[en] Advanced High Temperature Gas-cooled Reactor (HTGR) design concepts for energy production via gas turbine and process heat applications center on cores generating helium coolant outlet temperatures of up to 1000⁰C (1800⁰F). A preliminary analysis of a large HTGR core using a prismatic fuel with coolant gas core outlet temperatures of 950⁰C (1740⁰F) is presented. The purpose of this study was to provide detailed core design information in the areas of radial fuel zoning, power distribution, fuel performance, fuel temperatures, and fission product release for a large HTGR core operating under very high temperature conditions to identify potential problem areas and to suggest where improvements could be made in future design work