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of 5000 seconds, a hydrogen nucleus of average velocity has a kinetic energy which is about 75% as large as the .thermal energy. This comparison demonstrates that the flow motion of hydrogen should be included in the calculation of effective hydrogen scattering cross sections.

         Experimental and theoretical investigations are

 needed to determine the quantitative limitations of plasma heating by fission fragments. Additional heating mechanisms may be required to supplement the collisional energy transfer of the fission fragments.

         The problem of neutron and gamma radiation damage

 to the containment wall must be considered in the engineering design of the plasma reactor. It is likely that the use of additional liner materials adjacent to the inside face of the graphite chamber will sufficiently reduce the wall radiation. Experiments and analytical studies are needed to determine the quantitative effects of high velocity coolant flow on neutron streaming through the exhaust nozzle.

         In summary, the high performance potential of the fissioning plasma concept justifies additional theoretical and experimental analysis of the feasibility and engineering characteristics of this system. It is believed that a most useful theoretical analysis could be performed by describing the plasma reactor system as an optimization problem. In