Shielding design aspects of thermionic space nuclear reactors

It has been well documented that nuclear power sources will be required for the future exploration of space. Higher power levels [>10 kW (electric)] will be enabling, if not absolutely necessary, for the continued expansion of a human presence in the solar system and beyond. Space missions that will directly benefit continued life on Earth, including the monitoring for climate change and global warming, high-capacity communication satellites, and large, space-based radar systems to monitor the flow of airline traffic, will require progressively larger amounts of electrical power. Military applications, even with the ending of the Cold War, will continue to be needed for treaty verification activities. A thermionic energy conversion-based nuclear reactor system is one of the many different technologies proposed for the utilization of nuclear energy in space. How the energy conversion is accomplished and the equipment requiring shielding have a profound effect on the overall shielding requirements for the system. There exist two configurations of this technology that can be exploited and will have a significant effect on shielding needs. The paper discusses in-core thermionic conversion and out-of-core conversion concepts