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LostCosmonaut

I Learned Something Today

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This thread is intended to be a place for cool things that you just found out about, but that aren't necessarily major enough to merit their own thread.

 

 

For instance, today I learned why heavy water is/was used as a moderator in certain types of reactors. Since hydrogen atoms are small, they are very good at slowing down neutrons, but regular hydrogen also has a nasty tendency to absorb said neutrons (which you probably want to be absorbed by the uranium/plutonium in your reactor). Deuterium is a bit heavier, but still pretty damn good at slowing neutrons, and it's much less likely to absorb them.

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When I started my quest to improve my education on nuclear energy, I was shocked to learn that neutron collisions are governed by essentially Newtonian physics.  Unless the neutron is absorbed, a neutron collision is essentially a 100% elastic collision with the nucleus.  Momentum is of course conserved, and kinetic energy is also conserved.

 

Therefore, a collision with a hydrogen nucleus will split the kinetic energy about equally between the neutron and the proton, since they have close to the same mass.  A collision with a uranium nucleus will remove very little kinetic energy from the neutron, since the nucleus is 230-something times heavier.

 

Kirk Sorensen has a good discussion of moderator materials on his blog, further proving that he really does know what he's talking about.  His presentations on LFTRs are just hideously dumbed down for his bovine audiences.

 

Hmmm...

 

So, today I learned that you should not put liquid dish soap into dishwashers unless it is specifically formulated for them.

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I've been looking up info on Zoroastrianism lately. It is a quite revolutionary belief system that basically came up with monotheism independently of Judaism & Atenism in the same general area where Hinduism originated. The dualism in Zoroastrianism which pitted good vs. evil was significantly different than the combat/trickster gods of monotheism where a god would do mischief or start a war but wasn't necessarily evil. During the Babylonian Exile, the Jews sorta picked up this idea of having a their own Angra Mainyu which later became Satan. The concept of an underworld filled with punishment for earthly sins also appears in Zoroastrianism which was also picked up by the Abrahamic faiths along with angels and demons being subordinate to God and/or Satan. Zoroastrian teachings also don't really care about spiritualism and rely more on materialism. No one really knows for sure when Zoroaster lived(likely around 1100 BC, but with about +/- 500 years error) if he existed at all or if he is only a mythic figure. 

 

 

Anyway, all praise Ahura Mazda! zoom-zoom-zoom

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This didn't happen today, but I learned that the precursors to the famous British SMLE rifles - or at least the bolt and magazine - were originally chambered in 45-70 "Government". Now if only I can remember where I heard that from...

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This didn't happen today, but I learned that the precursors to the famous British SMLE rifles - or at least the bolt and magazine - were originally chambered in 45-70 "Government". Now if only I can remember where I heard that from...

 

http://milpas.cc/rifles/ZFiles/Bolt%20Action%20Rifles/M1885%20Remington-Lee%20US%20Navy/The%20US%20Militry%20Remington-Lee.html

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I learned today not to try even the simplest of car repair projects after being woken up out of a dead sleep when you're dreaming that you're a star of a 1980s John Hughes movie which then morphed into a "Creature Feature" with some anomaly that warped individuals into terrifying killers that resembled the ensemble in Bonnie Tyler's "Total Eclipse of the Heart" video.

 

 

Looking back, I think this can be chalked up to my wife making me watch the first Doctor Who reboot episode with Christopher Eccleston and eating copious amounts of homemade cinnamon rolls that she had just baked for that purpose.

 

Yes, I'm a lucky man.

 

I do distinctly remember in the dream saying "Oh, boy, I'm in a John Hughes film. I know all the tricks on how to be popular. I sure hope this doesn't turn into a Creature Feature later on."

 

If you have ever been around me in person, I have a tendency of saying stuff like that in real life...

 

So with that as a back story, you can imagine the state I was in as I stagger down to look at her Ford Escape that had a dead battery. No problem, I'll just push it out of the garage and give it a jump start with my Toyota truck. Out come the jumper cables. Red and black on the red and black terminals on the Escape. Red and black on the black and red terminals on the Toyota.

 

"Don. The cables are beginning to smoke."

 

Boom. I'm instantly awake, quickly switch the now rather hot cables and I begin to survey the damage, all while kicking myself for screwing up on a simple jump start that I have performed dozens and dozens of times.

 

Fortunately, I think the only thing wrong is the 120 amp mega fuse on the Escape which did its job of protecting all the electronic innards from people who do something idiotic like I just did. Although I'll be spending this evening going over the car's electrical system when it gets home.

 

So that concludes my episode of "I Learned Something Today".

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Today I learned that the NSWR probably wouldn't work. Showed Zubrin's paper to my nuclear propulsion professor, who had the following comments (quoted verbatim):

  • Geometry will not go critical at 20% enrichment
  • Neutron flux = 3.5*10^17 neutrons/(cm2*sec),  turn steel to jelly in minutes - rad damage
  • Power density = 232 MW/cm3 - yeah right
  • Heat flux = 700 MW/cm2 - heat flux will melt wall no matter what
  • Made many terrible assumptions on boundary conditions

Back to fantasizing about gas core NTRs and Orion drives instead.

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I learned today not to try even the simplest of car repair projects after being woken up out of a dead sleep when you're dreaming that you're a star of a 1980s John Hughes movie which then morphed into a "Creature Feature" with some anomaly that warped individuals into terrifying killers that resembled the ensemble in Bonnie Tyler's "Total Eclipse of the Heart" video.

 

 

Looking back, I think this can be chalked up to my wife making me watch the first Doctor Who reboot episode with Christopher Eccleston and eating copious amounts of homemade cinnamon rolls that she had just baked for that purpose.

 

Yes, I'm a lucky man.

 

I do distinctly remember in the dream saying "Oh, boy, I'm in a John Hughes film. I know all the tricks on how to be popular. I sure hope this doesn't turn into a Creature Feature later on."

 

If you have ever been around me in person, I have a tendency of saying stuff like that in real life...

 

So with that as a back story, you can imagine the state I was in as I stagger down to look at her Ford Escape that had a dead battery. No problem, I'll just push it out of the garage and give it a jump start with my Toyota truck. Out come the jumper cables. Red and black on the red and black terminals on the Escape. Red and black on the black and red terminals on the Toyota.

 

"Don. The cables are beginning to smoke."

 

Boom. I'm instantly awake, quickly switch the now rather hot cables and I begin to survey the damage, all while kicking myself for screwing up on a simple jump start that I have performed dozens and dozens of times.

 

Fortunately, I think the only thing wrong is the 120 amp mega fuse on the Escape which did its job of protecting all the electronic innards from people who do something idiotic like I just did. Although I'll be spending this evening going over the car's electrical system when it gets home.

 

So that concludes my episode of "I Learned Something Today".

 

I learned that lesson in high school when my friend used my GTO to jump his parents Suburban and melted the terminal off the battery. 

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Today I learned how to calculate the ratio of neutron production to absorbtion for various simple reactor geometries, such as rectangular prisms, cylinders, and spheres.

 

Fun fact: assuming a perfectly spherical geometry, roughly 18kg of U235 is needed to achieve criticality. This mass has roughly the same volume as a typical grapefruit. Coincidence?

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If the whole world used the 176 liters per person(US standard) then the yearly usage would be about 1/20 of the Amazon's yearly discharge. (I forgot the exact figure and the percent is likely a hell of a lot smaller but not smaller than 1/100)

How effective are nuclear plants as desalination plants?

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