Fissile v. fissionable

[GEORGE CICOTTE <GEORGE_CICOTTE@health.ohio.gov>]

     There are ANSI standards (the ones a web search found are below) on 
     handling of both fissile and fissionable materials.  The general 
     distinctions have already been captured in previous posts, but the 
     specifics in the definitions refer to the probability of induced 
     fission.  Obviously, just about anything can be fissioned, but it is 
     useful to consider the likelihood in deciding whether something is 
     actually considered fissile or fissionable.
     
     In effect, a nuclide is fissile if it "readily" fissions under thermal 
     neutron flux, e.g., U-235, Pu-239, and is fissionable if it "less 
     readily than fissile but still relatively easily fissions under 
     neutron flux" [quotation marks are for emphasis, not a direct quote], 
     e.g., Pu-238, U-238, Np-240, etc.
     
     The ANSI standards are available by contacting the American National 
     Standards Institute in New York, or their home page at:
                http://www.ansi.org/home.html
     
     ANSI N12.1-1989.  Warning Symbols D Fissile Material Symbol
     
     ANSI/ANS 8.7-1975 (R1987).  Guide to Nuclear Criticality Safety in the 
     Storage of Fissile Materials
     
     ANSI/ANS 8.1-1983 (R1988).  Nuclear Criticality Safety in Operations 
     with Fissionable Materials Outside Reactors
     
     ANSI/ANS 8.5-1996.  Use of Borosilicate-Glass Raschig Rings as a 
     Neutron Absorber in Solutions of Fissile Materials
     
     ANSI/ANS 8.9-1987 (R1995).  Steel Pipe Intersections Containing 
     Aqueous Solutions of Fissile Mater
     
     
     V/R
     George R. Cicotte
     george_cicotte@health.ohio.gov.us