A specific type of gaseous core reactor consists of a UF4/CF4 fuel mixture in chemical equilibrium with a graphite reflector wall. Criticality calculations show that such a system requires a relatively small fuel investment. Temperature-dependent fuel redistribution at power is shown to give a minor positive reactivity effect, which does not jeopardize safe reactor operation. Analysis of heat transport demonstrates that very high temperatures in the core center can be realized at moderate gas pressures, which opens a way to improve the efficiency of fission energy conversion processes.