Effective Thermal Conductivity of Prismatic MHTGR Fuel

Abstract

The Reactor Cavity Cooling System (RCCS) is an essential passive safety feature of the Modular High Temperature Gas-Cooled Reactor (MHTGR). Its function is to assure the protection of both public safety and owner investment. As shown schematically in Figure 1.1, the system relies upon all three of the classic modes of heat transfer: conduction through the graphic core dominates energy transport to the reactor vessel, from which radiation is the principal mechanism for heat transfer to the riser tubes, inside which natural convection transfers heat to ambient air which provides the ultimate heat sink. The latter two steps have been the subject of past and on-going analyses at MIT in the support of the MHTGR program, as document in references 1 through 10. In this report we focus attention on the in-vessel aspects of this sequence.