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Politics : Formerly About Advanced Micro Devices -- Ignore unavailable to you. Want to Upgrade?

To: combjelly who wrote (130929)	1/29/2001 1:13:28 PM
From: pgerassi	Read Replies (2) \| Respond to of 1571241

Dear Combjelly: The problem with your analysis is that you forget about the quantities of plutonium involved. When one little bit is close to another little bit the sum of the radiation of the little bits is greater than the sum of radiation when they are far apart. Since detonation requires that the density is high enough for the amplification be greater than the losses and a "suitcase bomb" has little extra room, the plutonium is near criticality. 1 unit of plutonium will radiate many more times than one unit spread over a wide area. The radiation is such that unprotected people are likely to die from short exposures at 1 meter. That takes many curies of radiation. That means high levels of radiation in the 10^12 levels or more per second. A few picocurie source of 50kev particles is detectable at ranges greater than 5 meters. I know, since I worked on testing software for Nuclear Cameras for medical purposes. One such camera could tell the power and direction of one alpha particle, photon, neutron, electron, or positron. Using this, I could tell what substance emitted it. Yes there is only two ways to shield neutrons, absorption and reflection. The latter is not typical and very difficult. The first requires both distance and a good absorber. The equation is quite simple, the detection noise floor must be above the signal or particles vs time. The signal varies with the inverse square of distance and the exponent of the sum of the products of distance and material absorption constants that are passed through. Air has a low absorption constant about 2000 times less than water. Certain materials have about one hundred times that of water. But they are very expensive and only are good at certain energy levels. Also you fail to take into account, the fission and decay byproducts. Some of them are very good beta and gamma emitters. The table you cite is for plutonium only and not them. Ditto for U-235 and the more esoteric ones. All it takes is one particle in the ranges cited to get a more detailed scan and tracking started. However, one thing can pass undetected, a submarine and the water will act as a good shield. The problem is the US military will take unkindly to such a vessel operating. We can detect any sub moving in either the Pacific or Atlantic courtesy of the Cold War. When they get close, they will be checked out by one of our hunter killers. Probably long before they come within a few dozen miles of the coast. The nice thing is that these techniques for stopping nuclear bomb smuggling can be done without much notice by the public at large and thus, can not be ruled out even now by our adversaries. Pete