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to 500 atm and temperatures from 40001K to 100,000'K. A typical calculated composition is shown in Figure 13, for a pressure of 100 atm. Additional calculated hydrogen plasma compositions for pressures from 100 atm to 500 atm are shown in Figures 35 through 39, Appendix B.

        For the range of pressures considered, the temperature dependence of the various hydrogen species is similar to that shown in Figure 13. The molecular hydrogen rapidly dissociates into atomic hydrogen as the temperature increases from 40000K. At a temperature of 10,0001K, atomic hydrogen constitutes about 99% of the total plasma particle density. Above 10,000°K the atomic hydrogen ionizes rapidly and for temperatures greater than about 40,0000K, the plasma consists of over 99% electrons and ionized atomic hydrogen, the remaining hydrogen species accounting for less than 1% of the total particle density.

        The effect of temperature on the total hydrogen density at constant pressure is shown in Figure 14. In order to estimate the neutron scattering and radiant energy absorption effects of the hydrogen coolant region, these curves can be used to determine the amount of hydrogen present at a given pressure and temperature. The hydrogen densities obtained from these curves account for the fact that, at high temperatures, the coolant is