Posted on 07/21/2005 11:25:01 AM PDT by Ditto
Well, Dr. Daglian was an accident, but the other was more like, "Hey guys, watch this!"......
I got some left over from physics 101 at Troy State - if you need any. We use it to make toast and deform cockroaches.
He was stacking WC blocks, by hand, around a spherical piece of Pu 239 weighing about 6 kg, and measuring the neutron flux as he did so. He wanted to see how the configuration of WC blocks changed the reactivity of the system. This was about nine months before the Slotin incident, on August 21, 1945.
Keep in mind that, at that time, these guys were deep into a heavyweight tech-out in pursuit of the atomic bomb. They had essentially no practical knowledge of what they were doing, especially as related to handling large amounts of Pu, which (if you recall) had never existed... anywhere before it was first manufactured in bulk in 1945 in Hanford WA. The guys at Los Alamos, including Daghlian and Slotin, were getting it "hot out of the reactor," literally (in more ways than one...).
You know how, when you were a kid, and someone told you "be careful of that fan, it can cut your finger off," and you had this almost irresistable urge to put your hand near the blades to see what it would be like? I've always wondered if, maybe, those guys at Los Alamos weren't subject, just a little bit, to that same mentality. I know I would have been. You have all these theoretical guys saying "be very, very careful with this stuff, and whatever you do, don't put more than "X" amount together in any one place at any one time," but no one's ever done it, and you find the question of what would happen if you did put "X" amount together almost irresistable.
Anyway, I doubt very much this is what happened, but I've wondered.
(steely)
ohh i think i get the picture. the ball is encased in bricks except for the top. then he lays a brick over the ball, and zap!
No, it's not that easy with plutonium; the design of plutonium device is not trivial. The nuclear characteristics of plutonium make it prone to pre-detonation (the chain reaction gets going before the optimum instant, with a decrease in the device's yield). The Manhattan Project had a great deal of difficulty in solving how to design the plutonium devices, which were used at Alomogordo and Nagasaki.
More accurate to say the trinity "blasting cap" was carried on his lap. The actual "device" was highly enriched uranium that weighed in at about 10,000 pounds (as big a load as a B-29 could carry).
Yeah, maybe. Or maybe, he gets the bricks stacked up around the core, and he's got a little "fort" of bricks stacked up (like a kid would make a "fort" out of toy blocks), and the geiger counters are really starting to sing, and he thinks "I'll just lower this piece by hand down through the middle of the 'fort' and see what happens with the radiation count." And then there's a sudden blue flash (just like the glow you see in those pictures of nuclear fuel elements under 25 feet of ultra-pure water in storage at nuclear power plants around the country). And maybe he hears something too... an alarm klaxon suddenly goes off, or the reaction itself makes a sound. And he jumps in alarm, and drops the brick (which is damn heavy, WC is really dense). The blue glow gets brighter, and he reaches in and grabs that sucker and pulls it the hell out of there.
Then he called his boss. He was worried, but not really scared.
(steely)
Something else, in turn, blasted that blasting cap, right?
Yes, you have described a plutonium implosion device. Although I have never designed such a device (I am not a nuclear engineer, nor do I play one on TV), I believe that one would also need a neutron source to initiate the chain reaction, a neutron reflector to keep it going, and a perhaps some kind of containment increase the explosive yield.
I am told that the high-explosive shaped charges are not easy to design or manufacture. Proper timing of the chemical implosion and the neutron initiation can be very difficult to achieve. My guess is that it wold be much easier to create a fairly large bomb that would fit in a tractor-trailer rig than a device that would fit in the trunk of a car. I doubt that a terrorist group could make a small plutonium explosive on its own.
No, the trinity device was Plutonium. The core was two nickle-coated hemispheres of Pu. At the center of the Pu core was a tiny assembly containing Polonium and some other materials to start the reaction; this was the "blasting cap," to use your analogy.
Surrounding the Pu core was roughly 10,000 lb of high explosives in a sphere about five feet in diameter.
This device was so complex and experimental that they had to test it before use; that is what happened at Trinity. It's first military use was at Nagasaki, Japan, on August 9, 1945.
The Hiroshima bomb used U 235, which, because it is not subject to pre-detonation, could be configured in a supercritical assembly in milliseconds, instead of microseconds (as required by Pu). Thus, it was determined that they could test the U 235 device in actual use over a target city.
(steely)
Was pre-detonation the reason that plutonium was deemed unsuitable for gun-type weapons?
Well, sort of, but the PU in "Fat Man" was the nuclear trigger, while in "Little Boy" it was conventional expolsives literally in a sawed-off hunk of a naval gun.
so, it would be easier for a low budget nuker to make a uranium bomb?
I think you have the terms a bit confused. Weapons that contain only fissionable material, uranium or plutonium are generally referred to as "atomic bombs". Weapons that obtain most of their power through the fusing of atoms rather than the splitting of atoms are the ones classified as thermonuclear weapons or hydrogen bombs.
Secondly, simply strapping some TNT or C-4 to a piece of plutonium will not cause it to go nuclear. First you need an initiator (the Trinity device used gold foil wrapped Beryllium) which is surrounded by a sphere of plutonium. The plutonium is then encased in a set of high explosive, shaped charges which must detonate in an exact sequence (all within a few milliseconds of each other) in order for the plutonium to be imploded correctly. If it works correctly then you will have nuclear yield. If it doesn't you simply have a loud boom. (This is why the emergency way to dispose of a nuclear weapon is to either burn it or blow it up. It will cause the high explosives to go off incorrectly and not produce nuclear yield.)
As a side note, all thermonuclear weapons contain a standard atomic bomb. It is used as the initiator for the thermonuclear detonation.
Yes, and far simpler in terms of design. (This was one reason the scientists on the Manhattan Project didn't feel the need to test the design. The other was they didn't have enough uranium for more than one bomb.) However, one needs highly enriched uranium (HEU) to make a nuclear weapon and that is very hard to come by. The uranium used in nuclear power plants cannot be used as fuel in a nuclear weapon. It does not contain enough Uranium-235.
I don't think you have that right. The Pu in Fat Man was the fuel, the trigger was a large sphere of shaped high-explosive charges which carefully and precisely squeezed the Pu core until it went critical.
Not really. The thing about U 235 is that it has to be separated from its far-more-plentiful cousin isotope U 238, which which makes up more than 99% of naturally occuring U. This separation cannot be accomplished by means of chemistry, because the two isotopes are the same chemical. Instead, the isotope separation has to be done atomically, essentially by weighing mass quantities of the two isotopes and using the difference in their weights (which is very, very small) to sort them into separate bins. There are several ways to do this (in the Manhattan project they tried three or four, I'm not sure which) but all require a lot of space and a lot of equipment and a lot of energy and a hell of a lot of money.
The thing about Pu is that it can be manufactured by irradiating naturally occuring U with neutrons in the core of a nuclear reactor fueled with much-less-enriched U 235. Then, once the Pu has been formed by nuclear chemistry, it can be separated from the U by conventional chemistry, because it is chemically different from U. This makes the production of Pu a lot less costly on a "per bomb" basis than is the production of U 235.
Of course, there's a bit more to it than that. I think the only way a "low budget nuker" can get hold of a bomb is to steal one or buy one from a corrupt government source.
(steely)
No, the Trinity device was a plutonium device, not highly-enriched uranium. The fissile core of the device, whether plutonim or uranium, weighs a few kilograms, not 5000 kg. To be sure the entire device weighs a lot, due to the tamper, trigger, etc.
Yes
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