| Abstract Scope |
Historically, solid moderators have been relatively simple elemental or compound materials such as carbon, Be, BeO, certain metal hydrides, etc. This work will discuss the fundamental neutronics and materials processing of composite materials for moderator applications. Specifically, architectures designed and fabricated that synergistically combine attractive features of different materials into one radiation resistant composite structure. A specific example, made possible by a significant suppression of the MgO (matrix) sintering temperature by small additions of lithium bearing salts, two-phase moderators including Be, BeO, and ZrH2 as entrained phase are processed by direct current sintering with thermophysical properties and matrix integrity via X-ray tomography and electron microscopy evaluated. Issues of irradiation stability, hydrogen retention, and neutronic needs will be discussed. As example, composite materials a 60MgO-40BeO or 80MgO-20ZrH2 has the effect of extending small modular reactor core lifetime or reducing the critical core size by >30% as compared to graphite. |