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pressure P, the formation of each free electron by ionization is balanced by the removal of one uranium atom or ion. From Figures 8, 9, and 10, the electron fraction is seen to increase monotonically as the temperature increases, which means that any temperature increase at constant pressure requires a reduction in the amount of uranium in the fuel region. The quantitative effects of temperature on the uranium density are shown in Figure 11. The slope
              dN
of the curve (=) , gives the rate of uranium reduction
                  P
with increasing temperature at constant pressure. The uranium reduction rate decreases at higher temperatures, since the electron fraction changes very slowly for temperatures greater than 40,000°K. From Figure 10, a basic characteristic of the plasma core reactor is seen to be strong dependence on the uranium density on the plasma temperature. For a given constant pressure, there is only one temperature which will sustain the critical uranium mass. Suppose that the reactor is to be operated at a constant pressure of 400 atm and that the critical mass corresponds to a total uranium density of i019/cc. From Figure 11, it is seen that a temperature of 59,0000K would be required to sustain the desired uranium mass. An increase in the temperature would cause the reactor to become subcritical and similarly, a temperature decrease