, water and hydrocarbons are more effective than lead. I've seen the leaded glass windows he referred to at ORNL, and if I remember right they're ~4 feet thick and sandwiched with layers of mineral oil to shield against the neutrons, while the lead in the glass helps shield against the rest.

@@logicplague That makes sense. Thank you for your clarification.

nonsense! quite a valid question. Yes, they do technically become less effective over time. However, the two materials used, Pu-239 and U-235, have quite long half lives with Pu-239 at 24,110 years and U-235 at 70,000,000 years, so it's more or less irrelevant. The plutonium core from the Trinity Test in 1945 would only have lost about 0.22% of its Pu-239. So, very little but also not insignificant. If the bomb were designed to have *just* enough Pu-239 for a critical mass, that little bit lost would likely make it no longer work. I'm sure it's something that's controlled for. For a bomb with a half life of 1 year, it would likely not work after just a month or two (having lost 5-10% of the fissile material), maybe even sooner. Once you get below the critical mass the bomb was designed for, there's not much else you can do besides replace the core. Pu-239 is interesting because it decays to U-235, which is fissile. Even though Pu-239 has a much smaller critical mass than U-235, Pu-239 would probably be able to decay more than just the half life would indicate and still work because U-235 would be there.

@@TheAtomicAgeCM ah ok, i love chemistry, it was my favourite subject at school, obviously wee didnt go into nuclear materials, we stuck to fairly standard materials, but i take it the theory behind it is the same? i remember something else from chemistry, forgive me if im wrong, its been a while, the amount of electrons a substance has matters, if substances have odd numbers of electrons, they like to interact with other substances which have odd numbers of electrons, either spontaneously or by force, for example adding heat or some other man made influence, maybe somewhat irrelevant for what were talking about, but still interesting nuclear energy both intrigues me but scares me to death, whenever anyone mentions "nuclear" the brain always refers to accidents such as chernobyl, because the brain is wired to learn from mistakes, so you remember bad things that have happened easier than you remember good things, so what john cusack did was what they call the "death sphere" i have read about that before so, back to the question, would they have purposely used materials with a long half life to ensure detonation? or would it have been a coincidence of bomb making? would they have known about half lifes back then? love your videos, keep up the good work, your very informative, i found your channel by accident watching chernobyl videos, and im glad i did :)

Thank you for the kind words! I really appreciate it. Chemical theory with nuclear materials? Yeah there's a lot of chemistry with nuclear materials. The radioactivity can affect that, I suppose, when something decays - it might not like being bonded to whatever it was bonded to anymore. That sounds really interesting actually lol, I might ask my chemical engineer co-worker about that. My chemistry knowledge is rather tangential, though. Yes, they knew about half-lives back then. So, I've talked about U-235 and Pu-239 having rather long half lives. I think one could say it was just chance that U-235 and Pu-239 worked out to be suitable materials in terms of half life. It's likely explainable through their proton and neutron numbers (note that all the fissile isotopes I list have an even number of protons and an odd number of neutrons). The two other common fissile isotopes are Uranium-233 and Pu-241. Uranium-233 is made from Thorium-232 and Plutonium-241 is made as (roughly) U-238 -> Pu-239 -> Pu-240 -> Pu-241, so not very efficient to make and it has a ~14 year half life as I talked about in the video, which is too short. So Pu-241 isn't a good candidate and I actually don't know why U-233 isn't really used. There are also some odd-ball, random, exotic fissile isotopes, but U-235 and Pu-239 are the major ones.

You could ask a metal fabricator to make you two hemispheres out of aluminum. If the two halves of the sphere should also feel heavy, then they should be hollow on the inside and then filled with lead.

Sure Vladimir Putin has one ?

and a completely opposite personality haha

i just don't find it that interesting is all - perhaps i should say i have a very limited time to work on videos so I'd rather do other things

already have!

it would settle in to some constant power level, so more like critical instead of supercritical, like a reactor. The power would fluctuate up and down slightly over time. The power of the reaction would push the halves apart slightly. as the pieces heat up, the power would drop because as fuel heats, it loses reactivity, and the power would also drop from thermal expansion because hot things expand (more neutrons would leak out). It would then cool slightly, the pieces would come closer together, power would rise again, etc., etc. it could do this for some extended amount of time pumping out gamma rays and neutron radiation until someone came in and dismantled it.

@@TheAtomicAgeCM wow, thanks for the reply your explanations are thorough.

yay, thanks gwen!

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the first self-sustaining chain reaction was there

First reactor, called a pile at the time. Graphite bricks and Uranium.