The CC-MGR Combined Cycle - Modular Gas Reactor

Abstract

The Combined Cycle-Modular Gas Reactor (CC-MGR) takes advantage of established combined cycle gas turbine generation (CCGT) technology, utilizing a Modular High Temperature Gas Reactor (MHTGR) rather than natural gas to provide the heat source. Development of Helium cooled, graphite moderated High Temperature Gas Reactors (HTGRs) began with the Dragon project in the 1950s, and resulted in demonstration and commercial reactors being built in Germany (AVR-15 and THTR-300) and in the US (Peach Bottom 1 and Fort Saint Vrain). By the late 1980s all operating HTGRs were shut down and interest in the technology was fading. However, interest in HTGRs was revitalized over the past 15 years and HTGR research reactors now operating in Japan and in China and a commercial HTGR under construction in China. Two major MHTGR programmes currently in the design and development stage, the Pebble Bed Modular Reactor (PBMR) in South Africa, and the Gas Turbine-Modular Helium Reactor (GTMHR) by an international consortium headed by General Atomics, are focused on direct closed cycle technology in which the helium from the reactor is passed directly through a helium/gas turbine which subsequently drives a generator. In both of these designs, heat in the helium exhaust from the power turbine is transferred to the helium flow entering the reactor via a recuperator located downstream of the compressors. The amount of heat transferred in the recuperator is slightly greater than the reactor thermal power. In the CC-MGR power plant, the helium exhaust from the power turbine is directed to a steam generator which generates steam that subsequently drives a steam turbinegenerator. The helium leaving the steam generator passes through a recuperator, where heat is transferred to the helium flow entering the reactor downstream of the compressors. This arrangement reduces the amount of heat transferred in the recuperator by approximately half, and results in a reduced reactor helium inlet temperature, which in turn facilitates an increase of approximately 50% in reactor power without reducing the inherent residual heat removal safety characteristics of the MHTGR through the increase of the active reactor core length. This paper focuses on the power conversion system. The reference reactor design is the GT-MHR.