Modular High Temperature Gas-Cooled Reactor design

The Modular High-Temperature Gas-Cooled Reactor (MHTGR) is an advanced power plant concept which has been under development since 1984. The design utilizes basic high temperature gas-cooled reactor features of refractory coated fuel, helium coolant and a graphite moderator which are supported by design studies and experience of over 30 years. The design is being developed based on selections made in response to well defined requirements for safe, reliable and economic power. The geometric arrangement of the reactor and steam generator vessels, the core and the heat removal components has been selected to exploit the inherent characteristics associated with high-temperature materials. The design utilizes passively safe features which provide a higher margin of safety and investment protection than current generation reactors. Design features include an arrangement of four identical 350 MW(t) modular reactor units located in underground silos covered by a single reactor building. This Nuclear Island (NI) with the reactors and associated equipment is coupled to an Energy Conversion Area (ECA) with two turbine generators producing a combined total of approximately 540 MW(e). Nuclear heat is normally removed by a steam generation system featuring a once-through design. A shutdown cooling system utilizing water and a reactor cavity cooling system utilizing air driven by natural convection provide alternate heat removal paths. The design and development program, now in the preliminary design stage, is a cooperative effort by the U.S. government, the utilities and the nuclear industry. (author)