Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!linac!att!cbnews!cbnews!military From: john%ghostwheel.unm.edu@ariel.unm.edu (John Prentice) Newsgroups: sci.military Subject: Re: Terminology:Nuclear, Atomic, Neutron Message-ID: <1991Mar1.053313.93@cbnews.att.com> Date: 1 Mar 91 05:33:13 GMT References: <1991Feb21.030902.12162@cbnews.att.com> <1991Feb22.232819.4666@cbnews.att.com> <1991Feb27.021040.21923@cbnews.att.com> <1991Feb28.052457.10592@cbnews.att.com> Sender: military@cbnews.att.com (william.b.thacker) Organization: University of New Mexico, Albuquerque, NM Lines: 93 Approved: military@att.att.com From: john%ghostwheel.unm.edu@ariel.unm.edu (John Prentice) In article <1991Feb28.052457.10592@cbnews.att.com> deichman@cod.nosc.mil (Shane D. Deichman) writes: > >Are you using the term "atomic" to describe electrostatic repulsion? >This seems like something of a misnomer, since "atomic" is generally >applied to reactions involving the valence electrons. > I think most physicists would make the distinction of nuclear as phenomena associated with the strong nuclear force and the internal structure and dynamics of the nucleus. Atomic is usually taken to refer to phemonena associated with the interactions of electrons and nuclei with each other and with other atoms. This includes a good deal more than just valence electrons. I would say your definition is more appropiate to a chemist who is worrying about chemical reactions which involve the valance electrons than to a physicist interested in atomic structure and dynamics where you have to account for all the constituents of the atom but where nuclear forces play no part (except to bind the nucleus together). > >The energy from a fission reaction, while evidenced after the fact as >the repulsion of high-Z like-electric fields, still comes from the >nuclear binding energy. Fission is a weak nuclear process; the nuclei >involved are at the high end of the binding energy curve, where the >first derivative is small compared to lower-end processes (e.g., fusion). >When you figure in energy as a function of mass, then the disparity >between fission and fusion becomes all the more discernable. > This question of terminology has absorbed far more time already than I think it deserves. However, let me quote from an article by Harold Schmitt (Physics Division, Oak Ridge) in the "Encyclopedia of Physics" discussing fission: ..."As the compound nucleus begins to fission, this excitation energy transforms into deformation, and a sequence of shapes such as those shown in figure 1 may ensure. At the "scission point," i.e., the point of separation, the product nuclei (often called "fission fragments" or "fission products") are free to accelerate by mutual Coulomb repulsion. It is this Coulomb potential energy, and its subsequent transformation into fragement kinetic energy, which accounts for most (80 to 90%) of the energy released in fission." So, to oversimplify, once the nuclear forces are overcome by the deformation forces, you have two nuclei left which do not interact via nuclear forces and with a very small kinetic energy. Most of the 180 MeV or so of kinetic energy of the final reaction comes from the fact that you have two like charged nuclei in very close range and hence in a very high state of electrostatic potential energy. So, when I say that the majority of the kinetic energy comes from atomic forces, I am saying nothing more than that the energy is derived from non-nuclear sources, i.e., the Coulomb repulsion of the nuclei. In any case, as far as I can tell from your paragraph above, we are saying the same thing, so we are just hashing over semantics. I am not particularly trying to defend the use of the term atomic versus nuclear, as a physicist I tend to be more interested in the nuclear processes involved in causing a nucleus to fission than I am in the origin of the kinetic energy of the fission fragments, so nuclear is both more appropiate and acceptable to me as a terminology. All I was doing in my original posting (where all this started) was to explain why some people make a distinction. > >The term "atomic" bomb was misapplied. Some may recall an old H.G. >Wells story (c. turn of the century) in which there was a "nuclear >bomb" -- in actuality, this device derived it's energy from purely >atomic forces (as conventional high explosives). So, misapplication >of scientific terms is nothing new, even in the bomb business. > I think this question of whether to call it an atomic or nuclear weapon is in effect a distinction without a difference. As a physicist, I would say the correct term is nuclear, but inside the weapons community the term atomic is often generic for fission weapons and nuclear generic for fusion weapons. Samuel Glasstone wrote in the 1962 version of "The Effects of Nuclear Weapons": "A distinction is sometimes made between atomic weapons in which the energy arises from fission, on the one hand, and hydrogen (or thermonuclear) weapons, involving fusion, on the other hand. In each case, however, the explosive energy results from nuclear reactions, so that they may both be correctly described as nuclear (or atomic) weapons." John -- John K. Prentice john@unmfys.unm.edu (Internet) Dept. of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA Computational Physics Group, Amparo Corporation, Albuquerque, NM, USA