Lead P.I. - Dr. Jason R. Trelewicz

Solid moderator and reflector materials employed in research, space, and commercial power reactors have historically been simple forms of naturally existing materials focused primarily on graphite but with alternatives including beryllium- and hydride-based materials.  While these alternative moderators offer improvements in moderating power, they (along with graphite) possess relatively poor resistance to irradiation, which places limitations on the upper design temperature and service life of a reactor.  The objective of this research is to advance engineered composites composed of an environmentally and radiation stable continuous matrix containing a highly moderating entrained phase to mitigate the shortcomings of historic monolithic moderator materials.  From ARPA-E funded research under the Modeling-Enhanced Innovations Trailblazing Nuclear Energy Reinvigoration (MEITNER) program, EMREL has produced the first known ceramic composite moderator containing a magnesia (MgO) structural matrix with either a hydride (ZrHx or YHx) or beryllium-containing (BeO, Be2C, or Be) entrained moderating phase.  Processing innovations have enabled the synthesis of these fully dense and functional ceramic matrix composites, which are now being researched for other applications in compact fusion devices such as shielding for high temperature superconducting magnet technologies. In the figure above, we highlight ceramic matrix composites of MgO-BeO and MgO-ZrH1.6 as advanced nuclear moderators enabling reductions in core volume for microreactor technologies.  The MgO-BeO system is intrinsically high temperature stable while encapsulating the ZrH in MgO provides a pathway for hydrogen retention.