From hotrod@Dixie.Com Sun Jan 2 19:41:00 1994 Subject: Re: depleted uranium From: hotrod@dixie.com (The Hotrod List) To: hotrod@dixie.com X-Sequence: 7287 X-Archives: ece.rutgers.edu -> Yes, depleted Uranium is used in aircraft as counterweights. Why -> does that seem strange? Weight, mainly. It seems to me that any control surface needing counterweights to function would be poorly designed to start with. But I guess that's a topic for an airplane list. Tungsten is some ferociously expensive stuff and hard to work too. On the other hand, I don't know that depleted uranium is good for anything. I wondered if it might be less expensive than tungsten, but John says it's pretty hard to get. [It's not hard to get per se, it just requires a license because it is a component of THE BOMB. Uncle Sammy doesn't particularly want to sell U to people who want to make mushroom clouds. There's a BUNCH of depleted uranium around as the result of the weapons programs. After all, the U-235 content of natural uranium is only about 0.3 to 0.6% of the whole. A bit of it is used as tampers and breeding blankets in nuclear weapons and a bit more is used in nuclear reactor fuel but the bulk of it just sits around in DOE storage facilities. So once the license is procured (and who worries about spending $500 on getting a license for a bazillion dollar aircraft?), U is plentiful and cheaper than equivalent heavy materials such as tungsten. It has a few pesky properties such as being pyrophoric which means it must be machined in an argon atmosphere (it burns readily in nitrogen), it is harder'n hell which makes machining difficult, and it tends to corrode, though a flash of nickel handles that OK. JGD] ---------- Posted by: emory!chaos.lrk.ar.us!dave.williams (Dave Williams) From hotrod@Dixie.Com Mon Jan 3 17:37:12 1994 Subject: Re: depleted uranium From: hotrod@dixie.com (The Hotrod List) To: hotrod@dixie.com X-Sequence: 7290 X-Archives: ece.rutgers.edu -> component of THE BOMB. Uncle Sammy doesn't particularly want to sell -> U to people who want to make mushroom clouds. There's a BUNCH of Waitaminnit. High school physics was long ago, but I thought the normal uranium was pretty well worthless; ie only the fancy stuff would fizz? [Unfortunately, most of what is common knowledge about atomic bombs is wrong and is the product of the government's rather intense disinformation campaign. Here's a quick summary: For weapons under about 3/4 megaton and excluding subsurface, deep penetrating weapons, the typical design is the so-called "boosted implosion" design. This design uses multiple spheres of plutoninum surrounded by high explosive and tamped with either natural or depleted uranium. When the weapon is detonated, the high explosives are fired to implode the plutonium. After implosion but before the initiation of the chain reaction, a small quantity of tritium/deuterium gas is injected under several thousand pounds of pressure into the core. Then an external neutron howitzer is fired to initiate the reaction. The fission completes in a few nanoseconds and the conditions in the center of the pit are such that the tritium/deuturium undergo fusion reactions. (NOTE: this is NOT a hydrogen bomb - little to no yield results from this.) The fusions supply a very intense flux of fast neutrons which then fast fission the natural uranium blanket. All this happens before the weapon casing disassembles. Typically, about 40% of the energy release is from the pit, up to perhaps 2% is from the fusion booster and the rest is from the fission of the blanket/tamper. BTW, for anyone who read Clancy's "Sum of all Fears", the mechanism of tritium boosting is one of those details he intentionally mucked up in order to assuage his conscience. The basic hydrogen bomb consists of a small boosted fission trigger stacked atop a cylinder of Lithium Deuteride (LiD). A thick natural uranium disk shields the LiD assembly from the thermal effects of the trigger. A hole in the center allows neutrons through. The center of the LiD is filled with a plutonium rod. The whole assembly is suspended with dense rigid foam inside a thick walled natural uranium cylinder that serves as both a tamper and an X-ray reflector. When the weapon is detonated, the bulk of the trigger's energy is released as soft X-rays. These X-rays travel outward at the speed of light (the explosive effects are over 10X slower). They strike the walls of the tamper and spall off an intense plasma, a plasma so dense that it will exert millions of psi of pressure on anything it strikes. At the same time, neutrons traveling at about half the speed of light stream through the hole in the shield and initiate bulk fission in the plutonium core of the LiD fusion cylinder. The spacing is such that the Pu fission and the plasma wave arrive at the LiD cylinder at the same time. The plasma compresses inward and the fission reaction compresses outward while simultaneously the neutrons liberated from the fission transmute the Li in the cylinder to tritium. This compression initiates fusion in the (formerly) LiD cylinder. The bulk of the energy released in this reaction is fast neutrons which proceed outward and fast fission the natural uranium tamper/blanket. This "single stage" design is good for up to about 1.5 megaton. About 15-20% of the yield comes from the initiator, about 30-40% from the fusion reaction and the rest from the fission of the tamper. This design is sometimes referred to as a "fission-fusion-fission" device. For higher yields, the fusion pits are simply stacked so that the first one servers as the initiator for the second and so on. Both our and the Soviet high yield (up to 10 megaton) weapons are 3 stage weapons, that is, three LiD fusion assemblies. Oh, and to answer a common question, the Dial-A-Yield facility, whereby the weapons officer can select the bomb's yield before delivery, simply varies the amount of Du/T injected into the trigger. This varies the yield of the trigger which varies the yield of the fusion package, etc. More modern designs use X-ray mirrors to focus the energy from much smaller yield triggers on the LiD fusion package. How these mirrors are made are still highly classified so I can't talk about it. Probably freely available in the literature, however :-) JGD] -> (and who worries about spending $500 on getting a license for a -> bazillion dollar aircraft?), U is plentiful and cheaper than I've seen Mallory metal priced at $50 to $100 per inch for 1" bar. If you ran a crank shop you'd use a lot of stuff doing strokers, internal balancing, etc. Does the license restrict what you do with the metal? Specifically, would it prohibit selling cranks with slugs of uranium in them? [Yes, the license requires you to account for any SNM you might possess. The auditing process is commonly referred to as Safeguards. Several companies, D.S. Davidson among them, make portable Safeguards monitors whereby an inspector can examine a cache of SNM and by analyzing the gamma ray spectrum with some proven heuristics, can determine with great accuracy how much SNM is present. If you built a crankshaft using an SNM as a balancing weight, your customer would also have to be licensed and would have to submit to Safeguards. That means that when the engine blows up and the U burns up, he's gonna have to account for where it went. If you observe that this is structured to discourage ownership of said material, you would be correct. JGD] -> heavy materials such as tungsten. It has a few pesky properties such -> as being pyrophoric which means it must be machined in an argon -> atmosphere (it burns readily in nitrogen), it is harder'n hell which -> makes machining difficult, and it tends to corrode, though a flash of -> nickel handles that OK. JGD] My Machinery's Handbook doesn't mention all that neat stuff. <grin> Seriously, is it more likely to catch fire than aluminum or magnesium? Would directing argon at the cutting edge be sufficient, or would it require a chamber, like welding titanium? [More likely. Uranium is really strange stuff. Plutonium even more so. There are a pair of thick books still in print called "The Metallurgy of {Uranium, Plutonium}" that detail all the weirdnesses. Both metals exist in numerous allotropes and the transition from one to the other can be fairly energetic. I don't know if an argon purge on the cutting tool would be enough or not. I do know that the government's machining centers that I've seen are contained either in argon glove boxes or in tents. JGD] I never considered corrosion, but I guess you're right, since uranium's "natural" form is an oxide. Considering the way today's safety nazis act, half the government would probably shit bricks if someone actually used uranium in a crank, but I have this curiosity problem... [Me too :-) For strictly practical reasons, I'm not sure I'd want to try to use U. I have a small square of depleted U. This stuff is as hard as a rock. A carbide scribe will mar the surface but not much. About the only way I've found to cut it is to fracture off a chunk and even that takes some effort. Nuclear properties aside, it is not a friendly metal. JGD] ---------- Posted by: emory!chaos.lrk.ar.us!dave.williams (Dave Williams) From hotrod@Dixie.Com Tue Jan 4 15:43:08 1994 Subject: Re: depleted uranium From: hotrod@dixie.com (The Hotrod List) To: hotrod@dixie.com X-Sequence: 7298 X-Archives: ece.rutgers.edu JGD: >Unfortunately, most of what is common knowledge about atomic bombs is >wrong and is the product of the government's rather intense disinformation >campaign. Here's a quick summary: [surprising burse of knowledge deleted] John, I'm surprised you haven't applied this knowledge to the old Lawnmowers From Hell thread. Bet you could come up with one hell of a stump chewer ;) . Ron "Well, I Enjoyed It Anyway" Rader [ :-) Well I always have regarded nukes as simply hotrod firecrackers :-) Only problem is getting and keeping the goodies. I once worked on a helicoptor-borne instrument used by NEST that could detect a kg of plutonium in a 100 ft deep well while the helo was flying over the area at full tac. I figured that I'd never have the opportunity to collect a critical mass or live to tell about it. On the other hand, what a show it would be! Imagine my little firecracker set off in front of 1600 Pennsylvania Avenue :-) JGD] ---------- Posted by: emory!bbt.com!rlr (Powdered Toast Man) |
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