Fission reactions? Fission power generation? Fission weapons?

Sussinctly, without bringing math into it:
(fission reactions)
1. Subatomic particles interact with forces that pull them together and push them apart.

2. Atomic nuclei form when the forces between subatomic particles are more or less at equilibrium; therefore nuclei are tension structures.

3. If you poke the structure properly with sufficient force, it breaks.

(fission power)
4. If you arrange enough of right sort of atoms in a certain space, when they break up they'll shoot off things that will poke nearby atoms the same way. If you do it right, it'll produce a controllable chain reaction that will release a known amount of energy over a certain amount of time in the form of heat. Set the rate to something you can engineer a solution that transfers the heat away into water, boils it, and passes the steam through turbines.

(fission weapons)
5. But if you want to blow shit up, your design maximizes the amount of pokes as fast as possible so you split as many atoms as you can before the device blows itself apart. Think of it like designing a motor without a throttle that just runs at max output the moment it kicks over and the goal is to empty the fuel tank as fast as possible before the motor eats itself.

@deadelk well? You satisfied?

Come again??? Decay as in delayed neutrons from the fission fragments like Br-87??? I hope you mean in U-238 and not U-235

Shift Supervisor here.

I think GD rules require that you wait to page 2 for intelligent responses.   Page 1 is comedy only.  

Shitty touche'

For what it's worth, depending the decay reaction, you're correct. Decay neutrons do cause fission, otherwise there'd be no chain reaction.

Physicist here.

Yes, decay neutrons do cause fission, and are a critical part of reactors. Decay neutrons are delayed in time, the very small percentage of decay neutrons that are delayed allows a fission chain reaction in a reactor to be controlled. Without that delay, once you got your k factor above 1.000, the power would accelerate to an extreme level in a fraction of a second and melt down the reactor. This was a concern when the first reactor was constructed and tested, but the theoreticians had predicted the effect from the delayed decay neutrons, so they were reasonably confident it would be controllable. They had a "suicide squad" of a few guys with jugs of a liquid solution of neutron-absorbing material to dump into the reactor if it went out of control, but if that was the case they wouldn't have had time to respond anyway.

Fission fragments undergoing beta decay, end up releasing neutrons from their daughters nearly immediately.

Someone else mentioned they don't have enough energy, which is also poppycock. U235 captures thermal neutrons on the 0.01-0.025ev range. A lot of the delayed neutrons are on the hundreds of kev range.

https://en.m.wikipedia.org/wiki/Nuclear_reactor_physics

To steal from Wiki, this is a great writeup on delayed neutrons and why they are important.



Fission reactions and subsequent neutron escape happen very quickly; this is important for nuclear weapons, where the objective is to make a nuclear pit release as much energy as possible before it physically explodes. Most neutrons emitted by fission events are prompt: they are emitted effectively instantaneously. Once emitted, the average neutron lifetime (
?) in a typical core is on the order of a millisecond, so if the exponential factor
? is as small as 0.01, then in one second the reactor power will vary by a factor of (1 + 0.01)1000, or more than ten thousand. Nuclear weapons are engineered to maximize the power growth rate, with lifetimes well under a millisecond and exponential factors close to 2; but such rapid variation would render it practically impossible to control the reaction rates in a nuclear reactor.

Fortunately, the effective neutron lifetime is much longer than the average lifetime of a single neutron in the core. About 0.65% of the neutrons produced by 235U fission, and about 0.20% of the neutrons produced by 239Pu fission, are not produced immediately, but rather are emitted from an excited nucleus after a further decay step. In this step, further radioactive decay of some of the fission products (almost always negative beta decay), is followed by immediate neutron emission from the excited daughter product, with an average life time of the beta decay (and thus the neutron emission) of about 15 seconds. These so-called delayed neutrons increase the effective average lifetime of neutrons in the core, to nearly 0.1 seconds, so that a core with
? of 0.01 would increase in one second by only a factor of (1 + 0.01)10, or about 1.1: a 10% increase. This is a controllable rate of change.

Nuclear Engineer who doesn't want to type all this on his phone.

Ran a Californium Flux Multiplier AKA "CFX" that would undergo "fission" if you will, but required HEU.  Commercial reactors use a lower enrichment.  (puny) percentages of U-235 compared to a CFX which used 93.3% U-235.  It couldn't be made critical by design.  Maybe he meant "critical" instead of can't produce fission?

Californium-252 "decay" was the source of the neutrons - essentially controlled reaction throttle by geometry

Germany could not have built a bomb during WWII, the industrial base required was just too great. They just didn't have the resources to do it. Of course prior to actually completing the theoretical and practical work to build a bomb it wasn't known exactly how challenging it would be, so it had to be considered a threat until it was known for certain that it wasn't.

Here's an example. If I remember the statistic correctly, for a good part of 1944-5, the Manhattan Engineer District was consuming 1/7th of the total electrical power consumption of the United States. Contemplate the magnitude of that... 1/7th of the entire countries electricity for a year and a half to make effectively 4 bombs worth of fissile material. And it was 4 instead of 1 only because they'd figured out the physics, chemistry and engineering issues to make plutonium work in an implosion bomb and built the massive infrastructure needed to produce plutonium on an industrial scale from natural uranium reactors.

Neils Bohr was one of the top scientific minds in the world. Some time after the discovery of fission, he made a statement that an atomic bomb would not be built, because you'd have to turn your entire country into a factory to make one. Later in the war he escaped from the Nazi occupation of Denmark and eventually came to the US where he was brought on to the Manhattan project as a consultant. Some of the scientific folks were about to chide him over his pre-war comments that a bomb couldn't be built, and he cut them off... saying something to the effect of "I said you couldn't build a bomb unless you turned the whole country into a factory to make them. I see you've done just that." The scale of the industrial plants at Hanford and Oak Ridge was monumental.

It was easier for the Soviet Union to make a bomb after WWII because they already had all the right answers in how to do it, the US gave them the info.

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And the same exact things could be said about the Japanese efforts as well.

Thanks for the informative posts in the thread, Gamma.  Two questions:  1) You mentioned that U-238 captured thermal neutrons of too high an energy (but not so high, like with neutrons from D-T fusion, that they'd fission the -238), which is why a moderator was required to lower neutron energies to where U-235 would be more likely to capture them.  
What happens to the -238 nucleus with a captured unmoderated neutron?  Does it become U-239?  Or transmute to another element?  Does it re-emit the neutron after some period of time?

2) i gather you want low Z materials for moderators.  Has anyone tried beryllium or lithium?

Thanks again.

Radiative capture of neutrons by U238 is how we breed Pu239. When U238 captures a neutron and becomes U239, it beta decays twice to Pu239.

And with much faster fuel replacement and reprocessing cycles, AIUI, to drastically reduce the proportion of either Pu-238 or -240, both of which greatly increase the risk of spontaneous fission in the pit such that it practically rules out the Pu's use as bomb material.

Thanks, Justin.  

And for your very extensive posts and photos of your trip to the camps in Poland.  Some of the best threads ever in GD.

I really appreciate that, thank you!

invisible shit hits other invisinlt shit and the shit the invisible shit comes from gets hot AF

So like you put it in water to maek sum steam....steam turns the generator to make volts that then goes to your house and you can plug in your penis pump

also...you put some different shit in between the hot shit, and it makes the hot shit not hot.

Also...the hot shit can get too hot and melt...then the hot shit keeps getting hotter until is stops...like in 500,000 years or someshit

Accident Tolerant Fuel enters the chat.

There were some attempts to throw a monkey wrench into the soviet program.  At the close of WW2 the Russians were thrown a few red herrings.  

One was The US government led them to believe that Thorium-232 could fission and gifted materials to work on it.  

I am uncertain on the specifics as if they were even  aware of the possibility of U-233 breading at that time, but it gave the Russians something to waste time on when we evidently knew it was a dead end - or dead enough to have them waste resources on.  Eastman Kodak sold them 9 rail cars of thorium nitrate powder.  Kodak had the largest supply chain on hand for making Thoriated glass lenses.  I record retentioned  the docs Kodak had at the time, but they had records of the rail cars, the shipper info etc. and correspondence letters.  I was tempted to retain docs and hand them over to Paul Frame at Oak Ridge out of historical interest but that didn't happen.

I was never able to find any further info on their use of it or if they actually pursued it, it was gifted by the US government and they may have taken it knowing it was a ruse or not.  

I probably could to someone with some underlying knowledge of what an atom is.  I couldn't explain why certain isotopes are more stable than others though.

And if I was stuck in 13th century Europe, it would be hopeless.

I actually did a presentation on fission versus fusion back in my junior year in high school, with graphics drawn up in whatever Macintosh we used back then.
In my copy of Chuck Hansen's "U.S. Nuclear Weapons, the Secret History" somewhere it talks about the real magic.  I can't remember the exact wording, but the gist of it was that the protons and neutrons of the uranium have more mass when they are together, than when they are apart.  Which makes no sense in the macro world.  To us, two 5lb weights stacked on top of each other weigh 10lbs total.  But when the protons and neutrons are split apart, that weight that goes missing is converted to energy.  And it's a LOT of energy.  I wish I had the book around to quote it better, but it's at my parents house.

Better make sure they aren't using it to prop up a flower pot. Average quality copies go for around 160-200 on eBay regularly.

....

So....

Let me shit in this thread. Maybe someone will actually respond before it locks.

'Creating a Natural Uranium-Based Research Reactor'

You couldn't boil water with such a thing, right? This is like the theoretical underground monsters, right? Could you do this with just a trip or three to Colorado? There's plenty of youtube videos on how to go from ore to metal on a lab benchtop scale.

What am I missing?


(Thread legal: as a nine year old, I used to give lectures and demonstrations at the American Museum of Science and Energy in Oak Ridge. I hold the dubious record of being the only person to figure out how to 'melt down' the giant pwr reactor display lol) I can absolutely explain it, even if I constantly forget the difference between ionizing and non-ionizing sources...

Yes, I can.

330 tons of nuclear-grade graphite.

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They had a substantial crew of people working for several months to cut and machine the graphite blocks and build the "pile".

It's going to take more than a trip or three to Colorado... CP1 had 40 tons of uranium oxide and 6 tons of uranium metal for fuel.

As I posted a page back...

If you can make highly-enriched uranium you can make a reactor this size:

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Or

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Which is essentially what killed Louis Slotin, set up to be operated mechanically.

Easy.
You have a nuclear family, the wife leaves with half his shit and jumps into the middle of another relationship, causing that one to break up. Now you have TWO free roaming wimmenz out on the prowl to bust up marriages.
Keeps going.

Nick

So how did they figure out the geometric lattice used for fuel?  I’m sure it’s all math and wavelength/energy.

That always fascinated me. The reaction is “simple”. Controlling it?  Not so much.

I remember the first experiments were like a Lego brick structure the size of a small garage?  The ones leading up to development of the bomb?

Math/theory and testing different configurations on small-scale arrangements to figure out the reaction coefficients.

The first reactor was "CP-1", I just posted an image of it. Incredibly there were apparently no photos taken of the completed reactor, or "pile" as they called it at the time. There are a few photos during construction, as they were stacking the blocks of graphite.

https://www.atomicarchive.com/media/photographs/chicago-pile-1/index.html

With the foundation of the small scale experiments and measurements and experience from CP-1 they designed and built the full scale plutonium production reactors at Hanford. IIRC they were already building the Hanford site prior to CP-1 being completed, just going off of best estimates. Groves wasn't messing around.

That’s it!  The pile. Thanks.

So the lattice was math along with physical verification?  Amazing more people weren’t killed to be honest.

I was thinking more wavelength and that damn wave/particle duality thing.

I did go to a top engineering school that had their own reactor. Nuclear fission/decay shit was covered in depth my sophomore year

To this day I still don’t totally get wave/particle duality.

You didn't ask about bombs, reactors, chain reactions, criticality, or any of that. You just asked about fission. So here is the most general, encompassing, and simple one sentence explanation.

Fission is when an atom's nucleus is destabilized in a certain way, usually by hitting it with a neutron, overcoming the forces that holds the nucleus together causing it to split apart forming two or more new atoms, each of a smaller mass than the original, along with emissions of radiation of various types.

yes

So here goes my simple answer.

You are literally splitting the atom. The forces that hold the nucleus of the atom together are incredibly strong, the strongest of the 4 known forces. It is quite literally what makes matter matter.

In splitting the atom a tremendous amount of energy is released. The energy of that force holding that atom together.

I like the previous poster “1 atom enter, two atom leave”. I’d add “and a shit ton of energy as well”

When I win the lotto we're talking.

...

For some reason, I swear I thought you guys were talking about being able to significantly compress the size by using water (regular or heavy)?

Hearing that;
I envisioned something the size of a medium-sized commercial washing machine basket laid on its side, with depletalloy in an annular configuration, with a central array of U_nat

Perhaps a Be or a poly sleeve outside of the central array?




I figured you would have referenced SHEBA over those two lol That one was less than 25% enrichment, if I recall correctly.



Damn. You know what, I think you're right! I could have SWORN I saw some operating photos in an article about the Safety Control Rod Axe Man where Fermi was watching the dials or ... something. That's weird. Wonder if the flux ruined that slow film?



YOU KNOW THAT'S RIGHT

(I have said for years that this kind of shit is why God will never bless me with a ton of disposable income or access to a privately-held nuclear research facility...)

lol

I may have gotten SHEBA and BIG TEN mixed up, but I only studied this area because I strongly believe they were using weapon components in these reactors, and I wanted to see the shapes.

For the non-nuke nerds:

A History of Critical Experiments at Pajarito Site

catch the upcoming Oppenheimer movie, Universal of Chicago, first chain reaction sustained, next was the mission at Hanford to end World War II

This guy explains it.

Fun fact. "I split atoms for a living" is a great pick up line.

Randy Quaid has really let himself go.

Around these parts, all you have to do is let them find out you work for TVA or DOE and you don't even have to talk... lol

Wish they had a photo of the critical assembly they made with 0.8kg of HEU. That is not much material.

I also found the photo of the original Godiva strung up on those light poles to be unintentionally hilarious.

This. Figure a pro player makes the break. Each ball in the rack goes off in a random direction with near the speed of the original cue ball. Picture neatly racked balls all around in 3d. It goes on and on....

The enrichment program is fascinating as well. People had no idea what they were working on.

Agreed on both counts.
They still classify exactly what are in the 'converters' used at K25, and assuming currently at PGDP. (Is that place still running or hot standby??)

My grandmother worked at K25. When she was made aware of what she was working with, she suffered a mental breakdown that she never recovered from.

On a more cheery note, since no one wants to help me make my own personal reactor, would one of you like to explain the difference between an xray and a gamma?

It's very simple.

When you release the angry neutrons you want to try to catch enough of them to keep your neutron farm profitable.

It ain't much but it's honest work.

The Movie

Whoa … I think you are confused. The OP asked you to explain “fission” not this criticality and super critically bullshit.
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