Mechanical Irradiation Investigation of In Irradiation of Glassy Polymeric Carbon to Enhance Nuclear Safety

ABSTRACT

The TRISO fuel that is planned to be used in some of the Generation IV nuclear reactor designs consists of a fuel kernel composed of UO_x coated with several layers of materials, generally a porous buffer layer of carbon, followed by a dense inner layer of pyrolytic carbon, then a ceramic layer of silicon carbide, and finally, a dense outer layer of pyrolytic carbon. In this study we are investigating the possibility of using glassy polymeric carbon (GPC) to replace one or both layers of pyrolytic carbon. GPC is a type of polymer used in the production of artificial heart valves, heat-shields for space crafts, heat-exchangers, and many other high-tech products developed for the space and medical industries. It is also a lightweight material that can maintain dimensional and chemical stability in adverse environment and very high temperatures (up to 3000°C). GPC’s structure consists of long ribbon-like of graphite sheets that are arranged randomly in space, creating a structure that has a very low (sometimes negative) coefficient of thermal expansion and almost impenetrable (zero diffusion) even for most mobile elements (like helium). Here we present changes in the material’s structure after bombardment at 600 and 800 °C by using scanning electron microscopy (SEM), microindentation, three-point bending, and Raman measurements.