The thermal conductivity of mixed beryllia/li ceramic in sphere-pac forms

Abstract

Lithium-containing ceramic tritium-breeder materials have been envisaged to be deployed within the blanket region of a fusion reactor in several possible configurations. One of these is the sphere-pac configuration. For this configuration an important material parameter is its thermal conductivity ( K sp ). It is well known that K sp demonstrates rather complex behavior as a function of temperature, gas pressure, gas composition, particle size, and packing fraction. The interrelationship of these parameters has been satisfactorily accounted for with a hierarchical effective media theory (HEMT). For tritium self sufficiency, most lithium ceramic breeder materials would require the presence of a neutron-multiplier (e.g., Be or BeO). Here, the influence of configuration on K sp (i.e., how one put the different solid components together in the sphere-pac bed) becomes important. Using a generalized HEMT (i.e., a model with capability to describe systems with more than one solid material component), we have analyzed in detail the configurational dependence of K sp for sphere-pac beds composed of lithium ceramic/BeO microspheres. Substantial improvements in K sp can be achieved if a configuration of lithium ceramic spheres coated with BeO is chosen. Increases in K sp would lead to enhanced mechanical and thermal performance of the breeder materials.