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order to determine the radiative emission and absorption characteristics of the uranium plasma fuel region, the particle densities of the various uranium species must be considered, because each ion has different radiative properties. In order to determine the nuclear criticality characteristics of the reactor, only the total uranium density is considered, since neutron induced fission is a nuclear effect and is not influenced by ionization of uranium atoms. This is not meant to imply that plasma effects have no influence on nuclear criticality, since the plasma characteristics of uranium actually determine the critical uranium mass. This static coupling between plasma and nuclear effects is shown by the equation of state (4.3), which can be written as 12
                     p = p  +  Y p.                 (4.46)
                            e i=O


where

         Pe = N ekT, partial pressure of electrons

         P. = N.kT, partial pressure of the uranium species
         1     1
              Ui+

 This expression shows that in thermodynamic equilibrium, one free electron creates the same partial pressure as one uranium atom or ion. Thus, for a given constant reactor