Pu fissionable vs. fissile

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

     From Al Tschaeche's re-post of Erik Nielson's post, regarding the 
     statement:
     ". . .  4.7 tonnes of plutonium at the end of 1993, of which some 3.4 
     tonnes are likely to be fissile. . . ."
     
     Al,
     
     Try checking the ANSI standards on handling of fissile and fissionable 
     materials.  There are quantity and isotope identities that define 
     which category a particular material fits into.  In fact, not all 
     isotopes of Pu are fissile.  Pu-238 is fissionable, but not fissile.  
     The distinction is rather complex, but suffice it to say that the 
     difference is mainly as to whether it is possible to achieve a 
     sustained criticality.  Pu-238 has decay properties such that the heat 
     generated disassociates the material before you can get it close 
     enough to itself to maintain a chain reaction, but it does fission 
     some, hence the term, "fissionable."  I suspect, however, that the 
     distinction in the news report refers to concentration.  Probably 1.3 
     tonnes are in fuel which is sufficiently spent that the poisons make 
     it infeasible to use.
     
     V/R
     GRCicotte
     
     
     ------------------------------
     
     Date: Thu, 23 Jan 1997 16:20:31 -0700
     From: xat@inel.gov (Alden Tschaeche)
     Subject: Re: Japan to switch to MOX?
     
     Erik C. Nielsen wrote:
      For the full
     > story, see http://www.merc.com/stories/cgi/story.cgi?id=1208803-116
     
     Another statement in the full story is: "Japan had about 4.7 tonnes of
     plutonium at the end of 1993, of which some 3.4 tonnes are likely to 
     be
     fissile, according to latest government figures available."
     
     I was told that ALL isotopes of plutonium are fissile.  Is that not
     true?  Al Tschaeche xat@inel.gov