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Critical Mass?

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SteezePatrol
Posts: 10281 - Karma: 36
okay so I've been told something about a professor talking in front of his class had something like a hunk of uranium and some other radioactive substance, and one was at critical mass and the other wasn't, and he was talking about what would happen if one touched the other.

well, I've forgotten the rest of the story but he inadvertently touched the two together, and some chain reaction or something took place and he died a week or so later due to radiation poisoning and the whole class had to have blood transfutions.

1. what the hell happened.
2....what the hell happened
Jun 18 2006 1:18AM
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ride_switch
Posts: 586 - Karma: 22
Well, I don't know anything about Critical Mass, but with Uranium, it is very radioactive. That means that neutrons are coming off it at high speeds or something like that. The reaction with the other thing must of caused the neutrons to be released, that causes cancer and radiation sickness. The closer you are the radioactive element, the higher the chance of cancer.
But don't listen to me, I learned that a while ago, it's probably wrong.
Jun 18 2006 1:28AM
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Itsbackfliptime
Posts: 18901 - Karma: 75
that would probably be on the news. Find a link.
Jun 18 2006 2:08AM
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jonnydub
Posts: 940 - Karma: 10
oh shit i should know this. I believe that critical mass is the amount of uranium that is needed to cause a nuclear reaction like in a nuclear bomb. If you have a critical mass of uranium and a stray neutron is intoduced to the mass the uranium will split causing a chain reaction. This is how the bombs we droped on japan worked.

That doesn't sound like what happened to your teacher so what probably happened was some sort of reaction took place and it released gamma rays which are highly radioactive
Jun 18 2006 2:32AM
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wang_bong
Posts: 766 - Karma: 13
you're usually not supposed to hold chunks of radioactive uranium in your hands...
Jun 18 2006 2:35AM
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Paul-o-Rama
Posts: 3301 - Karma: 13
critical mass is a bike ride on the last friday of every month in big cities like SF and NY. Thousands of people ride together. people dress up. people ride naked. great fun.
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Jun 18 2006 2:38AM
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SkiFakie614
Posts: 541 - Karma: 10
Critical mass is the amount of Uraniun-235 or Plutonium-239 you can have in a certain volume of space before a chain reaction occurs where each neutron knocked loose will knock more than 1 neutron loose. Hence, a chain reaction. The result is an energy release... it's called Fission.

These materials alone will initiate a reaction on their own if enough is present. The lesser forms of Uranium and Plutonium will not chain react no matter how much of it you have nearby.

The creator of this thread is full of fucking shit.

There is no school in this country below the graduate level that has possession of, or access to, materials that are capable of a chain reaction. There are several graduate schools who have Nuclear Engineering programs with experimental reactors which will use other Uranium isotopes with much lower levels of neutron flux.
Jun 18 2006 3:26AM
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SkiFakie614
Posts: 541 - Karma: 10
I'm applying to grad school for Nuke E... but don't ask me, I'm fucking blacked out right now.
Jun 18 2006 3:28AM
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grubix2
Posts: 2628 - Karma: 25
uranium just isn't lying around you know. A teacher can't just pick up his gen chem experiment catalog and order up uranium. Radioactive isotopes are heavily regulated.
Jun 18 2006 3:34AM
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David_N
Posts: 384 - Karma: 10
Ugh, I can't remember who that was... It was during the cold war when a team of American scientists were trying to create the A-bomb.
Jun 18 2006 9:49AM
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SkiFakie614
Posts: 541 - Karma: 10
There was an accident like this in Los Alamos during the actual project (WWII). Somebody accidently dropped a piece onto the larger pile he had been manipulating. The air around the Uranium went blue as it ionized and the scientist dove and shoved the piece off. It had only been critical, or near critical, for a split second. He died a few days later of radiation poisoning.

There are only a handful of elements/isotopes (Uranium, Plutonium, Thorium, etc...) that are even capable of a chain reaction and many of them must be enriched or purified for it to happen.

The university physics lab that I work in (U. Penn) has radioactivity experiments but the isotope used has a half-life of like 15 minutes and the setup does not allow any release of dangerous radioactivity.
Jun 18 2006 11:46AM
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SteezePatrol
Posts: 10281 - Karma: 36
hey man what the fuck. I just asked if that was possible, and apparently a few people know what I'm talking about.

ahole
Jun 18 2006 3:59PM
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Badfish2
Posts: 3453 - Karma: 21
When they were trying to find the critical mass for the atomic bomb, the physicists basically mixed the two together by hand until it started reacting, then pulled it apart..
some would later die of radiation sickness

lookup "criticality experiments", Trinity, Robert Otto Frisch, and 'Dragon Experiment'
I believe they were done in Los Alamos
Jun 18 2006 5:02PM
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Badfish2
Posts: 3453 - Karma: 21
And yes, it did happen with 7 other observers.. not a classroom though.

from http://en.wikipedia.org/wiki/Louis_Slotin :

On May 21, the screwdriver slipped, the two hemispheres touched and created a burst of hard radiation. Slotin's instant reaction was to separate the masses by hand, by flipping the upper one to the floor. While he succeeded in ending the critical reaction and shielding seven other observers in the room, he exposed himself to a lethal dose (around 2100 rems, or 21 sv) of neutron and gamma radiation, in history's second criticality accident. Slotin experienced an intense burning sensation in his left hand. As soon as Slotin left the building, he vomited, a common reaction from exposure to extremely intense ionizing radiation.

Slotin's colleagues rushed him to hospital but Slotin was aware of his condition and, realizing he would die, is said to have remarked: "You'll be OK, but I think I'm done for." His parents were informed and a number of volunteers wanted to donate blood but the efforts proved futile. The accident ended all hands-on assembly work at Los Alamos. The incident was at first classified.

Louis Slotin died nine days later on May 30, in the presence of his parents. Two of the other observers also died a few years later with symptoms of radiation poisoning.
Jun 18 2006 5:07PM
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Badfish2
Posts: 3453 - Karma: 21
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Jun 18 2006 5:08PM
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hk_
Posts: 1403 - Karma: 12
Ouch
Jun 18 2006 5:10PM
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garrett.
Posts: 9304 - Karma: 3,670
SO HE DIDNT EVEN HAVE GLOVES ON?oops, damn caps
Jun 18 2006 5:15PM
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SkiCrzy
Posts: 1211 - Karma: 10
thats sad
Jun 18 2006 6:35PM
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jibjim
Posts: 1814 - Karma: 10
hes right, the critical mass is the amount of a radioactive isotope to attain a chain reaction. They use U235 and Plutonium because you dont need as much to attain that critical mass
Jun 18 2006 6:59PM
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SkiFakie614
Posts: 541 - Karma: 10
You're close, but not quite.

They used what was like a guillotine type machine. There would be a bunch of it surrounding the machine, then they would drop a piece through thereby hitting criticality for just a SPLIT second. A burst of radiation would be emitted and based upon how much was emitted they could tell what it would take for critical mass.

The key thing here is that it's not just "how much" of the material, but how much in what volume.

And to the thread creator, I apologize... I was really fuckin drunk when I posted and yeah, I was pretty skeptical.
Jun 18 2006 7:45PM
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SkiFakie614
Posts: 541 - Karma: 10
For anybody who finds this stuff interesting (as I do) I recommend these books. A couple of them are like 800 pages but shit, the stuff we did to get the bomb first during WWII was INSANE.

The Making of the Atomic Bomb
Dark Sun: The Making of the Hydrogen bomb
(both by Richard Rhodes)

The Los Alamos Primer (you'll want some background in physics and calculus to appreciate it)

Brotherhood of the Bomb

And for general physicist "war stories"-

Surely You're Joking Mr. Feynmann?
Jun 18 2006 7:50PM
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Ghst
Posts: 5820 - Karma: 10
All he asked was if anyone knows the story, don't be a dick

It's probably just an urban myth though
Jun 18 2006 8:36PM
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mattyb.
Posts: 6041 - Karma: 2,091
exactly what i was thinking, my sister is a big critcal mass'er
Jun 18 2006 8:37PM
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Paul-o-Rama
Posts: 3301 - Karma: 13
yeah, i am to, i love riding it, what city does she ride in? I ride in SF
Jun 19 2006 4:13AM
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