Thermionic Power Production for Dry-Wall Inertial Confinement Fusion Systems

Abstract

Thermionic power production is shown to be a viable technique for increasing dry-wall inertial confinement fusion (ICF) power output. Thermionic cells produce electricity directly in a topping cycle run off the high temperatures generated at the first vacuum wall by the absorption of fusion product x rays and charged particles. The high temperatures are used to heat the thermionic emitter, which is an integral part of the first wall. The principal engineering consideration is the means of providing the emitter with a high steady-state operating temperature, while the reactor itself operates a pulsed mode with ICF events occurring at between 1 and 20/s. It is shown that several design variables, including materials selection, first-wall thickness, and target firing rate can be chosen to satisfy the emitter temperature requirements. Furthermore, heating requirements do not rely on neutron attenuation, so neutrons can be conserved to meet tritium breeding requirements in the blanket. Several other aspects of the thermionic system design and engineering are discussed. These are related to the current state of development of thermionic convertors, and to possible further advances in the technology.