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• Friday, September 12, 2008 07:45 AM

  Fizzle and other nuclear issues

  Godot,

  While you haven't replied, I think I've found a better method to educate you on how nuclear warheads work. There are a number of terms used to describe failed detonations. Words like fizzle.

  http://www.sciam.com/article.cfm?id=kims-big-fizzle

  Plutonium weapons have several ways of misfiring. The first depends on the triggering of the plutonium by an implosion process. The implosion must be extremely symmetrical to be fully successful. Typically a combination of fast and slow conventional explosives surrounds a sphere of plutonium (the "core" or "pit"). Engineers must carefully machine all the pieces that make up this explosive shell into shapes that, when detonated simultaneously, produce a precisely spherical shock wave that compresses the plutonium to two to five times its normal density (the more compression, the greater the explosive yield). At the higher density, what was a subcritical mass of plutonium becomes supercritical--that is, one in which a sustained chain reaction takes place, producing the blast.

  If the shock wave fails to be completely symmetrical--for example, if a detonator goes off 100 nanoseconds later than the rest--the compression will be less efficient because the core will tend to squirt out in the directions where the shock wave is weaker or arrives late. Another potential troublemaker is the initiator, a small device at the center of the core that emits a burst of neutrons to start the chain reaction reliably at a precise stage of the implosion. An initiator going off early or late--or not at all--reduces the yield.

  This is written by a layperson, but the basics are correct.

  http://www.milnet.com/nukbang.htm

  Placing two pieces of subcritical mass together will generate heat and deadly radiation. However this will not create a nuclear explosion and unless your are using your hands to put the sub-critical masses together, the danger is minimal.

  What is necessary for a nuclear detonation is to simultaneously (we are talking VERY simultaneously...nuclear triggers are devices which make the events occur within fractions of a second akin to computer speeds) compress sub critical pieces together in just the right configuration. We are trying to lodge loose neutrons which in turn bump other neutrons, and so on, creating the chain reaction. Dropping two pieces of critical mass from the top of a ten story building will not make this work. The pieces must be brought together in a certain form, then a huge compression of the entire mass must take place very quickly after that.

  A large mass will generate heat, and this heat will eventually create an explosion, but it's not a nuclear blast, it's order of magnitude less powerful and the fundamentals are very different.

  —Xanthro Read Xanthro's other letters
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