Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site mit-eddie.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!harvard!think!mit-eddie!greg From: greg@mit-eddie.UUCP (Greg McMullan) Newsgroups: net.bizarre Subject: Re: Re: plutonium Message-ID: <4882@mit-eddie.UUCP> Date: Tue, 6-Aug-85 16:05:19 EDT Article-I.D.: mit-eddi.4882 Posted: Tue Aug 6 16:05:19 1985 Date-Received: Fri, 9-Aug-85 02:20:47 EDT References: <541@bentley.UUCP> <499@mit-vax.UUCP> <217@kitty.UUCP> <544@mit-vax.UUCP> Reply-To: greg@mit-eddie.UUCP (Greg McMullan) Organization: MIT, Cambridge, MA Lines: 106 FLAME ON!!!!!!!!!!!!!!!!!!!!!!! > >>> Nothing, probably. Plutonium is VERY VERY VERY poisonous, but not >>> particularly explosive (the amount needed to make a bomb is not easily >>> transported). >> >>This is pure bull. > > One atom of plutonium can cause cancer. A hundreth of a mole (6.02 x > 10^20) atoms is about a gram. That could be carried by anybody -- > safely. One atom of plutonium can cause cancer, but the probability is infinitesimal. If you want to cause cancer with small numbers of radioactive atoms, I would think that you could do much better than plutonium by choosing a more common isotope and/or one that concentrates by chemical processes in critical parts of the body. Some examples: - Strontium 90, which is made in nuclear explosions and some in reactors, and which concentrates in the bones, being chemically similar to calcium. - Iodine 131 (I think, my references aren't here now), which is a decay product of uranium 235, and thus is made in reactors. This one concentrates in the thyroid, which is why it is used to diagnose thyroid problems by doctors. (It has a short half life, so not much harm is done.) - Carbon 14, which is made by natural processes (I believe cosmic rays, mostly, but I'm not sure), and is a major ingredient in DNA and RNA, and so is a very good candidate for causing cancer, anyway. >> And to make a bomb all you need is a couple times critical mass. > > THIS is pure bull. If you have ONE times critical mass it will blow up, > you lunkhead! That's what critical mass MEANS! Bombs contain LESS than > critical mass so that they're stable. The activation energy is supplied > by a conventional bomb set off as to compress the matter an "fool" it > into thinking it's critical mass. Take a high school physics course. I > did, and look where it got me! This is a common misconception. What critical mass REALLY means is that on average, one neutron in the assembly will cause exactly one fission neutron to be created. Specifing a certain mass as "critical mass" without giving other relevant factors (what shape your material is, how dense it is, what chemical form it is in, what other materials are around it, how isotopically pure it is, etc) is meaningless. A nuclear reactor is a large assembly of material, some radioactive, that is kept exactly critical, within very close tolerances, except when changing power level, and it categorically CANNOT explode atomically. Bombs are assemblies of material which are not critical until the chemical explosives around the radioactives are set off, when the materials rearrange themselves into a configuration which is more than critical (supercritical) for a short time. The explosoves do not provide any significant amount of energy in terms of activation, and the bomb is not "fooled" into anything. It contains a small number greater than one times the criticsl mass of radioactives (when in the intermediate state - after the high explosives go off, but before the chain reaction has really gotten going). Try taking a nuclear engineering survey course (22.001 at MIT is a good one), or even an introductory reactor design class. >>That can >>be carried in a briefcase. The whole bomb can be fit into a backpack. In >>fact the army has a low-weild backpack bomb. > >Fine, why don't I just fill your briefcase with plutonium and see how >long you can carry it around before you drop dead. 8 grams of plutonium >will boil a liter of water in about a minute. I don't think you want to >carry around a breifcaseful. I'm not sure where your 8 minute figure came from, and I don't have the time to check it right now, but the dangerous form of the energy to humans (as long as it isn't released to quickly, which would not be the case for a usable suitcase bomb before detonation) is neutrons, which can be significantly attenuated by relatively small amount of many plastics, which aren't very dense, so your suitcase bomb would probably contain maybe 8 or 10 kg of Pu, 1 or 2 kg of high explosive, 8 kg of polyethelyene, and some other structural materials. If we allow 5 kg for the structural materials and suitcase, we have a 25 kg bomb that might yield something on the order of a kiloton, (probably between .1 and 5 kT), and would not be extremely radioactive from the outside. See _The Curve Of Binding Energy_ by John McPhee, I think, for more information, and better details. FLAME OFF Sorry about the length of this factual posting to net.bizarre, but this exchange hit a sensitive spot, and I haven't slept enough recently. >Charles Forsythe >CSDF@MIT-VAX Greg McMullan (Soon to receive a bachelor's in nuclear engineering from MIT, so I know what I'm talking about.) uucp: !genrad!mit-eddie!greg arpa: greg@grape-nehi%mit-mc or g.mcmullan@mit-eecs%mit-mc us snail: 500 memorial drive cambridge, ma, 02139[-4326] (617) 225-8942