A Review of Graphite Properties Relevant to Micro-Reactor Design

Micro-reactors are advanced reactors that are designed to be small, scalable, and portable with up to 20 MW power. These reactors could operate independently, or as part of a microgrid, without need of frequent refueling. Micro-reactors are designed to be deployable to provide electric power in remote locations, therefore providing greater flexibility in energy distribution and access. Several micro-reactors are under development in the US. These reactors are based on advanced gas-cooled or heat-pipe concepts. While graphite can be found in various applications, some high-temperature reactors plan to employ graphite in their core components due to its role as a moderator and its ability to maintain its structural integrity when subjected to elevated temperatures and high neutron fluence. Although there is significant experience with use of graphite in nuclear applications, there are still unknowns that should be addressed. Graphite properties depend on the graphite type and are affected by the fabrication procedures. Material properties are functions of the temperature and radiation dose and are often affected by the oxidation environment. Therefore, in-depth understanding of graphite properties, including the effect of irradiation, oxidation, and other influencing parameters are required to evaluate the design accurately. This paper aims to provide a review of material properties for graphite relevant to micro-reactor design. For this work, two distinct grades of graphite were considered, namely IG-110 and Mersen-2114. Physical, thermal, and mechanical properties for these grades were comparatively evaluated. The properties that are discussed in this draft aim to serve as a basis for design and safety analysis.